Red line in VirtualDub capture histogram
 

Hi - using a DMR-ES15 into a ATI HD 600 USB. What's this vertical red line at the lower left of the histogram? Is this the black crushing / hard clamping at y=16 that I've read about? With other devices, changing the brightness/contrast will control how much of the waveform is red, but here it just disappears once it hits that line.

What red line at which end of the histogram? The left side or the right side?
The left end represents darks. You don't see red at the left end below y=16 because the ATi 600 clips everything below y=16. It's a well-known characteristic of the device.

Thanks for the confirmation. Yeah, lower left. Looks like the forum mangled my screenshot.

Curious where the line itself is coming from -- some kind of signal to indicate what it's doing (as identified by Vdub?) or if it's an actual byproduct of the clipping process.

I see the line better now. It indicates that clipped data stops abruptly at the point shown. There is no sharp clipping at the bright end, so you have output into the red area -- however, data in the red areas will be sharply clipped in RGB display or RGB conversion, but some of it can be recovered with levels filters in YUV before any color conversion takes place.