Ron P. wrote:Not everyone agrees on why or when to use 2-pass encoding. My opinion and thoughts are that one the first pass, it will analyze your video for parts that need higher bit-rates, and parts where lower bit-rates would suffice. Then on the 2nd pass the video is actually encoded, using the different, varying bit-rates. Higher bit-rates would be need for fast moving actions, and the lower for slow, still or no movement.
I don't think it has much to do with the quality, it seems to be more for being able to squeeze more video onto a disc, while maintaining the same quality.
From the perspective of a video editor, It's everything to do with quality! CBR tries to hit the same bitrate for both action* and sleepy** scenes. At the same average bitrate, VBR will yield the same filesize as CBR. You don't get any more data on the disc, but the bits will be apportioned more appropriately for the content, improving the perceived quality.
It might be possible to drop the average bitrate with VBR and still maintain the same perceived quality as the higher CBR rate. That would mean you can fit more on the disc, but it's dependent on the footage, and you're still starting with quality as a criterion and getting the discspace as a result, not the other way around.
Having said all that, if you use something like Nero to recode a >4.7GB disc to fit into 4.7GB, then VBR will help.
* Action might be explosions, rainfall, leaves or grass in a breeze, a waterfall, confetti etc.
** Sleepy might be a "talking head" newscaster, slow pan over a static room scene etc.