Transcode_Wiki: Command Examples/Multi-Audio AVI-Files

Before you start, try to find the best bitrate for video encoding with multiple audio tracks by using tcprobe with option -b n*128, for example, if you want n MP3 audio tracks with 128kbps bitrate each.

A first session produces the file movie.avi with a single audio track -a 0. Now, we use a similar command to extract a second audio track from the source. Suppose, we used the example modules vmod,amod for video and audio extraction.

The second session goes as follows. This session will be much faster, since no video is de/encoded.

(1) transcode the second audio track "-a 1" into an AVI container file named add-on.avi This looks like

 transcode -i (...) -x null,amod -g 0x0 -y raw -a 1 -o add-on.avi -u 50

The resulting file is only a temporary file but enables proper processing with avimerge. The export module -y raw is fine, since it writes proper (0 bytes) video frames. Set video import module to null. If all goes well, both files should be identical with respect to the number of frames. Choose the proper audio track with -a. Try also to increase the internal buffers -u for speedup.

(2) merge this track into movie.avi

 avimerge -i movie.avi -o dualaudiomovie.avi -p add-on.avi

(3) Repeat steps (1-2) for even more audio tracks, if you wish. For best results, I recommend doing this procedure with a single AVI movie file. All avi* post-processing tools now support multiple audio tracks.