Quantcast Proper black level setup - digitalFAQ Forum
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12-03-2005, 12:42 PM
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Sometimes I will capture with my Canopus 110. I generally feed in the video to the 110 with the analog black levels set to 7.5 IRE using my sign video proc amp. I set up the 110 to convert the analog video to digital level 16. This works out correct when I burn to DVD using Procoder 2.0.

My question pertains to when I use my ATI AIW card with the HUFFYUV codec.

Is the ATI capture card and HUFFYUV codec converting my analog video to digital level 16 as does the Canopus 110 converter?

...and therefore, when I feed my analog video to my ATI AIW card should I continue to keep my analog IRE levels to 7.5 using my SignVideo proc amp?

This seems to make sense to me, but I wanted to check with you to make sure.

Thanks
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12-04-2005, 04:14 PM
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IRE is one of those mystical video aspects that nobody seems to understand, including the most experienced professionals. Like everything else in video, IRE has both its theory and its practice.

Analog was all around a value of 7.5 in the USA. Everybody else in the world was at 0.0. Or at least closely thereabouts. Nobody was ever perfect, from hardware to hardware.

Digital is even worse, hardware is all over the place. Whether it's made in Japan or China, all over the place in terms of being done correctly. Some of the worldwide equipment even shoots for the middle, about 3-4 value.

If you REALLY want the long-winded response that will likely make your (and my) head spin, just give the word.

But, as a direct response to your question, the SIMPLE ANSWER is that your ATI card, by my experience and testing, is doing as it should. Your MPEG video should be correct when handled by ATI MMC, assuming your input signal was not loopy.

This is one of those areas where you should just ignore theory, and let your eyes be your judge. Only remember to use a monitor is calibrated decently with a normal tv set, you don't want to correct for a device that doesn't look normal. Most computer monitors show video too dark.

When it comes to the HuffYUV codec, I really just don't know. I don't use that codec enough to remember any errors, but the various HuffYUV versions have been known to act odd/different in the past. Uncompressed AVI and MPEG-2 are always fine.

Not to mention, you can always adjust for it in the encoder later on, and then some encoders may change the values too when going from AVI to MPEG.

So many variables... and no master list to refer to. This is where test clips come in handy. Do a small clip 3-4 times and then author all of them on a DVD-RW and test visually for what you think looked best. Just remember to keep a log of what you did, so you can repeat it when you've decided on the one you like.

Hopefully that gave an answer.

In other words, doing nothing will probably be fine. If you want to really nitpick and verify everything is perfect, just test it out thoroughly. If you have Vegas Video by chance, then you can always view the clips in the scopes that show IRE values.


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