Video structure of a DivX

[Chelmon]

Hi,

Excuse my poor english, it's a long time since I haven't pratice...

I've ripped my first movies one month ago, using GK 0.27, and the result is good (for me :p ).
In GK forum, I've read many things about avisynth 2.5, VDMod... which are supposed to be better because they can read directly YV12 and do not have to convert in RGB (I've tried to install them, but it seems not to work properly with GK 0.27 :( - this is not my question however).

I'd like to know what is the video structure of a divx ? I DVD2AVI give me a RGB, will the DivX be also in RGB or transcoded in YUY2 ? If not, how can I know the video structure of a Divx ?

Chelmon

[killingspree]

hi and welcome to the forum!

to your question: i don't really understand what you want to know by the structure of a divx.

but i'll explain the colorspace to you. divx can encode in RGB, YUV2 an YV12. it is true that dvd2avi gives you an RGB result, but if you use avisynth, this colorsetting is ignored. this works, since dvd2avi is only used for frameserving and therefore avisynth can get the information directly from the vob-files. These vob-files are usually encoded in YV12 format.
it depends mostly on avisynth which colourspace is used. most filters work with YUV2 and the newer ones also with YV12. but if you told avisynth to use RGB (which will not make sense) the divx would be encoded in RGB.

anyway, when you use gknot .27 you will usually get a divx file that is encoded in YUV12, since both avisynth 2.07 and virtualdub do not support YV12.

if you are somewhat familiar with avisynth scripting, you can check the colourspace manually. just load the divx - avi into a script and add the info() command. this will display some basic information about the avi (framerate, colourspace, etc) in the video field when you load it into your favourite mediaplayer...
here's a cript you could use to check this... just copy and paste it into a text file and rename it to ***.avs and save it into the directory where the movie is (afaik this only works with avisynth 2.5)

avisource("***.avi") #replace **** with the name of your avi file
info()


hope this helps and was kind of clear enough formulated without too much techtalk (:

regards
steVe

PS: if i didn't make everything clear search the forum and afterwards ask here

[hakko504]

As killingspree managed to get an answer in before I could post my reply I'm not gonna feel guilty for making it a little bit more technical. I'll try to explain this as simple as possible.

On a DVD the data is stored as YV12
DVD2AVI creates a .d2v file that is a file telling mpeg2dec how to read the .vob files. In the .d2v file there is a note on how DVD2AVI wants the file to be decoded. Mpeg2dec ignores this, and returns YUY2 in AviSynth2.0x. In AviSynth2.5 you can choose whether you want YV12 (faster) or YUY2. YV12 requires mpeg2dec3.
If you use AviSynth2.5 and VirtualDubMod set to 'Fast recompress' then the whole chain can use YV12 without colorspace conversion (very fast)
The final DivX uses YV12 to store data.

So the gain of using AviSynth2.5 is that you
a) process less data (12 bits/pixel in YV12 instead of 16 in YUY2) and
b) does not need to convert between colorspaces.


AviSynth 2.5 will work with GordianKnot, but maybe not to the full potential. You will need the latest version of VirtualDubMod, both the release version and the 030131 patch. You also need new versions of the plugins that Gordian Knot uses.

The latest version of VirtualDubMod can be found at sourceforge.net (https://sourceforge.net/projects/virtualdubmod). Be sure to get all three packages! Also AviSynth2.5 can be found at sourceforge (https://sourceforge.net/projects/avisynth2.5) together with the most common plugins. And reading up as much as you can on AviSynth.org (http://www.avisynth.org) is always a good idea, the FAQ (http://www.avisynth.org/index.php?page=AviSynthFaq) in particular.

Good luck.

[Chelmon]

Thanks to you, both Killingspree and Hakko504.
You understood excatly what my question was :)

I gonna try to re-install Avisynth and VDMod now.

Chelmon