我使用以下命令分割文件，但自从从 12.04 升级到 14.04 后，它出现了错误。生成的文件只包含音频，没有视频。
avconv -i cam.mp4 -ss 00:14:00 -t 00:28:00 -c:a copy -c:v copy output-clip.mp4
有什么建议可以解决这个问题吗？
完整输出：
built on Aug 10 2014 18:16:02 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
[mov,mp4,m4a,3gp,3g2,mj2 @ 0xb6d000] multiple edit list entries, a/v desync might occur, patch welcome
[h264 @ 0xb74520] A non-intra slice in an IDR NAL unit.
[h264 @ 0xb74520] decode_slice_header error
[mov,mp4,m4a,3gp,3g2,mj2 @ 0xb6d000] max_analyze_duration reached
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'cam.mp4':
Metadata:
major_brand : isom
minor_version : 0
compatible_brands: mp41avc1qt
creation_time : 2014-08-26 08:07:33
encoder : vlc 2.0.8 stream output
encoder-eng : vlc 2.0.8 stream output
Duration: 01:02:16.95, start: 0.000000, bitrate: 2023 kb/s
Stream #0.0(eng): Video: h264, 720x576, PAR 16:15 DAR 4:3, 1001 tbn
Metadata:
creation_time : 2014-08-26 08:07:33
Stream #0.1(eng): Audio: mp2, 44100 Hz, stereo, s16p, 127 kb/s
Metadata:
creation_time : 2014-08-26 08:07:33
Stream #0.2(eng): Video: h264 (High), yuv420p, 720x576 [PAR 16:15 DAR 4:3], 1887 kb/s, 25 fps, 25 tbr, 1001 tbn, 50 tbc
Metadata:
creation_time : 2014-08-26 08:07:33
Output #0, mp4, to 'output-clip.mp4':
Metadata:
major_brand : isom
minor_version : 0
compatible_brands: mp41avc1qt
creation_time : 2014-08-26 08:07:33
encoder-eng : vlc 2.0.8 stream output
encoder : Lavf54.20.4
Stream #0.0(eng): Video: libx264, 720x576 [PAR 16:15 DAR 4:3], q=2-31, 1001 tbn, 1001 tbc
Metadata:
creation_time : 2014-08-26 08:07:33
Stream #0.1(eng): Audio: mp2, 44100 Hz, stereo, 127 kb/s
Metadata:
creation_time : 2014-08-26 08:07:33
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:1 -> #0:1 (copy)
Press ctrl-c to stop encoding
frame= 0 fps= 0 q=-1.0 size= 0kB time=10000000000.00 bitrate= 0.0kbiframe= 0 fps= 0 q=-1.0 size= 0kB time=10000000000.00 bitrate= 0.0kbiframe= 0 fps= 0 q=-1.0 size= 0kB time=10000000000.00 bitrate= 0.0kbiframe= 0 fps= 0 q=-1.0 size= 0kB time=10000000000.00 bitrate= 0.0kbiframe= 0 fps= 0 q=-1.0 size= 0kB time=10000000000.00 bitrate= 0.0kbiframe= 0 fps= 0 q=-1.0 size= 0kB time=1090.27 bitrate= 0.0kbits/s frame= 0 fps= 0 q=-1.0 size= 0kB time=1455.51 bitrate= 0.0kbits/s frame= 0 fps= 0 q=-1.0 size= 0kB time=1497.23 bitrate= 0.0kbits/s frame= 0 fps= 0 q=-1.0 size= 0kB time=1680.01 bitrate= 0.0kbits/s frame= 0 fps= 0 q=-1.0 size= 0kB time=1680.01 bitrate= 0.0kbits/s frame= 0 fps= 0 q=-1.0 size= 0kB time=1680.01 bitrate= 0.0kbits/s frame= 0 fps= 0 q=-1.0 Lsize= 26770kB time=1680.01 bitrate= 130.5kbits/s
video:0kB audio:26190kB global headers:0kB muxing overhead 2.214985%