使用 ffmpeg 从 .webm 文件中提取子剪辑

Question

我正在尝试从webm文件中提取子剪辑并写入文件mp4。我有以下命令行：

ffmpeg -ss 560 -i input.webm -ss 20 -t 46 -acodec copy -vcodec copy output.mp4

但我收到以下错误：

ffmpeg version 1.2 Copyright (c) 2000-2013 the FFmpeg developers
  built on Mar 22 2013 10:42:11 with gcc 4.7.2 (GCC)
  configuration: --prefix=/path/to/installations --enable-shared --enable-gpl --en
able-nonfree --enable-version3 --enable-libx264                           
  libavutil      52. 18.100 / 52. 18.100
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.104 / 54. 63.104
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 42.103 /  3. 42.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, matroska,webm, from '/path/to/input.webm':                                          
  Duration: 01:13:20.32, start: 0.000000, bitrate: 2006 kb/s
    Stream #0:0(eng): Video: vp8, yuv420p, 640x480, SAR 1:1 DAR 4:3, 30 fp,
 30 tbr, 1k tbn, 1k tbc (default)                                         
    Stream #0:1(eng): Audio: vorbis, 44100 Hz, stereo, fltp (default)
[mp4 @ 0x1493c340] track 0: could not find tag, codec not currently support
ed in container                                                           
Output #0, mp4, to '/path/to/output.mp4':                         
  Metadata:
    encoder         : Lavf54.63.104
    Stream #0:0(eng): Video: vp8, yuv420p, 640x480 [SAR 1:1 DAR 4:3], q=2-3
1, 30 fps, 90k tbn, 1k tbc (default)                                      
    Stream #0:1(eng): Audio: vorbis ([221][0][0][0] / 0x00DD), 44100 Hz, st
ereo (default)                                                            
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Could not write header for output file #0 (incorrect codec parameters ?): O
peration not permitted                                                    

奇怪的是，下面可以很好地用于从提取文件mp4到mp4

ffmpeg -ss 560 -i input.mp4 -ss 20 -t 46 -acodec copy -vcodec copy output.mp4

Answer 1

... codec not currently supported in container

MP4 容器不接受 VP8 视频和 Vorbis 音频流 ( -acodec copy -vcodec copy)。要对此进行测试，请将输出文件名更改为output.mkv或output.webm，该作业将起作用。如果输出容器必须是 MP4，则您需要在某个时候进行转码。