IRE levels and overshoot - Hi8 transfer DV to DVD

CoolBlue wrote on 8/7/2007, 11:11 AM
I am capturing Hi8 tapes using a Canopus ADVC-300 to DV format, and then to DVD. I would like to know if overshoot is allowed in the digital domain on DV and DVD?

My Workflow
The Canopus ADVC is set for 7.5 IRE. I have the Vegas scopes set for Studio RGB (16-235). The Canopus ADVC has an auto-gain feature, but when I turn it on, it always boosts incoming whites to (235-255).

The Problem
The problem is, if I manually set gain on the ADVC, so the range is (16-235), the digital transfer turns out much darker than the original analog recording.

I believe the consumer camcorder used the super-white range for actual video content above 235. So for a consumer video transfer, should I leave Auto-Gain on, and allow super-white when transfered to DV and DVD?

The ADVC software also has options for white peak adjust and White step. Should these be used instead of manually adjusting gain?

I've also tried using the Broadcast Colors filter, but this totally messes up the videos color. It washes out all black definition. I assume it's because the capture has a small black border around it, and Vegas thinks this should be set to IRE 16, which is wrong.

Comments

GlennChan wrote on 8/7/2007, 1:17 PM
I'm not sure if this helps but...

DV is Y'CbCr colorspace with 16-235 range for Y' values. Values outside that range allow for overshoot and undershoot... that signal will get recorded.

2- Vegas has to decode everything to RGB. DV--> conversion is determined by the codec you use... the default DV codec (vegas'; version ~5+ only) decodes to studio RGB color space. In studio RGB space, 16-235 is the range for legal R'G'B' values. 0-15 and 236-255 are headroom and footroom (same as Y'CbCr).

3- The scopes should be setup to match what codec you are using.

4- Vegas scopes can only read the RGB values, not IRE and not Y'CbCr. Improper conversions and improper setup will throw the readings off. It is not always helpful in figuring out if something is wrong.
farss wrote on 8/7/2007, 2:56 PM
I've used the same box to transfer lots of VHS, Hi8 and 8mm film. I just went with the autogain function. Technically the overshoot is allowed in the DV spec. DVD players may legalise or clip the overshoot and I used to legalise the footage before encoding however it's a bit of a tough call as it looks like playing the DVD back in a PC this doesn't happen so now I tend to pass on doing a legalise.

If you do use the BC FX try setting the Smoothness slider(s) to 1.000.

Bob.