Merge CBR and VBR for video-codecs? [DONE]

Post by **exp** » Fri Sep 19, 2003 8:02 am

Note from wahaha:
In File information: How do I determine VBR or CBR?!?, it has been said that nearly all divx encodes use VBR. Thus the following thread:

Well,

if there is really no good way to distinguish between CBR/VBR for divx codecs (i.e. they are all VBR or there are no tools to see the difference) we could merge the CBR/VBR codec options for divx.
what are the thoughts on this one?

BYe!
EXP

BMan · Post by **BMan** » Fri Sep 19, 2003 8:17 am

there are only very few cbr-files out there...if any...
i always wondered about that vbr-thingie within the vid-selection...
just drop it...no need for "vbr"...because it's always vbr...
upto now i used the divx3-option for fast-motion divx3...but even those are rare...and they're mostly not cbr either...

just drop it...divxX is fine...just as we have "xvid" only...though it's possible to encode in cbr with xvid...but who does? not worth wasting options, imho...

Guest · Post by **Guest** » Fri Sep 19, 2003 8:22 am

I'm too lazy to register, so I'm using the Guest account

lamer_de here

There are CBR modes for DivX 3,5 and Xvid. These are the 1-pass modes. Maybe DivX and Xvid use some kind of ABR, e.g. the manipulate the bitrate a bit but the overall stays the same, i'm not 100% sure. But you can't tell it from the fourCC or another Info which is directly readable by a program. Maybe using DRFAnalyzer would help. If the encode only usues one quantisizer, it could be CBR. Could be wrong, because there's a "constant quant" function in XVID, and that's something different than CBR

So, long story short: I don'T think there's apossibility to determine if the video is CBR or VBR. The only difference is the CBR encodes almost always look like shit in high motion scenes ^_^

My guess would be to screw these entry in anidb. Imho the use of these should be to help people which codec they need. You can't use them for quality purposes (like: Oh, this file has DivX5, it must be higher quality than DivX3).

You could keep the Audio CBR/VBR, but I don't think that it matters much nowadays. Everybody can play VBR files, and the audio bitrate is more important than VBR vs. CBR (for anime, as it's mostly speech anyway)

CU,
lamer_de

zaufany · Post by **zaufany** » Fri Sep 19, 2003 12:00 pm

There is no need to have vbr for divx, because every decent encoder use vbr. However, the vbr option for mp3 is usefull. All 128 kbps mp3 cbr encodes I've heard sound good. Some vbr encodes don't.

Iceman[grrrr] · Post by **Iceman[grrrr]** » Sat Sep 20, 2003 1:23 am

Yup merge the CBR and VBR for the DivX but leave them alone for audio!

Skywalka · Post by **Skywalka** » Sun Sep 21, 2003 2:37 pm

I agree. While the AVI format was not made for VBR audio there is a way to "hack" that so that you can actually find AVI files that have VBR MP3.
And of course other file formats such as OGG and Matroska or XviD can incorporate VBR audio, therefor the Audio MP3 VBR option should definately stay.

Post by **nwa** » Tue Sep 23, 2003 6:40 am

also agree,
CBR and VBR for audio only, merge the DivXx and DivXx VBR together, it's way more convenient and understandable that way

Depeupleur · Post by **Depeupleur** » Thu Oct 02, 2003 6:11 am

lamer_de wrote:There are CBR modes for DivX 3,5 and Xvid. These are the 1-pass modes.

I have to disagree. The MPEG4 video standard as a whole is meant to be VBR, the concept of keyframes (pretty much a good ol' jpeg image : DCT quantized compression) storing most of the information of the video stream while delta-frames only store the variations, defeats any sort of real CBR. 1-pass merely means that the codec will apply its compression process once, possibly with a variable quantizer depending on the perceived complexity of a particular scene. But if you have a still image for some period of time, the instant bitrate will be very high on the keyframe leading to that still image, and then pretty much null as delta-frames have no variation informations to store (thanks to that, some pretty long avi slideshows can be small files: essentially they are jpeg images separated by long "huh, nothing happens" spaces).

CBR is meant for streaming media, when the instant bitrate matters and should not exceed a very low ceiling compared to what is availlable for offline media playing (pretty much what the hard-disk or CD-ROM can spew on the fly). RealMedia, Sorenson, wmv are some examples of CBR or rather quasi-CBR codecs. They use a different compression scheme than MPEG4, or an adapted scheme (say a periodical, highly compressed keyframe and 9 delta frames afterwards, with enough buffering to have a few complete keyframe+deltaframes sets ready for the codec to decompress at any time). Most of those codecs also have 1 or 2-pass VBR modes, as well, as VBR considerably improves the quality of information allocation over the whole file. The benefit of VBR for video data is much higher than for sound data.

I hope this is clear enough... To sum it up, the CBR/VBR difference is meaningless for MPEG4 compression (DivX, XviD, MS-MPEG4...), it only matters for streaming formats and hopefully, ther are very few files encoded with those.

egg · Post by **egg** » Mon Nov 17, 2003 6:01 am

I was just doing a search to see what "VBR" meant and came across this topic. It looks like the consensus was to drop the VBR, but since it is not in the bug or feature request forums I was wondering if it made it onto a "todo" list. Maybe the post should be moved to one of these forums by a moderator.

Just making sure it wasn't forgotten.

egg

Iceman[grrrr] · Post by **Iceman[grrrr]** » Tue Nov 18, 2003 11:18 pm

drop the VBR only for video codec... leave it for audio !

I also second the idea of moving this thread to the Feature Request forum... dare ka ?

wahaha · Post by **wahaha** » Wed Nov 19, 2003 7:49 pm

Iceman[grrrr] wrote:I also second the idea of moving this thread to the Feature Request forum... dare ka ?

[X] Done

Post by **PetriW** » Thu Nov 20, 2003 12:32 pm

Wee, get rid of that video VBR crap!

(Then we won't have to code it into AOM!)

Post by **nwa** » Thu Nov 20, 2003 5:31 pm

hmm..it still hasnt been done?

come on...

rowaasr13 · Post by **rowaasr13** » Sun Aug 22, 2004 10:33 pm

Seems like it was common agreement that because all DivX is VBR, there shouldn't be separate DivX? and DivX? VBR entries for video codecs, but nothing happened since then and this thread silently sunk to bottom...

So I'm bumping it up.

Elberet · Post by **Elberet** » Tue Aug 24, 2004 11:19 am

Agreed. As it was already said before, all MPEG4 streams are inherently of a variable bitrate over play time. DivX's CBR-encoding is merely fancy words for encoding the video in a single pass rather then multiple passes.

It would be much more interesting to see whether a file is encoding with VFR (variable frame rate) or not and whether it's anamorphic or not.