I just ran across MPEG-4 SLS [1] (née "AAZ" for "Advanced Audio Zip", aka HD-AAC), which is a lossless format on top of AAC's MDCT, and which is patented, unfor

I just ran across MPEG-4 SLS [1] (née "AAZ" for "Advanced Audio Zip", aka HD-AAC), which is a lossless format on top of AAC's MDCT, and which is patented, unfortunately. That led me to other coders: DTS-HD Master Audio [2] (née DTS++) and OptimFROG DualStream [3]. OptimFROG's DualStream mode is similar to WavPack's hybrid mode, and DTS-HD MA uses DTS Coherent Acoustics (based on ADPCM), so none of these are based on a perceptual lossy codec besides MPEG-4 SLS. (Sorry to keep replying here, I keep stumbling on interesting things after the edit window closes) [1] https://en.wikipedia.org/wiki/MPEG-4_SLS https://en.wikipedia.org/wiki/MPEG-4_SLS [2] https://en.wikipedia.org/wiki/DTS-HD_Master_Audio https://en.wikipedia.org/wiki/DTS-HD_Master_Audio [3] http://losslessaudio.org/DualStream.php http://losslessaudio.org/DualStream.php