VBR-CBR Challenge

[rhegedus]

Sorry bugster but CBR is Constant Bit Rate just like VBR is Variable Bit Rate you should look it up on the Glossary.
(use exactly the same compression schemes) but you miss read what I read efficient compression like let say we use winzip at 50% compression and but let say that wan't good enough so bump it to 75% compression which in turn get more efficient compression.

I'm confused. What has compression got to do with the way that CBR and VBR encoding allocates data? Smaller files sizes are not due to compression but a smaller average bit-rate - if a CBR and VBR encode have the same average bit-rate then the file sizes will be near equal.

[bugster]

Sorry bugster but CBR is Constant Bit Rate just like VBR is Variable Bit Rate you should look it up on the Glossary.
(use exactly the same compression schemes) but you miss read what I read efficient compression like let say we use winzip at 50% compression and but let say that wan't good enough so bump it to 75% compression which in turn get more efficient compression.

I'm confused. What has compression got to do with the way that CBR and VBR encoding allocates data? Smaller files sizes are not due to compression but a smaller average bit-rate - if a CBR and VBR encode have the same average bit-rate then the file sizes will be near equal.

yes, you are right, it is SHS that is incorrect when he says that.

CBR mode dose all full frames all the time just like AVI, DV, etc but it dosen't give you very efficient compression.

Complete rubbish.

[macm]

Hi all,

as a remark, I'd like to state that capping (or enconding) with 9600K bitrate for DVD, really makes things better. If you plan to put up to 1 hour only in a DVD, and you source is clean and good enough, it really worth. Why? Test it. You will improve quality a lot. A simple test is, after burning a DVD with, say, 6000K and another with 9600k (of course the same footage!), play them on a standalone DVD connected to a TV set. FF or RW both and check the quality as the DVD moves backward or forward. Also, there is an improve on sharpness as well.

[Gazorgan]

Don't confuse single pass VBR with CQ. It's not true VBR, since it's not allocating bitrate throughout the entire video. It is simply limiting any given frame/GOP to you 'max' setting. And yes, it's impossible to predict the file size, except to say it will be less than some high bitrate CBR.

Try capturing VBR with a max of 9500 and a min of 300 and see what you get..... I mean it's VBR, why set your max to 6000?

[ta2]

lordsmurf it is very to unstand the diff from VBR vs CBR
CBR mode dose all full frames all the time just like AVI, DV, etc but it dosen't give you very efficient compression.
VBR mode only dose part of the frame as in the part that change from certain scenes before it which in turn is more efficient compression as much as 15% smaller file size sometime even more.

Google Translation (LOL, J/K):

Lordsmurf, it is very difficult to understand the difference between VBR and CBR.

CBR mode does all full frames all the time just like AVI, DV, etc but it doesn't give you very efficient compression.
VBR mode only does part of the frame (the part that changes between frames) which is more efficient compression as sometimes your filesize is 15% smaller, even more.

Was that a good translation do you think?

Compression isn't really applicable to video in the same way it is with ZIP/RAR. Video 'compression' is just trying to recreate a frame in as much detail as possible with the amount of bits a program is allowed to allocate. VBR just determines which scenes can make best use of having more bits.

Anyway. The difference betwenn VBR and CBR is...

CBR has the same amount of bits allocated to each GOP. VBR has different amounts of bits allocated to each GOP.

Using infomation from previous GOPs is completely irrelevant. That is termed 'Closed/Open GOP' respectively. VBR works by analysing how much detail/movement there is in a frame, and allocates more bits to GOPs (which, in turn gives more bits to each frame) where there is a lot of detail.

Am I right in saying this?

I'm pretty sure I got at least most of that right.

[BJ_M]

CBR really means that the bit rate is constant into the buffer .. the acual measured bitrate may go up and down a bit .... not as much as CQ or VBR though ....

[rebarlow]

One thing I've noticed is that when using editing software, the seek time to a new edit location is much faster with CBR files than with VBR files.

[SHS]

bugster
It could recall that ULR page that show the diff of CBR vs VBR I would post it but I can't seem to find it rigth now.
The page I'm ref to had picture show this so I guest he could done it wrong I though it was on 100fps.com but that not it so someday I run across it againe and sent you the URL to it.

[bugster]

bugster
It could recall that ULR page that show the diff of CBR vs VBR I would post it but I can't seem to find it rigth now.

See BJ_M's post above for a brief but accurate description of the diff between VBR and CBR. This is assuming we are talking about mpeg compression of course. You are right that DV is CBR and that it compresses each frame to be the same size as the previous and there is no reference to previous or future frames, but this isn't how CBR mpeg's work.
As for Avi which you mentioned also, this is just a wrapper format and can contain video encoded in many different forms, including mpeg 1 or 2, though this is rare.

[jgandara]

Do you know what is used in comercial DVD's? CBR or VBR?

[BJ_M]

Do you know what is used in comercial DVD's? CBR or VBR?

both

[macm]

I agree with BJ_M.

But most are CBR, since most source the industry use are perfect, noiseless.