Broadcast safe colors...

newUzer wrote on 6/6/2006, 11:10 PM
I set up a video bus to have both Gaussian blur and Broadcast safe color filters, so I could minimize flicker and not have whites be too bright. I'm happy with the result in the preview, and during preview in DVD Architect. Ok, I've heard all the arguments about previewing on a real TV, and I can do that by using passthrough on my camcorder, but my question is the following: When I go to a frame on the timeline, save a jpeg, and look at the color values for white using an external app, I get (235,235,235) as one would expect. However, if I render to a DVDA MPEG2 stream, author a DVD with DVDA, and then capture the same frame from WInDVD, "white" is back up to (255, 255, 255). What gives? My overlays settings are at there defaults, but I guess software players do all kinds of funny things to colors. That said, any advise on some decent settings to get watchable results in a software player as well as a set top box?

Comments

logiquem wrote on 6/7/2006, 5:12 AM
I guess it's a simple matter of gamma correction on the fly by WinDVD. If you want to know how is your mpeg stream, just put it back it the timeline and compare the color values with the same, unencoded material.
Chienworks wrote on 6/7/2006, 5:21 AM
Correct. WinDVD knows that the computer display can handle the full 0-255 range and expands the video stream so that the DVD playback doesn't look flat and dull compared to everything else you see on your computer monitor. WinDVD does have contrast settings you can adjust if it looks too contrasty.
GlennChan wrote on 6/7/2006, 8:41 AM
Actually what you have now is right.

This is because video like MPEG2 is in Y'CbCr form, where the legal luma (Y') values are always from 16-235.

For things displayed on a video computer, your legal values are from 0-255 RGB (blacks at 0, whites at 255).

Vegas uses sort of an intermediate RGB color space, which is a RGB color space but with blacks at 16 and whites at 235. This means you lose less information when converting from Y'CbCr to RGB. Vegas passes the 16-235 RGB values straight-through to the video preview window without any conversion. The picture will appear lacking in contrast and saturation, and you will be able to see all the information in the picture (i.e. values over 235).

If you encode a DVD with proper Y'CbCr levels, then devices will typically play it back correctly. (Ok, some DVD players have incorrect levels. But you can't do much about that.) To get the right Y'CbCr levels, you have to make sure you're feeding the MPEG2 encoder the levels it wants (Vegas' wants to see 16-235 RGB "studio RGB"). In this case it looks like you've done that.