CBR vs VBR

[compuball]

What's the quality difference between A CBR SVCD and a VBR SVCD? I hope that it's not much because I would like to use CCE, but I can only get it to work with CBR.

[Ricardo]

I've not found much difference.

CBR seems to give more consistant results, though if you don't mind waiting longer a two pass VBR can be better.

[Stinky]

CBR = larger files = less per VCD
VBR = smaller files = more per VCD

[lukebrenner]

In TMPGEnc if I want to prepare the file to be burned as a SVCD I should select MPEG-2, put a bitrate calculated with a calculator (ex. 1412) BUT : should I select VBR or CBR ???? Is it a qusetion of personal choice ????

Thnx

Luke

[Stinky]

I'm too lazy to look up the exact specs right now but from memory I think...

if you want to the "standard" SVCD then it's CBR and you can get 30 or so minutes per disk!

if you go to VBR and or go off the 480x480 resolution so you can get more per disk then your actually xSVCD...

or maybe I'm wrong ... or sorta-right ...

I do VBR MPEG-2 and I get =~1 hour per disk - and it looks great - just takes a hell of a long time to do the 2-Pass VBR

[Vejita-sama]

Ok, CBR - constant bitrate vs. VBR - variable bit rate.

CBR is just what it says, the same bitrate will be used throughout the whole movie.

VBR (in TMPGenc) comes in two forms. CQ_VBR and 2pass VBR. CQ_VBR - constant quaility VBR, makes only one pass and will (attempt) to keep the movie quaility constant for all scneces. You enter a min/max and ave bitrate and a 'CQ number' from 0-100. No one really knows what this number is/does. But below 70, quaility wise, everything looks the same, and 100 is the best.

2pass VBR makes, 2 passes. The first is to judge the amount of motion in each scence. The 2nd is to use that info to make another encode. TMPGenc only does 2passes, CCE will do up to 5. Each pass makes a better quaility MPEG but takes 2~6x the time to encode.

How much movie you can fit on a x(S)VCD is 100% dependant on the bitrate you enter. Just use a bitrate calculator (look under tools on the left), I use the vcdhelp.com one as it's easy to use.

Here's what everyone agress on:

1) The higher the bitrate the better the movie quaility
2) Multipass VBR produces better quaility then CBR, esp at low bitrates. But at higher bitrates CBR and VBR look the same (makes since as at VBR min=0, max=2500, ave=2500 you've got a CBR encode). So if you're making a x(S)VCD with high bitrate just use CBR and save time.
3) MPEG2 is better than MPEG1. But at low resolutions MPEG1 actually looks better than MPEG2, because it's at a lower resolution and all the 'noise' kind of blends together.

However, no one agrees on what these 'magic bitrate cut off points' are. Further, quaility is a personal thing, for some the quaility hit from a CBR 900kbit/s video is ok, others only encode at 2500kbit/s and just use as many CDRs as it takes (they are cheap after all).

Not sure if that confused you more or not, but that's CBR vs. VBR in a nut shell.

[Freddie100]

I find that my CBR's are better than my VBR's. I do double the bitrate used for VBR's but are not as good.

[shardison]

TMPGenc 12a VBR is broke. Doesn't work. Might even make things worse. I read that the latest versions of TMPgenc do have working VBR. VBR buys you some extra SVCD bits when the video gets simple, so your movie is smaller.

Don't expect VBR to fix blockiness or improve the quality on action scenes; there aren't enough bits per second available in the SVCD standard to do that even with CBR max'd out.

[kinneera]

Theoretically, VBR should give you higher quality for the same amount of space, since it can use fewer bits where needed and save them to use more bits in other places with lots of motion or whatever... results seem to vary widely however.

[shardison]

It is very true that VBR can give you better quality by saving bits for the hard to encode parts --- if you can actually play those high data-rate portions of the video.

Maybe your video encode can make-do with 2000kbs most of the time, and bump up to 6000kbs for those action scenes. That would sure save space and improve quality.

Too bad the SVCD video data rate is max'd out at 2400kbs or so. Most if not all DVD players will choke on 6000kbs XSVCDs.

We'll all use VBR when we start burning DVD's