python - 使用 ffmpeg 从 Python : why the sound is cut only when streaming into a mp4 file ? 进行流式视频合成

Question

我在 Python 中使用 ffmpeg 来自动化一些视频合成。为此，我使用 Python 的 subprocess 模块并使用管道输入运行 ffmpeg 命令。这允许我将原始图像数组(numpy 矩阵)中的视频合成逐帧流式传输到 ffmpeg。在以下示例中，我将视频合成缩减为持续时间为 12 秒的简单视频。生成的 ffmpeg 命令是:

ffmpeg -i stream_audio.mp3 -re -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt rgb24 -r 25 -i - -map 0:a -map 1:v -y -strict -2 -f mp4 -pix_fmt yuv420p out.mp4

文件 stream_audio.mp3 是格式良好的 mp3 文件，对应于输出 mp4 文件的音频输出。但是，输出文件 out.mp4 中的声音在结束前 3 秒被剪切。

如果我尝试输出任何其他格式(例如 avi)，我不会观察到这个问题。以下命令生成格式良好的 avi 文件。

 ffmpeg -i ./stream_audio.mp3 -re -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt rgb24 -r 25 -i - -map 0:a -map 1:v -y -b 4096k -f avi -pix_fmt yuv420p out.avi

我试图用最简单的 ffmpeg 命令重现该错误而不通过 Python，但没有成功。我所做的最接近的是以下内容:

Building a raw video file with the correct specifications

ffmpeg -i samplevideo.mp4 -f rawvideo -vcodec rawvideo -acodec none -s 1280x720 -pix_fmt rgb24 -r 25 samplevideo.raw

Streaming the raw video file into the ffmpeg command

cat samplevideo.raw | ffmpeg -i /tmp/stream_audio.mp3 -re -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt rgb24 -r 25 -i - -map 0:a -map 1:v 
-y -strict -2 -f mp4 -pix_fmt yuv420p  -ss 00:00:00 -t 00:00:12 out.mp4

这是我正在使用的 ffmpeg 版本:

ffmpeg version 3.1.9 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.1 (GCC) 20161221 (Red Hat 6.3.1-1)
  configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic' --extra-ldflags='-Wl,-z,relro -specs=/usr/lib/rpm/redhat/redhat-hardened-ld' --enable-bzlib --disable-crystalhd --enable-fontconfig --enable-frei0r --enable-gcrypt --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libcdio --enable-indev=jack --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmp3lame --enable-nvenc --extra-cflags=-I/usr/include/nvenc --enable-openal --enable-opencl --enable-opengl --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-libmfx --enable-runtime-cpudetect
  libavutil      55. 28.100 / 55. 28.100
  libavcodec     57. 48.101 / 57. 48.101
  libavformat    57. 41.100 / 57. 41.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 47.100 /  6. 47.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
Hyper fast Audio and Video encoder

文件 samplevideo.mp4 可以在这里找到: sample videos ，stream_audio.mp3 文件是对 samplevideo.mp4 文件音轨的简单提取:

ffmpeg -i samplevideo.mp4 stream_audio.mp3

谢谢你的帮助。

p.s:以下是 ffmpeg 命令的不同日志:

我的 Python 脚本使用 mp4 生成的命令:

Input #0, mp3, from './stream_audio.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.41.100
  Duration: 00:00:29.59, start: 0.023021, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 48000 Hz, stereo, s16p, 128 kb/s
    Metadata:
      encoder         : Lavc57.48
Input #1, rawvideo, from 'pipe:':
  Duration: N/A, start: 0.000000, bitrate: 552960 kb/s
    Stream #1:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 1280x720, 552960 kb/s, 25 tbr, 25 tbn, 25 tbc
[libx264 @ 0xf5cb748ac0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0xf5cb748ac0] profile High, level 3.1
[libx264 @ 0xf5cb748ac0] 264 - core 148 r2708 86b7198 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[mp4 @ 0xf5cb7462a0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times
Output #0, mp4, to 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.41.100
    Stream #0:0: Audio: aac (LC) ([64][0][0][0] / 0x0040), 48000 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc57.48.101 aac
    Stream #0:1: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=-1--1, 25 fps, 12800 tbn, 25 tbc
    Metadata:
      encoder         : Lavc57.48.101 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (native) -> aac (native))
  Stream #1:0 -> #0:1 (rawvideo (native) -> h264 (libx264))
[rawvideo @ 0xf5cb722860] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
frame=   14 fps=0.0 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   27 fps= 27 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   40 fps= 26 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   52 fps= 26 q=28.0 size=     113kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   65 fps= 26 q=28.0 size=     188kB time=00:00:00.49 bitrate=3145.8kbits/s speed=0.194x    
frame=   77 fps= 25 q=28.0 size=     320kB time=00:00:01.00 bitrate=2615.3kbits/s speed=0.331x    
frame=   90 fps= 25 q=28.0 size=     450kB time=00:00:01.51 bitrate=2431.3kbits/s speed=0.428x    
frame=  103 fps= 25 q=28.0 size=     592kB time=00:00:02.00 bitrate=2418.9kbits/s speed=0.496x    
frame=  116 fps= 25 q=28.0 size=     731kB time=00:00:02.52 bitrate=2376.1kbits/s speed=0.554x    
frame=  128 fps= 25 q=28.0 size=     849kB time=00:00:03.02 bitrate=2295.6kbits/s speed=0.599x    
frame=  141 fps= 25 q=28.0 size=     931kB time=00:00:03.54 bitrate=2153.0kbits/s speed=0.637x    
frame=  153 fps= 25 q=28.0 size=     983kB time=00:00:04.03 bitrate=1996.7kbits/s speed=0.665x    
frame=  166 fps= 25 q=28.0 size=    1067kB time=00:00:04.56 bitrate=1914.5kbits/s speed=0.695x    
frame=  179 fps= 25 q=28.0 size=    1123kB time=00:00:05.04 bitrate=1824.8kbits/s speed=0.712x    
frame=  191 fps= 25 q=28.0 size=    1213kB time=00:00:05.54 bitrate=1791.0kbits/s speed=0.732x    
frame=  204 fps= 25 q=28.0 size=    1271kB time=00:00:06.05 bitrate=1718.5kbits/s speed=0.749x    
frame=  217 fps= 25 q=28.0 size=    1346kB time=00:00:06.57 bitrate=1678.1kbits/s speed=0.764x    
frame=  230 fps= 25 q=28.0 size=    1452kB time=00:00:07.08 bitrate=1678.9kbits/s speed=0.778x    
frame=  242 fps= 25 q=28.0 size=    1567kB time=00:00:07.59 bitrate=1690.3kbits/s speed=0.79x    
frame=  255 fps= 25 q=28.0 size=    1660kB time=00:00:08.08 bitrate=1682.4kbits/s speed=0.799x    
frame=  267 fps= 25 q=28.0 size=    1739kB time=00:00:08.59 bitrate=1657.1kbits/s speed=0.81x    
frame=  280 fps= 25 q=28.0 size=    1751kB time=00:00:09.08 bitrate=1578.1kbits/s speed=0.817x    
frame=  291 fps= 24 q=-1.0 Lsize=    1864kB time=00:00:11.52 bitrate=1325.7kbits/s speed=0.954x    
video:1707kB audio:149kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.437266%
[aac @ 0xf5cb747540] Qavg: 202.422
[libx264 @ 0xf5cb748ac0] frame I:2     Avg QP:15.83  size: 78710
[libx264 @ 0xf5cb748ac0] frame P:183   Avg QP:21.13  size:  7293
[libx264 @ 0xf5cb748ac0] frame B:106   Avg QP:26.82  size:  2406
[libx264 @ 0xf5cb748ac0] consecutive B-frames: 47.8% 10.3%  2.1% 39.9%
[libx264 @ 0xf5cb748ac0] mb I  I16..4: 22.1% 32.5% 45.4%
[libx264 @ 0xf5cb748ac0] mb P  I16..4:  0.8%  1.4%  0.2%  P16..4: 25.3%  6.3%  3.1%  0.0%  0.0%    skip:62.9%
[libx264 @ 0xf5cb748ac0] mb B  I16..4:  0.1%  0.2%  0.0%  B16..8: 39.0%  1.7%  0.2%  direct: 0.4%  skip:58.5%  L0:47.3% L1:49.6% BI: 3.1%
[libx264 @ 0xf5cb748ac0] 8x8 transform intra:50.3% inter:57.9%
[libx264 @ 0xf5cb748ac0] coded y,uvDC,uvAC intra: 49.5% 65.3% 23.0% inter: 7.8% 10.2% 0.5%
[libx264 @ 0xf5cb748ac0] i16 v,h,dc,p: 30% 32% 11% 27%
[libx264 @ 0xf5cb748ac0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 21% 23%  4%  5%  7%  5%  5%  5%
[libx264 @ 0xf5cb748ac0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 15% 11%  8%  8%  9%  7% 12%  7%
[libx264 @ 0xf5cb748ac0] i8c dc,h,v,p: 51% 20% 21%  8%
[libx264 @ 0xf5cb748ac0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0xf5cb748ac0] ref P L0: 79.8% 11.4%  7.6%  1.2%
[libx264 @ 0xf5cb748ac0] ref B L0: 96.9%  2.8%  0.4%
[libx264 @ 0xf5cb748ac0] ref B L1: 97.7%  2.3%
[libx264 @ 0xf5cb748ac0] kb/s:1200.72
Exiting normally, received signal 15.

我的 Python 脚本使用 avi 生成的命令:

Input #0, mp3, from './stream_audio.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.41.100
  Duration: 00:00:29.59, start: 0.023021, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 48000 Hz, stereo, s16p, 128 kb/s
    Metadata:
      encoder         : Lavc57.48
Input #1, rawvideo, from 'pipe:':
  Duration: N/A, start: 0.000000, bitrate: 552960 kb/s
    Stream #1:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 1280x720, 552960 kb/s, 25 tbr, 25 tbn, 25 tbc
Please use -b:a or -b:v, -b is ambiguous
[avi @ 0x82147c30e0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times
Output #0, avi, to 'out.avi':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    ISFT            : Lavf57.41.100
    Stream #0:0: Audio: mp3 (libmp3lame) (U[0][0][0] / 0x0055), 48000 Hz, stereo, s16p
    Metadata:
      encoder         : Lavc57.48.101 libmp3lame
    Stream #0:1: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 1280x720, q=2-31, 4096 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc57.48.101 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/4096000 buffer size: 0 vbv_delay: -1
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (native) -> mp3 (libmp3lame))
  Stream #1:0 -> #0:1 (rawvideo (native) -> mpeg4 (native))
[rawvideo @ 0x821479f820] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
frame=   14 fps=0.0 q=2.6 size=     553kB time=00:00:00.56 bitrate=8082.6kbits/s speed= 1.1x    
frame=   27 fps= 27 q=5.4 size=     858kB time=00:00:01.08 bitrate=6507.5kbits/s speed=1.06x    
frame=   40 fps= 26 q=5.9 size=    1089kB time=00:00:01.60 bitrate=5574.9kbits/s speed=1.05x    
frame=   52 fps= 26 q=5.5 size=    1332kB time=00:00:02.08 bitrate=5225.6kbits/s speed=1.03x    
frame=   65 fps= 26 q=4.9 size=    1582kB time=00:00:02.60 bitrate=4985.6kbits/s speed=1.03x    
frame=   78 fps= 26 q=4.3 size=    1816kB time=00:00:03.12 bitrate=4768.1kbits/s speed=1.03x    
frame=   90 fps= 25 q=2.8 size=    2035kB time=00:00:03.60 bitrate=4631.7kbits/s speed=1.02x    
frame=  103 fps= 25 q=2.3 size=    2288kB time=00:00:04.12 bitrate=4549.8kbits/s speed=1.02x    
frame=  116 fps= 25 q=2.4 size=    2558kB time=00:00:04.64 bitrate=4516.3kbits/s speed=1.02x    
frame=  128 fps= 25 q=2.3 size=    2835kB time=00:00:05.12 bitrate=4535.4kbits/s speed=1.01x    
frame=  141 fps= 25 q=3.1 size=    3103kB time=00:00:05.64 bitrate=4506.6kbits/s speed=1.01x    
frame=  154 fps= 25 q=2.8 size=    3381kB time=00:00:06.16 bitrate=4495.9kbits/s speed=1.01x    
frame=  166 fps= 25 q=3.4 size=    3648kB time=00:00:06.64 bitrate=4494.9kbits/s speed=1.01x    
frame=  179 fps= 25 q=3.3 size=    3894kB time=00:00:07.16 bitrate=4455.7kbits/s speed=1.01x    
frame=  192 fps= 25 q=3.2 size=    4128kB time=00:00:07.68 bitrate=4402.9kbits/s speed=1.01x    
frame=  204 fps= 25 q=3.4 size=    4404kB time=00:00:08.16 bitrate=4420.9kbits/s speed=1.01x    
frame=  217 fps= 25 q=2.0 size=    4592kB time=00:00:08.68 bitrate=4334.0kbits/s speed=1.01x    
frame=  230 fps= 25 q=2.0 size=    4657kB time=00:00:09.20 bitrate=4147.2kbits/s speed=1.01x    
frame=  242 fps= 25 q=2.0 size=    4736kB time=00:00:09.68 bitrate=4007.9kbits/s speed=1.01x    
frame=  255 fps= 25 q=2.0 size=    4830kB time=00:00:10.20 bitrate=3879.0kbits/s speed=1.01x    
frame=  267 fps= 25 q=2.0 size=    4953kB time=00:00:10.68 bitrate=3799.5kbits/s speed=1.01x    
frame=  280 fps= 25 q=2.0 size=    5093kB time=00:00:11.20 bitrate=3722.3kbits/s speed=1.01x    
frame=  291 fps= 25 q=2.0 Lsize=    5209kB time=00:00:11.68 bitrate=3650.9kbits/s speed=1.01x    
video:4998kB audio:183kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.542552%
Exiting normally, received signal 15.

mp4 格式的纯命令行:

Input #0, mp3, from './stream_audio.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.41.100
  Duration: 00:00:29.59, start: 0.023021, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 48000 Hz, stereo, s16p, 128 kb/s
    Metadata:
      encoder         : Lavc57.48
Input #1, rawvideo, from 'pipe:':
  Duration: N/A, start: 0.000000, bitrate: 552960 kb/s
    Stream #1:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 1280x720, 552960 kb/s, 25 tbr, 25 tbn, 25 tbc
[libx264 @ 0x75fc583aa0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0x75fc583aa0] profile High, level 3.1
[libx264 @ 0x75fc583aa0] 264 - core 148 r2708 86b7198 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[mp4 @ 0x75fc581280] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times
Output #0, mp4, to 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.41.100
    Stream #0:0: Audio: aac (LC) ([64][0][0][0] / 0x0040), 48000 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc57.48.101 aac
    Stream #0:1: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=-1--1, 25 fps, 12800 tbn, 25 tbc
    Metadata:
      encoder         : Lavc57.48.101 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (native) -> aac (native))
  Stream #1:0 -> #0:1 (rawvideo (native) -> h264 (libx264))
[rawvideo @ 0x75fc55d840] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
frame=   14 fps=0.0 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   27 fps= 27 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   39 fps= 26 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   52 fps= 26 q=28.0 size=     113kB time=00:00:00.00 bitrate=N/A speed=   0x    
frame=   65 fps= 26 q=28.0 size=     188kB time=00:00:00.48 bitrate=3209.4kbits/s speed=0.191x    
frame=   77 fps= 26 q=28.0 size=     320kB time=00:00:01.00 bitrate=2615.3kbits/s speed=0.332x    
frame=   90 fps= 26 q=28.0 size=     450kB time=00:00:01.51 bitrate=2431.3kbits/s speed=0.43x    
frame=  102 fps= 25 q=28.0 size=     591kB time=00:00:01.98 bitrate=2442.1kbits/s speed=0.493x    
frame=  115 fps= 25 q=28.0 size=     731kB time=00:00:02.51 bitrate=2377.6kbits/s speed=0.556x    
frame=  128 fps= 25 q=28.0 size=     845kB time=00:00:03.00 bitrate=2307.7kbits/s speed=0.596x    
frame=  140 fps= 25 q=28.0 size=     930kB time=00:00:03.52 bitrate=2164.6kbits/s speed=0.636x    
frame=  153 fps= 25 q=28.0 size=     983kB time=00:00:04.03 bitrate=1996.7kbits/s speed=0.668x    
frame=  165 fps= 25 q=28.0 size=    1063kB time=00:00:04.52 bitrate=1925.2kbits/s speed=0.691x    
frame=  178 fps= 25 q=28.0 size=    1122kB time=00:00:05.03 bitrate=1826.2kbits/s speed=0.714x    
frame=  191 fps= 25 q=28.0 size=    1203kB time=00:00:05.52 bitrate=1783.6kbits/s speed=0.732x    
frame=  203 fps= 25 q=28.0 size=    1270kB time=00:00:06.03 bitrate=1723.7kbits/s speed=0.749x    
frame=  216 fps= 25 q=28.0 size=    1339kB time=00:00:06.52 bitrate=1680.5kbits/s speed=0.763x    
frame=  228 fps= 25 q=28.0 size=    1443kB time=00:00:07.06 bitrate=1674.1kbits/s speed=0.779x    
frame=  241 fps= 25 q=28.0 size=    1558kB time=00:00:07.55 bitrate=1690.0kbits/s speed=0.789x    
frame=  254 fps= 25 q=28.0 size=    1654kB time=00:00:08.04 bitrate=1685.0kbits/s speed=0.799x    
frame=  266 fps= 25 q=28.0 size=    1738kB time=00:00:08.55 bitrate=1664.6kbits/s speed=0.809x    
frame=  279 fps= 25 q=28.0 size=    1750kB time=00:00:09.06 bitrate=1581.2kbits/s speed=0.818x    
frame=  291 fps= 25 q=28.0 size=    1765kB time=00:00:09.55 bitrate=1512.7kbits/s speed=0.825x    
frame=  300 fps= 25 q=28.0 size=    1779kB time=00:00:11.73 bitrate=1242.1kbits/s speed=0.971x    
frame=  300 fps= 24 q=-1.0 Lsize=    1917kB time=00:00:12.01 bitrate=1307.2kbits/s speed=0.955x    
video:1720kB audio:188kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.488004%
[aac @ 0x75fc582520] Qavg: 221.585
[libx264 @ 0x75fc583aa0] frame I:2     Avg QP:15.83  size: 78710
[libx264 @ 0x75fc583aa0] frame P:185   Avg QP:21.02  size:  7259
[libx264 @ 0x75fc583aa0] frame B:113   Avg QP:26.59  size:  2298
[libx264 @ 0x75fc583aa0] consecutive B-frames: 46.3% 10.0%  1.0% 42.7%
[libx264 @ 0x75fc583aa0] mb I  I16..4: 22.1% 32.5% 45.4%
[libx264 @ 0x75fc583aa0] mb P  I16..4:  0.8%  1.4%  0.2%  P16..4: 25.2%  6.3%  3.1%  0.0%  0.0%    skip:63.0%
[libx264 @ 0x75fc583aa0] mb B  I16..4:  0.1%  0.2%  0.0%  B16..8: 37.3%  1.6%  0.2%  direct: 0.4%  skip:60.2%  L0:47.3% L1:49.6% BI: 3.0%
[libx264 @ 0x75fc583aa0] 8x8 transform intra:50.5% inter:58.1%
[libx264 @ 0x75fc583aa0] coded y,uvDC,uvAC intra: 49.4% 65.2% 22.9% inter: 7.7% 10.0% 0.5%
[libx264 @ 0x75fc583aa0] i16 v,h,dc,p: 29% 32% 11% 28%
[libx264 @ 0x75fc583aa0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 21% 23%  4%  5%  6%  5%  5%  5%
[libx264 @ 0x75fc583aa0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 15% 11%  8%  8%  9%  7% 12%  7%
[libx264 @ 0x75fc583aa0] i8c dc,h,v,p: 51% 20% 21%  8%
[libx264 @ 0x75fc583aa0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x75fc583aa0] ref P L0: 79.7% 11.4%  7.7%  1.2%
[libx264 @ 0x75fc583aa0] ref B L0: 96.8%  2.9%  0.4%
[libx264 @ 0x75fc583aa0] ref B L1: 97.7%  2.3%
[libx264 @ 0x75fc583aa0] kb/s:1173.39

Answer 1

我终于找到了问题所在。在 python 中，ffmpeg 命令是使用 subprocess 模块运行的。输入视频的每个图像都被放入到 ffmpeg 的管道中。在迭代结束时，进程被终止。

但是，音频和视频编码没有并行执行:音频编码没有在视频编码结束时终止。结果，ffmpeg 命令在音频终止之前就被杀死了。