Aquí está el comando que estoy usando para combinar varios videos:

ffmpeg -i 75_540_38HQ2.mp4 -i 76_70_20.mp4 -i 76_173_80.mp4 -i 81_186_35.mp4 -vcodec copy -acodec copy Mux1.mp4

La resultanteMux1.mp4 no contiene todos los videos. Solo el primer video 75_540_38HQ2.mp4). El tamaño del archivo de la fuente y el video resultante es inferior (como puede ver, el video resultante es un poco más grande que el primer video):

$ ls -lh
-rw-r--r-- 1 dbaker dbaker  42M 2011-03-24 11:59 75_540_38HQ2.mp4
-rw-r--r-- 1 dbaker dbaker 236M 2011-03-24 12:09 76_173_80.mp4
-rw-r--r-- 1 dbaker dbaker  26M 2011-03-24 12:05 76_70_20.mp4
-rw-r--r-- 1 dbaker dbaker  54M 2011-03-24 12:15 81_186_35.mp4
-rw-r--r-- 1 dbaker dbaker  44M 2011-03-24 14:48 Mux1.mp4

Aquí está la salida de laffmpeg comando. Para mí, se ve bien, mostrando las entradas de múltiples fuentes y la única salida.

FFmpeg version SVN-r26402, Copyright (c) 2000-2011 the FFmpeg developers
  built on Mar 21 2011 18:05:32 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil     50.36. 0 / 50.36. 0
  libavcore      0.16. 1 /  0.16. 1
  libavcodec    52.108. 0 / 52.108. 0
  libavformat   52.93. 0 / 52.93. 0
  libavdevice   52. 2. 3 / 52. 2. 3
  libavfilter    1.74. 0 /  1.74. 0
  libswscale     0.12. 0 /  0.12. 0
  libpostproc   51. 2. 0 / 51. 2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '75_540_38HQ2.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.93.0
  Duration: 00:00:29.99, start: 0.000000, bitrate: 11517 kb/s
    Stream #0.0(eng): Video: h264, yuv420p, 1280x960 [PAR 1:1 DAR 4:3], 11575 kb/s, 29.94 fps, 29.97 tbr, 30k tbn, 59.94 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
    Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16, 127 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from '76_70_20.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.93.0
  Duration: 00:00:19.98, start: 0.000000, bitrate: 10901 kb/s
    Stream #1.0(eng): Video: h264, yuv420p, 1280x960 [PAR 1:1 DAR 4:3], 10804 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
    Stream #1.1(eng): Audio: aac, 48000 Hz, stereo, s16, 128 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Input #2, mov,mp4,m4a,3gp,3g2,mj2, from '76_173_80.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.93.0
  Duration: 00:03:09.99, start: 0.000000, bitrate: 10393 kb/s
    Stream #2.0(eng): Video: h264, yuv420p, 1280x960 [PAR 1:1 DAR 4:3], 10321 kb/s, 29.96 fps, 29.97 tbr, 30k tbn, 59.94 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
    Stream #2.1(eng): Audio: aac, 48000 Hz, stereo, s16, 128 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00

Seems stream 0 codec frame rate differs from container frame rate: 119.88 (120000/1001) -> 30000.00 (30000/1)
Input #3, mov,mp4,m4a,3gp,3g2,mj2, from '81_186_35.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.93.0
  Duration: 00:00:35.00, start: 0.000000, bitrate: 12700 kb/s
    Stream #3.0(eng): Video: h264, yuv420p, 1280x720 [PAR 1:1 DAR 16:9], 12620 kb/s, 59.91 fps, 30k tbr, 60k tbn, 119.88 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
    Stream #3.1(eng): Audio: aac, 48000 Hz, stereo, s16, 128 kb/s
    ,Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'Mux1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf52.93.0
    Stream #0.0(eng): Video: libx264, yuv420p, 1280x960 [PAR 1:1 DAR 4:3], q=2-31, 11575 kb/s, 30k tbn, 29.97 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
    Stream #0.1(eng): Audio: libfaac, 48000 Hz, stereo, 128 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #2.1 -> #0.1
Press [q] to stop encoding
frame=  883 fps=632 q=-1.0 Lsize=   44730kB time=29.40 bitrate=12465.1kbits/s    
video:41678kB audio:2969kB global headers:0kB muxing overhead 0.184548%

¿Estoy haciendo algo cegadoramente estúpido aquí?

os videos de origen provienen de una cámara de video y son pequeños fragmentos tomados conffmpeg -i bigfile.mp4 -ss 20 -t 10 -vcodec copy etc..

¡¡Montones de gracias!! Dave

Edit: no pude resolverlo, así que solo uso una herramienta GUI avidemux. Parecía agregar muy bien los MP4.

ebe ser un problema con los MP4 o solo con los que salen de una cámara gopr