ffmpeg 不能正确使用 mkv

Question

现在我正在尝试使用 ffmpeg 命令修剪 mkv 文件。

ffmpeg -y -i 1.mkv -filter_complex "[0:0]trim=start=201:duration=28,setpts=PTS-STARTPTS" a.mp4

处理后用length(28s)创建了a.mp4，但是有问题。

1. 视频在播放时有些抖动。
2. 尽管播放已超过 28 秒，但音频仍在继续。

那么你们能告诉我我能做什么吗？

ffmpeg 处理时出现如下错误：

D:\Work\ffmpeg\files> ffmpeg -y -i 1.mkv -filter_complex "[0:0]trim=start=201:duration=28,setpts=PTS-STARTPTS" a.mp4
ffmpeg version N-77883-gd7c75a5 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.2.0 (GCC)
  configuration: --disable-static --enable-shared --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 13.100 / 55. 13.100
  libavcodec     57. 22.100 / 57. 22.100
  libavformat    57. 21.101 / 57. 21.101
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 25.100 /  6. 25.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Guessed Channel Layout for  Input Stream #0.1 : mono
Input #0, matroska,webm, from '1.mkv':
  Metadata:
    ENCODER         : Lavf56.1.0
  Duration: 00:35:40.08, start: 0.000000, bitrate: 348 kb/s
    Stream #0:0: Video: vp8, yuv420p, 640x480, SAR 1:1 DAR 4:3, 29.97 fps, 29.97 tbr, 1k tbn, 1k tbc
    Stream #0:1: Audio: pcm_mulaw ([7][0][0][0] / 0x0007), 8000 Hz, 1 channels, s16, 64 kb/s
[libx264 @ 000002859baf3300] using SAR=1/1
[libx264 @ 000002859baf3300] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 000002859baf3300] profile High, level 3.0
[libx264 @ 000002859baf3300] 264 - core 148 r2638 7599210 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - 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
Output #0, mp4, to 'a.mp4':
  Metadata:
    encoder         : Lavf57.21.101
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 640x480 [SAR 1:1 DAR 4:3], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc
    Metadata:
      encoder         : Lavc57.22.100 libx264
    Side data:
      unknown side data type 10 (24 bytes)
    Stream #0:1: Audio: aac (LC) ([64][0][0][0] / 0x0040), 8000 Hz, mono, fltp, 48 kb/s
    Metadata:
      encoder         : Lavc57.22.100 aac
Stream mapping:
  Stream #0:0 (vp8) -> trim (graph 0)
  setpts (graph 0) -> Stream #0:0 (libx264)
  Stream #0:1 -> #0:1 (pcm_mulaw (native) -> aac (native))
Press [q] to stop, [?] for help
[vp8 @ 000002859d9ae460] Discarding interframe without a prior keyframe!
[vp8 @ 000002859d9aeb00] Discarding interframe without a prior keyframe!
[vp8 @ 000002859e8eee40] Discarding interframe without a prior keyframe!
[vp8 @ 000002859e8f5460] Discarding interframe without a prior keyframe!
Error while decoding stream #0:0: Invalid data found when processing input
    Last message repeated 3 times
frame=    0 fps=0.0 q=0.0 size=      62kB time=00:00:22.27 bitrate=  22.6kbits/s
frame=    0 fps=0.0 q=0.0 size=     154kB time=00:00:41.08 bitrate=  30.6kbits/s
frame=    0 fps=0.0 q=0.0 size=     255kB time=00:01:02.20 bitrate=  33.6kbits/s
frame=    0 fps=0.0 q=0.0 size=     340kB time=00:01:19.34 bitrate=  35.1kbits/s
frame=    0 fps=0.0 q=0.0 size=     423kB time=00:01:39.31 bitrate=  34.9kbits/s
frame=   88 fps= 29 q=29.0 size=     518kB time=00:01:43.79 bitrate=  40.9kbits/
frame=  140 fps= 40 q=29.0 size=     613kB time=00:01:45.46 bitrate=  47.6kbits/
frame=  194 fps= 48 q=29.0 size=     719kB time=00:01:47.38 bitrate=  54.8kbits/

...


frame=  839 fps= 14 q=29.0 size=   10881kB time=00:34:51.52 bitrate=  42.6kbits/
frame=  839 fps= 14 q=29.0 size=   10962kB time=00:35:10.46 bitrate=  42.5kbits/
frame=  839 fps= 14 q=29.0 size=   11031kB time=00:35:25.44 bitrate=  42.5kbits/
frame=  839 fps= 14 q=-1.0 Lsize=   11266kB time=00:35:40.16 bitrate=  43.1kbits/s dup=284 drop=328 speed=34.6x
video:1083kB audio:10104kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.706855%
[libx264 @ 000002859baf3300] frame I:4     Avg QP:15.24  size: 22651
[libx264 @ 000002859baf3300] frame P:305   Avg QP:19.95  size:  2626
[libx264 @ 000002859baf3300] frame B:530   Avg QP:25.41  size:   408
[libx264 @ 000002859baf3300] consecutive B-frames: 15.7%  0.0%  0.4% 83.9%
[libx264 @ 000002859baf3300] mb I  I16..4: 15.9% 63.7% 20.4%
[libx264 @ 000002859baf3300] mb P  I16..4:  0.3%  1.9%  0.3%  P16..4: 22.3%  6.2%  2.4%  0.0%  0.0%    skip:66.5%
[libx264 @ 000002859baf3300] mb B  I16..4:  0.0%  0.1%  0.0%  B16..8: 16.1%  0.6%  0.1%  direct: 0.2%  skip:82.9%  L0:48.2% L1:48.5% BI: 3.4%
[libx264 @ 000002859baf3300] 8x8 transform intra:71.1% inter:71.4%
[libx264 @ 000002859baf3300] coded y,uvDC,uvAC intra: 72.2% 78.3% 40.7% inter: 5.9% 4.0% 0.1%
[libx264 @ 000002859baf3300] i16 v,h,dc,p: 29% 30% 21% 20%
[libx264 @ 000002859baf3300] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 28% 18% 14%  5%  6%  9%  6%  9%  6%
[libx264 @ 000002859baf3300] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 38% 20% 11%  5%  5%  7%  5%  6%  4%
[libx264 @ 000002859baf3300] i8c dc,h,v,p: 46% 16% 27% 11%
[libx264 @ 000002859baf3300] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 000002859baf3300] ref P L0: 63.4% 21.5% 11.5%  3.6%
[libx264 @ 000002859baf3300] ref B L0: 92.6%  6.4%  1.0%
[libx264 @ 000002859baf3300] ref B L1: 96.4%  3.6%
[libx264 @ 000002859baf3300] kb/s:316.59
[aac @ 000002859baf4400] Qavg: 65377.508

D:\Work\ffmpeg\files>

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Answer 1

试试这两个步骤：

ffmpeg -y -i 1.mkv -c copy 1new.mkv

ffmpeg -y -i 1new.mkv -vf "trim=start=201:duration=28,setpts=PTS-STARTPTS" -af "atrim=start=201:duration=28,asetpts=PTS-STARTPTS" a.mp4

我已经添加了第一步，因为我在格式错误的 MKV 中看到了这个错误 - Discarding interframe without a prior keyframe，ffmpeg 无法正确读取这些错误。重新包装通常可以解决这个问题。

你可能应该升级你的 ffmpeg，这是一个相当老的版本。