How to segment a video and then concatenate back i

问题:

I am surveying on distributed video transcoding with FFmpeg. I have found that there is a good script on https://github.com/nergdron/dve/blob/master/dve.

The script mainly uses the segment and concatenate filters of FFmpeg. I want to do a simple test first. However, I can not split the video into segments and then concatenate back to original video (with the same codec). I have tried with the following command:

a. Chunk the video

ffmpeg -fflags +genpts -i Test.avi -map 0 -codec copy -f segment -segment_format avi -v error chunk-%03d.seg

b. Building the chunking list:

#!/bin/bash -e
set -e
echo "ffconcat version 1.0" > concat.txt
for f in `ls chunk-*.seg | sort`; do
echo "file $f" >> concat.txt
done

c. Concatenate the chunks

ffmpeg  -y -v error -i concat.txt -f concat -map 0 -c copy -f avi output.avi

Then when I run ffprobe I get the following message which says it is a non-interleaved AVI:

    ffprobe version N-82301-g1bbb18f Copyright (c) 2007-2016 the FFmpeg developers
  built with gcc 5.4.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-libebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --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. 35.100 / 55. 35.100
  libavcodec     57. 66.101 / 57. 66.101
  libavformat    57. 57.100 / 57. 57.100
  libavdevice    57.  2.100 / 57.  2.100
  libavfilter     6. 66.100 /  6. 66.100
  libswscale      4.  3.100 /  4.  3.100
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
[avi @ 00000000028e3700] non-interleaved AVI
Input #0, avi, from 'output.avi':
  Metadata:
    encoder         : Lavf57.57.100
  Duration: 74:43:47.82, start: 0.000000, bitrate: 17 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 640x368 [SAR 1:1 DAR 40:23], 23.98 fps, 23.98 tbr, 23.98 tbn, 23.98 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, s16p, 112 kb/s

I have tried a few other things without success. Any help would be greatly appreciated. Thanks in advance!!

回答1:

The segment muxer, by default, preserves input timestamps. And the way that the concat demuxer works is that it adds the relative timestamp of incoming files to the net duration processed so far. e.g. If first file is 10 seconds, and second file is 5 seconds but with a start time of 10 seconds. Then the first frame of the 2nd file in the output will have a timestamp of 20 seconds. This, I believe, is leading to the AVI warning.

Also keeping in mind that the segment muxer can create the concat list for you, use

ffmpeg -fflags +genpts -i Test.avi -map 0 -c copy -f segment -segment_format avi -segment_list Test.ffcat -reset_timestamps 1 -v error chunk-%03d.seg

and then

ffmpeg -y -v error -i Test.ffcat -map 0 -c copy output.avi