vp10 wishlist: please extend the range of delta-q for ydc and uvdc/ac

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Right now in vp9 (and I assume vp10), the deltas are only 4+sign bits, which 
means I can go at most 15 qidx units above/below the yac quantizer index.

In the higher qidx range (around qidx=150-200), we'd have need a delta qidx of 
around 35 (pow(1.01975,35)=~2) to get an halving/doubling of quantizer. In the 
medium range, this is even higher because the effective deltas are higher in 
the low-qidx range. For example, qidx=219 has an effective dc q of 128.25, and 
qidx of effective dc q of 64 is 170, so a delta qidx of 49 (219-170) would be 
required to half the effective quantizer in this particular example. I don't 
think expecting doubling/halving of effective q is far-fetched, so please 
extend the bit-range of ydc/uvdc/uvac to at least 6+sign bits. Possibly just 
remove the whole delta thing and go back to what vp8 had, where we specify the 
full quantizer (if the delta bit is set).

Original issue reported on code.google.com by rsbul...@gmail.com on 27 Jul 2015 at 12:05

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Original comment by ya...@google.com on 29 Jul 2015 at 11:07

• Added labels: Hotlist-VP10-must-fix

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Original comment by fgalli...@google.com on 12 Aug 2015 at 10:06

• Changed state: Assigned