SVCD CBR vs VBR - Quality

[NearlyCritical]

I know this topic has been discussed previously in many posts, but I think my question is slightly different.

Which method is going to give the best quality?

CBR at 2300 or VBR (multi-pass) at MIN 1000 AVG 1800 MAX 2300.


Points to consider:

1. The VBR method will obviously have a smaller filesize, but quality is what we are comparing. So assume we are encoding a short movie that will fit on 2 CDs regardless of CBR or VBR, filesize isn't relevant in this case.

2. Notice the CBR bitrate is equal to the MAX bitrate for the VBR method. Even at it's best the VBR method is only using an equal amount of bitrate as the CBR and is probably using less for most of the movie.

Doesn't this mean that because the CBR method is always using equal or more bitrate it will have equal or better quality in every case?

The only way I can see the VBR method giving better quality is if during a multi-pass encode it can distribute the bitrate more efficiently per second.

[ritmo2k]

As far as my tests have shown, your right.
But, I am no expert, there are things to consider.
1) Yea, the distributed bitrate in VBR can help, but you might take data away from low motion scenes that could have used it.
2) Generally, I like cbr, as long as it is high enough, I think you nothing to worry about, as in the case of svcd, 2520 kbps is very large!

Hope that helps,

[ChristianHJW]

When encoding in VBR mode you can always achieve better results than in CBR.

a. VBR will save bits on certain frames ( = lower bitrate ) and these may be redistributed on other frames ( = higher bitrate than CBR ). Result : same file size ( = same average bitrate ), better quality

b. you use VBR with smaller average bitrate than CBR. This will probably result in same picture quality with smaller file size.

[dvd2svcd]

ChristianHJW is absolutely right on the issue.

[NearlyCritical]

Originally posted by ChristianHJW
When encoding in VBR mode you can always achieve better results than in CBR.

a. VBR will save bits on certain frames ( = lower bitrate ) and these may be redistributed on other frames ( = higher bitrate than CBR ). Result : same file size ( = same average bitrate ), better quality

b. you use VBR with smaller average bitrate than CBR. This will probably result in same picture quality with smaller file size.


I totally agree with the 2 points you have made, but as it relates to my specific example, are you saying that an encoder will use more btrate than what you specify by MAX bitrate?

"these may be redistributed on other frames ( = higher bitrate than CBR )"

In my example I stated that the MAX bitrate set for the VBR is the same as the CBR bitrate. In this case I assume the image quality will be very similar in high motion scenes as both methods are using the same bitrate, and in low motion scenes the CBR will often look better.