I realized too late SAO = Session At Once. Oops.
I know that audio tracks which don't end at the correct sector boundary will have an audible gap when burned and played back. The CDR burned from .wav files is fine. I then converted those files to .flac, and that burned CDR has some gaps. Not between every song, but some. The tracks do not have any sector boundary errors, so what's causing the gaps, the Directshow filter?
A single .flac file with multiple cue/track points, which I tried later, burns and plays without gaps. But most of my music is individual tracks.
Not sure what to try next. Any ideas? Would more information help? Has anyone else tried burning gapless FLACs? Or any other lossless compressed audio, for that matter.