Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Capturing and Editing Video > Avisynth Usage

Reply
 
Thread Tools Search this Thread Display Modes
Old 19th May 2004, 01:24   #1  |  Link
Magno
Registered User
 
Join Date: Feb 2003
Posts: 73
IYUV or YV12 colorspace?

I have been searching the forum for two hours to get information about a doubt i have about colorspace converisions and i haven't been able to understand this...

MPEG2DEC3.dll outputs the image in YV12 format nativelly, but the colorspace used in MPEG-2 4:2:0 is, actually, IYUV (or I420, as you like) so... where is the point about getting the output in YV12, in which the chroma components are changed in order (before V, then U)?

I suppose that the YUY2 output is used with MPEG-2 sources which have 4:2:2 profile in them. Maybe am i wrong?
Magno is offline   Reply With Quote
Old 19th May 2004, 09:04   #2  |  Link
Wilbert
Moderator
 
Join Date: Nov 2001
Location: Netherlands
Posts: 6,337
Quote:
MPEG2DEC3.dll outputs the image in YV12 format nativelly, but the colorspace used in MPEG-2 4:2:0 is, actually, IYUV (or I420, as you like) so...
Indeed. Well, I think that mpeg2dec3 outputs I420, and AviSynth converts it to YV12 internally. But, the user won't notice this.

Quote:
where is the point about getting the output in YV12, in which the chroma components are changed in order (before V, then U)?
Good one. Maybe it is stored in DivX/Xvid as YV12 (and not I420). But, I'm not sure.

Quote:
I suppose that the YUY2 output is used with MPEG-2 sources which have 4:2:2 profile in them. Maybe am i wrong?
Maybe Neuron2 can comment on this. Btw, I have never seen such streams.
Wilbert is offline   Reply With Quote
Old 19th May 2004, 09:52   #3  |  Link
Magno
Registered User
 
Join Date: Feb 2003
Posts: 73
I am developing a program which debugs a MPEG-2 stream, in any level and profile, and so, i have some 4:2:2 streams to test the program.
If anyone would like to take a look at them, contact me
Magno is offline   Reply With Quote
Old 19th May 2004, 14:21   #4  |  Link
trevlac
budala
 
Join Date: Oct 2003
Location: U.S.
Posts: 545
Hi,

I just wanted to clarify because there is a common misuse of terms. As a newbie this confused the heck out of me. Still does.

A color space is a mathimatical description of color. Most contain 3 components such as RGB, HSV, YCbCr. You can convert between these. Each component is basically a variable in an equation.

IYUY and YUV12 are pixel formats. They both reside in the YCbCr color space.

Especially within the YCbCr color space you find a number of different flavors. These are due to:

1) Subsampling such as 4:2:0 vs 4:2:2 vs 4:1:1 etc ...

2) Bit depth such as 8 or 10 or 15

3) Pixel storage format aka (I believe) FourCC. IYUV or YV12


So ... there is no color space conversion from IYUV to YV12. I don't even think it would be proper to call up sampling or down sampling a color space conversion .... YCbCr 4:2:0 to YCbCr 4:2:2 etc.

Here are some nice M$ article on the topic...
http://support.microsoft.com/default...b;EN-US;294880
http://msdn.microsoft.com/library/de...yuvformats.asp


PS: YUV is an unfortunate term that describes many things. In it's general use, YUV referrs to the YCbCr color space in digital. YUV is also a reference to the PAL analog color space. Yuv is a reference to the color science Luminance/chromiance, which is not the same as YUV in video. Poynton goes on and on about this here: http://www.poynton.com/PDFs/YUV_and_...ce_harmful.pdf


PPS: Unfortunately there do seem to be a number of YCbCr color spaces. SMPTE vs 601 vs 709 I believe. The difference is due to what combination of colors is considered to make up the Y component. The difference exists because YCbCr is intended to be projected back thru a display device (your monitor or TV). Standards changed as monitors changed. 709 is for modern monitors, but 601 is what is used for non HD video.


This was ment to help future readers ... but hey ... I don't work in the field. Just read about it and play. Maybe I got the details wrong.
trevlac is offline   Reply With Quote
Old 19th May 2004, 15:32   #5  |  Link
Wilbert
Moderator
 
Join Date: Nov 2001
Location: Netherlands
Posts: 6,337
Quote:
So ... there is no color space conversion from IYUV to YV12
Details ... "color format conversion" if you prefer
Wilbert is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 20:04.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.