ffmpeg视频剪切错误：音频不同步

Question

我希望能够将视频上传到服务器并根据需要进行剪切。

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所以，首先我对其进行编码：

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ffmpeg -i input.mp4 -vcodec h264 -acodec aac -strict -2 -preset slow output.mp4\n

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然后我尝试剪掉它：

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ffmpeg -i input.mp4 -ss 00:30:00 -c copy -t 00:30:00 output.mp4\n

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并且音频和视频轨道不同步，音频大约延迟了10秒......

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那么，有没有办法修复 ffmpeg 剪切或者有其他方法在 Linux 中剪切视频？

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更新\n这是剪切时的 ffmpeg 输出

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ffmpeg version 2.8 Copyright (c) 2000-2015 the FFmpeg developers\n  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)\n  configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libdcadec --enable-libfreetype --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvo-aacenc --enable-libvidstab\n  libavutil      54. 31.100 / 54. 31.100\n  libavcodec     56. 60.100 / 56. 60.100\n  libavformat    56. 40.101 / 56. 40.101\n  libavdevice    56.  4.100 / 56.  4.100\n  libavfilter     5. 40.101 /  5. 40.101\n  libavresample   2.  1.  0 /  2.  1.  0\n  libswscale      3.  1.101 /  3.  1.101\n  libswresample   1.  2.101 /  1.  2.101\n  libpostproc    53.  3.100 / 53.  3.100\nInput #0, mov,mp4,m4a,3gp,3g2,mj2, from '/mnt/storage/19b7c850b0c05c6f6fd26a7eda34841dddd55e33.mp4.prot':\n  Metadata:\n    major_brand     : isom\n    minor_version   : 512\n    compatible_brands: isomiso2avc1mp41\n    encoder         : Lavf56.40.101\n  Duration: 00:45:24.92, start: 0.042667, bitrate: 492 kb/s\n    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 736x414 [SAR 1:1 DAR 16:9], 345 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)\n    Metadata:\n      handler_name    : VideoHandler\n    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 139 kb/s (default)\n    Metadata:\n      handler_name    : SoundHandler\n[mp4 @ 0x2aff400] Codec for stream 0 does not use global headers but container format requires global headers\n[mp4 @ 0x2aff400] Codec for stream 1 does not use global headers but container format requires global headers\nOutput #0, mp4, to '/home/videohosting/uploads/output7.mp4':\n  Metadata:\n    major_brand     : isom\n    minor_version   : 512\n    compatible_brands: isomiso2avc1mp41\n    encoder         : Lavf56.40.101\n    Stream #0:0(eng): Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 736x414 [SAR 1:1 DAR 16:9], q=2-31, 345 kb/s, 25 fps, 25 tbr, 12800 tbn, 12800 tbc (default)\n    Metadata:\n      handler_name    : VideoHandler\n    Stream #0:1(eng): Audio: aac ([64][0][0][0] / 0x0040), 48000 Hz, stereo, 139 kb/s (default)\n    Metadata:\n      handler_name    : SoundHandler\nStream mapping:\n  Stream #0:0 -> #0:0 (copy)\n  Stream #0:1 -> #0:1 (copy)\nPress [q] to stop, [?] for help\nframe=22873 fps=22858 q=-1.0 Lsize=   53406kB time=00:15:24.87 bitrate= 473.0kbits/s\nvideo:36732kB audio:15765kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.732541%\n

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更新2

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同时剪切和转换只会输出空视频文件

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命令

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ffmpeg -ss 00:05:00 -i input.mp4 -t 00:10:00 -vcodec h264 -acodec aac -strict -2 -preset slow output.mp4

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输出

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ffmpeg version 2.8 Copyright (c) 2000-2015 the FFmpeg developers\n built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)\n configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libdcadec --enable-libfreetype --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvo-aacenc --enable-libvidstab\n libavutil 54. 31.100 / 54. 31.100\n libavcodec 56. 60.100 / 56. 60.100\n libavformat 56. 40.101 / 56. 40.101\n libavdevice 56. 4.100 / 56. 4.100\n libavfilter 5. 40.101 / 5. 40.101\n libavresample 2. 1. 0 / 2. 1. 0\n libswscale 3. 1.101 / 3. 1.101\n libswresample 1. 2.101 / 1. 2.101\n libpostproc 53. 3.100 / 53. 3.100\nGuessed Channel Layout for Input Stream #0.0 : stereo\nInput #0, asf, from '/mnt/storage/tmp/e7ff19971eab45abf06d034444d94549ef3b5584.mp4':\n Metadata:\n SfOriginalFPS : 299700\n WMFSDKVersion : 11.0.6001.7000\n WMFSDKNeeded : 0.0.0.0000\n comment : Footage: Small World Productions, Inc; Tourism New Zealand | Producer: Gary F. Spradling | Music: Steve Ball\n title : Wildlife in HD\n copyright : \xc2\xa9 2008 Microsoft Corporation\n IsVBR : 0\n DeviceConformanceTemplate: AP@L3\n Duration: 00:00:30.09, start: 0.000000, bitrate: 6977 kb/s\n Stream #0:0(eng): Audio: wmav2 (a[1][0][0] / 0x0161), 44100 Hz, 2 channels, fltp, 192 kb/s\n Stream #0:1(eng): Video: vc1 (Advanced) (WVC1 / 0x31435657), yuv420p, 1280x720, 5942 kb/s, 29.97 fps, 29.97 tbr, 1k tbn, 1k tbc\n[libx264 @ 0x306fb80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX\n[libx264 @ 0x306fb80] profile High, level 3.1\n[libx264 @ 0x306fb80] 264 - core 142 r2491 24e4fed - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=5 deblock=1:0:0 analyse=0x3:0x113 me=umh subme=8 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=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=2 b_bias=0 direct=3 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=50 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00\nOutput #0, mp4, to '/home/videohosting/uploads/output6.mp4':\n Metadata:\n SfOriginalFPS : 299700\n WMFSDKVersion : 11.0.6001.7000\n WMFSDKNeeded : 0.0.0.0000\n comment : Footage: Small World Productions, Inc; Tourism New Zealand | Producer: Gary F. Spradling | Music: Steve Ball\n title : Wildlife in HD\n copyright : \xc2\xa9 2008 Microsoft Corporation\n IsVBR : 0\n DeviceConformanceTemplate: AP@L3\n encoder : Lavf56.40.101\n Stream #0:0(eng): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc\n Metadata:\n encoder : Lavc56.60.100 libx264\n Stream #0:1(eng): Audio: aac ([64][0][0][0] / 0x0040), 44100 Hz, stereo, fltp, 128 kb/s\n Metadata:\n encoder : Lavc56.60.100 aac\nStream mapping:\n Stream #0:1 -> #0:0 (vc1 (native) -> h264 (libx264))\n Stream #0:0 -> #0:1 (wmav2 (native) -> aac (native))\nPress [q] to stop, [?] for help\nframe= 0 fps=0.0 q=0.0 Lsize= 0kB time=00:00:00.00 bitrate=N/A\nvideo:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown\n

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Answer 1

我遇到了类似的问题，并通过以下方式解决了，也许对未来的读者有所帮助。

ffmpeg -i test.mp4 -ss 2 -to 10 -c:v copy -c:a aac out.mp4

也就是说，我重新编码了音频。这样，音频就同步了。我认为这没有什么区别，但请注意，我的用例需要该-to选项而不是-t.

Answer 2

由于关键帧的存在，组合-ss和-t选项-c copy会导致视频不同步和/或持续时间不精确。

更好的方法是进行一个解码/编码周期（尽管这会导致一些质量损失）以获得更好的时序。同时切割和转换是一个更好的选择，并且没有上述缺点。