I found this command line online for converting videos to H263 .3gp files in Linux:

ffmpeg -i inputfile.avi -s qcif -vcodec h263 -acodec mp3 -ar 8000 -ab 32 -y outputfile.3gp

It seems to be a bit out of date, as it gives:

WARNING: The bitrate parameter is set too low. It takes bits/s as argument, not kbits/s
Unknown encoder 'mp3'

Those two problems are easily fixed:

ffmpeg -i inputfile.avi -s qcif -vcodec h263 -acodec libmp3lame -ar 8000 -ab 32 -y outputfile.3gp

But that gives a different error:

[3gp @ 0x1983b4]track 1: could not find tag for codec
Could not write header for output file #0 (incorrect codec parameters ?)


One can use MPEG-4 instead, since that's supported by the N82 (and other Symbian S60 3rd edition phones, I think)

ffmpeg -i inputfile.avi -f mp4 -vcodec mpeg4 -b 250000 -r 15 -acodec libfaac -ar 24000 -ab 64k -ac 2 -s qvga outputfile.mp4