How to set Max. Bitrate for Un-Certified DivX?

[AsTimeGoesBy]

Hi - supposed i wan't to make a DivX with GMC and QPel Features, then i also have the possibility to set the max. bitrate myself. - But which value?

The codec's default make me belive it schould be 10x more than the average bitrate - is that true/optmal?

[jggimi]

The "max bitrate" setting, available on 1-pass and Multipass Nth pass encodes, appears to only affect the Video Buffer Verifier (-vbv) setting, useful for IP streaming or sustained bitrate limitation in certified devices. Its use is explained in the DivX User Guide, starting on page 97.

[AsTimeGoesBy]

So checking video puffer....
... hmmm, there is not written much. The 'reading from disc' example is ok, but it's hard to estimate the cache size of a device in haven't yet and i would like to buy for X-Mas. Moreover i'm bothering more about data-overflows and the abilities of common decoding chips.
DivX 5.21 PDF Guide
Each DivX Certified DivX Profile has specitic VBV parameters associated with it
to ensure playback on DivX Certified devices. ...

Profile Bitrate
------- -------
...
high-definition 8000000
...



For my un-certified DivX files best would be perhaps to consider the VBV value of the 'high-definition' definition profile that seems to be (only) 8Mbit/s.

8Mbit is not much..., or is it? - I mean the 'max. bitrate' field suggests i should set a value 10x bigger than my average bitrate of 1500kbit/s, thus 15Mbit/s.

Moreover i'm a bit confused about a value called 'maxiumum peak bitrate during any 1 second of video' (page 106).
I guess this is another maximum bitrate i have no direct influence on!?


So when setting up an un-certified DivX encoding job i should never set a 'max. bitrate' higher than 8Mbit/s in order to have optimal playback compatibility?
What 1-sec-max-peak-bitrate is allowed/possible if i would set the 'max. bitrate' on 8Mbit/s for un-certified DivX encoding? - 32Mbit/s too?

I would like to see both values as high as possible - as long they keep within hardware limits.

[jggimi]

...Moreover i'm a bit confused about a value called 'maxiumum peak bitrate during any 1 second of video' (page 106)...

AFAIK that is -vbv (page 99), which is described as "Max Bitrate" in the DivX GUI. I learned this by adjusting the value, and seeing what changed in the CLI (the "Settings" button).

[AsTimeGoesBy]

Originally posted by jggimi
...Moreover i'm a bit confused about a value called 'maxiumum peak bitrate during any 1 second of video' (page 106)...

AFAIK that is -vbv (page 99), which is described as "Max Bitrate" in the DivX GUI. I learned this by adjusting the value, and seeing what changed in the CLI (the "Settings" button). So the highest value for this peak value could be 32000kbit/s, right!?

More concrete, I'd like to use the follow setting with a max. bitrate of about 24Mbit.
May this value be highter to improve quality without losing playback compatibility?
(Supposed the device is able to handle GMC, QPel and 'Adaptive Multi-Consecutie B-Frames')

http://homepage.hispeed.ch/audiold/DivX-Un-Certified1.png

[Blue_MiSfit]

a tip - don't use GMC :)

DivX's 1 warp-point method does essentially nothing but eat CPU time.

If you see any tangible benefit then go ahead, but in my experience, and from several technical explanations that I partially understood on the XviD forum, it does absolutely nothing. A 3 warp-point solution (like XviD's) is needed to accomplish anything with GMC.

~misfit

[SeeMoreDigital]

Originally posted by Blue_MiSfit
a tip - don't use GMC :)

DivX's 1 warp-point method does essentially nothing but eat CPU time.

If you see any tangible benefit then go ahead, but in my experience, and from several technical explanations that I partially understood on the XviD forum, it does absolutely nothing. A 3 warp-point solution (like XviD's) is needed to accomplish anything with GMC. Agreed...

But it must be pointed out that currently no stand-alone player supports 3warp-point GMC... So if you're intending to spin encodes in stand-alones... don't use it either!


Cheers

[AsTimeGoesBy]

After watching some of my test samples and already encoded DivX files i have canceled my intentions to use the 'DivX un-certified' features of v5.21.

The benefit of GMC must be rather low. Specially too low to risk hardware compatibility.
Generally I wasn't able to see a any differeces in my test samples. Of course I must admit i had no possibility to check how far/strong GMC was used.

Multiple Consecutive B-Frames seem very attractive. It's a pitty that no hardware player of my friends (i know them by real name, not by IP ;)) was able to play the samples (tested with EKG for consecutive B-Frames).

To use QPel would be nice too specially to hold details. But also here stand-alone decoding gets problematical at higher bitrates due to the higher processing load - if the decoding chip understands QPel at all.


BTW, concerning 'details' - i hope DivX Labs will improve (=>weaken!?) the 'light preprocessing' level, at least the one of v5.11 was better with medium/higher bitrate. And no preprocessing (with v5.21) stresses the bandwidth and makes the movie look instable sometimes.