Pixel aspect

sunep · December 22, 2009, 2:18pm

Hi All

Since this seems to be a time where we dig out the little things that we have discovered as suboptimal or little errors, I have this little thing that used to annoy me, but now I have just gotten used to the way vvvv does not detect the pixel aspect of video.

It would be pretty practical if either the VideoTexture nodes or FileStream could output the pixel aspect so that it would be possible to handle video content with mixed pixel aspect ratios automagically.

An example would be a situation where you in a live setting are getting video from different sources with cameras in different formats: 4:3 and 16:9 probably PAL. In this case it would be pretty handy to be able to just throw the captured clips straight into vvvv regardles where it came from.

As often before I have no clue if this would be difficult to implement or not, quicktime for one cannot do it by itself (At least, I have only found out a very complex way to set it manually)

-sunep

joreg · December 22, 2009, 7:00pm

ai sune,

wouldn’t videotexture in NonPow2 mode in combination with a Info (EX9.Texture) give you all the parameters you need to do this?

sunep · December 23, 2009, 2:08am

Hi joreg

not unless there is some feature I have not seen. the classic example is to mix 4:3 PAL with 16:9 PAL recorded on eg. miniDV. both are 720 by 576 and are just stretched differently. When I use VideoTexture in NonPow2 mode, I get the correct pixel dimensions from the info node, but for a 4:3 and a 16:9 in DV those figures would be excactly the same. Some extra info is needed to determine the format, That is the pixel aspect.

Or I might have missed something in the info node? Is this information in the depth or levels pins of the info node?

joreg · December 25, 2009, 7:15pm

you’re right, that information is not accessible anywhere. i’ll have to see if we can read that out somewhere…

sunep · December 25, 2009, 8:32pm

That sounds awesome!
And you guys are cooler than the quicktime guys that have not yet figured that on out in quicktime player. so I have my hopes high :)

dEp · January 20, 2010, 1:53am

ugh, working with non-square pixel aspect ratios is such a pain. i just convert everything i shoot in dv to square pixels…

it’s a hairy issue, if you want to find out more than you’d like about it, have a read: http://provideocoalition.com/index.php/cmg_keyframes/story/par_for_the_course/

joreg · January 20, 2010, 10:08pm

beta>22 has one additional output on the VideoTexture nodes: Pixel Aspect. that should be it.