Bitrate 2 pass VBR vs. CBR

[fitte]

I´ve encoded my first XVCD with 2 pass VBR. I used dvtool as bitrate calculater. After encoding the filesize was "only" 680 MB (i use 700 MB/80 min. CD-R). When i encode the same file with CBR the filesize is about 720-730 MB! In my opinion i could use a higher bitrate for 2 pass VBR to improve quality.

But how do i know what bitrate i have to use to get more data on my CD-R.

2 pass VBR Settings: min. 1200 / avg. 1800 / max. 2400
CBR Settings: 1800

Any help would be great.
Thanx in advance!!

[SatStorm]

You can set average bitrate to a higher value, if you are not satisfy with the overall look of your xvcd
If you have blocks etc, then set to a higher value the Maximum bitrate, but don't change the average one.
In both cases, you will end up with a bigger (and qualtiy better) file

[fitte]

That´s my problem. The bitrate calculator says 1800 kbps. In my opinion there is more free space on the CD-R. But how do i know the filesize if i encode with e.g. 1850 or 1900 average bitrate? The quality is pretty good no blockness and stuff but i wanna use the whole space on my CD-R and thats not the case with an average of 1800 kbps. I cant go to a higher max. bitrate this will give a choppy sound. I tried one with max. 3000 kbps but the sound is choppy in high motion scenes.

So why is the whole space on my CD-R with CBR but not with 2 pass VBR?

Any ideas?

[therick]

The whole space is taken up by the CBR because is it a constant rate, while the two pass VBR CHANGES due to the motion in a scene, color, etc..so although, the average will be 1800, it will drop below that for some scenes...and doing two passes allows the encoder to have a full look at the video file BEFORE encoding to ensure that is does a better job at deciding where to put the bitrate for all of the scenes...and thus you have the smaller size...

fitte: how long is the clip that you are wanting to encode to one CD-R?

If I want 48 minutes on an 80 min. CD-R I am having to drop down to about a 1861 kbit/s average...which is the neighborhood you are talking about...

[fitte]

@therick:
The Clip is about 48 min. long. Does it mean if i want the whole space used i should encode with 1860 kbps avg.??
And how do i know if my movie fits on CD-R with 1860 kpbs/avg.? Cause the bitrate calculator says: 1800 avg.

Does anybody know a bitrate calculator for 2 pass VBR, or can i put + 50 kpbs on the calculated avg bitrate?

By the way: My movies look excellent, but if i burn a CD i want to use the whole space thats why i´m asking!

[kinneera]

Did you tell the bitrate calculator you were doing XVCD? It sounds like it calculated the bitrate necessary to fit a Divx movie onto a 700 MB disc.

If you use 2-pass VBR in TMPGEnc, the resulting size will always be almost exactly the same as encoding CBR at the same bitrate as the VBR average. The only difference is that it can save some bits from some scenes and apply them where they are needed more, exceeding the average bitrate.

[therick]

@fitte- yeah, 1860 is the avgerage. I think that is what I said...isn't it? Yeah...another thing to think about if you are more a of a picture than sound guy (like me) is dropping the audio down to 192...ups your avg. video bit rate to almost 1900...sorry to take so long...I am smack in the middle of finals.