xiph
Introduce subdivide_tukey apodization
Subdivide_tukey is intended to replace partial_tukey and punchout_tukey. It works in rougly the same way, but uses a more efficient algorithm, recyling more data.
subdivide_tukey has 2 arguments, of which 1 is optional. The first states the maximum number of parts the signal has to be split up in, the second is the tukey parameter, divided by the max num of parts.
subdivide_tukey(3) analyses audio with an unsplit block, with the block split in 2 and split in 3. Here the default p of 0.5 applies to the smallest parts, so the unsplit block effectively has a p of 0.5/3. subdivide_tukey(3/2e-1) does the same but with p of 0.2.
With this change, encoding with compression levels 6, 7 and 8 is approximately 10% faster with on average (depending on the input material) no change in compression. Other compression levels are not affected.
