Video ADC

Ahh wait, I maligned Cirrus unnecessarily. It's the C-Media ADCs that melt.

Is AKM back from the dead yet?

My #2 daughter works for Cirrus in Austin. I'm generally a fan of theirs.

It looks like the strange ADC is meant to be run mostly in 10-bit mode, which as you say is generally lots for video.

It also runs CID chips, though, which are mostly used in machine vision and other such applications, where there are lots of bright glints and where blooming is very bad news. (CCDs tend to dump charge into a whole line of pixels when one gets overdriven.)

CIDs work oppositely to CCDs: the wells start out full, and the photocurrent empties them. Thus there's no blooming.

So the extra bits may be intended for things such as flat-fielding, where you want to do a bunch of averaging to get lower noise. (You compute the gain and offset frames occasionally, and then use them for many data frames, so calibration errors give rise to fixed-pattern noise.)

Or it may have been a design blunder that didn't affect the main operation of the chip and so wasn't worth fixing.

I agree that it's weird, though.

Cheers

Phil Hobbs

Thanks for your thoughtful response Phil.

I guess I could ask Cirrus. But I wonder if your daughter might be more likely to get an honest answer, if you feel you could request that?

Clifford Heath

10-bit processing isnt peculiar at all for standard 8-bit video signals (ITU Rec 709, etc), since some LSB errors may accumulate with subsequent signal processing (which there will be, much of, in typical consumer video products). Moreso, HDR or High- dynamic range, video products & content are in the marketplace associated with "4K" UHD TV, where 10-bit video is the standard (ITU Rec 2020). So > 10bit digital video is internal to the product.

Almost all 4K UHD TVs claim HDR capability (10-bit disaplys, >1000:1 contrast ratios), but still fall short (mostly because of low luminance output range, rather than visible D/A artifacts.)

regards, RS

Yes. The real question is why are there 16 bits, and how many of them can you actually use? I'm not interested in video, but inexpensive SDR.

Clifford Heath