Last week I wrote about my x264 patch that would enable B-frames heuristic decisions in x264.
Today I finally managed to do some proper testing using the Big Buck Bunny PNG image sequence from xiph.org, and found out that for reasonable settings (b-frames 8, b-heuristic 4) we have an overall 4% speed gain and for more extreme settings (b-frames 16, b-heuristic 4) we gain 17% overall.
The base command line used in this test is –b-adapt 2 –b-pyramid -r 4 –crf 26 -A all –direct auto -w -m 9 –psy-rd –mixed-refs -8 -t 2 –threads 3 –thread-input.
In the following pretty graph™ I plotted the frames-per-second for various settings (b-frames/b-heuristic):
The following are the raw results taken from the x264 logs: