whisper_utils.py

# SPDX-FileCopyrightText: Copyright (c) 2022-2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# 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 logging
import os
from collections import defaultdict
from functools import lru_cache
from pathlib import Path
from subprocess import CalledProcessError, run
from typing import Dict, Iterable, List, Optional, TextIO, Tuple, Union

import kaldialign
import numpy as np
import soundfile
import torch
import torch.nn.functional as F

Pathlike = Union[str, Path]

SAMPLE_RATE = 16000
N_FFT = 400
HOP_LENGTH = 160
CHUNK_LENGTH = 30
N_SAMPLES = CHUNK_LENGTH * SAMPLE_RATE  # 480000 samples in a 30-second chunk


def load_audio(file: str, sr: int = SAMPLE_RATE):
    """
    Open an audio file and read as mono waveform, resampling as necessary

    Parameters
    ----------
    file: str
        The audio file to open

    sr: int
        The sample rate to resample the audio if necessary

    Returns
    -------
    A NumPy array containing the audio waveform, in float32 dtype.
    """

    # This launches a subprocess to decode audio while down-mixing
    # and resampling as necessary.  Requires the ffmpeg CLI in PATH.
    # fmt: off
    cmd = [
        "ffmpeg", "-nostdin", "-threads", "0", "-i", file, "-f", "s16le", "-ac",
        "1", "-acodec", "pcm_s16le", "-ar",
        str(sr), "-"
    ]
    # fmt: on
    try:
        out = run(cmd, capture_output=True, check=True).stdout
    except CalledProcessError as e:
        raise RuntimeError(f"Failed to load audio: {e.stderr.decode()}") from e

    return np.frombuffer(out, np.int16).flatten().astype(np.float32) / 32768.0


def load_audio_wav_format(wav_path):
    # make sure audio in .wav format
    assert wav_path.endswith(
        '.wav'), f"Only support .wav format, but got {wav_path}"
    waveform, sample_rate = soundfile.read(wav_path)
    assert sample_rate == 16000, f"Only support 16k sample rate, but got {sample_rate}"
    return waveform, sample_rate


def pad_or_trim(array, length: int = N_SAMPLES, *, axis: int = -1):
    """
    Pad or trim the audio array to N_SAMPLES, as expected by the encoder.
    """
    if torch.is_tensor(array):
        if array.shape[axis] > length:
            array = array.index_select(dim=axis,
                                       index=torch.arange(length,
                                                          device=array.device))

        if array.shape[axis] < length:
            pad_widths = [(0, 0)] * array.ndim
            pad_widths[axis] = (0, length - array.shape[axis])
            array = F.pad(array,
                          [pad for sizes in pad_widths[::-1] for pad in sizes])
    else:
        if array.shape[axis] > length:
            array = array.take(indices=range(length), axis=axis)

        if array.shape[axis] < length:
            pad_widths = [(0, 0)] * array.ndim
            pad_widths[axis] = (0, length - array.shape[axis])
            array = np.pad(array, pad_widths)

    return array


@lru_cache(maxsize=None)
def mel_filters(device,
                n_mels: int,
                mel_filters_dir: str = None) -> torch.Tensor:
    """
    load the mel filterbank matrix for projecting STFT into a Mel spectrogram.
    Allows decoupling librosa dependency; saved using:

        np.savez_compressed(
            "mel_filters.npz",
            mel_80=librosa.filters.mel(sr=16000, n_fft=400, n_mels=80),
        )
    """
    assert n_mels in {80, 128}, f"Unsupported n_mels: {n_mels}"
    if mel_filters_dir is None:
        mel_filters_path = os.path.join(os.path.dirname(__file__), "assets",
                                        "mel_filters.npz")
    else:
        mel_filters_path = os.path.join(mel_filters_dir, "mel_filters.npz")
    with np.load(mel_filters_path) as f:
        return torch.from_numpy(f[f"mel_{n_mels}"]).to(device)


def log_mel_spectrogram(
    audio: Union[str, np.ndarray, torch.Tensor],
    n_mels: int,
    padding: int = 0,
    device: Optional[Union[str, torch.device]] = None,
    return_duration: bool = False,
    mel_filters_dir: str = None,
):
    """
    Compute the log-Mel spectrogram of

    Parameters
    ----------
    audio: Union[str, np.ndarray, torch.Tensor], shape = (*)
        The path to audio or either a NumPy array or Tensor containing the audio waveform in 16 kHz

    n_mels: int
        The number of Mel-frequency filters, only 80 and 128 are supported

    padding: int
        Number of zero samples to pad to the right

    device: Optional[Union[str, torch.device]]
        If given, the audio tensor is moved to this device before STFT

    Returns
    -------
    torch.Tensor, shape = (80 or 128, n_frames)
        A Tensor that contains the Mel spectrogram
    """
    if not torch.is_tensor(audio):
        if isinstance(audio, str):
            if audio.endswith('.wav'):
                audio, _ = load_audio_wav_format(audio)
            else:
                audio = load_audio(audio)
        assert isinstance(audio,
                          np.ndarray), f"Unsupported audio type: {type(audio)}"
        duration = audio.shape[-1] / SAMPLE_RATE
        audio = pad_or_trim(audio, N_SAMPLES)
        audio = audio.astype(np.float32)
        audio = torch.from_numpy(audio)

    if device is not None:
        audio = audio.to(device)
    if padding > 0:
        audio = F.pad(audio, (0, padding))
    window = torch.hann_window(N_FFT).to(audio.device)
    stft = torch.stft(audio,
                      N_FFT,
                      HOP_LENGTH,
                      window=window,
                      return_complex=True)
    magnitudes = stft[..., :-1].abs()**2

    filters = mel_filters(audio.device, n_mels, mel_filters_dir)
    mel_spec = filters @ magnitudes

    log_spec = torch.clamp(mel_spec, min=1e-10).log10()
    log_spec = torch.maximum(log_spec, log_spec.max() - 8.0)
    log_spec = (log_spec + 4.0) / 4.0
    if return_duration:
        return log_spec, duration
    else:
        return log_spec


def store_transcripts(filename: Pathlike, texts: Iterable[Tuple[str, str,
                                                                str]]) -> None:
    """Save predicted results and reference transcripts to a file.
    https://github.com/k2-fsa/icefall/blob/master/icefall/utils.py
    Args:
      filename:
        File to save the results to.
      texts:
        An iterable of tuples. The first element is the cur_id, the second is
        the reference transcript and the third element is the predicted result.
    Returns:
      Return None.
    """
    with open(filename, "w") as f:
        for cut_id, ref, hyp in texts:
            print(f"{cut_id}:\tref={ref}", file=f)
            print(f"{cut_id}:\thyp={hyp}", file=f)


def write_error_stats(
    f: TextIO,
    test_set_name: str,
    results: List[Tuple[str, str]],
    enable_log: bool = True,
) -> float:
    """Write statistics based on predicted results and reference transcripts.
    https://github.com/k2-fsa/icefall/blob/master/icefall/utils.py
    It will write the following to the given file:

        - WER
        - number of insertions, deletions, substitutions, corrects and total
          reference words. For example::

              Errors: 23 insertions, 57 deletions, 212 substitutions, over 2606
              reference words (2337 correct)

        - The difference between the reference transcript and predicted result.
          An instance is given below::

            THE ASSOCIATION OF (EDISON->ADDISON) ILLUMINATING COMPANIES

          The above example shows that the reference word is `EDISON`,
          but it is predicted to `ADDISON` (a substitution error).

          Another example is::

            FOR THE FIRST DAY (SIR->*) I THINK

          The reference word `SIR` is missing in the predicted
          results (a deletion error).
      results:
        An iterable of tuples. The first element is the cur_id, the second is
        the reference transcript and the third element is the predicted result.
      enable_log:
        If True, also print detailed WER to the console.
        Otherwise, it is written only to the given file.
    Returns:
      Return None.
    """
    subs: Dict[Tuple[str, str], int] = defaultdict(int)
    ins: Dict[str, int] = defaultdict(int)
    dels: Dict[str, int] = defaultdict(int)

    # `words` stores counts per word, as follows:
    #   corr, ref_sub, hyp_sub, ins, dels
    words: Dict[str, List[int]] = defaultdict(lambda: [0, 0, 0, 0, 0])
    num_corr = 0
    ERR = "*"
    for cut_id, ref, hyp in results:
        ali = kaldialign.align(ref, hyp, ERR)
        for ref_word, hyp_word in ali:
            if ref_word == ERR:
                ins[hyp_word] += 1
                words[hyp_word][3] += 1
            elif hyp_word == ERR:
                dels[ref_word] += 1
                words[ref_word][4] += 1
            elif hyp_word != ref_word:
                subs[(ref_word, hyp_word)] += 1
                words[ref_word][1] += 1
                words[hyp_word][2] += 1
            else:
                words[ref_word][0] += 1
                num_corr += 1
    ref_len = sum([len(r) for _, r, _ in results])
    sub_errs = sum(subs.values())
    ins_errs = sum(ins.values())
    del_errs = sum(dels.values())
    tot_errs = sub_errs + ins_errs + del_errs
    tot_err_rate = "%.2f" % (100.0 * tot_errs / ref_len)

    if enable_log:
        logging.info(f"[{test_set_name}] %WER {tot_errs / ref_len:.2%} "
                     f"[{tot_errs} / {ref_len}, {ins_errs} ins, "
                     f"{del_errs} del, {sub_errs} sub ]")

    print(f"%WER = {tot_err_rate}", file=f)
    print(
        f"Errors: {ins_errs} insertions, {del_errs} deletions, "
        f"{sub_errs} substitutions, over {ref_len} reference "
        f"words ({num_corr} correct)",
        file=f,
    )
    print(
        "Search below for sections starting with PER-UTT DETAILS:, "
        "SUBSTITUTIONS:, DELETIONS:, INSERTIONS:, PER-WORD STATS:",
        file=f,
    )

    print("", file=f)
    print("PER-UTT DETAILS: corr or (ref->hyp)  ", file=f)
    for cut_id, ref, hyp in results:
        ali = kaldialign.align(ref, hyp, ERR)
        combine_successive_errors = True
        if combine_successive_errors:
            ali = [[[x], [y]] for x, y in ali]
            for i in range(len(ali) - 1):
                if ali[i][0] != ali[i][1] and ali[i + 1][0] != ali[i + 1][1]:
                    ali[i + 1][0] = ali[i][0] + ali[i + 1][0]
                    ali[i + 1][1] = ali[i][1] + ali[i + 1][1]
                    ali[i] = [[], []]
            ali = [[
                list(filter(lambda a: a != ERR, x)),
                list(filter(lambda a: a != ERR, y)),
            ] for x, y in ali]
            ali = list(filter(lambda x: x != [[], []], ali))
            ali = [[
                ERR if x == [] else " ".join(x),
                ERR if y == [] else " ".join(y),
            ] for x, y in ali]

        print(
            f"{cut_id}:\t" + " ".join((ref_word if ref_word == hyp_word else
                                       f"({ref_word}->{hyp_word})"
                                       for ref_word, hyp_word in ali)),
            file=f,
        )

    print("", file=f)
    print("SUBSTITUTIONS: count ref -> hyp", file=f)

    for count, (ref, hyp) in sorted([(v, k) for k, v in subs.items()],
                                    reverse=True):
        print(f"{count}   {ref} -> {hyp}", file=f)

    print("", file=f)
    print("DELETIONS: count ref", file=f)
    for count, ref in sorted([(v, k) for k, v in dels.items()], reverse=True):
        print(f"{count}   {ref}", file=f)

    print("", file=f)
    print("INSERTIONS: count hyp", file=f)
    for count, hyp in sorted([(v, k) for k, v in ins.items()], reverse=True):
        print(f"{count}   {hyp}", file=f)

    print("", file=f)
    print("PER-WORD STATS: word  corr tot_errs count_in_ref count_in_hyp",
          file=f)
    for _, word, counts in sorted([(sum(v[1:]), k, v)
                                   for k, v in words.items()],
                                  reverse=True):
        (corr, ref_sub, hyp_sub, ins, dels) = counts
        tot_errs = ref_sub + hyp_sub + ins + dels
        ref_count = corr + ref_sub + dels
        hyp_count = corr + hyp_sub + ins

        print(f"{word}   {corr} {tot_errs} {ref_count} {hyp_count}", file=f)
    return float(tot_err_rate)