尝试通过Python将subs用ffmpeg刻录成视频。在命令行中工作正常，但从Python子进程调用时：p = subprocess.Popen('cd ~/Downloads/yt/; ffmpeg -i ./{video} -vf subtitles=./{subtitles} {out}.mp4'.format(video=vid.replace(' ', '\ '), subtitles=subs, out='out.mp4'), shell=True)

我得到：

^{pr2}$

完全回溯：'ffmpeg version 2.7.2 Copyright (c) 2000-2015 the FFmpeg developers

built with Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)

configuration: --prefix=/usr/local/Cellar/ffmpeg/2.7.2_1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libfreetype --enable-libvpx --enable-libass --enable-libfdk-aac --enable-nonfree --enable-vda

libavutil 54. 27.100 / 54. 27.100

libavcodec 56. 41.100 / 56. 41.100

libavformat 56. 36.100 / 56. 36.100

libavdevice 56. 4.100 / 56. 4.100

libavfilter 5. 16.101 / 5. 16.101

libavresample 2. 1. 0 / 2. 1. 0

libswscale 3. 1.101 / 3. 1.101

libswresample 1. 2.100 / 1. 2.100

libpostproc 53. 3.100 / 53. 3.100

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './OnHub - a router for the new way to Wi-Fi-HNnfHP7VDP8.mp4':

Metadata:

major_brand : isom

minor_version : 512

compatible_brands: isomiso2avc1mp41

encoder : Lavf56.36.100

Duration: 00:00:53.94, start: 0.000000, bitrate: 2092 kb/s

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 1961 kb/s, 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc (default)

Metadata:

handler_name : VideoHandler

Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)

Metadata:

handler_name : SoundHandler

[NULL @ 0x7fc07b077600] Unable to find a suitable output format for 'pipe:'

pipe:: Invalid argument'