使用 ffmpeg 剪切視頻時的空流

Question

當我嘗試剪切視頻時，它輸出一個空流（262 字節視頻，持續時間為 0 秒）。 希望有任何見解，謝謝。

使用的命令： ffmpeg -i /path/to/long/video.mp4 -ss 37.69 -t 4.96 -c copy /path/to/short/video.mp4

但是，當我執行以下（更不准確的）命令時，它會輸出視頻。 這個視頻也有一些問題，因為最后一幀重復了幾次，使視頻長了一秒鍾（凍結圖像一秒鍾）。

ffmpeg -ss 37.69 -i /path/to/long/video.mp4 -t 4.96 -c copy /path/to/short/video.mp4

ffmpeg 版本： ffmpeg version 3.4.6-0ubuntu0.18.04.1

這兩個命令的輸出是：

第一條命令：

  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/proj/vondrick/datasets/HowTo100M/video/Cars_&_Other_Vehicles/Motorcycles/52907/video_nVbIUDjzWY4.mp4':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: iso6avc1mp41
    creation_time   : 2015-06-26T00:39:04.000000Z
  Duration: 00:07:14.40, start: 0.000000, bitrate: 244 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 426x240 [SAR 1:1 DAR 71:40], 2 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc (default)
    Metadata:
      creation_time   : 2015-06-26T00:39:04.000000Z
      handler_name    : VideoHandler
Output #0, mp4, to '/proj/vondrick/datasets/HowTo100M/cropped_video/Cars_&_Other_Vehicles/Motorcycles/52907/nVbIUDjzWY4/video_000000_p.mp4':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: iso6avc1mp41
    encoder         : Lavf57.83.100
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 426x240 [SAR 1:1 DAR 71:40], q=2-31, 2 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 90k tbc (default)
    Metadata:
      creation_time   : 2015-06-26T00:39:04.000000Z
      handler_name    : VideoHandler
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame=    0 fps=0.0 q=-1.0 Lsize=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

第二個命令：

ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/proj/vondrick/datasets/HowTo100M/video/Cars_&_Other_Vehicles/Motorcycles/52907/video_nVbIUDjzWY4.mp4':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: iso6avc1mp41
    creation_time   : 2015-06-26T00:39:04.000000Z
  Duration: 00:07:14.40, start: 0.000000, bitrate: 244 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 426x240 [SAR 1:1 DAR 71:40], 2 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc (default)
    Metadata:
      creation_time   : 2015-06-26T00:39:04.000000Z
      handler_name    : VideoHandler
Output #0, mp4, to '/proj/vondrick/datasets/HowTo100M/cropped_video/Cars_&_Other_Vehicles/Motorcycles/52907/nVbIUDjzWY4/video_000000_3.mp4':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: iso6avc1mp41
    encoder         : Lavf57.83.100
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 426x240 [SAR 1:1 DAR 71:40], q=2-31, 2 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 90k tbc (default)
    Metadata:
      creation_time   : 2015-06-26T00:39:04.000000Z
      handler_name    : VideoHandler
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame=  159 fps=0.0 q=-1.0 Lsize=     159kB time=00:00:04.95 bitrate= 263.0kbits/s speed=1.89e+03x    
video:158kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.909119%

Answer 1

兩個問題：

1. 3.4是舊的。 在做任何其他事情之前更新到最近的構建。 對於 Linux，您可以下載或編譯.

2. 將流復制模式 ( -c copy ) 與 H.264 和其他類似格式一起使用時，不能保證剪切是准確的，因為它需要包括解碼片段所需的所有其他幀。 因此，要么剪切關鍵幀，要么通過刪除-c copy重新編碼。