使用子进程从python执行ffmpeg命令

时间：2019-06-19 16:01:30

标签： python ffmpeg

以下命令在命令行中可以正常运行：

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（转义不起作用）时，它将'http'后面的'：'作为选项分隔符，而当直接从shell执行时，转义可以正常工作。

如何解决此问题？

4 个答案:

答案 0 :(得分：1)

在ffmpeg看到命令行之前，shell丢弃了长字符串周围的双引号。您只需在Python中用单引号将它们替换即可。在ffmpeg选项解析器中抛出单引号内的文字双引号。

答案 1 :(得分：1)

谢谢你们的建议和帮助。我已经尝试按照建议的方式将三引号引起来，但它又产生了另一个问题，该问题包括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，它将参数列表视为段/播放列表文件名。而且，它生成一个输出而不是两个输出（一个在本地，另一个在远程服务器）。

实际上，解决方案是保留相同的命令，并且仅在远程服务器URL中的“：”之前添加“ \”。因此，从python代码正常工作的最终命令是：

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。因为我们只有一个输入，所以可以忽略它。

谢谢。

答案 2 :(得分：0)

您是如何生成 cmd_ffmpeg 的？手动吗？它与shlex.split返回的内容不同。例如， cmd_ffmpeg 在 filter_complex 之后带有双引号，而 shlex.split 返回的内容则没有。 

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，与您的shell调用相比， cmd_ffmpeg 中缺少这两个开关：-var_stream_map和'v:0'。

尽管如此，您的问题似乎出在列表中的最后一个元素上。正如eatmeimadanish所建议的，请尝试三重引用。以下是您的 cmd_ffmpeg ，其中最后一个元素已更正并用三重单引号引起来。它打印出ffmpeg的stderr，根据我的经验，它很方便：

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

答案 3 :(得分：0)

如果要在python代码中运行ffmpeg命令，可以尝试以下操作：

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)
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