How to use the VBR (Variable BitRate)?

[F u r u y á]

I always use CBR when creating VCD and SVCD movies.

I was thinking that VBR would be usefull when the movie shows an almost static scene (need fewer bitrate) and with high action scenes (need higher bitrates). Thus, the file size is smaller without loosing image quality.


So, how can I use the VBR?

[Tommyknocker]

What program?

[F u r u y á]

Actually I want to know the concept of VBR, I know in TMPGEnc is just choose an option for Rate Control Mode.

So, the VBR works like I supposed? If yes, I will always use it instead CBR

[Tommyknocker]

I see. It is a better quality bit rate, so it takes more time to encode. As you guessed, it slows it bit rate for slower scenes, and increases it during higher action scenes.

[Gillies]

vbr is far supirior to cbr, unless u have cbr cranked to max but then u'll get a massive file size. vbr is much more efficient and is always preferable.

[ZippyP.]

Couple of things to know about VBR:

*VBR is best when the file size is an issue and bitrate is dropping enough so as to affect quality.
*CQ VBR is faster (1 pass) but file size is unpredictable.
*If using 2-pass it takes twice as long but it's the only one that makes a file of known size.
*In 2-pass set the maximum for the highest possible, eg vcd 1150, svcd 2550, dvd 9000.
*Use a minimum as low as possible.
*VBR is not VCD compliant but it will play on many players.

Hope that helps.

[F u r u y á]

So, if I set, for example, 1700 kbit/s in TMPGEnc and choose VBR, the movie will get maximum bitrate of 1700 kbit/s, thus it will be smaller that a CBR movie with 1700 kbit/s?

[F u r u y á]

Thanks for helping all of you, especially ZippyP. which is the second time that really answered a doubt of mine! 8)

[daamon]

So, if I set, for example, 1700 kbit/s in TMPGEnc and choose VBR, the movie will get maximum bitrate of 1700 kbit/s, thus it will be smaller that a CBR movie with 1700 kbit/s?

Not quite - For VBR there are three settings: Minimum, Average and Maximum.

The Min and Max set the lower and upper boundaries which aren't to be exceeded, and the Average is the target bitrate (on average) to be achieved overall. Then, with that in mind, it works as you first supposed.

This page will help answer your intial question on VBR vs CBR.

And this guide has a section in that explains VBR quite nicely. It's worth mentioning here that a low Min and a high Max (within the rules) are good to have - it gives the encoder room to work (so to speak).

Hope that helps.

[wulf109]

With VBR you need to set three bitrate's,minimum,average,and maximum. The average bitrate will determine how much can be encoded in time.

[ZippyP.]

...the movie will get maximum bitrate of 1700 kbit/s, thus it will be smaller that a CBR movie with 1700 kbit/s?

Min 200, avg 1700, max 2550 (assuming SVCD) and the file will be the same size (almost) as the 1700 CBR but much better quality.