XviD setting in Guardian Knot

[Neuman]

Hi,

I have bought a DVB card and are now getting a lot of intereseting movies :)

I transcode the movies to XviD in Guardian Knot, - and that works pretty nice. I am pretty much following the sceme given in the Guides area of Doom 9 (Thank you Doom9!) :thanks:

Especially I am doing this (http://www.doom9.org/gknot-xvid.htm)

And last but not least the compressibility check.

It's possible to run a short first pass to find out the optimal compressibility of a movie (and make an even better resolution choice). Turn the Compressibility check on and set it to 5%, then press the Now button, wait for a few minutes until GKnot comes up again. The Edit button allows you to edit the AviSynth script prior to performing the check but only experienced people should touch that. Same goes for Codec settings which allows you to manipulate the codec settings used for the compressibility check.




Once the check is done the Save as window will disappear and you'll notice some changes in the Bits/(Pixel*Frame) part of the window:



The compressibility check gives you a rough indication of how good a movie can be compressed. The 3 values shown above are related as follows: the 0.831 is the value that the compressibility check returned. If the Bits/(Pixel*Frame) value right above the Load button matches this value you have perfect quality, going for a higher value (= a lower resolution) would be overkill as the movie wouldn't look any better.. The limit of the codec has been reached. The 23.7 mean that with the given resolution, your movie will have a 100 - 23.7 = 76.3 % lower Bits/(Pixel*Frame) value than an ideal quality movie (note that ideal quality doesn't mean as good as the DVD.. it means as good as the selected codec allows). The percentage field is marked in red because the value is rather low and GKnot means to suggest that you should lower the resolution for a better result. A percentage value (as displayed) in the range of 40-60% should yield optimal results, a value above 80% is serious overkill. Note that features like B-frames will actually permit a lower Bits/(Pixel*Frame) value and the movie will still look good, so you should take those values with a grain of salt (I happen to know that the movie in question will still look OK with the settings chosen).
So basically I do a test, - find the 50% value. And then do a two-pass compression.

Now I heard that the first-pass is actually just to be trown away. I just uses this to know how hard it should compres the movie.

Then I was thinking, - can I somehow say 50% to it, - and skip the 1. pass and the test? That would make everything a lot faster for me!

Edit: Just to be explicit, - I always use the same resolution, - so my files have quite different filesizes/bitrates, - but that's o.k. to me

[Irakli]

Then I was thinking, - can I somehow say 50% to it, - and skip the 1. pass and the test? That would make everything a lot faster for me!

I think theoretically you can just use single-pass encoding with target quantizer. This should provide quite constant quality across the whole file. However, in reality, I think, you can do this only if you'll be able to work out which quantizer represents 50%.

I think the reason to use 2-pass encoding is to get maximum quality for given filesize. If filesize is not important then my suggestion is to use target quantizer of 3 or even 2.

[manono]

Hi-

However, in reality, I think, you can do this only if you'll be able to work out which quantizer represents 50%.

Try 1-pass for quant 4. If you don't like the quality, then change to quant 3. One or the other should satisfy you.

Edit later: GKnot works with 2-passes. You'll have to do your 1-pass encoding directly in VDubMod. AutoGK also does 1-pass encoding.