FFMPEG 無法修剪剪輯的開頭

Question

我有兩個按順序拍攝的.MTS文件，我想將它們修剪到前五秒。 此命令適用於第一個文件：

ffmpeg -ss 0 -to 5 -i 00117.MTS -vcodec copy -acodec copy start_00117.MTS

結果是 5 秒和 17 MB，而不是原始的 12 分鍾和 2 GB。

第二個文件上的相同命令失敗：

ffmpeg -ss 0 -to 5 -i 00118.MTS -vcodec copy -acodec copy start_00118.MTS

結果是 12 分鍾和 2 GB，就像它的原始文件一樣。

問題是什么？

完整日志：

$ rm start_00117.MTS; ffmpeg -ss 0 -to 5 -i 00117.MTS -vcodec copy -acodec copy start_00117.MTS
ffmpeg version 4.1.4 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 10.0.1 (clang-1001.0.46.4)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1.4_1 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include/darwin' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-videotoolbox --disable-libjack --disable-indev=jack --enable-libaom --enable-libsoxr
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Input #0, mpegts, from '00117.MTS':
  Duration: 00:12:36.02, start: 1.040000, bitrate: 22490 kb/s
  Program 1 
    Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 50 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s
    Stream #0:2[0x1200]: Subtitle: hdmv_pgs_subtitle ([144][0][0][0] / 0x0090), 1920x1080
Output #0, mpegts, to 'start_00117.MTS':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 25 fps, 50 tbr, 90k tbn, 90k tbc
    Stream #0:1: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=  304 fps=0.0 q=-1.0 Lsize=   16601kB time=00:00:06.02 bitrate=22590.4kbits/s speed=25.8x    
video:15162kB audio:189kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 8.143849%
$ rm start_00118.MTS; ffmpeg -ss 0 -to 5 -i 00118.MTS -vcodec copy -acodec copy start_00118.MTS
rm: start_00118.MTS: No such file or directory
ffmpeg version 4.1.4 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 10.0.1 (clang-1001.0.46.4)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1.4_1 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include/darwin' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-videotoolbox --disable-libjack --disable-indev=jack --enable-libaom --enable-libsoxr
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Input #0, mpegts, from '00118.MTS':
  Duration: 00:12:36.59, start: 756.592000, bitrate: 22471 kb/s
  Program 1 
    Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 50 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s
    Stream #0:2[0x1200]: Subtitle: hdmv_pgs_subtitle ([144][0][0][0] / 0x0090), 1920x1080
Output #0, mpegts, to 'start_00118.MTS':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 25 fps, 50 tbr, 90k tbn, 90k tbc
    Stream #0:1: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=37804 fps=923 q=-1.0 Lsize= 2130467kB time=00:12:36.54 bitrate=23069.0kbits/s speed=18.5x    
video:1946718kB audio:23627kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 8.126621%

Answer 1

這看起來是 input -to的錯誤。 現在，使用-ss和-to作為輸出選項。

ffmpeg -i 00118.MTS -ss 0 -to 5 -c copy start_00118.MTS

Answer 2

在多種情況下使用-c copy可能會失敗，這就是其中之一。 從文檔：

流復制是通過將copy參數提供給-codec選項來選擇的模式。 它使 ffmpeg 省略了指定流的解碼和編碼步驟，因此它只進行解復用和復用。 它對於更改容器格式或修改容器級元數據很有用。 在這種情況下，上圖將簡化為：

 _______ ______________ ________ | | | | | | | input | demuxer | encoded data | muxer | output | | file | ---------> | packets | -------> | file | |_______| |______________| |________|

由於沒有解碼或編碼，因此速度非常快且沒有質量損失。 但是，由於許多因素，它在某些情況下可能不起作用。

這是一個這樣的因素。 請參閱已關閉的錯誤報告以獲得更長的解釋以及為什么該命令適用於長記錄的第一部分而不是第二部分的巧合。

刪除-c copy （或-vcodec copy -acodec copy ）修復了-vcodec copy -acodec copy情況，即：

ffmpeg -ss 0 -to 5 -i 00122.MTS start_00122.MTS

另請參閱 Gyan 使用-ss和-to作為輸出選項的解決方案，這也解決了極端情況。