needed to merge some ogg vorbis files into a single file, after searching a bit, I find out that ogmtools< operates on audio ogg files using any codec and on video ogm files using any codecs

$ ogmcat file1.ogg file2.ogg file3.ogg -o merged.ogg
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as for avi files, you can use avimerge from transcode<

$ avimerge -i file1.avi file2.avi file3.avi -o merged.avi
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mpegs are even nicer, you can simply concatenate them together

$ cat file1.mpg file2.mpg file3.mpg > merged.mpg
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both transcode and ogmtools are available as mandrake packages, transcode is in Mandrake PLF Repository< and ogmtools is in Mandrake Contrib Repository<