[FFmpeg-user] Strange mapping/tagging/stream correlation behavior

Christian plymouth78 at googlemail.com
Thu Jun 21 20:29:28 CEST 2012


so here comes my second question about ffmpeg on this list!

The map options are not working as I would expect. Infact, i can't
think of a reason why it's behaving this way.
I tried several combinations, to get it working i ended up with this,
which makes no sense to me:

Output #0, ipod, to 'movie.m4v':
    creation_time   : 2011-11-15 15:39:28
    encoder         : Lavf54.6.100
    Stream #0:0(eng): Video: h264 (avc1 / 0x31637661), yuv420p,
1920x800 [SAR 1:1 DAR 12:5], q=2-31, 23.98 fps, 1k tbn, 1k tbc
    Stream #0:1(ger): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 3.0,
s16, 128 kb/s (default)
    Stream #0:2(ger): Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz,
5.1(side), flt, 448 kb/s (default)
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #1:1 -> #0:1 (dca -> libfaac)
  Stream #0:1 -> #0:2 (dca -> ac3)

To accomplish this i used the following options:

[localhost:/Volumes/Various/Movies]% ffmpeg -i movie.mkv -i movie.mkv
-c:v:0:0 copy -c:a:0:1 libfaac -c:a:1:1 ac3 -tag:0 avc1 -tag:1 mp4a
-tag:2 ac-3 -map 0:0 -map 1:1 -map 0:1 movie.m4v

To summarize it up:
a:0:1 is encoded with libfaac, then catched with the third and last
map command, but in the mapping output it is listed as: "Stream #0:1
-> #0:2 (dca -> ac3)".

a:1:1 is encoded with ac3, then catched with the second map command,
but in the mapping output listed as: "Stream #1:1 -> #0:1 (dca ->

For me, the "tag" option seems to be similar confused. Tag:1, getting
mp4a, correlates to second map. But second map is 1:1 which is in turn
encoded to ac3!

Surely, this stuff was given a lot more thought and i'am just
misunderstanding the whole thing. Right?


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