whisper/whisper/utils.py

import json
import os
import sys
import zlib
from typing import Callable, TextIO

system_encoding = sys.getdefaultencoding()

if system_encoding != "utf-8":

    def make_safe(string):
        # replaces any character not representable using the system default encoding with an '?',
        # avoiding UnicodeEncodeError (https://github.com/openai/whisper/discussions/729).
        return string.encode(system_encoding, errors="replace").decode(system_encoding)

else:

    def make_safe(string):
        # utf-8 can encode any Unicode code point, so no need to do the round-trip encoding
        return string


def exact_div(x, y):
    assert x % y == 0
    return x // y


def str2bool(string):
    str2val = {"True": True, "False": False}
    if string in str2val:
        return str2val[string]
    else:
        raise ValueError(f"Expected one of {set(str2val.keys())}, got {string}")


def optional_int(string):
    return None if string == "None" else int(string)


def optional_float(string):
    return None if string == "None" else float(string)


def compression_ratio(text) -> float:
    text_bytes = text.encode("utf-8")
    return len(text_bytes) / len(zlib.compress(text_bytes))


def format_timestamp(
    seconds: float, always_include_hours: bool = False, decimal_marker: str = "."
):
    assert seconds >= 0, "non-negative timestamp expected"
    milliseconds = round(seconds * 1000.0)

    hours = milliseconds // 3_600_000
    milliseconds -= hours * 3_600_000

    minutes = milliseconds // 60_000
    milliseconds -= minutes * 60_000

    seconds = milliseconds // 1_000
    milliseconds -= seconds * 1_000

    hours_marker = f"{hours:02d}:" if always_include_hours or hours > 0 else ""
    return (
        f"{hours_marker}{minutes:02d}:{seconds:02d}{decimal_marker}{milliseconds:03d}"
    )


class ResultWriter:
    extension: str

    def __init__(self, output_dir: str):
        self.output_dir = output_dir

    def __call__(self, result: dict, audio_path: str):
        audio_basename = os.path.basename(audio_path)
        audio_basename = os.path.splitext(audio_basename)[0]
        output_path = os.path.join(
            self.output_dir, audio_basename + "." + self.extension
        )

        with open(output_path, "w", encoding="utf-8") as f:
            self.write_result(result, file=f)

    def write_result(self, result: dict, file: TextIO):
        raise NotImplementedError


class WriteTXT(ResultWriter):
    extension: str = "txt"

    def write_result(self, result: dict, file: TextIO):
        for segment in result["segments"]:
            print(segment["text"].strip(), file=file, flush=True)


class SubtitlesWriter(ResultWriter):
    always_include_hours: bool
    decimal_marker: str

    def iterate_result(self, result: dict):
        for segment in result["segments"]:
            segment_start = self.format_timestamp(segment["start"])
            segment_end = self.format_timestamp(segment["end"])
            segment_text = segment["text"].strip().replace("-->", "->")

            if word_timings := segment.get("words", None):
                all_words = [timing["word"] for timing in word_timings]
                all_words[0] = all_words[0].strip()  # remove the leading space, if any
                last = segment_start
                for i, this_word in enumerate(word_timings):
                    start = self.format_timestamp(this_word["start"])
                    end = self.format_timestamp(this_word["end"])
                    if last != start:
                        yield last, start, segment_text

                    yield start, end, "".join(
                        [
                            f"<u>{word}</u>" if j == i else word
                            for j, word in enumerate(all_words)
                        ]
                    )
                    last = end

                if last != segment_end:
                    yield last, segment_end, segment_text
            else:
                yield segment_start, segment_end, segment_text

    def format_timestamp(self, seconds: float):
        return format_timestamp(
            seconds=seconds,
            always_include_hours=self.always_include_hours,
            decimal_marker=self.decimal_marker,
        )


class WriteVTT(SubtitlesWriter):
    extension: str = "vtt"
    always_include_hours: bool = False
    decimal_marker: str = "."

    def write_result(self, result: dict, file: TextIO):
        print("WEBVTT\n", file=file)
        for start, end, text in self.iterate_result(result):
            print(f"{start} --> {end}\n{text}\n", file=file, flush=True)


class WriteSRT(SubtitlesWriter):
    extension: str = "srt"
    always_include_hours: bool = True
    decimal_marker: str = ","

    def write_result(self, result: dict, file: TextIO):
        for i, (start, end, text) in enumerate(self.iterate_result(result), start=1):
            print(f"{i}\n{start} --> {end}\n{text}\n", file=file, flush=True)


class WriteTSV(ResultWriter):
    """
    Write a transcript to a file in TSV (tab-separated values) format containing lines like:
    <start time in integer milliseconds>\t<end time in integer milliseconds>\t<transcript text>

    Using integer milliseconds as start and end times means there's no chance of interference from
    an environment setting a language encoding that causes the decimal in a floating point number
    to appear as a comma; also is faster and more efficient to parse & store, e.g., in C++.
    """

    extension: str = "tsv"

    def write_result(self, result: dict, file: TextIO):
        print("start", "end", "text", sep="\t", file=file)
        for segment in result["segments"]:
            print(round(1000 * segment["start"]), file=file, end="\t")
            print(round(1000 * segment["end"]), file=file, end="\t")
            print(segment["text"].strip().replace("\t", " "), file=file, flush=True)


class WriteJSON(ResultWriter):
    extension: str = "json"

    def write_result(self, result: dict, file: TextIO):
        json.dump(result, file)


def get_writer(output_format: str, output_dir: str) -> Callable[[dict, TextIO], None]:
    writers = {
        "txt": WriteTXT,
        "vtt": WriteVTT,
        "srt": WriteSRT,
        "tsv": WriteTSV,
        "json": WriteJSON,
    }

    if output_format == "all":
        all_writers = [writer(output_dir) for writer in writers.values()]

        def write_all(result: dict, file: TextIO):
            for writer in all_writers:
                writer(result, file)

        return write_all

    return writers[output_format](output_dir)