steve@desktop:~/Asztal$ ffmpeg -i video.mp4 -i audio.mp3 -vcodec copy out.mp4
ffmpeg version 0.8.7-6:0.8.7-1ubuntu2, Copyright (c) 2000-2013 the Libav developers
built on Oct 11 2013 08:46:16 with gcc 4.8.1
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
Input #0, avi, from 'video.mp4':
Metadata:
encoder : MEncoder svn r34540 (Ubuntu), built with gcc-4.7
Duration: 00:04:24.66, start: 0.000000, bitrate: 1166 kb/s
Stream #0.0: Video: mpeg4 (Simple Profile), yuv420p, 1024x768 [PAR 1:1 DAR 4:3], 24 tbr, 24 tbn, 24 tbc
[mp3 @ 0x9852f00] max_analyze_duration reached
[mp3 @ 0x9852f00] Estimating duration from bitrate, this may be inaccurate
Input #1, mp3, from 'audio.mp3':
Duration: 00:14:48.48, start: 0.000000, bitrate: 128 kb/s
Stream #1.0: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
encoder 'aac' is experimental and might produce bad results.
Add '-strict experimental' if you want to use it.
steve@desktop:~/Asztal$
A hang nem is aac...
steve@desktop:~/Asztal$ file audio.mp3
audio.mp3: MPEG ADTS, layer III, v1, 128 kbps, 44.1 kHz, JntStereo
steve@desktop:~/Asztal$