Q's about how Vegas handles YUV colorspace

discdude wrote on 2/10/2003, 1:45 PM
Now that the SF techs seems to be returning to the forum after burning the midnight oil to get Vegas 4 out the door (thanks guys!), I think I will ask some "tech" questions.

Recently, I managed to bug the coders at XviD into making their codec compatible with Vegas (and Video Factory). They said that previous versions of XviD were not compatible with Vegas because "... when queried, xvid returns YUY2 at the default colorspace format. vegas v3 always uses the default value, however it only supports RGB 16/24/32-bit colorspaces. thus you get a black screen, or none at all." Sure enough, now that XviD returns RGB24 as the default colorspace, everything works fine. I assume DivX was fixed in a similar fashion.

Is it true that Vegas doesn't support YUV colorspaces? I find this strange since it is my understanding that many codecs, including DV and MPEG (probably the most common codecs used by Vegas users), store everything internally as YUV. Also, those codecs work fine in spite being YUV based. How is that acomplished? Through codec specific workarounds? If Vegas doesn't support YUV colorspaces, shouldn't it request RGB output from codecs that return YUV by default so there won't be any problems in the future?

Also, while a YUV->RGB->YUV conversion shouldn't result in any (noticable) image degredation, one would think this would slow down rendering by a lot.

Obviously, since both XviD and DivX are working fine with Vegas now, these questions are to satisfy my own morbid curiosity.

Comments

taliesin wrote on 2/10/2003, 3:57 PM
VegasVideo and Vegas 4 decompress into RGB, so - yes - there is a YUV-RGB-YUV conversion in rendering. But Vegas does not do any changes to the color-space during in the end. If you feed the render process with a color range of 0-255 you'll get same range after rendering. And even regarding artifacts there is no noticable loss.

Marco