Mark Vojkovich ([EMAIL PROTECTED]): > On Mon, 4 Feb 2002, Billy Biggs wrote: > > > Arguably we shouldn't be using the 601 transfer functions anyway, we > > should use the ITU-R BT.709 ones instead since CRTs are likely > > closer to the HDTV standard. I'd also add that MPEG2 video actually > > specifies the 709 transfer function (those mmx'ified yuv2rgb > > routines everywhere are usually doing the outdated transfer). > > MPEG2 supports many functions, DVD is 601.
I did some research and I now agree with you. MPEG2 specs that if you don't indicate what colourspace you're using, default to Rec.709. In my DVD collection, many don't indicate, and I was (wrongly) assuming they were encoded for 709. The ones that do indicate all use S170M or Rec.460, which go by the 601 transfers, and I bet that's specified somewhere in the DVD standard I don't have access to. That said, the colour primaries for 709 match sRGB, while S170M does not. So if I have an sRGB calibrated monitor, couldn't I maybe fudge things by doing the conversion Y'CbCr->R'G'B' using the 709 function instead of the 601 function and get (subjectively?) better colour? The more I think about it, the more I think I'm on crack. I should instead just use the Rec.601 transfer and then correct if I feel so inclined. Two wrongs don't make a right. > Everybody's hardware does 601 except for 3dfx, as far as I can tell. > And 3dfx looks like crap because of it - all washed out. The poor > software conversion routines look bad because they're not clamping to > the 16-240 (or whatever it was) range. Yeah, if they're not using the right excursions, it will look like crap no matter what transform they use. > > Where best is defined as stretchy. 720x480 at 4:3 or 16:9 isn't > > square pixel so unless you're lucky you always need to scale. :) > > Pixels on the monitor don't have to be square unless you're on a flat > panel. Fine, but unless you're 'really lucky' you'll need to scale. -- Billy Biggs [EMAIL PROTECTED] _______________________________________________ Xpert mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/xpert
