Quote:
Originally Posted by Katie Boundary
In an attempt to see if Q-pel, GMC, and VHQ wide-area searches were worth using, I ran a bunch of XviD first-passes with different settings and compared the resulting file sizes. XviD first-passes have a constant quantizer (2), so anything that improved compression should have resulted in smaller file sizes. To my surprise, all of the files had the exact same size down to the byte.
This reminded me of the "full quality first pass" option, and the fact that it resulted in larger file sizes despite using the exact same quantizer. And then I remembered that it also resulted in slower encoding times, and something something might not be fully mpeg-4-compliant.
So my question is: Does an XviD first-pass disable all those doodads, regardless of what your actual settings are? And does "full quality first pass" mean "screw that, use the settings that I tell you to use"?
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Huh, it feels like ages since I have been using XviD, but as far as I remember:
In a standard 2-pass encode, the first pass disables by default many of the encoder settings which become effective and useful in the 2nd pass only. In particular this applies for VHQ. Also to mention that only the small stats file is produced in pass1 rather than the fully encoded video.
When you select Full Quality First Pass however, all encoder parameters settings are enabled in pass 1 already, making pass 1 much slower with little benefit for the final 2-pass quality. Also, the fully encoded video is kept from pass 1 rather than the stats file only.
As for GMC I think to remember that it has little to nil effect on compressability but increases the encoding time substantially.