Question about XviD output size

Bushido Philosopher · Post by **Bushido Philosopher** » Sat Jan 04, 2003 12:59 am

It's a little strange, but here goes.

When I follow the directions to the XviD encoding, my impression is that the first pass should be a little smaller than the final output with audio.

However, when I do everything the final output is actually smaller than the 1st pass, audio and all. And of course the first pass didn't even have any audio attatched at all.

Is this what is supposed to happen, or what?

Output looks just fine, no problems at all. That's what's so weird about it.

trythil · Post by **trythil** » Sat Jan 04, 2003 1:24 am

Depending on how you've set your parameters, yes, that is supposed to happen.

The first pass encode writes out bitrate curve data (which contains, among other things, how many bits are distributed per frame) and, if you tell XViD to, a first pass video.

The second pass uses the parameters you give the encoder (e.g. I-frame boost, which says how many more bits to give keyframes, curve compression percentages, which basically says how to skew the bitrate curve for the high and low-motion scenes, and so on) to optimize the bitrate curve for whatever condition you give it (for example, 2nd pass Int. allows you to specify a target file size).

In many cases, this can reduce the size of the video stream so much that, even with audio attached (and audio really isn't all that large in comparison to video, especially given modern compression techniques), the second-pass video is still smaller.

Bushido Philosopher · Post by **Bushido Philosopher** » Sat Jan 04, 2003 1:53 am

wow...how cool is that??

ErMaC's right, XviD rocks!!!