[FFmpeg-user] Trouble creating a mp4 remuxer.

[Anders Rein]

I am trying to create a mp4 remuxer. I open the source file and have 
copied all streams with all relevant codec info from the source stream 
to the output stream, but when I call avformat_write_header I get an 
error message:

[mp4 @ 0x61534a0] Tag mp4a/0x6134706d incompatible with output codec id 
'86018'

I get the same error for all codecs I try to use and it is only for mp4. 
If I try to use ts files. I works perfectly.

Does anyone have any clue what the problem could be?