Rec.709 at 1280x720?

[nhope]

Is there an actual spec. somewhere that recommends to use Rec.709 coefficients to convert between RGB and Y'CbCr at 720x1280?

The Rec.601 spec (http://www.itu.int/rec/R-REC-BT.601-6-200701-S/en) is pretty clear about standard definition, and the Rec.709 spec (http://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.709-5-200204-I!!PDF-E.pdf) is pretty clear about 1920x1080, but is there anything anywhere that is specific about 1280x720?

I have read somewhere that a width of 1280 is the threshold, but cannot find a reference to back this up.

Thanks!

[manono]

It's used (or supposed to be used) for anything Hi-Def which, as I understand it, means anything above 576 height. 720p is definitely Hi-Def.

[Ghitulescu]

1280x720p is described in SMPTE 296M, whose chapter 5 specifically says that the colorimetry is 709.

[nhope]

Thanks very much. Looks like it's not available to view online for free like the ITU specs are.

[Yellow_]

http://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.709-5-200204-I!!PDF-E.pdf

If it's not flagged in the header isn't it then about luma pixel count per frame?

[Mug Funky]

interestingly enough, DV100 (DVCPRO HD) seems to encode it in 601.

and there's confusion between final cut pro and apple color (sic) as far as how to treat this footage. i found i always had to render down to an intermediate codec to get consistent behavior out of both programs, so my colours didn't get messed with when i went from one to another.

so i guess there's confusion in the industry about it... but why anyone would touch Varicam with a 40 foot clown pole these days is beyond me. there's better options.

[Ghitulescu]

The 709 doesn't refer back to 720p (296M) but only to 1080p/i. On the other hand, 296M specifically requires 709 colours for 720p. Luckily 720p will disappear, also from the pro segment.
It's probably the same situation as for ITU vs. non-ITU aspect ratio.

[Ghitulescu]

interestingly enough, DV100 (DVCPRO HD) seems to encode it in 601.

I am not sure now whether I have the SMPTE 370M too, but from what I know, it appears that the colorimetry of DV100 is the same for HD as for SD (ie 601), changes are in subsampling (4:2:2) only, AFAIK.

[Ghitulescu]

SMPTE 370M does not impose any restrictions on colorimetry, other than
The source component signal to be processed shall comply with the video parameters as defined by SMPTE 274M and SMPTE 296M..

[nhope]

Thanks for the replies.

...296M specifically requires 709 colours for 720p. Luckily 720p will disappear, also from the pro segment...
Actually the question was born out of my current experiments with rendering for the web, where 720p is not going to disappear, at least not for a long time. I've been telling people they should be using 709 at 720p and upwards but didn't have the documentation to back that up.

Interestingly YouTube appear to use 709 for everything, even at 480p and below.

[Ghitulescu]

If one google for 720p it won't get on the first page I don't know which pro camcorders or gear, but thousands of BRrip 720p x264 PRoPeR & Co. So it would stay as long there's such a need (or an offer), in other words like DivX movies. The industry abandoned 720p, in Europe (only few stations broadcast now 720p) too, as the EBU endorses now 1080.

[ChiDragon]

Your viewpoint is very euro-centric, as two (i.e. half) of the major networks in the US continue to endorse 720p. And the largest satellite TV company here in Canada actually converts every 1080i signal they get to 720p.

[Ghitulescu]

I'm talking about industry, not about media distributors. There were no 720p equipment launched on the market in the last 1-2 years. Concerts and live shows are taped in 1080i, movies are scanned in 1080p (2k) or 4k (some claim even 8k like Baraka). Everything that's distributed in 720p is downscaled from 1080i/p or made using "old" equipment (BBC). There are no new "inventions" nor new "standards" in 720p. Dead.

Why distributors still endorse 720p? Because 1080p is not standardized in EBU/ATSC for HD over satellite and 1080i has interlacing artifacts. Changing to 1080p would require not only new standards, but also billions of new receivers. Who'll support the costs?