[x265] Optimize slice QP in PPS for x265

[xuefeng]

All,
hello! 

 x265 set the slice QP in PPS to 26.  Bits can be saved by calculating a closer approximation to the actual slice QP values utilized to encode the bitstream at different quality levels. The delta QP in each slice header is huge especially at low bit rate and quality levels.

My test command is as follows.
--repeat-headers --hash 1  --input-res 1280x720 --keyint 30 --min-keyint 30 --input "Johnny_1280x720.y4m" --fps 30 --output "test_new.mp4" 

There is a patch in the attachment for this method based on "Changeset: 11587 (d20b78d6d138)".
There is information for x265 coding to see that bitrate goes down.   There is informations for HM decoding to see that MD5 and QP are the same with the method. 





Regards,
 
             Xuefeng Jiang
 
xuefeng at multicorewareinc.com
 
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