VdubMod vs. DVD2AVI

[vlada]

Hello, I have noticed a big performance difference between VDubMod and DVD2AVI in DVD to XviD conversion. I tried two ways -
1) DVD2AVI -> AVISYNTH (resize) -> VDubMod.
2} Everything in VDubMod
I used the same encoding settings, but in 1st case I got about 20 fps, in second one I hvae only about 5 fps (on Athlon 2000). So the performance problem must be in MPEG-2 decoding or resize filtr in VDubMod. In both cases I used bicubic resize. It is really strange. Does anybody else have similiar problem< Thanks, Vlada

[celtic_druid]

To resize in VDubMod means using full processing mode, which in turn means converting to RGB.

Using AVISynth it is possible to keep the entire process in YV12.

[fccHandler]

Indeed, VirtualDubMod's RGB conversion for MPEG is pretty slow. I got a few complaints about Chroma Upsampling Error in earlier versions of my MPEG-2 code, because I was still using Avery Lee's fast YUV to RGB code. That code was optimized for MPEG-1, but it didn't properly handle all the variations of MPEG-2. In the end I had to write my own conversion code. Unfortunately it's never been fully optimized like Avery's, and I wouldn't be surprised if it consumes 50% of the total decoding time.

[Raptus]

Hmm, I just compared pure decoding speed of both and got 90fps avg for dvd2avi + AVS (no crop/resize or filter) and 55fps avg for pure VDM decoding. When activating fast recompress VDM is equaly fast (kinda obvious but worth noticing anyway).

While encoding to xvid (still no crop/resize/filter) the diference drops to 8,3fps against 7,8fps (VDM full precessing but no filters <- useles, for testing purpose). As you see, encoding at those higher resolutions make the codec consume most of the cpu time, narrowing down the diference in speed of both methods.

Now, encoding to xvid doing crop & resize, i got 14,3fps for the AVS method and 8,3fps for the pure VDM one. The speed isn´t even halved, so i can't understand how you got 20fps against 5fps...

Are there any plans to make VD(M) support yuv in full processing mode?

[fccHandler]

I don't know, but Avery Lee (phaeron) had some things to say in this thread (http://virtualdub.everwicked.com/index.php?act=ST&f=12&t=5139&) which may interest you.

[Raptus]

Thanx for the link. It seems we won't have a YUV12-fullprocessingmode-VDM around soon.. :(
To be honest, your sugestion to query filters that "support YUY2 I/O, and allow only those filters" sounds reasonable to me...
Or, when the major rewrite of VD & filters to 64bit becomes necessary, YUV12 support could be added. Hey, AVS 2.5 required new versions of the filters too...

[vlada]

Thanks for the explaining of the speed problem. I noticed later, that I had a lower resolution in the movie I was doing with AVS. This made the speed difference so big. But now I'd like to ask You, what do You think is the best way to compress a DVD to XviD? I prefer quality over speed and I'd like to use some VDub filters. Is YUV to RGB24 convwersion lossles? I think it must degrade the quality of the movie, but as I understood, I have to do it in order to use VD filters. What would You suggest, which MPEG-2 decoder is better? Thanks, Vlada

[fccHandler]

I don't recommend VirtualDubMod to convert DVD VOB files directly; instead I would use DVD2AVI + Mpeg2Dec3 + Avisynth + VirtualDub(Mod). There are tons of posts and guides here about how to set everything up for excellent results.

If you must use VirtualDub filters, then you will take a speed hit from the YUV-RGB-YUV conversion. The conversion isn't lossless, but it doesn't really become "degrading" unless you do a lot of them. I think just one conversion back and forth will hardly be noticeable.