Hey Andy, On Thu, Feb 4, 2010 at 11:15 PM, Andy Walls <awalls@xxxxxxxxx> wrote: > Hmmm. The AGC (or static gain level?) of the amplifier in the SAA7113 > before the anti-alias filter may be set too high causing the clipping > (intermods) there. It may be worth looking at the gain setting for that > amp. It's possible. One thing I did as a test though was I did a capture of the i2c traffic under Windows (using the same reference video source), and then compared the register programming (via some scripts I whipped up). There were some other registers that were different, but the only one that made *any* visible difference in the output was the AA flag. > The visible effects of the anti-alais filter could possibly be: > > 1. Less range of color, if high freqs of the color get attenuated. > (Most people likely will not perceive this as most people are not that > sensitive to small color variations.) > > 2. Loss of rapid variations in Luma - softer edges between light and > dark areas on a scan line - if higher freqs of the Luma get attenuated. > > but given that the anti-alais filter is essentially flat out to about > 5.6 MHz and has a slow rolloff (only 3 dB down at about 6.9 MHz), I > doubt anyone would ever notice it is on with NTSC. To give you a better idea of what I'm talking about, look at this image: http://imagebin.org/83458 The above image was taken with the generator via the s-video input (ruling out the possibility that it's any sort of product of intermodulation). For the sake of comparison, here's the exact same signal source against an a similar em28xx design but with the tvp5150. http://imagebin.org/83459 > Since you have a signal generator, you should run experiments with PAL-D > and SECAM-D with a grid containing vertical lines since those both have > a 6.0 MHz video bandwidth. SECAM also has FM color, so you might see > the greatest affect of an antialias filter on color on the Cyan color > bar in SECAM-D. Believe it or not, I'm actually having trouble with the generator right now with anything but NTSC. I'm going back and forth with Promax on repair options. So I cannot do any PAL or SECAM testing right now. On a separate note, I really should look at extending the v4l2 capture-example to a version that let's me do a direct capture of the YUYV frame and convert the output into a zero-loss RGB format. It's too easy to be mislead by things the applications are doing like deinterlacing, rescaling, blending, and compression of the screenshot when saving to a file. Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
