[FFmpeg-user] Mp4 Concat Demuxer Produces Incorrect Output

[Casey Bateman]

Hello,

I am in need of some assistance because of an issue I am seeing using the concat demuxer. I am trying to concatenate two .mp4 files. When I concatenate the two files together using the concat demuxer, the output file will display the first clip at normal speed, then the second clip exponentially faster. After inspecting the Ffmpeg output logs, the only thing that I can see different between these two files, is the tbn. Would the tbn being different on these files effect the output of the concat demuxer?

Concat.txt:
file 'input000.mp4'
file 'input001.mp4'

Command:
ffmpeg -f concat -i concat.txt -c  copy output.mp4

Ffprobe input000.mp4:
ffprobe version N-61821-gc05065a Copyright (c) 2007-2014 the FFmpeg developers
  built on Mar 26 2014 02:09:10 with gcc 4.8.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aa
cenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavp
ack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable
-zlib
  libavutil      52. 69.100 / 52. 69.100
  libavcodec     55. 54.100 / 55. 54.100
  libavformat    55. 35.101 / 55. 35.101
  libavdevice    55. 11.100 / 55. 11.100
  libavfilter     4.  3.100 /  4.  3.100
  libswscale      2.  5.102 /  2.  5.102
  libswresample   0. 18.100 /  0. 18.100
  libpostproc    52.  3.100 / 52.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp/input000.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf55.35.101
  Duration: 00:00:19.00, start: 0.000000, bitrate: 1138 kb/s
    Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yu
v420p, 852x480 [SAR 1:1 DAR 71:40], 1137 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc
(default)
    Metadata:
      handler_name    : VideoHandler

Ffprobe input001.mp4:
ffprobe version N-61821-gc05065a Copyright (c) 2007-2014 the FFmpeg developers
  built on Mar 26 2014 02:09:10 with gcc 4.8.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aa
cenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavp
ack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable
-zlib
  libavutil      52. 69.100 / 52. 69.100
  libavcodec     55. 54.100 / 55. 54.100
  libavformat    55. 35.101 / 55. 35.101
  libavdevice    55. 11.100 / 55. 11.100
  libavfilter     4.  3.100 /  4.  3.100
  libswscale      2.  5.102 /  2.  5.102
  libswresample   0. 18.100 /  0. 18.100
  libpostproc    52.  3.100 / 52.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp/input001.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.78.3
  Duration: 00:00:19.37, start: 0.000000, bitrate: 1099 kb/s
    Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yu
v420p, 852x480 [SAR 1:1 DAR 71:40], 1097 kb/s, 30 fps, 30 tbr, 30 tbn, 60 tbc (d
efault)
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    : VideoHandler

Ffmpeg output:
ffmpeg version N-61821-gc05065a Copyright (c) 2000-2014 the FFmpeg developers
  built on Mar 26 2014 02:09:10 with gcc 4.8.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aa
cenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavp
ack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable
-zlib
  libavutil      52. 69.100 / 52. 69.100
  libavcodec     55. 54.100 / 55. 54.100
  libavformat    55. 35.101 / 55. 35.101
  libavdevice    55. 11.100 / 55. 11.100
  libavfilter     4.  3.100 /  4.  3.100
  libswscale      2.  5.102 /  2.  5.102
  libswresample   0. 18.100 /  0. 18.100
  libpostproc    52.  3.100 / 52.  3.100
[concat @ 0272e700] Estimating duration from bitrate, this may be inaccurate
Input #0, concat, from 'temp/concat.txt':
  Duration: 00:00:00.00, start: 0.000000, bitrate: 1230 kb/s
    Stream #0:0: Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p
, 852x480 [SAR 1:1 DAR 71:40], 1137 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc

frame= 1151 fps=0.0 q=-1.0 Lsize=    5239kB time=00:00:19.00 bitrate=2258.1kbits
/s
video:5233kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing
overhead: 0.108556%



Casey Bateman
Hudl | Software Developer
casey.bateman at hudl.com<mailto:casey.bateman at hudl.com> | 402.817.0060