如何修复ffmpeg-python报错：ass滤镜original_size参数无效

环境 #

• Python 3.10
• Windows 11
• ffmpeg-python==0.2.0

背景 #

尝试使用FFmpeg结合Python给视频添加硬编码ASS字幕。

问题 #

FFmpeg无法正确识别ASS字幕文件路径，已尝试多种绝对路径、相对路径写法，以及ffmpeg-python直接调用、subprocess调用两种方式，均未解决。报错信息为：

Error applying option 'original_size' to filter 'ass': Invalid argument

测试代码 #

import os
import ffmpeg
import subprocess

def add_subtitles_with_ass(video_path, ass_path, output_path):

    video_path = os.path.abspath(video_path)
    ass_path = os.path.abspath(ass_path)
    output_path = os.path.abspath(output_path)

    print(f"🚀 Add susbtitiles with ASS : {ass_path}")
    ass_path_escaped = rf'"{ass_path}"'

    try:
        ffmpeg.input(video_path).output(output_path, vf=f"ass='{ass_path_escaped}'").run(overwrite_output=True)
        print(f"✅ Subtitles added with success : {output_path}")
    except Exception as e:
        print(f"❌ ERROR when adding subtitles : {e}")


def add_subtitles_with_ass_with_subprocess(video_path, ass_path, output_path):
    video_path = os.path.abspath(video_path)
    ass_path = os.path.abspath(ass_path)
    output_path = os.path.abspath(output_path)

    print(f"🚀 Add subtitles with ASS : {ass_path}")

    try:
        command = [
            'ffmpeg',
            '-i', video_path,
            '-vf', f"ass='{ass_path}'",
            '-c:a', 'copy',
            output_path,
            '-y'  # Overwrite output file without asking
        ]

        subprocess.run(command, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        print(f"✅ Subtitles added with success : {output_path}")
    except subprocess.CalledProcessError as e:
        print(f"❌ ERROR when adding subtitles : {e.stderr.decode('utf-8')}")


print(f"Test 1 -----------------------------------------------------------------------")
ass_path="G:\Mi unidad\Python\Scripts\shorts_videos\10000views_and_higher\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path="G:\Mi unidad\Python\Scripts\shorts_videos\10000views_and_higher\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path="G:\Mi unidad\Python\Scripts\shorts_videos\10000views_and_higher\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path, ass_path, output_path)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 2 -----------------------------------------------------------------------")
ass_path2="G:\\Mi unidad\\Python\\Scripts\\shorts_videos\\10000views_and_higher\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path2="G:\\Mi unidad\\Python\\Scripts\\shorts_videos\\10000views_and_higher\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path2="G:\\Mi unidad\\Python\\Scripts\\shorts_videos\\10000views_and_higher\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path2, ass_path2, output_path2)

print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 3 -----------------------------------------------------------------------")
ass_path3="G:/\Mi unidad/\Python/\Scripts/\shorts_videos/\10000views_and_higher/\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path3="G:/\Mi unidad/\Python/\Scripts/\shorts_videos/\10000views_and_higher/\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path3="G:/\Mi unidad/\Python/\Scripts/\shorts_videos/\10000views_and_higher/\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path3, ass_path3, output_path3)

print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 4 -----------------------------------------------------------------------")
ass_path4="G:/\\Mi unidad/\\Python/\\Scripts/\\shorts_videos/\\10000views_and_higher/\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path4="G:/\\Mi unidad/\\Python/\\Scripts/\\shorts_videos/\\10000views_and_higher/\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path4="G:/\\Mi unidad/\\Python/\\Scripts/\\shorts_videos/\\10000views_and_higher/\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path4, ass_path4, output_path4)




print(f"Test 1 with subprocess -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path, ass_path, output_path)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 2 with subprocess -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path2, ass_path2, output_path2)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 3 with subprocess -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path3, ass_path3, output_path3)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 4 with subprocess -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path4, ass_path4, output_path4)
print(50*"*")
print(50*"*")
print(50*"*")

#======================= IT DIDN'T WORK, SO LET'S DO WITH RELATIVE PATH ===================================


print(f"Test 1 with relative path -----------------------------------------------------------------------")
ass_path_relative="10000views_and_higher\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path_relative="10000views_and_higher\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path_relative="10000views_and_higher\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path_relative, ass_path_relative, output_path_relative)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 2  with relative path -----------------------------------------------------------------------")
ass_path2_relative="10000views_and_higher\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path2_relative="10000views_and_higher\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path2_relative="10000views_and_higher\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path2_relative, ass_path2_relative, output_path2_relative)

print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 3  with relative path -----------------------------------------------------------------------")
ass_path3_relative="10000views_and_higher/\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path3_relative="10000views_and_higher/\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path3_relative="10000views_and_higher/\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path3_relative, ass_path3_relative, output_path3_relative)

print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 4  with relative path -----------------------------------------------------------------------")
ass_path4_relative="10000views_and_higher/\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.ass"
video_path4_relative="10000views_and_higher/\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo.mp4"
output_path4_relative="10000views_and_higher/\\Li2zY7XcOf0_Matthew_Hussey_flip_h_BW_with_logo_EN.mp4"
add_subtitles_with_ass(video_path4_relative, ass_path4_relative, output_path4_relative)




print(f"Test 1 with subprocess  with relative path -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path, ass_path, output_path)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 2 with subprocess  with relative path -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path2_relative, ass_path2_relative, output_path2_relative)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 3 with subprocess  with relative path -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path3_relative, ass_path3_relative, output_path3_relative)
print(50*"*")
print(50*"*")
print(50*"*")

print(f"Test 4 with subprocess  with relative path -----------------------------------------------------------------------")
add_subtitles_with_ass_with_subprocess(video_path4_relative, ass_path4_relative, output_path4_relative)
print(50*"*")
print(50*"*")
print(50*"*")

输出 #

输出内容较多，包含详细报错信息及测试过程记录。

解决方案 #

1. 修正路径转义逻辑 #

代码中手动给路径添加多层引号导致ffmpeg解析参数错误，正确处理方式：

• ffmpeg-python调用：无需手动添加引号，直接传递路径字符串，ffmpeg-python会自动处理带空格的路径转义；
• subprocess调用：直接将路径作为列表元素传入，subprocess会自动处理空格转义，不需要在参数中添加额外引号。

修正后的核心代码：

# ffmpeg-python方式
ffmpeg.input(video_path).output(output_path, vf=f"ass={ass_path}", **{'c:a': 'copy', 'c:v': 'libx264'}).run(overwrite_output=True)

# subprocess方式
command = [
    'ffmpeg',
    '-i', video_path,
    '-vf', f"ass={ass_path}",
    '-c:a', 'copy',
    '-c:v', 'libx264',
    '-y',
    output_path
]

2. 检查ASS字幕文件参数 #

报错中的original_size来自ASS文件的配置，若ASS文件[Script Info]部分的PlayResX/PlayResY格式错误，或存在无效的original_size参数，会导致ffmpeg报错。可以：

• 打开ASS文件，删除original_size相关行，ffmpeg会自动适配视频分辨率；
• 确保PlayResX和PlayResY为有效整数（如PlayResX=1080、PlayResY=1920）。

3. 更新FFmpeg版本 #

老旧版本FFmpeg对ASS滤镜的参数兼容性较差，建议更新至最新稳定版，避免参数解析bug。

内容的提问来源于stack exchange，提问作者Gauthier Buttez