Which values for vbv settings?

[Selur]

afaik x264 got three values to specifiy vbv restrictions:
--vbv-maxrate <integer> Max local bitrate (kbit/s) [0]
--vbv-bufsize <integer> Enable CBR and set size of the VBV buffer (kbit) [0]
--vbv-init <float> Initial VBV buffer occupancy [0.9]

vbv-maxrate can be found in T-REC-H%5B1%5D.264-200503-I!!PDF-E.pdf over at neuron2s library or http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Levels

but how to know/calculate which values vbv-bufsize and vbv-init should have?

Is there a formular that explains how to calculate these or a table where to look them up?

Cu Selur

[Gabriel_Bouvigne]

You should choose them according to the buffer size of your decoder. (if you don't know what this mean, then it's likely that you don't need to care about it)

[Selur]

At the moment I use my pc for playback, so not problem there, but I would like to convert my files so that they'll play on future hardware devices which support a specific profile@level.
I thought that the whole vbv stuff (not only vbv-maxrate) is specified for all profile@level combinations.

Even if I would know that I'll never need vbv restrictions I'd like to be able to produce stuff that. (I'd like to write some megui profiles like I did for Xvid (http://forum.doom9.org/showthread.php?p=953730#post953730).)

-> Are you sure vbv-bufsize and vbv-init is not defined for each profile@level and only depends on a hardware decoder?

Cu Selur

[Manao]

vbv-init should be left untouched. vbv-bufsize is defined in the standard ( it's named CPB max size ).

[Selur]

thanks :)

[Gabriel_Bouvigne]

Also note that if you specify a level (--level XXX), x264 will warn you about options you could have specified which are in contradiction with the specified level.

[Sagittaire]

Actually official build don't support vbv in multipass mode. vbv work well only with cbr mode.

[Selur]

Actually official build don't support vbv in multipass mode.
Is there a reason for this? (I mean is there no code for it or is there another reason?)

Will cefs builds (the builds that megui use) support it?

Are there some patches somewhere that can be applied to svn checkout so that vbv is supported in multipass?

Cu Selur

[Gabriel_Bouvigne]

Is there a reason for this? (I mean is there no code for it or is there another reason?)
New code is not yet polished

[Selur]

Ok,.. :(

got another question:


Examples for high resolution @frame rate (max stored frames) in Level
128x96@30.9 (8)
176x144@15.0 (4)
is 'max stored frames' restricted the number of reference frames allowed or is there no restriction to this?

[Gabriel_Bouvigne]

"max stored frames" is likely to be the number of decoded frames within the DPB.

You could consider this as a limit to the number of refs, from a practical POV.
(even if an encoder could, for any reason, choose to put several times the same frame within the ref list)

[akupenguin]

(even if an encoder could, for any reason, choose to put several times the same frame within the ref list)
The only reason I can think of to do that would be for weighted prediction, if different pieces of the frame want different weights.

[DeathTheSheep]

Speaking of weighted prediction for pframes, are there any plans involving wpred...for the future...? :)

[Gabriel_Bouvigne]

The only reason I can think of to do that would be for weighted prediction, if different pieces of the frame want different weights.
That's a quite good idea, never thought of that.
I actually have some sequences that would benefit from that...