This IS the Avid L2: [Avid-L2] Re: Illegal levels clip fine with Safe Colors but don't clip UPON RENDER

Tuesday, February 5, 2013

[Avid-L2] Re: Illegal levels clip fine with Safe Colors but don't clip UPON RENDER

Here's an old thread that seems to be of a similar nature
http://movies.groups.yahoo.com/group/Avid-L2/message/62306

BCC Unsharp Mask Safe Color Issue on PC SN Classic 3.05 ish
Posted By:

johnrobmoore
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Wed Dec 3, 2008 3:28 am |

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PC Symphony Nitris Classic ver 3.0.5ish. When applying an unsharp mask to a
shot a found that checking the safe color, or whatever they call it, in the
general controls the shots level would jump up to about 10% from the actual
level of 0 units in setup and the video peak would drop about the same amount.
It looked about like the offset when 601 levels are imported as RGB. I didn't
get a chance to check any other effects but it sure seems like a mismatch
somewhere between 601 and RGB space in the AVX architecture. I'm not sure if
this is BCC 4 or 5, I'll check tomorrow. Anybody else see this? I tried the
plan unsharp mask and the advanced keyframe version and they both exhibited this
behavior.

John Moore

Barking Trout Productions

Studio City, CA

--- In Avid-L2@yahoogroups.com, "blafarm" wrote:
>
> For the record, I'm on W-7 Symphony 6.0.3.2 and Avid Safe Colors works correctly both pre- and post-rendering.
>
>
>
> --- In Avid-L2@yahoogroups.com, Mark Spano wrote:
> >
> > Hi folks,
> >
> > Here's a new one for me. Take any clip that has a few bits of information
> > below 0mV or above 700mV (luma, R, G, B, whatever). For example, here's an
> > external scope view, where everything green is above 0 and everything red
> > is below 0:
> >
> > http://i.imgur.com/rp94vzB.jpg
> >
> > Knowing that the particular clip in my edit would be fine to crush a bit, I
> > figure I'm fine with just dropping a Safe Color effect on to clamp at 0.
> > Using either the Avid Safe Color Limiter effect, or the Boris Color
> > Correction effect with Safe Colors checked, when I drop either one onto the
> > clip in my timeline, I get the desired result, which looks like this:
> >
> > http://i.imgur.com/jKh4Cxg.jpg
> >
> > I've got it set to clamp at 0mV low luma, 700mV high luma, and even 16/235
> > for my RGB. It does a PERFECT clamp across all my luma (as you can see) and
> > RGB channels, which is what I'm looking for.
> >
> > Now here's where it gets weird. If I render/mixdown/export, it still does
> > the clamp, but misses a lot of stuff! In this case, it ends up looking just
> > like the clip without the effect:
> >
> > http://i.imgur.com/rp94vzB.jpg
> >
> > WTF? This happens with stuff going on above 700mV too.
> >
> > Upon further testing, it appears that any of these effects work flawlessly
> > when you drop them in, but when rendered, they miss some stuff. If you
> > clamp without rendering, and park on an offending frame, zero alarms will
> > go off on the scopes. But as soon as you play/render/export/mixdown, the
> > effect goes from being precise to being approximate.
> >
> > This happens with almost any clip (AMA, native DNxHD, etc.), on every
> > system I have (Mac, Symphony 6.0.3.2) and user setting I have (new
> > included). I feel like it's better with progressive material than
> > interlaced. I wouldn't even mind it so much, but the unrendered effect is
> > PERFECT. But what good is that, when it stops being perfect on playback,
> > render, export, or mixdown?
> >
> > I am sufficiently boggled by this. Anyone else see this happening? To be
> > clear, I am talking about TINY infractions. But the pre-rendered effect
> > gets the outliers - that's the stumper.
> >
> >
> > [Non-text portions of this message have been removed]
> >
>