b-pyramid modes quality-difference?

Forteen88 · 26th October 2009, 21:57

About how much quality-difference is it between the b-pyramid modes (normal and strict)? Is 'normal'-mode like going from me-umh to me-tesa (almost placebo quality-difference), or is it bigger change?
I guess it depends on which source also.
EDIT: Ok, thanks DS! I guess it's more quality-difference than going from me-umh to me-tesa then

Dark Shikari · 26th October 2009, 22:00

Strict is always worse than normal and should never be used unless you absolutely need it.

shon3i · 27th October 2009, 18:40

What is averge gain in percent of quality with normal b-pyramid? i think than strict have no sense then if not have at least of 80% power as normal mode.

juGGaKNot · 27th October 2009, 22:48

strict is for blu-ray, normal is for the rest, what are you asking ?

egrimisu · 28th October 2009, 09:55

Quote:

Originally Posted by juGGaKNot

strict is for blu-ray, normal is for the rest, what are you asking ?

does MB-tree work with b-pyramid? if no what to chose MB tree or b-pyramid normal?

nm · 28th October 2009, 10:19

Quote:

Originally Posted by egrimisu

does MB-tree work with b-pyramid?

Not yet, but maybe soon.

Quote:

if no what to chose MB tree or b-pyramid normal?

MB-tree. Use presets if you don't know what you're doing.

juGGaKNot · 28th October 2009, 13:49

It will soon, ask dark when, i see 0.5 lower qp with mb-tree than with b-pyramid normal on my source.

RainyDog · 28th October 2009, 15:57

Quote:

Originally Posted by juGGaKNot

It will soon, ask dark when, i see 0.5 lower qp with mb-tree than with b-pyramid normal on my source.

Juggaknot, is that qcomp=0.5 or 0.5 less than the standard setting (qcomp=0.1)? Just curious as I preferred a lower qcomp value with mbtree on my tests as well (all film sources). I found the bitrate distribution was far too aggressive otherwise, sometimes with double the peaks of no-mbtree and in turn half as many, or even less than that, bits in dark/still scenes that clearly needed more.

juGGaKNot · 28th October 2009, 16:54

Quote:

Originally Posted by RainyDog

Juggaknot, is that qcomp=0.5 or 0.5 less than the standard setting (qcomp=0.1)? Just curious as I preferred a lower qcomp value with mbtree on my tests as well (all film sources). I found the bitrate distribution was far too aggressive otherwise, sometimes with double the peaks of no-mbtree and in turn half as many, or even less than that, bits in dark/still scenes that clearly needed more.

not qcomp, qp, as in average qp ( or final ratefactor smaller by 0.5 )

default is 0.6

BTW Raising qcomp lowers MB-tree strength

so less qcomp = more mbtree

RainyDog · 28th October 2009, 17:44

Quote:

Originally Posted by juGGaKNot

not qcomp, qp, as in average qp ( or final ratefactor smaller by 0.5 )

default is 0.6

BTW Raising qcomp lowers MB-tree strength

so less qcomp = more mbtree

Ok, cheers for clarifying. Yeah, I was aware that less qcomp=more mbtree and visa versa. But from all my tests, I found that lower qcomp led to less 'aggressive' bitrate distribution using mbtree, if that's the right word. Which led to compression balanced more akin to no-mbtree, at least for my sources (Blu-Ray, film). Though I don't claim to know whether it would even be possible, I still think it'd be ideal to have an mbtree rate control that was independent of qcomp...

shon3i · 28th October 2009, 20:29

Quote:

Originally Posted by juGGaKNot

strict is for blu-ray, normal is for the rest, what are you asking ?

I ask, what is point of B-pyramid strict then if incrase of quality is almots zero, or half of normal mode or anything?

LoRd_MuldeR · 28th October 2009, 20:37

B-Pyramid enabled will compress more efficient than B-Pyramid disabled. This applies to both modes, "normal" and "strict". But "normal" mode is even better than "strict" mode.

So if you can't use "normal" mode (e.g. BluRay compatibility is required) then it's still better to use "strict" mode than nothing. Otherwise you'd prefer "normal" mode

However it should be noted that at the moment MB-Tree RC will completely disable B-Pyramid anyway, no matter what mode you select. Unless you disable MB-Tree, of course.

Therefore this topic will become more important once MB-Tree starts supporting B-Pyramid...

Dark Shikari · 28th October 2009, 20:54

Quote:

Originally Posted by LoRd_MuldeR

B-Pyramid enabled will compress more efficient than B-Pyramid disabled. This applies to both modes, "normal" and "strict". But "normal" mode is even better than "strict" mode.

Not necessarily true. Though I can't say for sure until I write MB-tree support for B-pyramid and do some optimizing of the quantizer offsets, it's possible that strict will be worse than none in some cases.

LoRd_MuldeR · 28th October 2009, 20:55

Quote:

Originally Posted by Dark Shikari

Not necessarily true. Though I can't say for sure until I write MB-tree support for B-pyramid and do some optimizing of the quantizer offsets, it's possible that strict will be worse than none in some cases.

Good to know. Even more reason to stick with "normal", if possible

RainyDog · 28th October 2009, 22:55

Is b-pyramid normal any better/more efficient than the old b-pyramid?

LoRd_MuldeR · 28th October 2009, 23:09

Quote:

Originally Posted by RainyDog

Is b-pyramid normal any better/more efficient than the old b-pyramid?

The "normal" B-Pyramid in current x264 is like to the "old" B-Pyramid, but spec compliant. Only "strict" mode is really new.

Dark Shikari · 28th October 2009, 23:12

Quote:

Originally Posted by LoRd_MuldeR

The "normal" B-Pyramid in current x264 is identical to the "old" B-Pyramid.

No it isn't. It's worse than the old pyramid (albeit spec-compliant). It's probably only marginally worse though, nothing that seriously matters.

LoRd_MuldeR · 28th October 2009, 23:16

Quote:

Originally Posted by Dark Shikari

No it isn't. It's worse than the old pyramid (albeit spec-compliant). It's probably only marginally worse though, nothing that seriously matters.

Argh, he's replying faster than I can edit

Trahald · 29th October 2009, 00:18

Quote:

Originally Posted by LoRd_MuldeR

The "normal" B-Pyramid in current x264 is like to the "old" B-Pyramid, but spec compliant. Only "strict" mode is really new.

'Spec Compliance' involves making sure there is a spot in the dpb for possible delayed display time of a b-frame.

That part of normal involves removing frames from the dpb which leaves less references hurting quality. Normal only does it when it absolutely must (which is not every minigop especially when badapt == 1/2 is used.) But often enough to hurt quality a bit

Strict maintains h264 spec compliance by doing the following. After its bframes refer to it, bref is removed to maintain hierarchy (blu-ray requirement), then the frame with the lowest poc for spec compliance (even when there are no delayed frames that gop since its 'strict' )

benwaggoner · 5th November 2009, 17:49

Do we have any sense about the general relative value of B-pyramid versus MB-Tree? Since they're exclusive choices for the moment, any sense on what the appropriate choice would be.

Anime/animation/motion graphics clearly get a huge MB-tree win and so that should be a slam dunk, but what about film/video? Any cases where we're better off with B-pyramid?

26th October 2009, 21:57	#1 \| Link
Forteen88 Herr Join Date: Apr 2009 Location: North Europe Posts: 556	b-pyramid modes quality-difference? About how much quality-difference is it between the b-pyramid modes (normal and strict)? Is 'normal'-mode like going from me-umh to me-tesa (almost placebo quality-difference), or is it bigger change? I guess it depends on which source also. EDIT: Ok, thanks DS! I guess it's more quality-difference than going from me-umh to me-tesa then Last edited by Forteen88; 26th October 2009 at 22:08.

26th October 2009, 22:00	#2 \| Link
Dark Shikari x264 developer Join Date: Sep 2005 Posts: 8,666	Strict is always worse than normal and should never be used unless you absolutely need it. __________________ Follow x264 development progress \| akupenguin quotes \| x264 git status ffmpeg and x264-related consulting/coding contracts \| Doom10

28th October 2009, 20:37	#12 \| Link
LoRd_MuldeR Software Developer Join Date: Jun 2005 Location: Last House on Slunk Street Posts: 13,248	B-Pyramid enabled will compress more efficient than B-Pyramid disabled. This applies to both modes, "normal" and "strict". But "normal" mode is even better than "strict" mode. So if you can't use "normal" mode (e.g. BluRay compatibility is required) then it's still better to use "strict" mode than nothing. Otherwise you'd prefer "normal" mode However it should be noted that at the moment MB-Tree RC will completely disable B-Pyramid anyway, no matter what mode you select. Unless you disable MB-Tree, of course. Therefore this topic will become more important once MB-Tree starts supporting B-Pyramid... __________________ Go to https://standforukraine.com/ to find legitimate Ukrainian Charities 🇺🇦✊ Last edited by LoRd_MuldeR; 28th October 2009 at 20:41.

5th November 2009, 17:49	#20 \| Link
benwaggoner Moderator Join Date: Jan 2006 Location: Portland, OR Posts: 4,770	Do we have any sense about the general relative value of B-pyramid versus MB-Tree? Since they're exclusive choices for the moment, any sense on what the appropriate choice would be. Anime/animation/motion graphics clearly get a huge MB-tree win and so that should be a slam dunk, but what about film/video? Any cases where we're better off with B-pyramid? __________________ Ben Waggoner Principal Video Specialist, Amazon Prime Video My Compression Book

27th October 2009, 18:40	#3 \| Link
shon3i BluRay Maniac Join Date: Dec 2005 Posts: 2,419	What is averge gain in percent of quality with normal b-pyramid? i think than strict have no sense then if not have at least of 80% power as normal mode.

28th October 2009, 22:55	#15 \| Link
RainyDog Registered User Join Date: May 2009 Posts: 184	Is b-pyramid normal any better/more efficient than the old b-pyramid?