- Original, 4039kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/orig.wav
- MS ADPCM, 1022kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/ms_adpcm....
- QOA, 812kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/qoa.wav
IMA ADPCM is in the same ballpark as MS ADPCM. ADX (not listed) comes close to QOA, but at 1136kb is also larger than those traditional ADPCM flavors.
MS ADPCM sounds horrible, a lot of unpleasant high-pitched noise. QOA is much better but still audibly degraded from the source.
Not sure I would ship content at this quality.
> What makes QOA work is 1) a reasonably good predictor and 2) storing the scalefactor for a bunch of samples explicitly instead of guessing the right one from context, like ADPCM does.
suggests a comparison with DVI/IMA ADPCM [1] or derivatives, which go out of their way not to have too much state or use multiplies, and they also tend to be used at really low bitrates, so they have a somewhat deserved bad reputation. "Guessing" the scalefactor is overstating it, the scale does dynamically adjust but that's all considered from the encoder.
The 2-history-samples style ADPCMs in the BRR [2] family usually have very short frames (at most dozens of samples) and headers specifying scale and predictor/filter index.
I know a lot more about what's used on consoles than about the math of audio encoding, though, so I can't say whether QOA is making the wrong tradeoffs.
[1] https://wiki.multimedia.cx/index.php/IMA_ADPCM [2] https://en.wikipedia.org/wiki/Bit_Rate_Reduction