diff --git a/deepspeech/frontend/featurizer/text_featurizer.py b/deepspeech/frontend/featurizer/text_featurizer.py
index e4364f70a..7dc01c40a 100644
--- a/deepspeech/frontend/featurizer/text_featurizer.py
+++ b/deepspeech/frontend/featurizer/text_featurizer.py
@@ -76,7 +76,7 @@ class TextFeaturizer():
 
         Args:
             text (str): Text.
-        
+
         Returns:
             List[int]: List of token indices.
         """
@@ -89,7 +89,7 @@ class TextFeaturizer():
 
     def defeaturize(self, idxs):
         """Convert a list of token indices to text string,
-        ignore index after eos_id. 
+        ignore index after eos_id.
 
         Args:
             idxs (List[int]): List of token indices.
@@ -196,7 +196,12 @@ class TextFeaturizer():
             [(idx, token) for (idx, token) in enumerate(vocab_list)])
         token2id = dict(
             [(token, idx) for (idx, token) in enumerate(vocab_list)])
-
-        unk_id = vocab_list.index(UNK)
-        eos_id = vocab_list.index(EOS)
+        if UNK in vocab_list:
+            unk_id = vocab_list.index(UNK)
+        else:
+            unk_id = -1
+        if EOS in vocab_list:
+            eos_id = vocab_list.index(EOS)
+        else:
+            eos_id = -1
         return token2id, id2token, vocab_list, unk_id, eos_id
diff --git a/deepspeech/frontend/normalizer.py b/deepspeech/frontend/normalizer.py
index 73b3a4ba6..6ace4fc6d 100644
--- a/deepspeech/frontend/normalizer.py
+++ b/deepspeech/frontend/normalizer.py
@@ -130,7 +130,8 @@ class FeatureNormalizer(object):
 
     def _read_mean_std_from_file(self, filepath, eps=1e-20):
         """Load mean and std from file."""
-        mean, istd = load_cmvn(filepath, filetype='json')
+        filetype = filepath.split(".")[-1]
+        mean, istd = load_cmvn(filepath, filetype=filetype)
         self._mean = np.expand_dims(mean, axis=0)
         self._istd = np.expand_dims(istd, axis=0)
 
diff --git a/deepspeech/frontend/utility.py b/deepspeech/frontend/utility.py
index 72dfc98dd..c6781cd4e 100644
--- a/deepspeech/frontend/utility.py
+++ b/deepspeech/frontend/utility.py
@@ -69,19 +69,19 @@ def read_manifest(
 
     Args:
         manifest_path ([type]): Manifest file to load and parse.
-        max_input_len ([type], optional): maximum output seq length, 
-            in seconds for raw wav, in frame numbers for feature data. 
+        max_input_len ([type], optional): maximum output seq length,
+            in seconds for raw wav, in frame numbers for feature data.
             Defaults to float('inf').
-        min_input_len (float, optional): minimum input seq length, 
-            in seconds for raw wav, in frame numbers for feature data. 
+        min_input_len (float, optional): minimum input seq length,
+            in seconds for raw wav, in frame numbers for feature data.
             Defaults to 0.0.
-        max_output_len (float, optional): maximum input seq length, 
+        max_output_len (float, optional): maximum input seq length,
             in modeling units. Defaults to 500.0.
-        min_output_len (float, optional): minimum input seq length, 
+        min_output_len (float, optional): minimum input seq length,
             in modeling units. Defaults to 0.0.
-        max_output_input_ratio (float, optional): 
+        max_output_input_ratio (float, optional):
             maximum output seq length/output seq length ratio. Defaults to 10.0.
-        min_output_input_ratio (float, optional): 
+        min_output_input_ratio (float, optional):
             minimum output seq length/output seq length ratio. Defaults to 0.05.
 
     Raises:
@@ -131,7 +131,7 @@ def rms_to_dbfs(rms: float):
     """Root Mean Square to dBFS.
     https://fireattack.wordpress.com/2017/02/06/replaygain-loudness-normalization-and-applications/
     Audio is mix of sine wave, so 1 amp sine wave's Full scale is 0.7071, equal to -3.0103dB.
-   
+
     dB = dBFS + 3.0103
     dBFS = db - 3.0103
     e.g. 0 dB = -3.0103 dBFS
@@ -146,26 +146,26 @@ def rms_to_dbfs(rms: float):
 
 
 def max_dbfs(sample_data: np.ndarray):
-    """Peak dBFS based on the maximum energy sample. 
+    """Peak dBFS based on the maximum energy sample.
 
     Args:
         sample_data ([np.ndarray]): float array, [-1, 1].
 
     Returns:
-        float: dBFS 
+        float: dBFS
     """
     # Peak dBFS based on the maximum energy sample. Will prevent overdrive if used for normalization.
     return rms_to_dbfs(max(abs(np.min(sample_data)), abs(np.max(sample_data))))
 
 
 def mean_dbfs(sample_data):
-    """Peak dBFS based on the RMS energy. 
+    """Peak dBFS based on the RMS energy.
 
     Args:
         sample_data ([np.ndarray]): float array, [-1, 1].
 
     Returns:
-        float: dBFS 
+        float: dBFS
     """
     return rms_to_dbfs(
         math.sqrt(np.mean(np.square(sample_data, dtype=np.float64))))
@@ -185,7 +185,7 @@ def gain_db_to_ratio(gain_db: float):
 
 def normalize_audio(sample_data: np.ndarray, dbfs: float=-3.0103):
     """Nomalize audio to dBFS.
-    
+
     Args:
         sample_data (np.ndarray): input wave samples, [-1, 1].
         dbfs (float, optional): target dBFS. Defaults to -3.0103.
@@ -284,6 +284,13 @@ def load_cmvn(cmvn_file: str, filetype: str):
         cmvn = _load_json_cmvn(cmvn_file)
     elif filetype == "kaldi":
         cmvn = _load_kaldi_cmvn(cmvn_file)
+    elif filetype == "npz":
+        eps = 1e-14
+        npzfile = np.load(cmvn_file)
+        mean = np.squeeze(npzfile["mean"])
+        std = np.squeeze(npzfile["std"])
+        istd = 1 / (std + eps)
+        cmvn = [mean, istd]
     else:
         raise ValueError(f"cmvn file type no support: {filetype}")
     return cmvn[0], cmvn[1]
diff --git a/examples/v18_to_v2x/.gitignore b/examples/v18_to_v2x/.gitignore
new file mode 100644
index 000000000..a9a5aecf4
--- /dev/null
+++ b/examples/v18_to_v2x/.gitignore
@@ -0,0 +1 @@
+tmp
diff --git a/examples/v18_to_v2x/deepspeech2x/__init__.py b/examples/v18_to_v2x/deepspeech2x/__init__.py
new file mode 100644
index 000000000..d85a3dde7
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/__init__.py
@@ -0,0 +1,370 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from typing import Any
+from typing import List
+from typing import Tuple
+from typing import Union
+
+import paddle
+from paddle import nn
+from paddle.fluid import core
+from paddle.nn import functional as F
+
+from deepspeech.utils.log import Log
+
+#TODO(Hui Zhang): remove  fluid import
+logger = Log(__name__).getlog()
+
+########### hcak logging #############
+logger.warn = logger.warning
+
+########### hcak paddle #############
+paddle.half = 'float16'
+paddle.float = 'float32'
+paddle.double = 'float64'
+paddle.short = 'int16'
+paddle.int = 'int32'
+paddle.long = 'int64'
+paddle.uint16 = 'uint16'
+paddle.cdouble = 'complex128'
+
+
+def convert_dtype_to_string(tensor_dtype):
+    """
+    Convert the data type in numpy to the data type in Paddle
+    Args:
+        tensor_dtype(core.VarDesc.VarType): the data type in numpy.
+    Returns:
+        core.VarDesc.VarType: the data type in Paddle.
+    """
+    dtype = tensor_dtype
+    if dtype == core.VarDesc.VarType.FP32:
+        return paddle.float32
+    elif dtype == core.VarDesc.VarType.FP64:
+        return paddle.float64
+    elif dtype == core.VarDesc.VarType.FP16:
+        return paddle.float16
+    elif dtype == core.VarDesc.VarType.INT32:
+        return paddle.int32
+    elif dtype == core.VarDesc.VarType.INT16:
+        return paddle.int16
+    elif dtype == core.VarDesc.VarType.INT64:
+        return paddle.int64
+    elif dtype == core.VarDesc.VarType.BOOL:
+        return paddle.bool
+    elif dtype == core.VarDesc.VarType.BF16:
+        # since there is still no support for bfloat16 in NumPy,
+        # uint16 is used for casting bfloat16
+        return paddle.uint16
+    elif dtype == core.VarDesc.VarType.UINT8:
+        return paddle.uint8
+    elif dtype == core.VarDesc.VarType.INT8:
+        return paddle.int8
+    elif dtype == core.VarDesc.VarType.COMPLEX64:
+        return paddle.complex64
+    elif dtype == core.VarDesc.VarType.COMPLEX128:
+        return paddle.complex128
+    else:
+        raise ValueError("Not supported tensor dtype %s" % dtype)
+
+
+if not hasattr(paddle, 'softmax'):
+    logger.warn("register user softmax to paddle, remove this when fixed!")
+    setattr(paddle, 'softmax', paddle.nn.functional.softmax)
+
+if not hasattr(paddle, 'log_softmax'):
+    logger.warn("register user log_softmax to paddle, remove this when fixed!")
+    setattr(paddle, 'log_softmax', paddle.nn.functional.log_softmax)
+
+if not hasattr(paddle, 'sigmoid'):
+    logger.warn("register user sigmoid to paddle, remove this when fixed!")
+    setattr(paddle, 'sigmoid', paddle.nn.functional.sigmoid)
+
+if not hasattr(paddle, 'log_sigmoid'):
+    logger.warn("register user log_sigmoid to paddle, remove this when fixed!")
+    setattr(paddle, 'log_sigmoid', paddle.nn.functional.log_sigmoid)
+
+if not hasattr(paddle, 'relu'):
+    logger.warn("register user relu to paddle, remove this when fixed!")
+    setattr(paddle, 'relu', paddle.nn.functional.relu)
+
+
+def cat(xs, dim=0):
+    return paddle.concat(xs, axis=dim)
+
+
+if not hasattr(paddle, 'cat'):
+    logger.warn(
+        "override cat of paddle if exists or register, remove this when fixed!")
+    paddle.cat = cat
+
+
+########### hcak paddle.Tensor #############
+def item(x: paddle.Tensor):
+    return x.numpy().item()
+
+
+if not hasattr(paddle.Tensor, 'item'):
+    logger.warn(
+        "override item of paddle.Tensor if exists or register, remove this when fixed!"
+    )
+    paddle.Tensor.item = item
+
+
+def func_long(x: paddle.Tensor):
+    return paddle.cast(x, paddle.long)
+
+
+if not hasattr(paddle.Tensor, 'long'):
+    logger.warn(
+        "override long of paddle.Tensor if exists or register, remove this when fixed!"
+    )
+    paddle.Tensor.long = func_long
+
+if not hasattr(paddle.Tensor, 'numel'):
+    logger.warn(
+        "override numel of paddle.Tensor if exists or register, remove this when fixed!"
+    )
+    paddle.Tensor.numel = paddle.numel
+
+
+def new_full(x: paddle.Tensor,
+             size: Union[List[int], Tuple[int], paddle.Tensor],
+             fill_value: Union[float, int, bool, paddle.Tensor],
+             dtype=None):
+    return paddle.full(size, fill_value, dtype=x.dtype)
+
+
+if not hasattr(paddle.Tensor, 'new_full'):
+    logger.warn(
+        "override new_full of paddle.Tensor if exists or register, remove this when fixed!"
+    )
+    paddle.Tensor.new_full = new_full
+
+
+def eq(xs: paddle.Tensor, ys: Union[paddle.Tensor, float]) -> paddle.Tensor:
+    if convert_dtype_to_string(xs.dtype) == paddle.bool:
+        xs = xs.astype(paddle.int)
+    return xs.equal(
+        paddle.to_tensor(
+            ys, dtype=convert_dtype_to_string(xs.dtype), place=xs.place))
+
+
+if not hasattr(paddle.Tensor, 'eq'):
+    logger.warn(
+        "override eq of paddle.Tensor if exists or register, remove this when fixed!"
+    )
+    paddle.Tensor.eq = eq
+
+if not hasattr(paddle, 'eq'):
+    logger.warn(
+        "override eq of paddle if exists or register, remove this when fixed!")
+    paddle.eq = eq
+
+
+def contiguous(xs: paddle.Tensor) -> paddle.Tensor:
+    return xs
+
+
+if not hasattr(paddle.Tensor, 'contiguous'):
+    logger.warn(
+        "override contiguous of paddle.Tensor if exists or register, remove this when fixed!"
+    )
+    paddle.Tensor.contiguous = contiguous
+
+
+def size(xs: paddle.Tensor, *args: int) -> paddle.Tensor:
+    nargs = len(args)
+    assert (nargs <= 1)
+    s = paddle.shape(xs)
+    if nargs == 1:
+        return s[args[0]]
+    else:
+        return s
+
+
+#`to_static` do not process `size` property, maybe some `paddle` api dependent on it.
+logger.warn(
+    "override size of paddle.Tensor "
+    "(`to_static` do not process `size` property, maybe some `paddle` api dependent on it), remove this when fixed!"
+)
+paddle.Tensor.size = size
+
+
+def view(xs: paddle.Tensor, *args: int) -> paddle.Tensor:
+    return xs.reshape(args)
+
+
+if not hasattr(paddle.Tensor, 'view'):
+    logger.warn("register user view to paddle.Tensor, remove this when fixed!")
+    paddle.Tensor.view = view
+
+
+def view_as(xs: paddle.Tensor, ys: paddle.Tensor) -> paddle.Tensor:
+    return xs.reshape(ys.size())
+
+
+if not hasattr(paddle.Tensor, 'view_as'):
+    logger.warn(
+        "register user view_as to paddle.Tensor, remove this when fixed!")
+    paddle.Tensor.view_as = view_as
+
+
+def is_broadcastable(shp1, shp2):
+    for a, b in zip(shp1[::-1], shp2[::-1]):
+        if a == 1 or b == 1 or a == b:
+            pass
+        else:
+            return False
+    return True
+
+
+def masked_fill(xs: paddle.Tensor,
+                mask: paddle.Tensor,
+                value: Union[float, int]):
+    assert is_broadcastable(xs.shape, mask.shape) is True
+    bshape = paddle.broadcast_shape(xs.shape, mask.shape)
+    mask = mask.broadcast_to(bshape)
+    trues = paddle.ones_like(xs) * value
+    xs = paddle.where(mask, trues, xs)
+    return xs
+
+
+if not hasattr(paddle.Tensor, 'masked_fill'):
+    logger.warn(
+        "register user masked_fill to paddle.Tensor, remove this when fixed!")
+    paddle.Tensor.masked_fill = masked_fill
+
+
+def masked_fill_(xs: paddle.Tensor,
+                 mask: paddle.Tensor,
+                 value: Union[float, int]) -> paddle.Tensor:
+    assert is_broadcastable(xs.shape, mask.shape) is True
+    bshape = paddle.broadcast_shape(xs.shape, mask.shape)
+    mask = mask.broadcast_to(bshape)
+    trues = paddle.ones_like(xs) * value
+    ret = paddle.where(mask, trues, xs)
+    paddle.assign(ret.detach(), output=xs)
+    return xs
+
+
+if not hasattr(paddle.Tensor, 'masked_fill_'):
+    logger.warn(
+        "register user masked_fill_ to paddle.Tensor, remove this when fixed!")
+    paddle.Tensor.masked_fill_ = masked_fill_
+
+
+def fill_(xs: paddle.Tensor, value: Union[float, int]) -> paddle.Tensor:
+    val = paddle.full_like(xs, value)
+    paddle.assign(val.detach(), output=xs)
+    return xs
+
+
+if not hasattr(paddle.Tensor, 'fill_'):
+    logger.warn("register user fill_ to paddle.Tensor, remove this when fixed!")
+    paddle.Tensor.fill_ = fill_
+
+
+def repeat(xs: paddle.Tensor, *size: Any) -> paddle.Tensor:
+    return paddle.tile(xs, size)
+
+
+if not hasattr(paddle.Tensor, 'repeat'):
+    logger.warn(
+        "register user repeat to paddle.Tensor, remove this when fixed!")
+    paddle.Tensor.repeat = repeat
+
+if not hasattr(paddle.Tensor, 'softmax'):
+    logger.warn(
+        "register user softmax to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'softmax', paddle.nn.functional.softmax)
+
+if not hasattr(paddle.Tensor, 'sigmoid'):
+    logger.warn(
+        "register user sigmoid to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'sigmoid', paddle.nn.functional.sigmoid)
+
+if not hasattr(paddle.Tensor, 'relu'):
+    logger.warn("register user relu to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'relu', paddle.nn.functional.relu)
+
+
+def type_as(x: paddle.Tensor, other: paddle.Tensor) -> paddle.Tensor:
+    return x.astype(other.dtype)
+
+
+if not hasattr(paddle.Tensor, 'type_as'):
+    logger.warn(
+        "register user type_as to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'type_as', type_as)
+
+
+def to(x: paddle.Tensor, *args, **kwargs) -> paddle.Tensor:
+    assert len(args) == 1
+    if isinstance(args[0], str):  # dtype
+        return x.astype(args[0])
+    elif isinstance(args[0], paddle.Tensor):  #Tensor
+        return x.astype(args[0].dtype)
+    else:  # Device
+        return x
+
+
+if not hasattr(paddle.Tensor, 'to'):
+    logger.warn("register user to to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'to', to)
+
+
+def func_float(x: paddle.Tensor) -> paddle.Tensor:
+    return x.astype(paddle.float)
+
+
+if not hasattr(paddle.Tensor, 'float'):
+    logger.warn("register user float to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'float', func_float)
+
+
+def func_int(x: paddle.Tensor) -> paddle.Tensor:
+    return x.astype(paddle.int)
+
+
+if not hasattr(paddle.Tensor, 'int'):
+    logger.warn("register user int to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'int', func_int)
+
+
+def tolist(x: paddle.Tensor) -> List[Any]:
+    return x.numpy().tolist()
+
+
+if not hasattr(paddle.Tensor, 'tolist'):
+    logger.warn(
+        "register user tolist to paddle.Tensor, remove this when fixed!")
+    setattr(paddle.Tensor, 'tolist', tolist)
+
+
+########### hcak paddle.nn #############
+class GLU(nn.Layer):
+    """Gated Linear Units (GLU) Layer"""
+
+    def __init__(self, dim: int=-1):
+        super().__init__()
+        self.dim = dim
+
+    def forward(self, xs):
+        return F.glu(xs, axis=self.dim)
+
+
+if not hasattr(paddle.nn, 'GLU'):
+    logger.warn("register user GLU to paddle.nn, remove this when fixed!")
+    setattr(paddle.nn, 'GLU', GLU)
diff --git a/examples/v18_to_v2x/deepspeech2x/bin/test.py b/examples/v18_to_v2x/deepspeech2x/bin/test.py
new file mode 100644
index 000000000..3fa0a61de
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/bin/test.py
@@ -0,0 +1,56 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Evaluation for DeepSpeech2 model."""
+from deepspeech2x.model import DeepSpeech2Tester as Tester
+
+from deepspeech.exps.deepspeech2.config import get_cfg_defaults
+from deepspeech.training.cli import default_argument_parser
+from deepspeech.utils.utility import print_arguments
+
+
+def main_sp(config, args):
+    exp = Tester(config, args)
+    exp.setup()
+    exp.run_test()
+
+
+def main(config, args):
+    main_sp(config, args)
+
+
+if __name__ == "__main__":
+    parser = default_argument_parser()
+    parser.add_argument("--model_type")
+    # save asr result to
+    parser.add_argument(
+        "--result_file", type=str, help="path of save the asr result")
+    args = parser.parse_args()
+    print_arguments(args, globals())
+    if args.model_type is None:
+        args.model_type = 'offline'
+    print("model_type:{}".format(args.model_type))
+
+    # https://yaml.org/type/float.html
+    config = get_cfg_defaults(args.model_type)
+    if args.config:
+        config.merge_from_file(args.config)
+    if args.opts:
+        config.merge_from_list(args.opts)
+    config.freeze()
+    print(config)
+    if args.dump_config:
+        with open(args.dump_config, 'w') as f:
+            print(config, file=f)
+
+    main(config, args)
diff --git a/examples/v18_to_v2x/deepspeech2x/model.py b/examples/v18_to_v2x/deepspeech2x/model.py
new file mode 100644
index 000000000..1fe1e2d68
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/model.py
@@ -0,0 +1,427 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Contains DeepSpeech2 and DeepSpeech2Online model."""
+import time
+from collections import defaultdict
+from contextlib import nullcontext
+from pathlib import Path
+from typing import Optional
+
+import numpy as np
+import paddle
+from deepspeech2x.models.ds2 import DeepSpeech2InferModel
+from deepspeech2x.models.ds2 import DeepSpeech2Model
+from paddle import distributed as dist
+from paddle.io import DataLoader
+from yacs.config import CfgNode
+
+from deepspeech.io.collator import SpeechCollator
+from deepspeech.io.dataset import ManifestDataset
+from deepspeech.io.sampler import SortagradBatchSampler
+from deepspeech.io.sampler import SortagradDistributedBatchSampler
+from deepspeech.models.ds2_online import DeepSpeech2InferModelOnline
+from deepspeech.models.ds2_online import DeepSpeech2ModelOnline
+from deepspeech.training.gradclip import ClipGradByGlobalNormWithLog
+from deepspeech.training.trainer import Trainer
+from deepspeech.utils import error_rate
+from deepspeech.utils import layer_tools
+from deepspeech.utils import mp_tools
+from deepspeech.utils.log import Log
+#from deepspeech.utils.log import Autolog
+
+logger = Log(__name__).getlog()
+
+
+class DeepSpeech2Trainer(Trainer):
+    @classmethod
+    def params(cls, config: Optional[CfgNode]=None) -> CfgNode:
+        # training config
+        default = CfgNode(
+            dict(
+                lr=5e-4,  # learning rate
+                lr_decay=1.0,  # learning rate decay
+                weight_decay=1e-6,  # the coeff of weight decay
+                global_grad_clip=5.0,  # the global norm clip
+                n_epoch=50,  # train epochs
+            ))
+
+        if config is not None:
+            config.merge_from_other_cfg(default)
+        return default
+
+    def __init__(self, config, args):
+        super().__init__(config, args)
+
+    def train_batch(self, batch_index, batch_data, msg):
+        train_conf = self.config.training
+        start = time.time()
+
+        # forward
+        utt, audio, audio_len, text, text_len = batch_data
+        loss = self.model(audio, audio_len, text, text_len)
+        losses_np = {
+            'train_loss': float(loss),
+        }
+
+        # loss backward
+        if (batch_index + 1) % train_conf.accum_grad != 0:
+            # Disable gradient synchronizations across DDP processes.
+            # Within this context, gradients will be accumulated on module
+            # variables, which will later be synchronized.
+            context = self.model.no_sync
+        else:
+            # Used for single gpu training and DDP gradient synchronization
+            # processes.
+            context = nullcontext
+
+        with context():
+            loss.backward()
+            layer_tools.print_grads(self.model, print_func=None)
+
+        # optimizer step
+        if (batch_index + 1) % train_conf.accum_grad == 0:
+            self.optimizer.step()
+            self.optimizer.clear_grad()
+            self.iteration += 1
+
+        iteration_time = time.time() - start
+
+        msg += "train time: {:>.3f}s, ".format(iteration_time)
+        msg += "batch size: {}, ".format(self.config.collator.batch_size)
+        msg += "accum: {}, ".format(train_conf.accum_grad)
+        msg += ', '.join('{}: {:>.6f}'.format(k, v)
+                         for k, v in losses_np.items())
+        logger.info(msg)
+
+        if dist.get_rank() == 0 and self.visualizer:
+            for k, v in losses_np.items():
+                # `step -1` since we update `step` after optimizer.step().
+                self.visualizer.add_scalar("train/{}".format(k), v,
+                                           self.iteration - 1)
+
+    @paddle.no_grad()
+    def valid(self):
+        logger.info(f"Valid Total Examples: {len(self.valid_loader.dataset)}")
+        self.model.eval()
+        valid_losses = defaultdict(list)
+        num_seen_utts = 1
+        total_loss = 0.0
+        for i, batch in enumerate(self.valid_loader):
+            utt, audio, audio_len, text, text_len = batch
+            loss = self.model(audio, audio_len, text, text_len)
+            if paddle.isfinite(loss):
+                num_utts = batch[1].shape[0]
+                num_seen_utts += num_utts
+                total_loss += float(loss) * num_utts
+                valid_losses['val_loss'].append(float(loss))
+
+            if (i + 1) % self.config.training.log_interval == 0:
+                valid_dump = {k: np.mean(v) for k, v in valid_losses.items()}
+                valid_dump['val_history_loss'] = total_loss / num_seen_utts
+
+                # logging
+                msg = f"Valid: Rank: {dist.get_rank()}, "
+                msg += "epoch: {}, ".format(self.epoch)
+                msg += "step: {}, ".format(self.iteration)
+                msg += "batch : {}/{}, ".format(i + 1, len(self.valid_loader))
+                msg += ', '.join('{}: {:>.6f}'.format(k, v)
+                                 for k, v in valid_dump.items())
+                logger.info(msg)
+
+        logger.info('Rank {} Val info val_loss {}'.format(
+            dist.get_rank(), total_loss / num_seen_utts))
+        return total_loss, num_seen_utts
+
+    def setup_model(self):
+        config = self.config.clone()
+        config.defrost()
+        config.model.feat_size = self.train_loader.collate_fn.feature_size
+        #config.model.dict_size = self.train_loader.collate_fn.vocab_size
+        config.model.dict_size = len(self.train_loader.collate_fn.vocab_list)
+        config.freeze()
+
+        if self.args.model_type == 'offline':
+            model = DeepSpeech2Model.from_config(config.model)
+        elif self.args.model_type == 'online':
+            model = DeepSpeech2ModelOnline.from_config(config.model)
+        else:
+            raise Exception("wrong model type")
+        if self.parallel:
+            model = paddle.DataParallel(model)
+
+        logger.info(f"{model}")
+        layer_tools.print_params(model, logger.info)
+
+        grad_clip = ClipGradByGlobalNormWithLog(
+            config.training.global_grad_clip)
+        lr_scheduler = paddle.optimizer.lr.ExponentialDecay(
+            learning_rate=config.training.lr,
+            gamma=config.training.lr_decay,
+            verbose=True)
+        optimizer = paddle.optimizer.Adam(
+            learning_rate=lr_scheduler,
+            parameters=model.parameters(),
+            weight_decay=paddle.regularizer.L2Decay(
+                config.training.weight_decay),
+            grad_clip=grad_clip)
+
+        self.model = model
+        self.optimizer = optimizer
+        self.lr_scheduler = lr_scheduler
+        logger.info("Setup model/optimizer/lr_scheduler!")
+
+    def setup_dataloader(self):
+        config = self.config.clone()
+        config.defrost()
+        config.collator.keep_transcription_text = False
+
+        config.data.manifest = config.data.train_manifest
+        train_dataset = ManifestDataset.from_config(config)
+
+        config.data.manifest = config.data.dev_manifest
+        dev_dataset = ManifestDataset.from_config(config)
+
+        config.data.manifest = config.data.test_manifest
+        test_dataset = ManifestDataset.from_config(config)
+
+        if self.parallel:
+            batch_sampler = SortagradDistributedBatchSampler(
+                train_dataset,
+                batch_size=config.collator.batch_size,
+                num_replicas=None,
+                rank=None,
+                shuffle=True,
+                drop_last=True,
+                sortagrad=config.collator.sortagrad,
+                shuffle_method=config.collator.shuffle_method)
+        else:
+            batch_sampler = SortagradBatchSampler(
+                train_dataset,
+                shuffle=True,
+                batch_size=config.collator.batch_size,
+                drop_last=True,
+                sortagrad=config.collator.sortagrad,
+                shuffle_method=config.collator.shuffle_method)
+
+        collate_fn_train = SpeechCollator.from_config(config)
+
+        config.collator.augmentation_config = ""
+        collate_fn_dev = SpeechCollator.from_config(config)
+
+        config.collator.keep_transcription_text = True
+        config.collator.augmentation_config = ""
+        collate_fn_test = SpeechCollator.from_config(config)
+
+        self.train_loader = DataLoader(
+            train_dataset,
+            batch_sampler=batch_sampler,
+            collate_fn=collate_fn_train,
+            num_workers=config.collator.num_workers)
+        self.valid_loader = DataLoader(
+            dev_dataset,
+            batch_size=config.collator.batch_size,
+            shuffle=False,
+            drop_last=False,
+            collate_fn=collate_fn_dev)
+        self.test_loader = DataLoader(
+            test_dataset,
+            batch_size=config.decoding.batch_size,
+            shuffle=False,
+            drop_last=False,
+            collate_fn=collate_fn_test)
+        if "<eos>" in self.test_loader.collate_fn.vocab_list:
+            self.test_loader.collate_fn.vocab_list.remove("<eos>")
+        if "<eos>" in self.valid_loader.collate_fn.vocab_list:
+            self.valid_loader.collate_fn.vocab_list.remove("<eos>")
+        if "<eos>" in self.train_loader.collate_fn.vocab_list:
+            self.train_loader.collate_fn.vocab_list.remove("<eos>")
+        logger.info("Setup train/valid/test  Dataloader!")
+
+
+class DeepSpeech2Tester(DeepSpeech2Trainer):
+    @classmethod
+    def params(cls, config: Optional[CfgNode]=None) -> CfgNode:
+        # testing config
+        default = CfgNode(
+            dict(
+                alpha=2.5,  # Coef of LM for beam search.
+                beta=0.3,  # Coef of WC for beam search.
+                cutoff_prob=1.0,  # Cutoff probability for pruning.
+                cutoff_top_n=40,  # Cutoff number for pruning.
+                lang_model_path='models/lm/common_crawl_00.prune01111.trie.klm',  # Filepath for language model.
+                decoding_method='ctc_beam_search',  # Decoding method. Options: ctc_beam_search, ctc_greedy
+                error_rate_type='wer',  # Error rate type for evaluation. Options `wer`, 'cer'
+                num_proc_bsearch=8,  # # of CPUs for beam search.
+                beam_size=500,  # Beam search width.
+                batch_size=128,  # decoding batch size
+            ))
+
+        if config is not None:
+            config.merge_from_other_cfg(default)
+        return default
+
+    def __init__(self, config, args):
+        super().__init__(config, args)
+
+    def ordid2token(self, texts, texts_len):
+        """ ord() id to chr() chr """
+        trans = []
+        for text, n in zip(texts, texts_len):
+            n = n.numpy().item()
+            ids = text[:n]
+            trans.append(''.join([chr(i) for i in ids]))
+        return trans
+
+    def compute_metrics(self,
+                        utts,
+                        audio,
+                        audio_len,
+                        texts,
+                        texts_len,
+                        fout=None):
+        cfg = self.config.decoding
+        errors_sum, len_refs, num_ins = 0.0, 0, 0
+        errors_func = error_rate.char_errors if cfg.error_rate_type == 'cer' else error_rate.word_errors
+        error_rate_func = error_rate.cer if cfg.error_rate_type == 'cer' else error_rate.wer
+
+        vocab_list = self.test_loader.collate_fn.vocab_list
+        if "" in vocab_list:
+            space_id = vocab_list.index("")
+            vocab_list[space_id] = " "
+
+        target_transcripts = self.ordid2token(texts, texts_len)
+
+        result_transcripts = self.compute_result_transcripts(audio, audio_len,
+                                                             vocab_list, cfg)
+        for utt, target, result in zip(utts, target_transcripts,
+                                       result_transcripts):
+            errors, len_ref = errors_func(target, result)
+            errors_sum += errors
+            len_refs += len_ref
+            num_ins += 1
+            if fout:
+                fout.write(utt + " " + result + "\n")
+            logger.info("\nTarget Transcription: %s\nOutput Transcription: %s" %
+                        (target, result))
+            logger.info("Current error rate [%s] = %f" %
+                        (cfg.error_rate_type, error_rate_func(target, result)))
+
+        return dict(
+            errors_sum=errors_sum,
+            len_refs=len_refs,
+            num_ins=num_ins,
+            error_rate=errors_sum / len_refs,
+            error_rate_type=cfg.error_rate_type)
+
+    def compute_result_transcripts(self, audio, audio_len, vocab_list, cfg):
+        result_transcripts = self.model.decode(
+            audio,
+            audio_len,
+            vocab_list,
+            decoding_method=cfg.decoding_method,
+            lang_model_path=cfg.lang_model_path,
+            beam_alpha=cfg.alpha,
+            beam_beta=cfg.beta,
+            beam_size=cfg.beam_size,
+            cutoff_prob=cfg.cutoff_prob,
+            cutoff_top_n=cfg.cutoff_top_n,
+            num_processes=cfg.num_proc_bsearch)
+        return result_transcripts
+
+    @mp_tools.rank_zero_only
+    @paddle.no_grad()
+    def test(self):
+        logger.info(f"Test Total Examples: {len(self.test_loader.dataset)}")
+        self.model.eval()
+        cfg = self.config
+        error_rate_type = None
+        errors_sum, len_refs, num_ins = 0.0, 0, 0
+        with open(self.args.result_file, 'w') as fout:
+            for i, batch in enumerate(self.test_loader):
+                utts, audio, audio_len, texts, texts_len = batch
+                metrics = self.compute_metrics(utts, audio, audio_len, texts,
+                                               texts_len, fout)
+                errors_sum += metrics['errors_sum']
+                len_refs += metrics['len_refs']
+                num_ins += metrics['num_ins']
+                error_rate_type = metrics['error_rate_type']
+                logger.info("Error rate [%s] (%d/?) = %f" %
+                            (error_rate_type, num_ins, errors_sum / len_refs))
+
+        # logging
+        msg = "Test: "
+        msg += "epoch: {}, ".format(self.epoch)
+        msg += "step: {}, ".format(self.iteration)
+        msg += "Final error rate [%s] (%d/%d) = %f" % (
+            error_rate_type, num_ins, num_ins, errors_sum / len_refs)
+        logger.info(msg)
+
+    # self.autolog.report()
+
+    def run_test(self):
+        self.resume_or_scratch()
+        try:
+            self.test()
+        except KeyboardInterrupt:
+            exit(-1)
+
+    def export(self):
+        if self.args.model_type == 'offline':
+            infer_model = DeepSpeech2InferModel.from_pretrained(
+                self.test_loader, self.config, self.args.checkpoint_path)
+        elif self.args.model_type == 'online':
+            infer_model = DeepSpeech2InferModelOnline.from_pretrained(
+                self.test_loader, self.config, self.args.checkpoint_path)
+        else:
+            raise Exception("wrong model type")
+
+        infer_model.eval()
+        feat_dim = self.test_loader.collate_fn.feature_size
+        static_model = infer_model.export()
+        logger.info(f"Export code: {static_model.forward.code}")
+        paddle.jit.save(static_model, self.args.export_path)
+
+    def run_export(self):
+        try:
+            self.export()
+        except KeyboardInterrupt:
+            exit(-1)
+
+    def setup(self):
+        """Setup the experiment.
+        """
+        paddle.set_device(self.args.device)
+
+        self.setup_output_dir()
+        self.setup_checkpointer()
+
+        self.setup_dataloader()
+        self.setup_model()
+
+        self.iteration = 0
+        self.epoch = 0
+
+    def setup_output_dir(self):
+        """Create a directory used for output.
+        """
+        # output dir
+        if self.args.output:
+            output_dir = Path(self.args.output).expanduser()
+            output_dir.mkdir(parents=True, exist_ok=True)
+        else:
+            output_dir = Path(
+                self.args.checkpoint_path).expanduser().parent.parent
+            output_dir.mkdir(parents=True, exist_ok=True)
+
+        self.output_dir = output_dir
diff --git a/examples/v18_to_v2x/deepspeech2x/models/__init__.py b/examples/v18_to_v2x/deepspeech2x/models/__init__.py
new file mode 100644
index 000000000..185a92b8d
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/models/__init__.py
@@ -0,0 +1,13 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/examples/v18_to_v2x/deepspeech2x/models/ds2/__init__.py b/examples/v18_to_v2x/deepspeech2x/models/ds2/__init__.py
new file mode 100644
index 000000000..39bea5bf9
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/models/ds2/__init__.py
@@ -0,0 +1,17 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from .deepspeech2 import DeepSpeech2InferModel
+from .deepspeech2 import DeepSpeech2Model
+
+__all__ = ['DeepSpeech2Model', 'DeepSpeech2InferModel']
diff --git a/examples/v18_to_v2x/deepspeech2x/models/ds2/deepspeech2.py b/examples/v18_to_v2x/deepspeech2x/models/ds2/deepspeech2.py
new file mode 100644
index 000000000..f154ddb54
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/models/ds2/deepspeech2.py
@@ -0,0 +1,314 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Deepspeech2 ASR Model"""
+from typing import Optional
+
+import paddle
+from deepspeech2x.models.ds2.rnn import RNNStack
+from paddle import nn
+from yacs.config import CfgNode
+
+from deepspeech.models.ds2.conv import ConvStack
+from deepspeech.modules.ctc import CTCDecoder
+from deepspeech.utils import layer_tools
+from deepspeech.utils.checkpoint import Checkpoint
+from deepspeech.utils.log import Log
+logger = Log(__name__).getlog()
+
+__all__ = ['DeepSpeech2Model', 'DeepSpeech2InferModel']
+
+
+class CRNNEncoder(nn.Layer):
+    def __init__(self,
+                 feat_size,
+                 dict_size,
+                 num_conv_layers=2,
+                 num_rnn_layers=3,
+                 rnn_size=1024,
+                 use_gru=False,
+                 share_rnn_weights=True):
+        super().__init__()
+        self.rnn_size = rnn_size
+        self.feat_size = feat_size  # 161 for linear
+        self.dict_size = dict_size
+
+        self.conv = ConvStack(feat_size, num_conv_layers)
+
+        i_size = self.conv.output_height  # H after conv stack
+        self.rnn = RNNStack(
+            i_size=i_size,
+            h_size=rnn_size,
+            num_stacks=num_rnn_layers,
+            use_gru=use_gru,
+            share_rnn_weights=share_rnn_weights)
+
+    @property
+    def output_size(self):
+        return self.rnn_size * 2
+
+    def forward(self, audio, audio_len):
+        """Compute Encoder outputs
+
+        Args:
+            audio (Tensor): [B, Tmax, D]
+            text (Tensor): [B, Umax]
+            audio_len (Tensor): [B]
+            text_len (Tensor): [B]
+        Returns:
+            x (Tensor): encoder outputs, [B, T, D]
+            x_lens (Tensor): encoder length, [B]
+        """
+        # [B, T, D]  -> [B, D, T]
+        audio = audio.transpose([0, 2, 1])
+        # [B, D, T] -> [B, C=1, D, T]
+        x = audio.unsqueeze(1)
+        x_lens = audio_len
+
+        # convolution group
+        x, x_lens = self.conv(x, x_lens)
+        x_val = x.numpy()
+
+        # convert data from convolution feature map to sequence of vectors
+        #B, C, D, T = paddle.shape(x)  # not work under jit
+        x = x.transpose([0, 3, 1, 2])  #[B, T, C, D]
+        #x = x.reshape([B, T, C * D])  #[B, T, C*D]  # not work under jit
+        x = x.reshape([0, 0, -1])  #[B, T, C*D]
+
+        # remove padding part
+        x, x_lens = self.rnn(x, x_lens)  #[B, T, D]
+        return x, x_lens
+
+
+class DeepSpeech2Model(nn.Layer):
+    """The DeepSpeech2 network structure.
+
+    :param audio_data: Audio spectrogram data layer.
+    :type audio_data: Variable
+    :param text_data: Transcription text data layer.
+    :type text_data: Variable
+    :param audio_len: Valid sequence length data layer.
+    :type audio_len: Variable
+    :param masks: Masks data layer to reset padding.
+    :type masks: Variable
+    :param dict_size: Dictionary size for tokenized transcription.
+    :type dict_size: int
+    :param num_conv_layers: Number of stacking convolution layers.
+    :type num_conv_layers: int
+    :param num_rnn_layers: Number of stacking RNN layers.
+    :type num_rnn_layers: int
+    :param rnn_size: RNN layer size (dimension of RNN cells).
+    :type rnn_size: int
+    :param use_gru: Use gru if set True. Use simple rnn if set False.
+    :type use_gru: bool
+    :param share_rnn_weights: Whether to share input-hidden weights between
+                              forward and backward direction RNNs.
+                              It is only available when use_gru=False.
+    :type share_weights: bool
+    :return: A tuple of an output unnormalized log probability layer (
+             before softmax) and a ctc cost layer.
+    :rtype: tuple of LayerOutput
+    """
+
+    @classmethod
+    def params(cls, config: Optional[CfgNode]=None) -> CfgNode:
+        default = CfgNode(
+            dict(
+                num_conv_layers=2,  #Number of stacking convolution layers.
+                num_rnn_layers=3,  #Number of stacking RNN layers.
+                rnn_layer_size=1024,  #RNN layer size (number of RNN cells).
+                use_gru=True,  #Use gru if set True. Use simple rnn if set False.
+                share_rnn_weights=True  #Whether to share input-hidden weights between forward and backward directional RNNs.Notice that for GRU, weight sharing is not supported.
+            ))
+        if config is not None:
+            config.merge_from_other_cfg(default)
+        return default
+
+    def __init__(self,
+                 feat_size,
+                 dict_size,
+                 num_conv_layers=2,
+                 num_rnn_layers=3,
+                 rnn_size=1024,
+                 use_gru=False,
+                 share_rnn_weights=True,
+                 blank_id=0):
+        super().__init__()
+        self.encoder = CRNNEncoder(
+            feat_size=feat_size,
+            dict_size=dict_size,
+            num_conv_layers=num_conv_layers,
+            num_rnn_layers=num_rnn_layers,
+            rnn_size=rnn_size,
+            use_gru=use_gru,
+            share_rnn_weights=share_rnn_weights)
+        assert (self.encoder.output_size == rnn_size * 2)
+
+        self.decoder = CTCDecoder(
+            odim=dict_size,  # <blank> is in  vocab
+            enc_n_units=self.encoder.output_size,
+            blank_id=blank_id,  # first token is <blank>
+            dropout_rate=0.0,
+            reduction=True,  # sum
+            batch_average=True)  # sum / batch_size
+
+    def forward(self, audio, audio_len, text, text_len):
+        """Compute Model loss
+
+        Args:
+            audio (Tenosr): [B, T, D]
+            audio_len (Tensor): [B]
+            text (Tensor): [B, U]
+            text_len (Tensor): [B]
+
+        Returns:
+            loss (Tenosr): [1]
+        """
+        eouts, eouts_len = self.encoder(audio, audio_len)
+        loss = self.decoder(eouts, eouts_len, text, text_len)
+        return loss
+
+    @paddle.no_grad()
+    def decode(self, audio, audio_len, vocab_list, decoding_method,
+               lang_model_path, beam_alpha, beam_beta, beam_size, cutoff_prob,
+               cutoff_top_n, num_processes):
+        # init once
+        # decoders only accept string encoded in utf-8
+        self.decoder.init_decode(
+            beam_alpha=beam_alpha,
+            beam_beta=beam_beta,
+            lang_model_path=lang_model_path,
+            vocab_list=vocab_list,
+            decoding_method=decoding_method)
+
+        eouts, eouts_len = self.encoder(audio, audio_len)
+        probs = self.decoder.softmax(eouts)
+        print("probs.shape", probs.shape)
+        return self.decoder.decode_probs(
+            probs.numpy(), eouts_len, vocab_list, decoding_method,
+            lang_model_path, beam_alpha, beam_beta, beam_size, cutoff_prob,
+            cutoff_top_n, num_processes)
+
+    def decode_probs_split(self, probs_split, vocab_list, decoding_method,
+                           lang_model_path, beam_alpha, beam_beta, beam_size,
+                           cutoff_prob, cutoff_top_n, num_processes):
+        self.decoder.init_decode(
+            beam_alpha=beam_alpha,
+            beam_beta=beam_beta,
+            lang_model_path=lang_model_path,
+            vocab_list=vocab_list,
+            decoding_method=decoding_method)
+        return self.decoder.decode_probs_split(
+            probs_split, vocab_list, decoding_method, lang_model_path,
+            beam_alpha, beam_beta, beam_size, cutoff_prob, cutoff_top_n,
+            num_processes)
+
+    @classmethod
+    def from_pretrained(cls, dataloader, config, checkpoint_path):
+        """Build a DeepSpeech2Model model from a pretrained model.
+        Parameters
+        ----------
+        dataloader: paddle.io.DataLoader
+
+        config: yacs.config.CfgNode
+            model configs
+
+        checkpoint_path: Path or str
+            the path of pretrained model checkpoint, without extension name
+
+        Returns
+        -------
+        DeepSpeech2Model
+            The model built from pretrained result.
+        """
+        model = cls(feat_size=dataloader.collate_fn.feature_size,
+                    dict_size=len(dataloader.collate_fn.vocab_list),
+                    num_conv_layers=config.model.num_conv_layers,
+                    num_rnn_layers=config.model.num_rnn_layers,
+                    rnn_size=config.model.rnn_layer_size,
+                    use_gru=config.model.use_gru,
+                    share_rnn_weights=config.model.share_rnn_weights)
+        infos = Checkpoint().load_parameters(
+            model, checkpoint_path=checkpoint_path)
+        logger.info(f"checkpoint info: {infos}")
+        layer_tools.summary(model)
+        return model
+
+    @classmethod
+    def from_config(cls, config):
+        """Build a DeepSpeec2Model from config
+        Parameters
+
+        config: yacs.config.CfgNode
+            config.model
+        Returns
+        -------
+        DeepSpeech2Model
+            The model built from config.
+        """
+        model = cls(feat_size=config.feat_size,
+                    dict_size=config.dict_size,
+                    num_conv_layers=config.num_conv_layers,
+                    num_rnn_layers=config.num_rnn_layers,
+                    rnn_size=config.rnn_layer_size,
+                    use_gru=config.use_gru,
+                    share_rnn_weights=config.share_rnn_weights,
+                    blank_id=config.blank_id)
+        return model
+
+
+class DeepSpeech2InferModel(DeepSpeech2Model):
+    def __init__(self,
+                 feat_size,
+                 dict_size,
+                 num_conv_layers=2,
+                 num_rnn_layers=3,
+                 rnn_size=1024,
+                 use_gru=False,
+                 share_rnn_weights=True,
+                 blank_id=0):
+        super().__init__(
+            feat_size=feat_size,
+            dict_size=dict_size,
+            num_conv_layers=num_conv_layers,
+            num_rnn_layers=num_rnn_layers,
+            rnn_size=rnn_size,
+            use_gru=use_gru,
+            share_rnn_weights=share_rnn_weights,
+            blank_id=blank_id)
+
+    def forward(self, audio, audio_len):
+        """export model function
+
+        Args:
+            audio (Tensor): [B, T, D]
+            audio_len (Tensor): [B]
+
+        Returns:
+            probs: probs after softmax
+        """
+        eouts, eouts_len = self.encoder(audio, audio_len)
+        probs = self.decoder.softmax(eouts)
+        return probs, eouts_len
+
+    def export(self):
+        static_model = paddle.jit.to_static(
+            self,
+            input_spec=[
+                paddle.static.InputSpec(
+                    shape=[None, None, self.encoder.feat_size],
+                    dtype='float32'),  # audio, [B,T,D]
+                paddle.static.InputSpec(shape=[None],
+                                        dtype='int64'),  # audio_length, [B]
+            ])
+        return static_model
diff --git a/examples/v18_to_v2x/deepspeech2x/models/ds2/rnn.py b/examples/v18_to_v2x/deepspeech2x/models/ds2/rnn.py
new file mode 100644
index 000000000..e45db7c05
--- /dev/null
+++ b/examples/v18_to_v2x/deepspeech2x/models/ds2/rnn.py
@@ -0,0 +1,334 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import math
+
+import paddle
+from paddle import nn
+from paddle.nn import functional as F
+from paddle.nn import initializer as I
+
+from deepspeech.modules.activation import brelu
+from deepspeech.modules.mask import make_non_pad_mask
+from deepspeech.utils.log import Log
+logger = Log(__name__).getlog()
+
+__all__ = ['RNNStack']
+
+
+class RNNCell(nn.RNNCellBase):
+    r"""
+    Elman RNN (SimpleRNN) cell. Given the inputs and previous states, it
+    computes the outputs and updates states.
+    The formula used is as follows:
+    .. math::
+        h_{t} & = act(x_{t} + b_{ih} + W_{hh}h_{t-1} + b_{hh})
+        y_{t} & = h_{t}
+
+    where :math:`act` is for :attr:`activation`.
+    """
+
+    def __init__(self,
+                 hidden_size: int,
+                 activation="tanh",
+                 weight_ih_attr=None,
+                 weight_hh_attr=None,
+                 bias_ih_attr=None,
+                 bias_hh_attr=None,
+                 name=None):
+        super().__init__()
+        std = 1.0 / math.sqrt(hidden_size)
+        self.weight_hh = self.create_parameter(
+            (hidden_size, hidden_size),
+            weight_hh_attr,
+            default_initializer=I.Uniform(-std, std))
+        self.bias_ih = None
+        self.bias_hh = self.create_parameter(
+            (hidden_size, ),
+            bias_hh_attr,
+            is_bias=True,
+            default_initializer=I.Uniform(-std, std))
+
+        self.hidden_size = hidden_size
+        if activation not in ["tanh", "relu", "brelu"]:
+            raise ValueError(
+                "activation for SimpleRNNCell should be tanh or relu, "
+                "but get {}".format(activation))
+        self.activation = activation
+        self._activation_fn = paddle.tanh \
+            if activation == "tanh" \
+            else F.relu
+        if activation == 'brelu':
+            self._activation_fn = brelu
+
+    def forward(self, inputs, states=None):
+        if states is None:
+            states = self.get_initial_states(inputs, self.state_shape)
+        pre_h = states
+        i2h = inputs
+        if self.bias_ih is not None:
+            i2h += self.bias_ih
+        h2h = paddle.matmul(pre_h, self.weight_hh, transpose_y=True)
+        if self.bias_hh is not None:
+            h2h += self.bias_hh
+        h = self._activation_fn(i2h + h2h)
+        return h, h
+
+    @property
+    def state_shape(self):
+        return (self.hidden_size, )
+
+
+class GRUCell(nn.RNNCellBase):
+    r"""
+    Gated Recurrent Unit (GRU) RNN cell. Given the inputs and previous states,
+    it computes the outputs and updates states.
+    The formula for GRU used is as follows:
+    ..  math::
+        r_{t} & = \sigma(W_{ir}x_{t} + b_{ir} + W_{hr}h_{t-1} + b_{hr})
+        z_{t} & = \sigma(W_{iz}x_{t} + b_{iz} + W_{hz}h_{t-1} + b_{hz})
+        \widetilde{h}_{t} & = \tanh(W_{ic}x_{t} + b_{ic} + r_{t} * (W_{hc}h_{t-1} + b_{hc}))
+        h_{t} & = z_{t} * h_{t-1} + (1 - z_{t}) * \widetilde{h}_{t}
+        y_{t} & = h_{t}
+
+    where :math:`\sigma` is the sigmoid fucntion, and * is the elemetwise
+    multiplication operator.
+    """
+
+    def __init__(self,
+                 input_size: int,
+                 hidden_size: int,
+                 weight_ih_attr=None,
+                 weight_hh_attr=None,
+                 bias_ih_attr=None,
+                 bias_hh_attr=None,
+                 name=None):
+        super().__init__()
+        std = 1.0 / math.sqrt(hidden_size)
+        self.weight_hh = self.create_parameter(
+            (3 * hidden_size, hidden_size),
+            weight_hh_attr,
+            default_initializer=I.Uniform(-std, std))
+        self.bias_ih = None
+        self.bias_hh = self.create_parameter(
+            (3 * hidden_size, ),
+            bias_hh_attr,
+            is_bias=True,
+            default_initializer=I.Uniform(-std, std))
+
+        self.hidden_size = hidden_size
+        self.input_size = input_size
+        self._gate_activation = F.sigmoid
+        self._activation = paddle.relu
+
+    def forward(self, inputs, states=None):
+        if states is None:
+            states = self.get_initial_states(inputs, self.state_shape)
+
+        pre_hidden = states  # shape [batch_size, hidden_size]
+
+        x_gates = inputs
+        if self.bias_ih is not None:
+            x_gates = x_gates + self.bias_ih
+        bias_u, bias_r, bias_c = paddle.split(
+            self.bias_hh, num_or_sections=3, axis=0)
+
+        weight_hh = paddle.transpose(
+            self.weight_hh,
+            perm=[1, 0])  #weight_hh:shape[hidden_size, 3 * hidden_size]
+        w_u_r_c = paddle.flatten(weight_hh)
+        size_u_r = self.hidden_size * 2 * self.hidden_size
+        w_u_r = paddle.reshape(w_u_r_c[:size_u_r],
+                               (self.hidden_size, self.hidden_size * 2))
+        w_u, w_r = paddle.split(w_u_r, num_or_sections=2, axis=1)
+        w_c = paddle.reshape(w_u_r_c[size_u_r:],
+                             (self.hidden_size, self.hidden_size))
+
+        h_u = paddle.matmul(
+            pre_hidden, w_u,
+            transpose_y=False) + bias_u  #shape [batch_size, hidden_size]
+        h_r = paddle.matmul(
+            pre_hidden, w_r,
+            transpose_y=False) + bias_r  #shape [batch_size, hidden_size]
+
+        x_u, x_r, x_c = paddle.split(
+            x_gates, num_or_sections=3, axis=1)  #shape[batch_size, hidden_size]
+
+        u = self._gate_activation(x_u + h_u)  #shape [batch_size, hidden_size]
+        r = self._gate_activation(x_r + h_r)  #shape [batch_size, hidden_size]
+        c = self._activation(
+            x_c + paddle.matmul(r * pre_hidden, w_c, transpose_y=False) +
+            bias_c)  # [batch_size, hidden_size]
+
+        h = (1 - u) * pre_hidden + u * c
+        # https://www.paddlepaddle.org.cn/documentation/docs/zh/api/paddle/fluid/layers/dynamic_gru_cn.html#dynamic-gru
+        return h, h
+
+    @property
+    def state_shape(self):
+        r"""
+        The `state_shape` of GRUCell is a shape `[hidden_size]` (-1 for batch
+        size would be automatically inserted into shape). The shape corresponds
+        to the shape of :math:`h_{t-1}`.
+        """
+        return (self.hidden_size, )
+
+
+class BiRNNWithBN(nn.Layer):
+    """Bidirectonal simple rnn layer with sequence-wise batch normalization.
+    The batch normalization is only performed on input-state weights.
+
+    :param size: Dimension of RNN cells.
+    :type size: int
+    :param share_weights: Whether to share input-hidden weights between
+                          forward and backward directional RNNs.
+    :type share_weights: bool
+    :return: Bidirectional simple rnn layer.
+    :rtype: Variable
+    """
+
+    def __init__(self, i_size: int, h_size: int, share_weights: bool):
+        super().__init__()
+        self.share_weights = share_weights
+        if self.share_weights:
+            #input-hidden weights shared between bi-directional rnn.
+            self.fw_fc = nn.Linear(i_size, h_size, bias_attr=False)
+            # batch norm is only performed on input-state projection
+            self.fw_bn = nn.BatchNorm1D(
+                h_size, bias_attr=None, data_format='NLC')
+            self.bw_fc = self.fw_fc
+            self.bw_bn = self.fw_bn
+        else:
+            self.fw_fc = nn.Linear(i_size, h_size, bias_attr=False)
+            self.fw_bn = nn.BatchNorm1D(
+                h_size, bias_attr=None, data_format='NLC')
+            self.bw_fc = nn.Linear(i_size, h_size, bias_attr=False)
+            self.bw_bn = nn.BatchNorm1D(
+                h_size, bias_attr=None, data_format='NLC')
+
+        self.fw_cell = RNNCell(hidden_size=h_size, activation='brelu')
+        self.bw_cell = RNNCell(hidden_size=h_size, activation='brelu')
+        self.fw_rnn = nn.RNN(
+            self.fw_cell, is_reverse=False, time_major=False)  #[B, T, D]
+        self.bw_rnn = nn.RNN(
+            self.bw_cell, is_reverse=True, time_major=False)  #[B, T, D]
+
+    def forward(self, x: paddle.Tensor, x_len: paddle.Tensor):
+        # x, shape [B, T, D]
+        fw_x = self.fw_bn(self.fw_fc(x))
+        bw_x = self.bw_bn(self.bw_fc(x))
+        fw_x, _ = self.fw_rnn(inputs=fw_x, sequence_length=x_len)
+        bw_x, _ = self.bw_rnn(inputs=bw_x, sequence_length=x_len)
+        x = paddle.concat([fw_x, bw_x], axis=-1)
+        return x, x_len
+
+
+class BiGRUWithBN(nn.Layer):
+    """Bidirectonal gru layer with sequence-wise batch normalization.
+    The batch normalization is only performed on input-state weights.
+
+    :param name: Name of the layer.
+    :type name: string
+    :param input: Input layer.
+    :type input: Variable
+    :param size: Dimension of GRU cells.
+    :type size: int
+    :param act: Activation type.
+    :type act: string
+    :return: Bidirectional GRU layer.
+    :rtype: Variable
+    """
+
+    def __init__(self, i_size: int, h_size: int):
+        super().__init__()
+        hidden_size = h_size * 3
+
+        self.fw_fc = nn.Linear(i_size, hidden_size, bias_attr=False)
+        self.fw_bn = nn.BatchNorm1D(
+            hidden_size, bias_attr=None, data_format='NLC')
+        self.bw_fc = nn.Linear(i_size, hidden_size, bias_attr=False)
+        self.bw_bn = nn.BatchNorm1D(
+            hidden_size, bias_attr=None, data_format='NLC')
+
+        self.fw_cell = GRUCell(input_size=hidden_size, hidden_size=h_size)
+        self.bw_cell = GRUCell(input_size=hidden_size, hidden_size=h_size)
+        self.fw_rnn = nn.RNN(
+            self.fw_cell, is_reverse=False, time_major=False)  #[B, T, D]
+        self.bw_rnn = nn.RNN(
+            self.bw_cell, is_reverse=True, time_major=False)  #[B, T, D]
+
+    def forward(self, x, x_len):
+        # x, shape [B, T, D]
+        fw_x = self.fw_bn(self.fw_fc(x))
+
+        bw_x = self.bw_bn(self.bw_fc(x))
+        fw_x, _ = self.fw_rnn(inputs=fw_x, sequence_length=x_len)
+        bw_x, _ = self.bw_rnn(inputs=bw_x, sequence_length=x_len)
+        x = paddle.concat([fw_x, bw_x], axis=-1)
+        return x, x_len
+
+
+class RNNStack(nn.Layer):
+    """RNN group with stacked bidirectional simple RNN or GRU layers.
+
+    :param input: Input layer.
+    :type input: Variable
+    :param size: Dimension of RNN cells in each layer.
+    :type size: int
+    :param num_stacks: Number of stacked rnn layers.
+    :type num_stacks: int
+    :param use_gru: Use gru if set True. Use simple rnn if set False.
+    :type use_gru: bool
+    :param share_rnn_weights: Whether to share input-hidden weights between
+                              forward and backward directional RNNs.
+                              It is only available when use_gru=False.
+    :type share_weights: bool
+    :return: Output layer of the RNN group.
+    :rtype: Variable
+    """
+
+    def __init__(self,
+                 i_size: int,
+                 h_size: int,
+                 num_stacks: int,
+                 use_gru: bool,
+                 share_rnn_weights: bool):
+        super().__init__()
+        rnn_stacks = []
+        for i in range(num_stacks):
+            if use_gru:
+                #default:GRU using tanh
+                rnn_stacks.append(BiGRUWithBN(i_size=i_size, h_size=h_size))
+            else:
+                rnn_stacks.append(
+                    BiRNNWithBN(
+                        i_size=i_size,
+                        h_size=h_size,
+                        share_weights=share_rnn_weights))
+            i_size = h_size * 2
+
+        self.rnn_stacks = nn.LayerList(rnn_stacks)
+
+    def forward(self, x: paddle.Tensor, x_len: paddle.Tensor):
+        """
+        x: shape [B, T, D]
+        x_len: shpae [B]
+        """
+        for i, rnn in enumerate(self.rnn_stacks):
+            x, x_len = rnn(x, x_len)
+            masks = make_non_pad_mask(x_len)  #[B, T]
+            masks = masks.unsqueeze(-1)  # [B, T, 1]
+            # TODO(Hui Zhang): not support bool multiply
+            masks = masks.astype(x.dtype)
+            x = x.multiply(masks)
+        return x, x_len
diff --git a/examples/v18_to_v2x/exp_aishell/.gitignore b/examples/v18_to_v2x/exp_aishell/.gitignore
new file mode 100644
index 000000000..7024e0e95
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/.gitignore
@@ -0,0 +1,4 @@
+exp
+data
+*log
+tmp
diff --git a/examples/v18_to_v2x/exp_aishell/conf/augmentation.json b/examples/v18_to_v2x/exp_aishell/conf/augmentation.json
new file mode 100644
index 000000000..fe51488c7
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/conf/augmentation.json
@@ -0,0 +1 @@
+[]
diff --git a/examples/v18_to_v2x/exp_aishell/conf/deepspeech2.yaml b/examples/v18_to_v2x/exp_aishell/conf/deepspeech2.yaml
new file mode 100644
index 000000000..6e745e9d1
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/conf/deepspeech2.yaml
@@ -0,0 +1,67 @@
+# https://yaml.org/type/float.html
+data:
+  train_manifest: data/manifest.train
+  dev_manifest: data/manifest.dev
+  test_manifest: data/manifest.test
+  min_input_len: 0.0
+  max_input_len: 27.0 # second
+  min_output_len: 0.0
+  max_output_len: .inf
+  min_output_input_ratio: 0.00
+  max_output_input_ratio: .inf
+
+collator:
+  batch_size: 64 # one gpu
+  mean_std_filepath: data/mean_std.npz
+  unit_type: char
+  vocab_filepath: data/vocab.txt 
+  augmentation_config: conf/augmentation.json
+  random_seed: 0
+  spm_model_prefix: 
+  specgram_type: linear
+  feat_dim: 
+  delta_delta: False
+  stride_ms: 10.0
+  window_ms: 20.0
+  n_fft: None
+  max_freq: None
+  target_sample_rate: 16000
+  use_dB_normalization: True
+  target_dB: -20
+  dither: 1.0
+  keep_transcription_text: False
+  sortagrad: True
+  shuffle_method: batch_shuffle
+  num_workers: 2
+
+model:
+  num_conv_layers: 2
+  num_rnn_layers: 3
+  rnn_layer_size: 1024
+  use_gru: True 
+  share_rnn_weights: False
+  blank_id: 4333
+
+training:
+  n_epoch: 80
+  accum_grad: 1
+  lr: 2e-3
+  lr_decay: 0.83
+  weight_decay: 1e-06
+  global_grad_clip: 3.0
+  log_interval: 100
+  checkpoint:
+    kbest_n: 50
+    latest_n: 5
+  
+decoding:
+  batch_size: 32
+  error_rate_type: cer 
+  decoding_method: ctc_beam_search
+  lang_model_path: data/lm/zh_giga.no_cna_cmn.prune01244.klm
+  alpha: 2.6
+  beta: 5.0
+  beam_size: 300
+  cutoff_prob: 0.99
+  cutoff_top_n: 40
+  num_proc_bsearch: 8
diff --git a/examples/v18_to_v2x/exp_aishell/local/data.sh b/examples/v18_to_v2x/exp_aishell/local/data.sh
new file mode 100755
index 000000000..1cde0c6ea
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/local/data.sh
@@ -0,0 +1,86 @@
+#!/bin/bash
+
+stage=-1
+stop_stage=100
+
+source ${MAIN_ROOT}/utils/parse_options.sh
+
+mkdir -p data
+TARGET_DIR=${MAIN_ROOT}/examples/dataset
+mkdir -p ${TARGET_DIR}
+
+bash local/download_model.sh
+if [ $? -ne 0 ]; then
+   exit 1
+fi
+
+tar xzvf aishell_model_v1.8_to_v2.x.tar.gz
+mv aishell_v1.8.pdparams exp/deepspeech2/checkpoints/
+mv README.md exp/deepspeech2/
+mv mean_std.npz data/
+mv vocab.txt data/
+rm aishell_model_v1.8_to_v2.x.tar.gz -f
+
+
+if [ ${stage} -le -1 ] && [ ${stop_stage} -ge -1 ]; then
+    # download data, generate manifests
+    python3 ${TARGET_DIR}/aishell/aishell.py \
+    --manifest_prefix="data/manifest" \
+    --target_dir="${TARGET_DIR}/aishell"
+
+    if [ $? -ne 0 ]; then
+        echo "Prepare Aishell failed. Terminated."
+        exit 1
+    fi
+
+    for dataset in train dev test; do
+        mv data/manifest.${dataset} data/manifest.${dataset}.raw
+    done
+fi
+
+
+if [ ${stage} -le 1 ] && [ ${stop_stage} -ge 1 ]; then
+    # compute mean and stddev for normalizer
+    num_workers=$(nproc)
+    python3 ${MAIN_ROOT}/utils/compute_mean_std.py \
+    --manifest_path="data/manifest.train.raw" \
+    --specgram_type="linear" \
+    --delta_delta=false \
+    --stride_ms=10.0 \
+    --window_ms=20.0 \
+    --sample_rate=16000 \
+    --use_dB_normalization=True \
+    --num_samples=2000 \
+    --num_workers=${num_workers} \
+    --output_path="data/mean_std.json"
+
+    if [ $? -ne 0 ]; then
+        echo "Compute mean and stddev failed. Terminated."
+        exit 1
+    fi
+fi
+
+
+if [ ${stage} -le 2 ] && [ ${stop_stage} -ge 2 ]; then
+    # format manifest with tokenids, vocab size
+    for dataset in train dev test; do
+    {
+        python3 ${MAIN_ROOT}/utils/format_data.py \
+                --feat_type "raw" \
+                --cmvn_path "data/mean_std.json" \
+                --unit_type "char" \
+                --vocab_path="data/vocab.txt" \
+                --manifest_path="data/manifest.${dataset}.raw" \
+                --output_path="data/manifest.${dataset}"
+
+        if [ $? -ne 0 ]; then
+                echo "Formt mnaifest failed. Terminated."
+                exit 1
+        fi
+    } &
+    done
+    wait
+fi
+
+echo "Aishell data preparation done."
+exit 0
diff --git a/examples/v18_to_v2x/exp_aishell/local/download_lm_ch.sh b/examples/v18_to_v2x/exp_aishell/local/download_lm_ch.sh
new file mode 100755
index 000000000..ac27a9076
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/local/download_lm_ch.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+
+. ${MAIN_ROOT}/utils/utility.sh
+
+DIR=data/lm
+mkdir -p ${DIR}
+
+URL='https://deepspeech.bj.bcebos.com/zh_lm/zh_giga.no_cna_cmn.prune01244.klm'
+MD5="29e02312deb2e59b3c8686c7966d4fe3"
+TARGET=${DIR}/zh_giga.no_cna_cmn.prune01244.klm
+
+
+echo "Download language model ..."
+download $URL $MD5 $TARGET
+if [ $? -ne 0 ]; then
+    echo "Fail to download the language model!"
+    exit 1
+fi
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_aishell/local/download_model.sh b/examples/v18_to_v2x/exp_aishell/local/download_model.sh
new file mode 100644
index 000000000..2e4873ef6
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/local/download_model.sh
@@ -0,0 +1,19 @@
+#! /usr/bin/env bash
+
+. ${MAIN_ROOT}/utils/utility.sh
+
+URL='https://deepspeech.bj.bcebos.com/mandarin_models/aishell_model_v1.8_to_v2.x.tar.gz'
+MD5=4ade113c69ea291b8ce5ec6a03296659
+TARGET=./aishell_model_v1.8_to_v2.x.tar.gz
+
+
+echo "Download Aishell model ..."
+download $URL $MD5 $TARGET
+if [ $? -ne 0 ]; then
+    echo "Fail to download Aishell model!"
+    exit 1
+fi
+tar -zxvf $TARGET
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_aishell/local/test.sh b/examples/v18_to_v2x/exp_aishell/local/test.sh
new file mode 100755
index 000000000..9fd0bc8d5
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/local/test.sh
@@ -0,0 +1,39 @@
+#!/bin/bash
+
+if [ $# != 3 ];then
+    echo "usage: ${0} config_path ckpt_path_prefix model_type"
+    exit -1
+fi
+
+ngpu=$(echo $CUDA_VISIBLE_DEVICES | awk -F "," '{print NF}')
+echo "using $ngpu gpus..."
+
+device=gpu
+if [ ${ngpu} == 0 ];then
+    device=cpu
+fi
+config_path=$1
+ckpt_prefix=$2
+model_type=$3
+
+# download language model
+bash local/download_lm_ch.sh
+if [ $? -ne 0 ]; then
+   exit 1
+fi
+
+python3 -u ${BIN_DIR}/test.py \
+--device ${device} \
+--nproc 1 \
+--config ${config_path} \
+--result_file ${ckpt_prefix}.rsl \
+--checkpoint_path ${ckpt_prefix} \
+--model_type ${model_type}
+
+if [ $? -ne 0 ]; then
+    echo "Failed in evaluation!"
+    exit 1
+fi
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_aishell/path.sh b/examples/v18_to_v2x/exp_aishell/path.sh
new file mode 100644
index 000000000..080ab1f79
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/path.sh
@@ -0,0 +1,16 @@
+export MAIN_ROOT=`realpath ${PWD}/../../../`
+export LOCAL_DEEPSPEECH2=`realpath ${PWD}/../`
+
+export PATH=${MAIN_ROOT}:${MAIN_ROOT}/utils:${PATH}
+export LC_ALL=C
+
+# Use UTF-8 in Python to avoid UnicodeDecodeError when LC_ALL=C
+export PYTHONIOENCODING=UTF-8
+export PYTHONPATH=${MAIN_ROOT}:${PYTHONPATH}
+export PYTHONPATH=${LOCAL_DEEPSPEECH2}:${PYTHONPATH}
+
+export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/lib/
+
+MODEL=deepspeech2
+export BIN_DIR=${LOCAL_DEEPSPEECH2}/deepspeech2x/bin
+echo "BIN_DIR "${BIN_DIR}
diff --git a/examples/v18_to_v2x/exp_aishell/run.sh b/examples/v18_to_v2x/exp_aishell/run.sh
new file mode 100755
index 000000000..482ab2a09
--- /dev/null
+++ b/examples/v18_to_v2x/exp_aishell/run.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+set -e
+source path.sh
+
+stage=0
+stop_stage=100
+conf_path=conf/deepspeech2.yaml
+avg_num=1
+model_type=offline
+
+source ${MAIN_ROOT}/utils/parse_options.sh || exit 1;
+
+v18_ckpt=aishell_v1.8
+ckpt=$(basename ${conf_path} | awk -F'.' '{print $1}')
+echo "checkpoint name ${ckpt}"
+
+if [ ${stage} -le 0 ] && [ ${stop_stage} -ge 0 ]; then
+    # prepare data
+    mkdir -p exp/${ckpt}/checkpoints
+    bash ./local/data.sh || exit -1
+fi
+
+if [ ${stage} -le 1 ] && [ ${stop_stage} -ge 1 ]; then
+    # test ckpt avg_n
+    CUDA_VISIBLE_DEVICES=1 ./local/test.sh ${conf_path} exp/${ckpt}/checkpoints/${v18_ckpt} ${model_type}|| exit -1
+fi
+
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/.gitignore b/examples/v18_to_v2x/exp_baidu_en8k/.gitignore
new file mode 100644
index 000000000..7024e0e95
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/.gitignore
@@ -0,0 +1,4 @@
+exp
+data
+*log
+tmp
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/conf/augmentation.json b/examples/v18_to_v2x/exp_baidu_en8k/conf/augmentation.json
new file mode 100644
index 000000000..fe51488c7
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/conf/augmentation.json
@@ -0,0 +1 @@
+[]
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/conf/deepspeech2.yaml b/examples/v18_to_v2x/exp_baidu_en8k/conf/deepspeech2.yaml
new file mode 100644
index 000000000..fbc7466f2
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/conf/deepspeech2.yaml
@@ -0,0 +1,67 @@
+# https://yaml.org/type/float.html
+data:
+  train_manifest: data/manifest.train
+  dev_manifest: data/manifest.dev
+  test_manifest: data/manifest.test-clean
+  min_input_len: 0.0
+  max_input_len: .inf # second
+  min_output_len: 0.0
+  max_output_len: .inf
+  min_output_input_ratio: 0.00
+  max_output_input_ratio: .inf
+
+collator:
+  batch_size: 64 # one gpu
+  mean_std_filepath: data/mean_std.npz
+  unit_type: char
+  vocab_filepath: data/vocab.txt 
+  augmentation_config: conf/augmentation.json
+  random_seed: 0
+  spm_model_prefix: 
+  specgram_type: linear
+  feat_dim: 
+  delta_delta: False
+  stride_ms: 10.0
+  window_ms: 20.0
+  n_fft: None
+  max_freq: None
+  target_sample_rate: 16000
+  use_dB_normalization: True
+  target_dB: -20
+  dither: 1.0
+  keep_transcription_text: False
+  sortagrad: True
+  shuffle_method: batch_shuffle
+  num_workers: 2
+
+model:
+  num_conv_layers: 2
+  num_rnn_layers: 3
+  rnn_layer_size: 1024
+  use_gru: True
+  share_rnn_weights: False
+  blank_id: 28
+
+training:
+  n_epoch: 80
+  accum_grad: 1
+  lr: 2e-3
+  lr_decay: 0.83
+  weight_decay: 1e-06
+  global_grad_clip: 3.0
+  log_interval: 100
+  checkpoint:
+    kbest_n: 50
+    latest_n: 5
+  
+decoding:
+  batch_size: 32
+  error_rate_type: wer 
+  decoding_method: ctc_beam_search
+  lang_model_path: data/lm/common_crawl_00.prune01111.trie.klm
+  alpha: 1.4
+  beta: 0.35
+  beam_size: 500
+  cutoff_prob: 1.0
+  cutoff_top_n: 40
+  num_proc_bsearch: 8
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/local/data.sh b/examples/v18_to_v2x/exp_baidu_en8k/local/data.sh
new file mode 100755
index 000000000..8f9468b13
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/local/data.sh
@@ -0,0 +1,101 @@
+#!/bin/bash
+
+stage=-1
+stop_stage=100
+
+source ${MAIN_ROOT}/utils/parse_options.sh
+
+mkdir -p data
+TARGET_DIR=${MAIN_ROOT}/examples/dataset
+mkdir -p ${TARGET_DIR}
+
+
+bash local/download_model.sh
+if [ $? -ne 0 ]; then
+   exit 1
+fi
+
+tar xzvf baidu_en8k_v1.8_to_v2.x.tar.gz
+mv baidu_en8k_v1.8.pdparams exp/deepspeech2/checkpoints/
+mv README.md exp/deepspeech2/
+mv mean_std.npz data/
+mv vocab.txt data/
+rm baidu_en8k_v1.8_to_v2.x.tar.gz -f
+
+if [ ${stage} -le -1 ] && [ ${stop_stage} -ge -1 ]; then
+    # download data, generate manifests
+    python3 ${TARGET_DIR}/librispeech/librispeech.py \
+    --manifest_prefix="data/manifest" \
+    --target_dir="${TARGET_DIR}/librispeech" \
+    --full_download="True"
+
+    if [ $? -ne 0 ]; then
+        echo "Prepare LibriSpeech failed. Terminated."
+        exit 1
+    fi
+
+    for set in train-clean-100 train-clean-360 train-other-500 dev-clean dev-other test-clean test-other; do
+        mv data/manifest.${set} data/manifest.${set}.raw
+    done
+
+    rm -rf data/manifest.train.raw data/manifest.dev.raw  data/manifest.test.raw
+    for set in train-clean-100 train-clean-360 train-other-500; do
+        cat data/manifest.${set}.raw >> data/manifest.train.raw
+    done
+
+    for set in dev-clean dev-other; do
+        cat data/manifest.${set}.raw >> data/manifest.dev.raw
+    done
+
+    for set in test-clean test-other; do
+        cat data/manifest.${set}.raw >> data/manifest.test.raw
+    done
+fi
+
+
+if [ ${stage} -le 1 ] && [ ${stop_stage} -ge 1 ]; then
+    # compute mean and stddev for normalizer
+    num_workers=$(nproc)
+    python3 ${MAIN_ROOT}/utils/compute_mean_std.py \
+    --manifest_path="data/manifest.train.raw" \
+    --num_samples=2000 \
+    --specgram_type="linear" \
+    --delta_delta=false \
+    --sample_rate=16000 \
+    --stride_ms=10.0 \
+    --window_ms=20.0 \
+    --use_dB_normalization=True \
+    --num_workers=${num_workers} \
+    --output_path="data/mean_std.json"
+
+    if [ $? -ne 0 ]; then
+        echo "Compute mean and stddev failed. Terminated."
+        exit 1
+    fi
+fi
+
+
+if [ ${stage} -le 2 ] && [ ${stop_stage} -ge 2 ]; then
+    # format manifest with tokenids, vocab size
+    for set in train dev test dev-clean dev-other test-clean test-other; do
+    {
+        python3 ${MAIN_ROOT}/utils/format_data.py \
+        --feat_type "raw" \
+        --cmvn_path "data/mean_std.json" \
+        --unit_type ${unit_type} \
+        --vocab_path="data/vocab.txt" \
+        --manifest_path="data/manifest.${set}.raw" \
+        --output_path="data/manifest.${set}"
+
+        if [ $? -ne 0 ]; then
+            echo "Formt mnaifest.${set} failed. Terminated."
+            exit 1
+        fi
+    }&
+    done
+    wait
+fi
+
+echo "LibriSpeech Data preparation done."
+exit 0
+
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/local/download_lm_en.sh b/examples/v18_to_v2x/exp_baidu_en8k/local/download_lm_en.sh
new file mode 100755
index 000000000..dc1bdf665
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/local/download_lm_en.sh
@@ -0,0 +1,20 @@
+#!/bin/bash
+
+. ${MAIN_ROOT}/utils/utility.sh
+
+DIR=data/lm
+mkdir -p ${DIR}
+
+URL=https://deepspeech.bj.bcebos.com/en_lm/common_crawl_00.prune01111.trie.klm
+MD5="099a601759d467cd0a8523ff939819c5"
+TARGET=${DIR}/common_crawl_00.prune01111.trie.klm
+
+echo "Download language model ..."
+download $URL $MD5 $TARGET
+if [ $? -ne 0 ]; then
+    echo "Fail to download the language model!"
+    exit 1
+fi
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/local/download_model.sh b/examples/v18_to_v2x/exp_baidu_en8k/local/download_model.sh
new file mode 100644
index 000000000..6d06e3d6f
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/local/download_model.sh
@@ -0,0 +1,19 @@
+#! /usr/bin/env bash
+
+. ${MAIN_ROOT}/utils/utility.sh
+
+URL='https://deepspeech.bj.bcebos.com/eng_models/baidu_en8k_v1.8_to_v2.x.tar.gz'
+MD5=fdabeb6c96963ac85d9188f0275c6a1b
+TARGET=./baidu_en8k_v1.8_to_v2.x.tar.gz
+
+
+echo "Download BaiduEn8k model ..."
+download $URL $MD5 $TARGET
+if [ $? -ne 0 ]; then
+    echo "Fail to download BaiduEn8k model!"
+    exit 1
+fi
+tar -zxvf $TARGET
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/local/test.sh b/examples/v18_to_v2x/exp_baidu_en8k/local/test.sh
new file mode 100755
index 000000000..b5b68c599
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/local/test.sh
@@ -0,0 +1,39 @@
+#!/bin/bash
+
+if [ $# != 3 ];then
+    echo "usage: ${0} config_path ckpt_path_prefix model_type"
+    exit -1
+fi
+
+ngpu=$(echo $CUDA_VISIBLE_DEVICES | awk -F "," '{print NF}')
+echo "using $ngpu gpus..."
+
+device=gpu
+if [ ${ngpu} == 0 ];then
+    device=cpu
+fi
+config_path=$1
+ckpt_prefix=$2
+model_type=$3
+
+# download language model
+bash local/download_lm_en.sh
+if [ $? -ne 0 ]; then
+   exit 1
+fi
+
+python3 -u ${BIN_DIR}/test.py \
+--device ${device} \
+--nproc 1 \
+--config ${config_path} \
+--result_file ${ckpt_prefix}.rsl \
+--checkpoint_path ${ckpt_prefix} \
+--model_type ${model_type}
+
+if [ $? -ne 0 ]; then
+    echo "Failed in evaluation!"
+    exit 1
+fi
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/path.sh b/examples/v18_to_v2x/exp_baidu_en8k/path.sh
new file mode 100644
index 000000000..080ab1f79
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/path.sh
@@ -0,0 +1,16 @@
+export MAIN_ROOT=`realpath ${PWD}/../../../`
+export LOCAL_DEEPSPEECH2=`realpath ${PWD}/../`
+
+export PATH=${MAIN_ROOT}:${MAIN_ROOT}/utils:${PATH}
+export LC_ALL=C
+
+# Use UTF-8 in Python to avoid UnicodeDecodeError when LC_ALL=C
+export PYTHONIOENCODING=UTF-8
+export PYTHONPATH=${MAIN_ROOT}:${PYTHONPATH}
+export PYTHONPATH=${LOCAL_DEEPSPEECH2}:${PYTHONPATH}
+
+export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/lib/
+
+MODEL=deepspeech2
+export BIN_DIR=${LOCAL_DEEPSPEECH2}/deepspeech2x/bin
+echo "BIN_DIR "${BIN_DIR}
diff --git a/examples/v18_to_v2x/exp_baidu_en8k/run.sh b/examples/v18_to_v2x/exp_baidu_en8k/run.sh
new file mode 100755
index 000000000..c590312d1
--- /dev/null
+++ b/examples/v18_to_v2x/exp_baidu_en8k/run.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+set -e
+source path.sh
+
+stage=0
+stop_stage=100
+conf_path=conf/deepspeech2.yaml
+avg_num=1
+model_type=offline
+
+source ${MAIN_ROOT}/utils/parse_options.sh || exit 1;
+
+v18_ckpt=baidu_en8k_v1.8
+ckpt=$(basename ${conf_path} | awk -F'.' '{print $1}')
+echo "checkpoint name ${ckpt}"
+
+if [ ${stage} -le 0 ] && [ ${stop_stage} -ge 0 ]; then
+    # prepare data
+    mkdir -p exp/${ckpt}/checkpoints
+    bash ./local/data.sh || exit -1
+fi
+
+if [ ${stage} -le 1 ] && [ ${stop_stage} -ge 1 ]; then
+    # test ckpt avg_n
+    CUDA_VISIBLE_DEVICES=0 ./local/test.sh ${conf_path} exp/${ckpt}/checkpoints/${v18_ckpt} ${model_type}|| exit -1
+fi
+
diff --git a/examples/v18_to_v2x/exp_librispeech/.gitignore b/examples/v18_to_v2x/exp_librispeech/.gitignore
new file mode 100644
index 000000000..7024e0e95
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/.gitignore
@@ -0,0 +1,4 @@
+exp
+data
+*log
+tmp
diff --git a/examples/v18_to_v2x/exp_librispeech/conf/augmentation.json b/examples/v18_to_v2x/exp_librispeech/conf/augmentation.json
new file mode 100644
index 000000000..fe51488c7
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/conf/augmentation.json
@@ -0,0 +1 @@
+[]
diff --git a/examples/v18_to_v2x/exp_librispeech/conf/deepspeech2.yaml b/examples/v18_to_v2x/exp_librispeech/conf/deepspeech2.yaml
new file mode 100644
index 000000000..edef07972
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/conf/deepspeech2.yaml
@@ -0,0 +1,67 @@
+# https://yaml.org/type/float.html
+data:
+  train_manifest: data/manifest.train
+  dev_manifest: data/manifest.dev
+  test_manifest: data/manifest.test-clean
+  min_input_len: 0.0
+  max_input_len: 1000.0 # second
+  min_output_len: 0.0
+  max_output_len: .inf
+  min_output_input_ratio: 0.00
+  max_output_input_ratio: .inf
+
+collator:
+  batch_size: 64 # one gpu
+  mean_std_filepath: data/mean_std.npz
+  unit_type: char
+  vocab_filepath: data/vocab.txt 
+  augmentation_config: conf/augmentation.json
+  random_seed: 0
+  spm_model_prefix: 
+  specgram_type: linear
+  feat_dim: 
+  delta_delta: False
+  stride_ms: 10.0
+  window_ms: 20.0
+  n_fft: None
+  max_freq: None
+  target_sample_rate: 16000
+  use_dB_normalization: True
+  target_dB: -20
+  dither: 1.0
+  keep_transcription_text: False
+  sortagrad: True
+  shuffle_method: batch_shuffle
+  num_workers: 2
+
+model:
+  num_conv_layers: 2
+  num_rnn_layers: 3
+  rnn_layer_size: 2048
+  use_gru: False
+  share_rnn_weights: True
+  blank_id: 28
+
+training:
+  n_epoch: 80
+  accum_grad: 1
+  lr: 2e-3
+  lr_decay: 0.83
+  weight_decay: 1e-06
+  global_grad_clip: 3.0
+  log_interval: 100
+  checkpoint:
+    kbest_n: 50
+    latest_n: 5
+  
+decoding:
+  batch_size: 32
+  error_rate_type: wer 
+  decoding_method: ctc_beam_search
+  lang_model_path: data/lm/common_crawl_00.prune01111.trie.klm
+  alpha: 2.5
+  beta: 0.3
+  beam_size: 500
+  cutoff_prob: 1.0
+  cutoff_top_n: 40
+  num_proc_bsearch: 8
diff --git a/examples/v18_to_v2x/exp_librispeech/local/data.sh b/examples/v18_to_v2x/exp_librispeech/local/data.sh
new file mode 100755
index 000000000..22a86bb2e
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/local/data.sh
@@ -0,0 +1,101 @@
+#!/bin/bash
+
+stage=-1
+stop_stage=100
+
+source ${MAIN_ROOT}/utils/parse_options.sh
+
+mkdir -p data
+TARGET_DIR=${MAIN_ROOT}/examples/dataset
+mkdir -p ${TARGET_DIR}
+
+
+bash local/download_model.sh
+if [ $? -ne 0 ]; then
+   exit 1
+fi
+
+tar xzvf librispeech_v1.8_to_v2.x.tar.gz
+mv librispeech_v1.8.pdparams exp/deepspeech2/checkpoints/
+mv README.md exp/deepspeech2/
+mv mean_std.npz data/
+mv vocab.txt data/
+rm librispeech_v1.8_to_v2.x.tar.gz -f
+
+if [ ${stage} -le -1 ] && [ ${stop_stage} -ge -1 ]; then
+    # download data, generate manifests
+    python3 ${TARGET_DIR}/librispeech/librispeech.py \
+    --manifest_prefix="data/manifest" \
+    --target_dir="${TARGET_DIR}/librispeech" \
+    --full_download="True"
+
+    if [ $? -ne 0 ]; then
+        echo "Prepare LibriSpeech failed. Terminated."
+        exit 1
+    fi
+
+    for set in train-clean-100 train-clean-360 train-other-500 dev-clean dev-other test-clean test-other; do
+        mv data/manifest.${set} data/manifest.${set}.raw
+    done
+
+    rm -rf data/manifest.train.raw data/manifest.dev.raw  data/manifest.test.raw
+    for set in train-clean-100 train-clean-360 train-other-500; do
+        cat data/manifest.${set}.raw >> data/manifest.train.raw
+    done
+
+    for set in dev-clean dev-other; do
+        cat data/manifest.${set}.raw >> data/manifest.dev.raw
+    done
+
+    for set in test-clean test-other; do
+        cat data/manifest.${set}.raw >> data/manifest.test.raw
+    done
+fi
+
+
+if [ ${stage} -le 1 ] && [ ${stop_stage} -ge 1 ]; then
+    # compute mean and stddev for normalizer
+    num_workers=$(nproc)
+    python3 ${MAIN_ROOT}/utils/compute_mean_std.py \
+    --manifest_path="data/manifest.train.raw" \
+    --num_samples=2000 \
+    --specgram_type="linear" \
+    --delta_delta=false \
+    --sample_rate=16000 \
+    --stride_ms=10.0 \
+    --window_ms=20.0 \
+    --use_dB_normalization=True \
+    --num_workers=${num_workers} \
+    --output_path="data/mean_std.json"
+
+    if [ $? -ne 0 ]; then
+        echo "Compute mean and stddev failed. Terminated."
+        exit 1
+    fi
+fi
+
+
+if [ ${stage} -le 2 ] && [ ${stop_stage} -ge 2 ]; then
+    # format manifest with tokenids, vocab size
+    for set in train dev test dev-clean dev-other test-clean test-other; do
+    {
+        python3 ${MAIN_ROOT}/utils/format_data.py \
+        --feat_type "raw" \
+        --cmvn_path "data/mean_std.json" \
+        --unit_type ${unit_type} \
+        --vocab_path="data/vocab.txt" \
+        --manifest_path="data/manifest.${set}.raw" \
+        --output_path="data/manifest.${set}"
+
+        if [ $? -ne 0 ]; then
+            echo "Formt mnaifest.${set} failed. Terminated."
+            exit 1
+        fi
+    }&
+    done
+    wait
+fi
+
+echo "LibriSpeech Data preparation done."
+exit 0
+
diff --git a/examples/v18_to_v2x/exp_librispeech/local/download_lm_en.sh b/examples/v18_to_v2x/exp_librispeech/local/download_lm_en.sh
new file mode 100755
index 000000000..dc1bdf665
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/local/download_lm_en.sh
@@ -0,0 +1,20 @@
+#!/bin/bash
+
+. ${MAIN_ROOT}/utils/utility.sh
+
+DIR=data/lm
+mkdir -p ${DIR}
+
+URL=https://deepspeech.bj.bcebos.com/en_lm/common_crawl_00.prune01111.trie.klm
+MD5="099a601759d467cd0a8523ff939819c5"
+TARGET=${DIR}/common_crawl_00.prune01111.trie.klm
+
+echo "Download language model ..."
+download $URL $MD5 $TARGET
+if [ $? -ne 0 ]; then
+    echo "Fail to download the language model!"
+    exit 1
+fi
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_librispeech/local/download_model.sh b/examples/v18_to_v2x/exp_librispeech/local/download_model.sh
new file mode 100644
index 000000000..cc6a9ec75
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/local/download_model.sh
@@ -0,0 +1,19 @@
+#! /usr/bin/env bash
+
+. ${MAIN_ROOT}/utils/utility.sh
+
+URL='https://deepspeech.bj.bcebos.com/eng_models/librispeech_v1.8_to_v2.x.tar.gz'
+MD5=7b0f582fe2f5a840b840e7ee52246bc5
+TARGET=./librispeech_v1.8_to_v2.x.tar.gz
+
+
+echo "Download LibriSpeech model ..."
+download $URL $MD5 $TARGET
+if [ $? -ne 0 ]; then
+    echo "Fail to download LibriSpeech model!"
+    exit 1
+fi
+tar -zxvf $TARGET
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_librispeech/local/test.sh b/examples/v18_to_v2x/exp_librispeech/local/test.sh
new file mode 100755
index 000000000..b5b68c599
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/local/test.sh
@@ -0,0 +1,39 @@
+#!/bin/bash
+
+if [ $# != 3 ];then
+    echo "usage: ${0} config_path ckpt_path_prefix model_type"
+    exit -1
+fi
+
+ngpu=$(echo $CUDA_VISIBLE_DEVICES | awk -F "," '{print NF}')
+echo "using $ngpu gpus..."
+
+device=gpu
+if [ ${ngpu} == 0 ];then
+    device=cpu
+fi
+config_path=$1
+ckpt_prefix=$2
+model_type=$3
+
+# download language model
+bash local/download_lm_en.sh
+if [ $? -ne 0 ]; then
+   exit 1
+fi
+
+python3 -u ${BIN_DIR}/test.py \
+--device ${device} \
+--nproc 1 \
+--config ${config_path} \
+--result_file ${ckpt_prefix}.rsl \
+--checkpoint_path ${ckpt_prefix} \
+--model_type ${model_type}
+
+if [ $? -ne 0 ]; then
+    echo "Failed in evaluation!"
+    exit 1
+fi
+
+
+exit 0
diff --git a/examples/v18_to_v2x/exp_librispeech/path.sh b/examples/v18_to_v2x/exp_librispeech/path.sh
new file mode 100644
index 000000000..080ab1f79
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/path.sh
@@ -0,0 +1,16 @@
+export MAIN_ROOT=`realpath ${PWD}/../../../`
+export LOCAL_DEEPSPEECH2=`realpath ${PWD}/../`
+
+export PATH=${MAIN_ROOT}:${MAIN_ROOT}/utils:${PATH}
+export LC_ALL=C
+
+# Use UTF-8 in Python to avoid UnicodeDecodeError when LC_ALL=C
+export PYTHONIOENCODING=UTF-8
+export PYTHONPATH=${MAIN_ROOT}:${PYTHONPATH}
+export PYTHONPATH=${LOCAL_DEEPSPEECH2}:${PYTHONPATH}
+
+export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/lib/
+
+MODEL=deepspeech2
+export BIN_DIR=${LOCAL_DEEPSPEECH2}/deepspeech2x/bin
+echo "BIN_DIR "${BIN_DIR}
diff --git a/examples/v18_to_v2x/exp_librispeech/run.sh b/examples/v18_to_v2x/exp_librispeech/run.sh
new file mode 100755
index 000000000..05706a428
--- /dev/null
+++ b/examples/v18_to_v2x/exp_librispeech/run.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+set -e
+source path.sh
+
+stage=0
+stop_stage=100
+conf_path=conf/deepspeech2.yaml
+avg_num=1
+model_type=offline
+
+source ${MAIN_ROOT}/utils/parse_options.sh || exit 1;
+
+v18_ckpt=librispeech_v1.8
+ckpt=$(basename ${conf_path} | awk -F'.' '{print $1}')
+echo "checkpoint name ${ckpt}"
+
+if [ ${stage} -le 0 ] && [ ${stop_stage} -ge 0 ]; then
+    # prepare data
+    mkdir -p exp/${ckpt}/checkpoints
+    bash ./local/data.sh || exit -1
+fi
+
+if [ ${stage} -le 1 ] && [ ${stop_stage} -ge 1 ]; then
+    # test ckpt avg_n
+    CUDA_VISIBLE_DEVICES=0 ./local/test.sh ${conf_path} exp/${ckpt}/checkpoints/${v18_ckpt} ${model_type}|| exit -1
+fi