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Old 2009-01-27, 04:53   Link #1
j0x
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Join Date: Jan 2009
x264 CRF and ABR modes in high motion scenes question

is there some settings so that the lowering of bitrates on high motion can be controlled im encoding low bitrate anime i mean i know now that x264 lowers the bitrate on high motion or fast pace scenes and i can disable that x264 behavior entirely if i used CQ/QP mode but i just want to experiment on controlling that lowering of bitrate behavior

PS: is CQ/QP mode can be safely called constant bitrate mode already?
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Old 2009-01-27, 04:55   Link #2
TheFluff
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constant quantizer is most definitely not the same thing as constant bitrate, in fact it is pretty much the exact opposite
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17:43:13 <~deculture> Also, TheFluff, you are so fucking slowpoke.jpg that people think we dropped the DVD's.
17:43:16 <~deculture> nice job, fag!

01:04:41 < Plorkyeran> it was annoying to typeset so it should be annoying to read
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Old 2009-01-27, 05:02   Link #3
j0x
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you may be referring to constant quality or CRF that varies bitrates with every frame?

and about my question i was thinking of instead of lowering the bitrates on high motion scenes
it will higher the bitrates to it instead
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Old 2009-01-27, 05:03   Link #4
TheFluff
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Quote:
Originally Posted by ckmox View Post
you may be referring to constant quality or CRF that varies bitrates with every frame?
constant quantizer does the same thing, in fact it is quite similar to CRF, it's just that the quality is measured differently

e: to clarify what dark shikari said in the other thread: in constant quantizer mode every single frame is coded to achieve a given level of compression (quantizer) and the bitrate hence varies a lot. since high-motion scenes take more bitrate to compress to the same level of quality, bitrates will be higher in high-motion scenes. in CRF mode quality is not measured with quantizers, but rather in a perceptual kind of way that I do not fully understand, so that bits will be spent on improving quality where it is more likely to be noticed instead of in high-motion scenes where it's hard to notice details.

e2: http://forum.doom9.org/showthread.ph...275#post726275
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17:43:13 <~deculture> Also, TheFluff, you are so fucking slowpoke.jpg that people think we dropped the DVD's.
17:43:16 <~deculture> nice job, fag!

01:04:41 < Plorkyeran> it was annoying to typeset so it should be annoying to read

Last edited by TheFluff; 2009-01-27 at 05:23.
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Old 2009-01-27, 05:05   Link #5
j0x
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oh ok thanks for that but about my question regarding x264 behavior of lowering the bitrates on high motion scenes are there settings to controll or even reverse that lowering of bitrates?
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Old 2009-01-27, 05:13   Link #6
TheFluff
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yes, as dark shikari said in the other thread: use qcomp. lower qcomp => bitrate distribution will become more even. at qcomp=0, you will get constant (well, almost constant) bitrate. higher qcomp => bitrate distribution will become less even; higher complexity scenes will take more bitrate, at the expense of lower complexity scenes. at qcomp=1.0, you will get the equivalent of constant quantizer mode.

for more complex fiddling with x264's ratecontrol behavior you will probably (read: I only have a vague idea about what I'm talking about here, you'd better ask dark shikari or pengvado) have to modify the ratecontrol equation with --rceq, or patch the source.
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17:43:13 <~deculture> Also, TheFluff, you are so fucking slowpoke.jpg that people think we dropped the DVD's.
17:43:16 <~deculture> nice job, fag!

01:04:41 < Plorkyeran> it was annoying to typeset so it should be annoying to read
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Old 2009-01-27, 05:22   Link #7
j0x
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oh sounds complex if ill manually edit the lowering behavior to a higher bitrate giving behavior
i guess there is no available settings for the default options at the moment

thanks
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Old 2009-01-27, 05:27   Link #8
Dark Shikari
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Quote:
Originally Posted by TheFluff View Post
constant quantizer does the same thing, in fact it is quite similar to CRF, it's just that the quality is measured differently
More precisely, CRF = CQP + AQ + QCOMP.
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