Hello, Kilroy Hughes @ Microsoft wrote: Ø I reviewed the deck and am newly inspired to advocate allowing xvYCC (negative coefficient encoding in Y'CbCr). I prefer if you say: (encoding of negative R'G'B' values in Y'CbCr). But let's not forget that xvYCC can (and probably will) also encode larger-than-unity values of R'G'B'. BTW, if Y'CbCr stay within 16..235(240) and add only the previously illegal combinations of legal Y'CbCr values then (I think) the standard is called sYCC. Ø Any recommendation on how to correctly represent that in H.264 encoded content? I'm not sure what you mean, or if I did that I would know the answer, but I think that it makes no difference to the (video) content, only to the metadata that describes the way the content is encoded. Is that what you meant ? In that case I can only refer you to the HDMI 1.3 and 1.4 specs, where they have tackled the same problem. I think that there are similar references in MPEG-2. It's all in the metadata. The only purpose for the "this is wide gamut" metadata bit that I can think of is for switching between gamut extension (for standard gamut content) and gamut mapping (for wide gamut content). And this is not even very essential to have. I think that even in the absence of any metadata, xvYCC would still work quite well. Of course you do need information about the R'G'B'<->Y'CbCr matrix (Rec.601 for SD, Rec.709 for HD), but that applies also to standard YCC. Ø It looks like Transfer Characteristics = 11 signals IEC 6966-2-4; and Primaries and Matrix Coefficients are the same as Rec 709 (VUI value = 1). Ø Some inaccuracy there, but Transfer Characteristics different from Rec 709 should encourage some guessing as to what real primaries were encoded. True, basically you just need a few bits to signal that a wide-gamut standard has been used, and perhaps distinguish between a few variations. Nothing of it is essential IMO. On top of that, HDMI also allows to send "Gamut Boundary Metadata", which can describe very accurately what the source gamut is. This can be simplified to the original color primaries, i.e. the source gamut is an RGB cube with primaries that are different from Rec.709 (a.k.a. sRGB). But it is also possible to encode an irregular 3D shape in all its detail. I think that very few people really ever want to use this, so I don't know if this will ever be picked up by broadcasters or receivers. It's optional anyway. The real camera primaries themselves do not matter, of course, since they have been replaced by (color space converted to) the Rec.709 (sRGB) primaries for xvYCC encoding. The color space that is actually used will be smaller than an RGB cube, it is described by a 2D contour like the "Pointer color set" or the 3D "Munsell cascade" variant. Knowing the edges of the source gamut is supposed to help you with tuning of the gamut mapping or gamut extension. Note that HDMI 1.4 distinguishes a few of the professional (photo) color spaces, meaning that the data is referred to the actual (non-standard) color primaries. This avoids the conversion to the Rec.709 referred xvYCC color space, and permits a single conversion to the target (display) color space. There is no compatibility with Rec.709 standard displays, but if the target refuses to accept it then the source will have to convert the data to an acceptable format (xvYCC or even standard gamut). I suppose that these color spaces were added for connecting professional cameras directly to a display (via HDMI), and transfer the image data as in the JPEG files. Groeten, -- Jeroen Jeroen H. Stessen Specialist Picture Quality Philips Consumer Lifestyle Advanced Technology (Eindhoven) High Tech Campus 37 - room 8.042 5656 AE Eindhoven - Nederland ________________________________ The information contained in this message may be confidential and legally protected under applicable law. The message is intended solely for the addressee(s). If you are not the intended recipient, you are hereby notified that any use, forwarding, dissemination, or reproduction of this message is strictly prohibited and may be unlawful. If you are not the intended recipient, please contact the sender by return e-mail and destroy all copies of the original message.