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Old 27th December 2002, 17:08   #12  |  Link
BoNz1
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Join Date: Dec 2002
Location: Great White North
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@ drizztcanrender, you are quite right, that is exactly what rc averaging does. Say if your max min quantizers are at 2 and 12 and you have rc averaging set at 2000 it does not allow for much variation, it is like putting the codec in a straight jacket and it will not be able to compensate for it as you would like. It will have to average the quantizers between 2-12 in every 2000 frames. If it is set to half the number of frames then it will be able to average the quantizers better and get a much more accurate result. Of course, you do not have to set the rc averaging to half the frames, it is just a safe estimate. Larger values should give better quality to high motion scenes and lower values to low motion scenes. So if your movie had a lot of low motion scenes you could set the rc averaging to somewhat less than half and vice versa for a movie with a lot of high motion. This may explain why some people have different results if they set it to be much higher or much lower than 1/2.
@ ?¿öM¿? I am interested to see your results if it were a 2-pass encode. The rc averaging is needed for both passes so testing it with only one pass it may be harder to see the difference that it can make although your results definitely support what I have just said. What you have done is like a smart-1-pass encode instead of the usual 1-pass encode which is completely blind and usually gives unpredictable results.
I did The World Is Not Enough about a year ago with rc averaging set at 2000, using a bitate of about 1500, using b-frames and gmc and doing a 2-pass encode. The result was awful, it looks disguisting especially high bitrate scenes which had blocking everywhere. I was a bit of a n00b at the time so I don't think I really noticed too much. But since then, I have always set it to half and have been quite happy with that, high and low bitrate scenes look much better, and filesize predictability seems to have gotten a lot better. I would really like to encode that movie again though once with it set at 2000, then 1/2, and then maybe even try a 1/4 or even 3/4 just to see what it looks like.

Last edited by BoNz1; 27th December 2002 at 17:13.
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