使用子进程从python执行ffmpeg命令

Question

以下命令在命令行中可以正常工作：

ffmpeg -y -threads 4 -i /dev/video0 -filter_complex "[v:0]scale=-2:720:force_original_aspect_ratio=decrease[vout001]" -c:v libx264 -b:v 2800k -maxrate:v 2996k -bufsize:v 4200k -c:a aac -b:a 128k -ac 2 -ar 48000 -preset veryfast -x264opts keyint=25:min-keyint=25:no-scenecut -sc_threshold 0 -r 25 -pix_fmt yuv420p -segment_list_flags +live -map [vout001] -f tee -var_stream_map 'v:0' "[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='segment_%%06d_%Y%m%d%H%M%S.ts']playlist.m3u8|[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename=\'http://X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts\':method=PUT]http://X.X.X.X:pppp/ABCD/playlist.m3u8"

但是，当我使用以下命令通过子进程从 python 代码执行它时，它会引发错误：

cmd_ffmpeg = ['ffmpeg', '-y', '-threads', '4', '-i', '/dev/video0', '-filter_complex', '[v:0]scale=-2:720:force_original_aspect_ratio=decrease[vout001]', '-c:v', 'libx264', '-b:v', '2800k', '-maxrate:v', '2996k', '-bufsize:v', '4200k', '-c:a', 'aac', '-b:a', '128k', '-ac', '2', '-ar', '48000', '-preset', 'veryfast', '-x264opts', 'keyint=25:min-keyint=25:no-scenecut', '-sc_threshold', '0', '-r', '25', '-pix_fmt', 'yuv420p', '-segment_list_flags', '+live', '-map', '[vout001]', '-f', 'tee', '"[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename=\'segment_%%06d_%Y%m%d%H%M%S.ts\']playlist.m3u8|[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename=\'http://X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts\':method=PUT]http://X.X.X.X:pppp/ABCD/playlist.m3u8"']

错误如下：

No option found near "//X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts":method=PUT]http://X.X.X.X:pppp/ABCD/playlist.m3u8"

当它从 python 代码执行时，它认为 'http' 之后的 ':' 作为选项分隔符（转义不起作用），而当直接从 shell 执行时，转义工作正常。

我该如何解决这个问题？

Answer 1

在ffmpeg 看到命令行之前，shell 会丢弃长字符串周围的双引号。您可以在 Python 中简单地将它们替换为单引号。在单引号内使用文字双引号会导致 ffmpeg 选项解析器失效。

Answer 2

谢谢你们的建议和帮助。我已经按照建议尝试了三引号，但它会产生另一个问题，其中包含具有以下文件名的视频片段/播放列表：

"f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename=segment_%%06d_%Y%m%d%H%M%S.ts]playlist.m3u8

"f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename=segment_%%06d_%Y%m0%H%M%S.ts]playlist0.ts

"f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename=segment_%%06d_%Y%m11%H%M%S.ts]playlist11.ts

……

因此，它将参数列表视为片段/播放列表文件名。此外，它生成一个输出而不是两个输出（一个在本地，另一个到远程服务器）。

事实上，解决方案是保持相同的命令，只在远程服务器 url 中的 ':' 之前添加 ''。因此，在 python 代码中运行良好的最终命令是：

cmd_ffmpeg = ['ffmpeg', '-y', '-threads', '4', '-i', '/dev/video0', '-filter_complex', '[v:0]scale=-2:720:force_original_aspect_ratio=decrease[vout001]', '-c:v', 'libx264', '-b:v', '2800k', '-maxrate:v', '2996k', '-bufsize:v', '4200k', '-c:a', 'aac', '-b:a', '128k', '-ac', '2', '-ar', '48000', '-preset', 'veryfast', '-x264opts', 'keyint=25:min-keyint=25:no-scenecut', '-sc_threshold', '0', '-r', '25', '-pix_fmt', 'yuv420p', '-segment_list_flags', '+live', '-map', '[vout001]', '-f', 'tee', '-var_stream_map', 'v:0', '[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='segment_%%06d_%Y%m%d%H%M%S.ts']playlist.m3u8|[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='http\://X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts']http://X.X.X.X:pppp/ABCD/playlist.m3u8']

关于选项/值：'-var_stream_map' 和 'v:0'，我只是错过了。它可以被忽略，因为我们只有一个输入。

谢谢。

Answer 3

你是怎么产生的cmd_ffmpeg?手动？它与shlex.split 返回的不同。例如，cmd_ffmpeg后面有双引号filter_complex而什么shlex.split返回没有。

import shlex
shell_ffmpeg_cmd = r'''ffmpeg -y -threads 4 -i /dev/video0 -filter_complex "[v:0]scale=-2:720:force_original_aspect_ratio=decrease[vout001]" -c:v libx264 -b:v 2800k -maxrate:v 2996k -bufsize:v 4200k -c:a aac -b:a 128k -ac 2 -ar 48000 -preset veryfast -x264opts keyint=25:min-keyint=25:no-scenecut -sc_threshold 0 -r 25 -pix_fmt yuv420p -segment_list_flags +live -map [vout001] -f tee -var_stream_map 'v:0' "[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='segment_%%06d_%Y%m%d%H%M%S.ts']playlist.m3u8|[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='http://X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts':method=PUT]http://X.X.X.X:pppp/ABCD/playlist.m3u8"'''
popen_args = shlex.split(shell_ffmpeg_cmd)
print(" ".join(popen_args))

此外，对于它的价值，这两个开关从cmd_ffmpeg，与您的 shell 调用相比：-var_stream_map 和 'v:0'。

不过，您的问题似乎与列表中的最后一个元素有关。正如eatmeimadanish 建议的那样，尝试三重引用它。以下是你的cmd_ffmpeg最后一个元素更正并三重单引号。它打印 ffmpeg 的 stderr，根据我的经验，它派上用场：

from subprocess import Popen, PIPE

cmd_ffmpeg = ['ffmpeg', '-y', '-threads', '4', '-i', '/dev/video0', '-filter_complex', '[v:0]scale=-2:720:force_original_aspect_ratio=decrease[vout001]', '-c:v', 'libx264', '-b:v', '2800k', '-maxrate:v', '2996k', '-bufsize:v', '4200k', '-c:a', 'aac', '-b:a', '128k', '-ac', '2', '-ar', '48000', '-preset', 'veryfast', '-x264opts', 'keyint=25:min-keyint=25:no-scenecut', '-sc_threshold', '0', '-r', '25', '-pix_fmt', 'yuv420p', '-segment_list_flags', '+live', '-map', '[vout001]', '-f', 'tee', '''"[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='segment_%%06d_%Y%m%d%H%M%S.ts']playlist.m3u8|[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='http://X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts':method=PUT]http://X.X.X.X:pppp/ABCD/playlist.m3u8"''']
with Popen(cmd_ffmpeg, text=True, stdout=PIPE, stderr=PIPE) as p:
    for line in p.stderr:
        print(line, end="") # stderr already includes a newline

Answer 4

如果你想在 python 代码中运行 ffmpeg 命令，你可以试试这个：

import os
cmd_ffmpeg = """ffmpeg -y -threads 4 -i /dev/video0 -filter_complex "[v:0]scale=-2:720:force_original_aspect_ratio=decrease[vout001]" -c:v libx264 -b:v 2800k -maxrate:v 2996k -bufsize:v 4200k -c:a aac -b:a 128k -ac 2 -ar 48000 -preset veryfast -x264opts keyint=25:min-keyint=25:no-scenecut -sc_threshold 0 -r 25 -pix_fmt yuv420p -segment_list_flags +live -map [vout001] -f tee -var_stream_map 'v:0' "[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='segment_%%06d_%Y%m%d%H%M%S.ts']playlist.m3u8|[f=hls:hls_time=1:hls_playlist_type=event:strftime=1:hls_flags=independent_segments+program_date_time+second_level_segment_index:hls_segment_filename='http://X.X.X.X:pppp/ABCD/segment_%%06d_%Y%m%d%H%M%S.ts':method=PUT]http://X.X.X.X:pppp/ABCD/playlist.m3u8""""
print(cmd_ffmpeg)
os.system(cmd_ffmpeg)