2 pass XviD or DivX question

[Northstar]

I have just got into doing 2 pass encodes of my captures and have a question regarding filters. Do i add a filter in the first and second pass or do i add the filter in the second pass only? I want to deinterlace most stuff and use smart deintelacer in Vdub, now i know once you deinterlace something it cant be deintelaced again so im presuming that needs to be added in the second pass, but what about noise filters for videos that have noise... first and second pass, or just second? Should cropping be added in the first AND second pass? Also is there any particualr order that filters should be added?

Cheers for any replys.

[xtreemkareem]

Hmm... I would make sure that the second pass has the noise reduction filters... as for the resize and deinterlace, instead of using VDUB (which doesn't have the best resize or deinterlace filters) use avisynth to create a .avs file for you which is already set for resize and whatever style deinterlace filter you choose. That way the only thing you have to do in vdub is add the noise reduction filters to the second pass. Iff you don't know how to make an approriate avs file, use GKnot to make it for you... it's really easy. Just open the source file in the lower right hand corner (either an avs listing the source or d2v DVD2AVI project file if your source is DVD ) after having selected an output resolution in the resolution tab (which is helpful as it gives you the correct AR and tells you how many bits per pixel for a certain bitrate and resolution... best to keep @ about .2 bits per pixel). Chose save and you get a box gixing you obtions as to resize filters, noise reduction and deinterlace. Check those and save your avs and load that into vdub. Oh, and make sure avisynth is installed or it aint gonna work! Good luck!

[Northstar]

Now if only i could understand avisynth, which i downloaded a few days ago, had a look at it, thought, wtf is this all about? I am pretty new to the whole capture scene and am just learning the ins and outs of vdub, there is no way i understand avisynth at all, i wish i did as ive seen good things said about it, but im more of the point and click kind of person when it comes to this stuff. I will learn it i suppose, at some time, i just need to learn this stuff whch is easier for me to understand. I will do what you said with the filters in vdub though, do you still suggest adding deinterlace and cropping in the second pass, like the noise filter and not in the first pass at all?

Cheers.

[ronnylov]

You must use the same filters and settings on both passes because the first pass analyzes the result of the encoding and the second pass adjust the bitrate and use bits from easy to encode parts to hard to encode parts.

If you add a filter the results from the analyzing pass would be different fron the final pass and that is not good.

[Northstar]

Thanks, i'll be doing that from now on then, filters on both passes, except for any noise filter, i presume that should go into the second pass only, because if it has to go through both passes we are talking 7 hours plus per encode Not that i use filters much, but will in a couple of bad vhs videos i have, i tried a noise filter on clips and it looked much better, i would like to use the spotremover filter as its amazing, but its not free so i may consider paying for it in the near future.

[ronnylov]

As I said you need the same filters and settings on both passes, and that includes noise filters too. If you don't use noise filter on the first pass, then don't use it on the second pass either.

[xtreemkareem]

Why would it be important to use the noise reduction for the first pass as well? As for the other suff such as resize etc, all settings should be same both passes since they all have an effect od bitrate/data per pixel, etc. But since noise reduction woudn't have much of an effect on bitrate, why then must it be used for both passe? How much doe it change motion search parameters etc?

[Northstar]

Well imho 2 passes with a noise filter for a 1 and half hour video = 7 + hours encode (im guessing from the average), probably more, is a bit too much for me. I have tested 10 minute clips of my 'bad' videos with the noise filter on only the second pass and thought the quality was extremely good considering on how bad they looked to begin with. The size thing dosent seem to be affected, only a full encode instead of 10 min clips will tell. But cheers for the suggestions.

[ronnylov]

Some noise filters tries to remove noise but not affecting clean pictures. Let's say there is more noise in some parts of the video and the noise filter cleans it then the bitrate required to encode this part is lower than if the noise was left. So if the video is analyzed without the noise filter then more bitrate will be allocated to the noisy parts. Then on your second pass you clean out some noise and the bitrate is still distributed as if the noise was still there. This will cause ineffective bitrate distribution. Bits that could have been used elsewhere are wasted.

The final result may look good anyway, but the bitrate is not used in an optimal way.