Any further ideas on this? I've just checked again with the current ffmpeg/bs1770gain versions from sid... and still, the gapless playback of MP3s is broken when files are processed with --overwrite.
It does seem to work when not using --overwrite mode (but -a -o dir),... but that's no big surprise as files are decoded to flac (which is per se gapless), but this is probably not what most people want. Seems a bit as if something is going wrong when the mp3 stream is remuxed or stored again. With the unfortunate removal of python-rgain, bs1770gain seems to be the only remaining replaygain tool in Debian... so it would be really nice if ffmpeg could be made no breaking the output files :-) Cheers, Chris.