ref: 3120dbddb12b6299c2d4f2b09c529c6fb2633c47
parent: 790fb132157aab73b20c94a223dbe4470036d832
author: Ronald S. Bultje <rbultje@google.com>
date: Mon Mar 25 08:28:24 EDT 2013
Redo banding for all transforms. Now that the first AC coefficient in both directions use the same DC as their context, there no longer is a purpose in letting both have their own band. Merging these two bands allows us to split bands for some of the very high-frequency AC bands. In addition, I'm redoing the banding for the 1D-ADST col/row scans. I don't think the old banding made any sense at all (it merged the last coefficient of the first row/col in the same band as the first two of the second row/col), which was clearly an oversight from the band being applied in scan-order (rather than in their actual position). Now, coefficients at the same position will be in the same band, regardless what scan order is used. I think this makes most sense for the purpose of banding, which is basically "predict energy for this coefficient depending on the energy of context coefficients" (i.e. pt). After full re-training, together with previous patch, derf gains about 1.2-1.3%, and hd/stdhd gain about 0.9-1.0%. Change-Id: I7a0cc12ba724e88b278034113cb4adaaebf87e0c