High Speed Dubb
8th April 2003, 03:21
Hi all,
I just got myself a nicer video input card (a Lifeview 2000, with the Philips SAA 7134 chip). One of its features is a good quality 2D comb filter, and the current DScaler builds let you turn the filter on and off.
I was surprised by the difference — In addition to getting rid of (some) dot crawl and rainbows, it also improves horizontal detail.
In retrospect, this makes sense — Since the card is better able to separate Y and UV information, it can have more detail in both. (i.e., High frequency luma is correctly identified as luma information.)
That means the hardware comb filter has a definite advantage over Guava Comb — My comb filter only cancels incorrect chroma/luma information. It does not use the chroma/luma error to correct the other color component.
So to comb filter optimally, you would have to convert the chroma and luma to frequency information, properly combine the signals, and then separate them again using a smarter filter. That would be pretty hard — You’d need the color carrier wave, and you might need to know the original comb/notch filter used, if it caused the loss of any color information.
The moral: There’s lots of improvement still to be made in comb filtering — And the SA 7134 chip is very good for composite video input.
I just got myself a nicer video input card (a Lifeview 2000, with the Philips SAA 7134 chip). One of its features is a good quality 2D comb filter, and the current DScaler builds let you turn the filter on and off.
I was surprised by the difference — In addition to getting rid of (some) dot crawl and rainbows, it also improves horizontal detail.
In retrospect, this makes sense — Since the card is better able to separate Y and UV information, it can have more detail in both. (i.e., High frequency luma is correctly identified as luma information.)
That means the hardware comb filter has a definite advantage over Guava Comb — My comb filter only cancels incorrect chroma/luma information. It does not use the chroma/luma error to correct the other color component.
So to comb filter optimally, you would have to convert the chroma and luma to frequency information, properly combine the signals, and then separate them again using a smarter filter. That would be pretty hard — You’d need the color carrier wave, and you might need to know the original comb/notch filter used, if it caused the loss of any color information.
The moral: There’s lots of improvement still to be made in comb filtering — And the SA 7134 chip is very good for composite video input.