3 ms·

Yeah, I don't understand the disparaging of 4-bit ADPCM as being terrible quality when this is effectively a 3-bit ADPCM. Most ADPCM codecs I've seen shipped ha

Yeah, I don't understand the disparaging of 4-bit ADPCM as being terrible quality when this is effectively a 3-bit ADPCM. Most ADPCM codecs I've seen shipped have a similar table based system with a frame header with coefficients for your two history samples rather than the weight update scheme here, and it works quite well.

phoboslab 4y ago
Traditional ADPCM is not terrible, it's just "meh". Compare: - Original, 4039kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/orig.wav https://phoboslab.org/files/qoa-samples/adpcm_comp/orig.wav - MS ADPCM, 1022kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/ms_adpcm.wav https://phoboslab.org/files/qoa-samples/adpcm_comp/ms_adpcm.... - QOA, 812kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/qoa.wav 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.
- stephc_int13 4y ago
  I have a fairly decent audio system with a good dac and reasonable headphone. 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.
- deleted 4y ago
  [deleted]
hcs 4y ago
This bit > 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 https://wiki.multimedia.cx/index.php/IMA_ADPCM [2] https://en.wikipedia.org/wiki/Bit_Rate_Reduction https://en.wikipedia.org/wiki/Bit_Rate_Reduction

phoboslab 4y ago

Traditional ADPCM is not terrible, it's just "meh". Compare: - Original, 4039kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/orig.wav https://phoboslab.org/files/qoa-samples/adpcm_comp/orig.wav - MS ADPCM, 1022kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/ms_adpcm.wav https://phoboslab.org/files/qoa-samples/adpcm_comp/ms_adpcm.... - QOA, 812kb: https://phoboslab.org/files/qoa-samples/adpcm_comp/qoa.wav 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.

stephc_int13 4y ago
I have a fairly decent audio system with a good dac and reasonable headphone. 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.
deleted 4y ago
[deleted]

hcs 4y ago

This bit > 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 https://wiki.multimedia.cx/index.php/IMA_ADPCM [2] https://en.wikipedia.org/wiki/Bit_Rate_Reduction https://en.wikipedia.org/wiki/Bit_Rate_Reduction