ass字幕嵌入mp4带偏移

发布于:2025-05-31 ⋅ 阅读:(24) ⋅ 点赞:(0)
# 格式转化文件,包含多种文件的互相转化,主要与视频相关
from pathlib import Path
import subprocess
import random
import os
import re



class Utils(object):
    @staticmethod
    def get_decimal_part(x: float) -> float:
        s = format(x, '.15f')  # 格式化为15位小数字符串
        if '.' in s:
            _, decimal_part = s.split('.')
            decimal_str = decimal_part.rstrip('0')  # 移除末尾多余的0
            if not decimal_str:  # 如果小数部分全为0
                return 0.0
            result = float("0." + decimal_str)
            return -result if x < 0 else result  # 处理负数
        return 0.0
    
    @staticmethod
    def file_path_processor(*file_paths: str) -> str | list[str]:
        if len(file_paths) == 1:
            return file_paths[0].replace("\\", "\\\\")
        return [file_path.replace("\\", "\\\\") for file_path in file_paths]


class TimeConverter(object):
    def time_analysis(self, time_str, offset: float = 0.0) -> tuple[int, int, int, int]:
        pattern = r'^(\d{1,2})\D(\d{1,2})\D(\d{1,2})[.,](\d{1,3})$'
        match: re.Match = re.match(pattern, time_str)
        if not match:
            raise ValueError(f"无法解析的时间格式: {time_str}")
        results = list(match.groups())
        results[-1] = f"{results[-1]:0<3}"
        hours, minutes, seconds, milliseconds = map(int, results)
        if offset != 0:
            milliseconds += int(Utils.get_decimal_part(offset) * 1000)
            offset = int(offset)
            hours += (offset // 3600)
            minutes += (offset // 60)
            seconds += (offset % 60)
            # 注意进位
            seconds += milliseconds // 1000
            minutes += seconds // 60
            hours += minutes // 60
            seconds %= 60
            milliseconds %= 1000
            minutes %= 60
            
        return hours, minutes, seconds, milliseconds
    
    def format_number(self, input_str: str, length: int) -> str:
        if not input_str.isdigit():
            raise ValueError("输入必须是数字字符串")
        if not isinstance(length, int) or length <= 0:
            raise ValueError("长度必须是正整数")
        if len(input_str) > length:
            return input_str[:length]  # 截断超长部分
        else:
            return '0' * (length - len(input_str))  + input_str
    
    def format_copy(self, ref_time):
        match: re.Match = re.match("^(\d+)(\D)(\d+)(\D)(\d+)(\D)(\d+)$", ref_time)
        if not match:
            raise ValueError(f"无法复制的时间格式: {ref_time}")
        (h_str, sep1, m_str, sep2, s_str, sep3, ms_str) = match.groups()
        h_len, m_len, s_len, ms_len = map(len, (h_str, m_str, s_str, ms_str))
        def time_formater(hours: int, minutes: int, seconds: int, milliseconds: int) -> str:
            return (
                f"{self.format_number(str(hours), h_len)}{sep1}"
                f"{self.format_number(str(minutes), m_len)}{sep2}"
                f"{self.format_number(str(seconds), s_len)}{sep3}"
                f"{self.format_number(str(milliseconds), ms_len)}"
            )
        return time_formater


class SubtitleConverter(object):
    def ass_analyser(self, ass_file) -> list[dict]:
        ass_object = []
        with open(ass_file, "r", encoding="utf-8") as f:
            start_record = False
            record_fields = False
            for i in f:
                if i.strip() == "[Events]":
                    record_fields = True
                    continue
                if re.match("\[.*?\]$", i.strip()):
                    start_record = False
                    continue
                if record_fields:
                    record_fields = False
                    start_record = True
                    fields = [j.strip() for j in i.split(",")]
                    continue
                if start_record:
                    row = map(lambda j: j.strip(), i.split(",", maxsplit=len(fields) - 1))
                    ass_object.append({k: v for k, v in zip(fields, row)})
        return ass_object

    def ass2srt(self, ass_file: str, srt_file: str, offset: float) -> None:
        if not ass_file.endswith(".ass"):
            return
        time_analyser = TimeConverter()
        formatter = time_analyser.format_copy("00:00:00,000")
        srt_file_obj = open(srt_file, "w", encoding="utf-8")
        count = 1
        for row in self.ass_analyser(ass_file):
            if not re.match("标准", row["Style"]):
                continue
            start_time = formatter(*time_analyser.time_analysis(row["Start"], offset))
            end_time = formatter(*time_analyser.time_analysis(row["End"], offset))
            subtitle = row["Text"]
            srt_file_obj.write(
                f"{count}\n{start_time} --> {end_time}\n{subtitle}\n\n"
            )
            count += 1
        srt_file_obj.close()

    def ass2ass_eng(self, ass_file: str, output_file: str, remove_style='标准-Chi') -> None:
        """
        这个方法是纯AI写的,与ass_analyser脱节。
        其作用是处理ass文件中的样式,去除其中的描边设置,同时移除掉指定字幕。
        字幕文件下载自网站:http://154.17.3.217:8888/sub/new, 原生字幕可能中英夹杂,但有时
        我们出于学习目的,可能只想要英文字幕;或纯粹出于娱乐目的,只想保留中文字幕等;
        """
        with open(ass_file, 'r', encoding='utf-8-sig') as f:
            lines = f.readlines()
        output = []
        current_section = None
        for line in lines:
            line = line.rstrip('\r\n')
            stripped = line.strip()
            if stripped.startswith('[') and stripped.endswith(']'):
                current_section = stripped
                output.append(line)
                continue
            if current_section == '[V4+ Styles]':
                if line.startswith('Style:'):
                    parts = line[len('Style:'):].split(',')
                    if len(parts) >= 17:
                        parts[16] = '0'
                        output.append('Style:' + ','.join(parts))
                    else:
                        output.append(line)
                else:
                    output.append(line)
            elif current_section == '[Events]' and line.startswith('Dialogue:'):
                content = line[len('Dialogue:'):].strip()
                fields = content.split(',', 9)
                if len(fields) >= 4 and fields[3].strip() == remove_style:
                    continue
                output.append(line)
            else:
                output.append(line)
        with open(output_file, 'w', encoding='utf-8') as f:
            f.write('\n'.join(output))

    def ass2ass_offset(self, ass_file1, ass_file2, offset: float) -> None:
        time_analyser = TimeConverter()
        ref_time = "0:00:00.00"
        time_formatter = time_analyser.format_copy(ref_time)
        ass_object = self.ass_analyser(ass_file1)
        for row in ass_object:
            offset_start = time_analyser.time_analysis(row["Start"], offset)
            offset_end = time_analyser.time_analysis(row["End"], offset)
            row["Start"] = time_formatter(*offset_start)
            row["End"] = time_formatter(*offset_end)
        fields = ",".join(ass_object[0].keys())
        rows = "\n".join(",".join(row[k] for k in ass_object[0]) for row in ass_object)
        rows = rows.replace("\\", "\\\\")
        new_body = f"[Events]\n{fields}\n{rows}"
        pattern = r'\[Events\]\nFormat:.*(?:\nDialogue:.*)*'
        with open(ass_file1, "r", encoding="utf-8") as f:
            content = f.read()
        new_content = re.sub(pattern, new_body, content, re.MULTILINE)
        with open(ass_file2, "w", encoding="utf-8") as f:
            f.write(new_content)

    def srt2srt_offset(self, srt_file1, srt_file2, offset: float) -> None:
        time_analyser = TimeConverter()
        ref_time = "00:00:00,000"
        time_formatter = time_analyser.format_copy(ref_time)
        with open(srt_file1, "r", encoding="utf-8") as f1:
            f2 = open(srt_file2, "w", encoding="utf-8")
            for i in f1:
                res = re.match("^(.*?) --> (.*)$", i.strip())
                if res:
                    start_time, end_time = res.groups()
                    offset_start = time_analyser.time_analysis(start_time, offset)
                    offset_end = time_analyser.time_analysis(end_time, offset)
                    start_time = time_formatter(*offset_start)
                    end_time = time_formatter(*offset_end)
                    i = f"{start_time} --> {end_time}\n"
                f2.write(i)
            f2.close()        


class VedioConverter(object):
    def mkv2mp4(self, mkv_file: str, mp4_file: str) -> None:
        mkv_file, mp4_file = Utils.file_path_processor(mkv_file, mp4_file)
        command = [
            ffmpeg_file_path,
            '-i', Utils.file_path_processor(mkv_file),
            '-c:v', 'copy',
            '-c:a', 'copy',
            '-y',
            Utils.file_path_processor(mp4_file)
        ]
        subprocess.run(command, check=True)

    def ass_embed_mp4(self, mp4_file: str, ass_file: str, output_file: str, itsoffset: float = 0.0) -> None:
        mp4_file, ass_file, output_file = Utils.file_path_processor(
            mp4_file, ass_file, output_file
        )
        converter = SubtitleConverter()
        random_name = f"{random.randint(0, 1000000)}.ass"
        converter.ass2ass_offset(ass_file, random_name, itsoffset)
        command = [
            ffmpeg_file_path,
            '-i', mp4_file,
            '-vf', f"subtitles={random_name}",
            '-c:v', 'libx264',
            '-profile:v', 'high',
            '-pix_fmt', 'yuv420p',
            '-preset', 'fast',
            '-b:a', '192k',
            '-c:a', 'aac',
            '-movflags', '+faststart',
            '-y',
            output_file
        ]
        subprocess.run(command, check=True)
        os.remove(random_name)

    def ass_embed_mkv(self, mkv_file: str, ass_file: str, output_file: str, itsoffset) -> None:
        mkv_file, ass_file, output_file = Utils.file_path_processor(
            mkv_file, ass_file, output_file
        )
        command = [
            ffmpeg_file_path,
            '-i', mkv_file,
            '-itsoffset', str(itsoffset),
            '-i', ass_file,
            '-map', '0',
            '-map', '-0:s',
            '-map', '1',
            '-c', 'copy',
            '-metadata:s:s:0', 'language=eng',
            '-y',
            output_file
        ]
        subprocess.run(command, check=True)



ffmpeg_file_path = r"ffmpeg.exe"
vedio_converter = VedioConverter()
# 加入硬字幕(mp4)
vedio_converter.ass_embed_mp4(
     r"your_input_mp4_file.mp4",
     r"your_ass_subtitle_file.ass",
     r"your_output_mp4_file.mp4",
     itsoffset=6.3    # 指定的字幕偏移时间,让字幕对齐音频
)



为了方便字幕的视频嵌入,上述代码实现了一些较为重要的功能,部分如下:

ass文件转srt文件,见SubtitleConverter的ass2srt方法;

根据srt文件和ass文件的时间偏移指定时间生成新的srt文件和ass文件的方法,见SubtitleConverter的ass2ass_offset和srt2srt_offset

ass字幕文件嵌入mp4视频的方法(可指定时间偏移),见VedioConverter的ass_embed_mp4方法,注意是硬字幕嵌入,相对耗时。

这些方法的实现都不是很难,不过并不能保证没有Bug;经过简单而基本测试,暂时没有出现问题

在使用之前,请确保找到你的ffmpeg路径。如果已经添加到环境变量,可以直接使用;否则请自行修改里面ffmpeg的路径为绝对路径。此处提供ffmpeg的下载路径:

FFmpeg 最新 Windows 64 位 GPL 版本下载

关于为什么mp4视频嵌入硬字幕,而mkv视频却是嵌入软字幕(在代码中),其实是有原因的:

mp4被更加广泛的兼容,几乎所有视频播放器都可以正确播放。但如果是嵌入软字幕,mp4视频的字幕则不一定能被播放器支持。硬字幕嵌入能保证字幕一定显示,更凸显mp4兼容的优势。缺陷就是硬字幕不能选择隐藏,同时需要重新编码,比较耗时;

mkv视频的支持性就明显要差不少,如手机上很多视频播放器就对mkv视频的支持不好,或视频变形,或音频丢失;但是软字幕的显示往往不是问题,这得益于mkv视频是字幕的天然容器,所以只要能找到合适的mkv视频播放器,几乎就能正常的显示软字幕。