Posted May 29 2005 - 05:48 AM
I have quite a few things that are general, and a couple that are THX-specific. FYI: my system is CRT front-projection at 720p 72hz, so I'm viewing on a very revealing system. However, there will be more and more viewers using large-screen displays, and these issues will become more important. In any case, as THX strives for the best performance, I feel these are totally appropriate requests that should be done right regardless of the rarity (or not) of high-end large-screen playback systems.
1) as mentioned: high bitrates please!
2) second the NO edge enhancement. None. EVER. Totally unecessary. Users can apply sharpening in their own systems if they wish to degrade their performance. Please don't force this garbage on me.
3) make sure that colorspace is properly encoded in 601 for SD (presumably DVD)material, and 709 for any HD material or future formats.
4) And for THX very specifically: please, please, PLEASE figure out your optimode system. I cannot fathom how it ended up as convoluted as it has. If you want to discuss specifics please contact me privately, but having individualized test patterns for each transfer was a terrible idea if you weren't utilizing them to correct your mastering chain. ALL the patterns should be reference-correct when finalized. If they were inserted before the mastering stage and they came out off-standard, that means your chain is off. Fix your chain. Don't have consumers compensate by calibrating to individual titles. I have not heard specifics as to whether the patterns are now correct, but it still doesn't shed light on whether your mastering chains are still off a bit. This is why I *always* recommend that users NOT use the THX patterns, because they are unreliable. Please figure this mess out! Optimode patterns should be reference and on-standard, and your video should hopefully be the same. If you are gonna insert the patterns before the mastering chain, use them to make sure they come out correct in the end. If they don't, fix your chain until they do.
5) THX certified DVD players NEED to pass the full range of values including blacker-than-black, AND peak whites for analog outputs at both 0 and 7.5IRE. Further, digital outputs should be correctly aligned, and no expansion to PC levels should be applied in default settings. Options for these settings should be clearly labeled. Options like "enhanced black" are very misleading. You should definitley suggest to manufacturers that the IRE setting is just a clear selection between 0 and 7.5, and the digital output is between Video and PC levels. Avoid this "enhanced black" or "expanded" language. It is misleading. Too many unassuming users mess up their video because of this. Lastly, PLEASE make sure that the IRE setup option does *not* affect the digital outputs and is implemented only on the analog outputs. Cost-cutting player designs have screwed this up terribly by trying to do this digitally.
6) upscaling DVD players: should twist the colorspace to 709 before outputting an HD signal for YPbPr and YCbCr output. Some professionals disagree with me here, but since many displays do not have the ability to alter the decode, and I don't see any sources utilizing the colorspace flag, if the upscaling DVD player leaves the output in 601, it's gonna get decoded 709 by the display and the colors will be all wrong. At the very least make this clear in the literature as to what the player is doing/not doing to the colorspace. An option to select this is ok.
7) My last request: when you master a title, please take care to view it critically on a large-screen reference display system, something like 1080p LCOS, or high-end CRT on a system that is carefully designed to eliminate banding. There are a lot of films out there with banding problems, probably because of banding problems in the mastering chain. This is almost impossible to see on small monitors so while it is unacceptable, it is understandable. The R1 Finding nemo is an example of an otherwise awesome transfer that has this banding problem. Other masters of this film do not: it is evidence of a mastering chain limitation of this particular version.
My goal is the best possible video, and when the limitation is outside of my control it is frustrating. On the whole THX titles are very high-quality, but there is always room for improvement. If you strive for having your titles consistently be very high-quality, and near or among "reference" titles, there are still things to be done. There is perhaps more work to be done on the playback side of THX-certified sources as well, because even with reference titles if the sources are not doing things correctly there's still an obstacle to the best performance.