PaddleSpeech/paddlespeech/t2s/frontend/generate_lexicon.py

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"""Generate lexicon and symbols for Mandarin Chinese phonology.
The lexicon is used for Montreal Force Aligner.
Note that syllables are used as word in this lexicon. Since syllables rather 
than words are used in transcriptions produced by `reorganize_baker.py`.
We make this choice to better leverage other software for chinese text to 
pinyin tools like pypinyin. This is the convention for G2P in Chinese.
"""
import re
from collections import OrderedDict

INITIALS = [
    'b', 'p', 'm', 'f', 'd', 't', 'n', 'l', 'g', 'k', 'h', 'zh', 'ch', 'sh',
    'r', 'z', 'c', 's', 'j', 'q', 'x'
]

FINALS = [
    'a', 'ai', 'ao', 'an', 'ang', 'e', 'er', 'ei', 'en', 'eng', 'o', 'ou',
    'ong', 'ii', 'iii', 'i', 'ia', 'iao', 'ian', 'iang', 'ie', 'io', 'iou',
    'iong', 'in', 'ing', 'u', 'ua', 'uai', 'uan', 'uang', 'uei', 'uo', 'uen',
    'ueng', 'v', 've', 'van', 'vn'
]

SPECIALS = ['sil', 'sp']


def rule(C, V, R, T):
    """Generate a syllable given the initial, the final, erhua indicator, and tone.
    Orthographical rules for pinyin are applied. (special case for y, w, ui, un, iu)

    Note that in this system, 'ü' is alway written as 'v' when appeared in phoneme, but converted to 
    'u' in syllables when certain conditions are satisfied.

    'i' is distinguished when appeared in phonemes, and separated into 3 categories, 'i', 'ii' and 'iii'.
    Erhua is is possibly applied to every finals, except for finals that already ends with 'r'.
    When a syllable is impossible or does not have any characters with this pronunciation, return None
    to filter it out.
    """

    # 不可拼的音节, ii 只能和 z, c, s 拼
    if V in ["ii"] and (C not in ['z', 'c', 's']):
        return None
    # iii 只能和 zh, ch, sh, r 拼
    if V in ['iii'] and (C not in ['zh', 'ch', 'sh', 'r']):
        return None

    # 齐齿呼或者撮口呼不能和 f, g, k, h, zh, ch, sh, r, z, c, s
    if (V not in ['ii', 'iii']) and V[0] in ['i', 'v'] and (
            C in ['f', 'g', 'k', 'h', 'zh', 'ch', 'sh', 'r', 'z', 'c', 's']):
        return None

    # 撮口呼只能和 j, q, x l, n 拼
    if V.startswith("v"):
        # v, ve 只能和 j ,q , x, n, l 拼
        if V in ['v', 've']:
            if C not in ['j', 'q', 'x', 'n', 'l', '']:
                return None
        # 其他只能和 j, q, x 拼
        else:
            if C not in ['j', 'q', 'x', '']:
                return None

    # j, q, x 只能和齐齿呼或者撮口呼拼
    if (C in ['j', 'q', 'x']) and not (
        (V not in ['ii', 'iii']) and V[0] in ['i', 'v']):
        return None

    # b, p ,m, f 不能和合口呼拼，除了 u 之外
    # bm p, m, f 不能和撮口呼拼
    if (C in ['b', 'p', 'm', 'f']) and ((V[0] in ['u', 'v'] and V != "u") or
                                        V == 'ong'):
        return None

    # ua, uai, uang 不能和 d, t, n, l, r, z, c, s 拼
    if V in ['ua', 'uai',
             'uang'] and C in ['d', 't', 'n', 'l', 'r', 'z', 'c', 's']:
        return None

    # sh 和 ong 不能拼
    if V == 'ong' and C in ['sh']:
        return None

    # o 和 gkh, zh ch sh r z c s 不能拼
    if V == "o" and C in [
            'd', 't', 'n', 'g', 'k', 'h', 'zh', 'ch', 'sh', 'r', 'z', 'c', 's'
    ]:
        return None

    # ueng 只是 weng 这个 ad-hoc 其他情况下都是 ong
    if V == 'ueng' and C != '':
        return

    # 非儿化的 er 只能单独存在
    if V == 'er' and C != '':
        return None

    if C == '':
        if V in ["i", "in", "ing"]:
            C = 'y'
        elif V == 'u':
            C = 'w'
        elif V.startswith('i') and V not in ["ii", "iii"]:
            C = 'y'
            V = V[1:]
        elif V.startswith('u'):
            C = 'w'
            V = V[1:]
        elif V.startswith('v'):
            C = 'yu'
            V = V[1:]
    else:
        if C in ['j', 'q', 'x']:
            if V.startswith('v'):
                V = re.sub('v', 'u', V)
        if V == 'iou':
            V = 'iu'
        elif V == 'uei':
            V = 'ui'
        elif V == 'uen':
            V = 'un'
    result = C + V

    # Filter  er 不能再儿化
    if result.endswith('r') and R == 'r':
        return None

    # ii and iii, change back to i
    result = re.sub(r'i+', 'i', result)

    result = result + R + T
    return result


def generate_lexicon(with_tone=False, with_erhua=False):
    """Generate lexicon for Mandarin Chinese."""
    syllables = OrderedDict()

    for C in [''] + INITIALS:
        for V in FINALS:
            for R in [''] if not with_erhua else ['', 'r']:
                for T in [''] if not with_tone else ['1', '2', '3', '4', '5']:
                    result = rule(C, V, R, T)
                    if result:
                        syllables[result] = f'{C} {V}{R}{T}'
    return syllables