b-pyramid modes quality-difference?

[Sharc]

Use "--b-adapt 2" and "--bframe 16" ;)
Ah yes, the speed-killer combo!
But as far as I know --bframe 16 would be beyond Blu-Ray specs. I may have to try with my standalone what it accepts.
Anyway, it seems that even for Blu-ray compliant settings of --bframes 3 the --b-pyramid compensates the speed loss of b-adapt 2 compared to b-adapt 1.

[LoRd_MuldeR]

AFAIK there should be no encoder-side limit on consecutive B-Frames. Also with B-Adapt 2 and B-Pyramid enabled, significant more B-Frames are useful:

[B-Pyramid: normal]
x264 [info]: frame I:1
x264 [info]: frame P:43
x264 [info]: frame B:156
x264 [info]: consecutive B-frames: 0.5% 7.0% 12.1% 14.1% 20.1% 15.1% 3.5% 16.1% 0.0% 5.0% 0.0% 0.0% 6.5% 0.0% 0.0%

[B-Pyramid: none]
x264 [info]: frame I:1
x264 [info]: frame P:66
x264 [info]: frame B:133
x264 [info]: consecutive B-frames: 2.5% 23.1% 31.7% 14.1% 15.1% 6.0% 3.5% 4.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%

[Trahald]

What B-pyramid normal exactly does to break compatibility? incrase b-frames?
Its what it doesnt do. It leaves bframes in the dpb after the mini-gop is over. bluray doesnt allow p frames referencing b frames and doesnt allow b frames to reference B refs that arent next to it (the h264 spec does .)

I P B b b P B b b P...
0 4 2 1 3 8 6 5 7 12
ref frame 2 is removed during frame 8
ref frame 6 is removed during frame 12
with b-pyramid strict. with b-pyramid normal the frames are not removed early (until they get forced out in order later)

[nurbs]

Do you know why they implemented it like that on blu-ray? What's the benefit?

[Dark Shikari]

Do you know why they implemented it like that on blu-ray? What's the benefit?You can guarantee (as long as there are B-frames) are relatively effective fast-forward capability, since you can simply drop all B-frames.