YV12 questions

[MattO]

Hello all,

Is YV12 & AVISynth 2.5 just for Xvid etc ... or can it be used for conversions to MPEG1 or MPEG2 (DVD to(S)VCD) via TMPGenc or CCE?

Or do these 2 encoders not support YV12?

I ask because the speed gains people have posted are very impressive.

If not, are the improvements to the plugins, like MPEG2DEC3 (up to 0.91) etc, going to be made to the plugin versions for AVISynth 2.06, or are the changes just YV12 specific?

thank you for your patience.

MattO

[hakko504]

AFAIK neither CCE or TMPEG can use YV12 input. This only means that the last line of AVIsynth must be a ConvertToYUY2() call, and that you will not be able to take full advantage of YV12 colorspace. All internal filtering in AVIsynth will be faster though (less data to filter,better structure to filter,and a very fast conversion from YV12 to YUY2), and you will definitely be able to tell the difference between 2.06 and 2.5.

[Dali Lama]

hakko504, if what you say is true (which I think it is) then how do DVD Authoring Studios that make Big Name DVDs encode MPEG-2 into YV12 format? Maybe a higher end MPEG-2 Encoder? Hardware Based?

Man, I thought CCE was high end!

Dali

[hakko504]

@Dali

The full advantage I mentioned is the ability to use one single colorspace for all stages of the transcoding, thus reducing losses due to colorspace conversions. The transition from YUY2 to YV12 is pontentially lossy, but in our case, transcoding MPEG-2 DVD's to MPEG-x, just adding a ConvertToYUY2() at the end of the script will not cause any losses, as the U/V components are just doubled.

Remember that YUY2 is a higher quality format than YV12! It uses 16bits/pixels instead of 12bppp.

Also, big studios usually scan their films at something like 2000x2000 pixels[1] and filter the data at that level before resizing down to DVD size. I also recall reading somewhere that they do not use 8 bits/sample but rather 10 or 12 increasing precision even more.
And I suspect that some studios/DVD producers, running on lower budgets may very well be using a combo of Adobe Premiere and CCE to do this. Top-of-the-line studios probably have even better stuff, but in most cases this is more than sufficient.

[1] I know I saw the exact numbers in a post in the general forum a couple of months ago. A search may reveal some details.

[RadicalEd]

Originally posted by hakko504
The transition from YUY2 to YV12 is pontentially lossy, but in our case, transcoding MPEG-2 DVD's to MPEG-x, just adding a ConvertToYUY2() at the end of the script will not cause any losses, as the U/V components are just doubled.

Remember that YUY2 is a higher quality format than YV12! It uses 16bits/pixels instead of 12bppp.


yeah but CCE/TMPG are then converting that YUY2 source back to YV12 so there is a conversion YV12 -> YUY2 -> YV12 which could be avoided if CCE and TMPG accepted YV12 source. I also heard that TMPG actually converts YUY to RGB internally before encoding which is a waste (please tell me I'm wrong there)

[hakko504]

@Ed

The conversion YV12->YUY2->YV12 should be without losses if it is done correctly. Incorrect conversion will introduce rounding errors but shouldn't be that much of a problem. Going the route via RGB is definitely the wrong way, but most of the time it shouldn't create too much errors. It will take time though, quite unnecessary. I usually does DivX so I'm not familiar with TMPEG so if someone know whether it actually uses RGB or not, please post here and say. The conversion YV12->YUY2->RGB->YV12 is both stupid and slow. If CCE is able to deal with YUY2 directly this may be a cause of the presumed higher quality of this encoder compared to TMPEG.

[RadicalEd]

Actually YUY to RGB and back causes much more of a difference than is given credit, take a look at this post (http://animemusicvideos.org/phpBB/viewtopic.php?t=5885&highlight=) and compare the pictures, so the loss isnt just speed unfortunately

[hakko504]

Point taken. Quite convincing pictures really, I have never looked at the conversion close before as I almost always use straight YUY2 in AVIsynth for my encodes to DivX5.02.