Friday, March 28, 2008

Tektronix WVR7100 & NTSC gamut in HD

Talking about NTSC colour gamut on an HD recording seems a nonsense (how could something in 709 colour space have any relation to composite legality?) - however, since Sky take delivery on HD-Cam (and increasingly SR) they insist that all recordings also conform to a composite colour space. For those recordings in 29.97 and 59.94 it's an NTSC colour space they need to also conform to. This seems a bit daft to me - knobble your nice HD production so we don't have to worry about it. Surely the best way would be to transmit the HD and then stick a legaliser across the down-converted output rather than making the HD master conform to a small colour space so that down-conversion is easier. Talk about casting your pearls before swine!

Anyhow - one of our customers uses Tektronix WVR7100 rasteriser waveform monitors and has been QC'ing for delivery to Sky and noticed that with an NTSC master (either SD or HD) the Tek consistently throws composite gamut errors. The second screen-grab shows that the legaliser feeding the Tek has had the colour gamut wound right down (see how cropped the two diagonals on the arrow-head are) yet the 'scope continues to flag errors. It even does this with monochrome material!
So - I have to get on to Tek. The problem isn't there on 24, 25 or 50i material, just NTSC-derived stuff.

1 comment:

Phil Crawley said...

v.3.04 of the firmware fixes it!