Avid Quicktime-Ref to Avisynth problems

[hanfrunz]

Hello everyone,

it should be simple, but it isn't...

What i try to do:
i have an Avid project, all the material is captured in avid 2:1 resolution. I export my sequence to a Quicktime-Ref file, this files references to the mxf-video files in the AvidMediaFiles directories. This works very well and saves time and discspace. The problem is if i want to open this file with avisynth. I use tateu's great QTInput filter, but i get wrong levels if i use YUY2 as return-colorspace:


QTinput("QTRef.mov", color=2,mode=0)

on a 75% colorbar i get y'=215 for the 100% white, but it should be 235. The yellow bar is y'=146 (should be 162)
If i use RGB32 the levels are okay. white:r=g=b=235, black:r=g=b=16 I can't use the RAW-mode because it's compressed material (avid 2:1)
Any ideas how i can get correct levels in YUY2 colorspace out of a QT-ref file? And why are the levels wrong? Is it a "Quicktime-feature" :devil: or a bug in QTInput?

BTW if use no compression (Avid 1:1) then i can use mode=1, raw="2vuy" which works perfect! But if i use mode=0 i get the same wrong levels.

regards
hanfrunz

[tateu]

I've never been able to figure out exactly what the problem is and therefore have no real solution, but it is Quicktime's fault, as far as I can tell. It has something to do with the gamma levels. I've read through numerous posts on the Quicktime dev mailing list of people having similar issues but have never read about a way to just make it all work correctly. For compressed material, I just use RGB mode and let AviSynth do the YUY2/YV12 conversion.

I think I did some tests a few years ago, changing the gamma levels of the decoder, and that would fix it...sometimes (it would work for this codec, but not that one; it would work for files from this encoder but not that one, etc.)...but since it didn't always work, I abandoned it.

[chaynik]

The best solution I've found is to use Uncompressed 4:2:2 video. Then you can use the RawSource AviSynth filter to load the raw YCbCr data out of the MOV container and into AviSynth. Take a look at a recent thread I've posted here: http://forum.doom9.org/showthread.php?t=140820

Btw, what are you using to find out the levels of the bars? I'd love to be able to do so to make sure all of my levels are correct as well without leaving the YUV colorspace (right now I take screenshots and "colorpick" them in Photoshop, probably not that accurate of a practice..)

[hanfrunz]

Btw, what are you using to find out the levels of the bars? I'd love to be able to do so to make sure all of my levels are correct as well without leaving the YUV colorspace (right now I take screenshots and "colorpick" them in Photoshop, probably not that accurate of a practice..)

i have written a filter with gui where you can move a cursor over a pixel and get it's values. Mmmh i think i never published the latest version. When i'm at my main machine again i'll upload it.
Another way is to crop a small part of the bar (only one color) and use ColorYUV(analyse=true)

hanfrunz

[krisq]

Btw, what are you using to find out the levels of the bars? I'd love to be able to do so to make sure all of my levels are correct as well without leaving the YUV colorspace (right now I take screenshots and "colorpick" them in Photoshop, probably not that accurate of a practice..)


You can try AvsP, it lets you see pixel values under the cursor. And is the best script editor for avisynth IMO.
Find it here (http://avisynth.org/qwerpoi/).

[Mug Funky]

i'm all for an mxfsource :) or an omfsource for the oldschool aviders.

quicktime is in dire need of a rewrite. apple suck. it's not quick, and it's barely even time :)

optimists and mac apologists are saying that snow leopard should solve a lot of quicktime's problems, but i don't believe a word of it.

[Blue_MiSfit]

I've heard some very interesting things from Apple engineers, saying that 10.6 will have a complete and total QuickTime rewrite. As we all know, QuickTime hasn't been completely rewritten since version 3, back in the early nineties :D

Hopefully this will mean the Windows version will get a complete rewrite too, since it's also horribly outdated.

It's too bad, the MOV format and QuickTime in general has some really fantastic ideas.

-Derek