Technical Q&A QA1089

Quality of QuickTime video effects

Q: I'm trying to improve the quality of a QuickTime video effect used in my application. I'm specifying the codecHighQuality flag in my image description, but when I run the effect it seems there is some sort of "color clipping" taking place (the end result is blotchy). What can I do?

A: You are likely not seeing "color clipping".

What you are seeing is when an effect is applied to an image, the image is converted from the YUV format into the RGB format by software (QuickTime). When you look at this same clip directly, you are (most likey) seeing this conversion take place in hardware. The result thus looks different.

You can verify this is the case by using a source image which is already in RGB format. The simplest way to do this is to compress an image using QuickTime specifying "None" for the compressor and "Millions of Colors".

[Oct 26 2001]