Oddity: Broadcast Colors

fausseplanete wrote on 4/4/2008, 12:55 AM
Oddity: Bug or unreasonable expectation?
Broadcast Colors FX doesn't affect the background, only explicit media.

I ask for this to be discussed here in forum prior to following it up with Sony Support, so they can see what most people think.

Just to set the context first:
16:9 Project containing standard camcorder (TV colorspace, Y=16+) footage in 4:3, hence appearing pillarboxed. The background showing through either side of the footage is RGB-black i.e. Y=0. In contrast the "black" parts of the footage look grey. This is all normal so far - not a problem.

I placed Broadcast Colors filter (as a master filter i.e. near the Preview) with minimum level as 0% on a 16-235 scale, i.e. Y=16.
The result was not affected - the background was still at Y-0. Seting the minimum to 50% confirmed that only the image from the footage was affected, not the background either side of it.

Of course this can be worked around, e.g. by placing a Y-16 solid color in the track below, but surely the point of a Broadcast Colors FX is to act as a safety net for when we forget to do things like that. This "safety net" has a "hole" when it comes to the background - it only seems to act on areas of the image derived from explicit media. Surely the background is at least in concept a "Solid Color" of PC Black, and regardless of its actual implementation should be treated as such.

If you agree or disagree that this "Oddity" is a bug, then please say.

Comments

farss wrote on 4/4/2008, 1:43 AM
No FX will work on nothing!
Struck your situation years ago. It's logically consistent. It can't be fixed I just realised. What we're seeing isn't black , as a colour, we're seeing 100% transparency rendered into a format that doesn't support transparency, so in the absense of colour, it becomes black.

Bob.
fausseplanete wrote on 4/4/2008, 12:56 PM
Aha you are right, it is transparency - I just tested it (first paragraph below). But that brings up more ideas (the other paragraphs),

The transparency gets maintained when rendering to a format that supports transparency, as does uncompressed AVI. I just tried that, importing the result to a new project on top of a solid colour which indeed showed through. However when I rendered to DV AVI, which does not support transparency, a default substitute of PC-Black (RGB=0,0,0) appeared in the result. I guess this happens in the renderer which is subsequent to the Broadcast Colors FX,

Given the transparency, it would be more obvious if the default background displayed in the Preview was a grey-and-white checkerboard as in the Transitions and Media Generator views. Also as in PaintShop Pro 8 (the version I still have) and The Gimp (open source), when creating an image with transparent background (under "new>advanced" or whatever).

I wonder if in principle at least, Broadcast Colors FX could send its user (slider) defined minimum to the Renderer, to use this level, rather than the fixed RGB=0 level as at present, when rendering to a format that did not support transparency. Not altering the image directly, just sending information in parallel with it, for use by the Renderer (or a wrapper around the Renderer, doing a quick on-the-fly composite when it knew the render type did not support transparency).
farss wrote on 4/4/2008, 3:08 PM
Agreed, it might be nicer if Vegas did display by default something other than black for transparency. However Vegas isn't a compositing application and could create a lot of overhead.
Trying to rework the BC FX could be a bit messy. Although we mostly use it at the track or bus level it doesn't have to be there.
I believe you can also resolve the issue using nesting, that makes a lot of sense. On the other hand it kind of implies that transparency is not sent to the parent project. Perhaps I should test this one day. For the minute I'm coping quite well just adding a track of black.

Bob.
GlennChan wrote on 4/5/2008, 12:15 AM
Perhaps the broadcast colors FX should just get rid of transparency?? And then it would do its thing.

farss wrote on 4/5/2008, 3:59 AM
"Perhaps the broadcast colors FX should just get rid of transparency??"

It'd probably need to be controlled by a check box that defaulted to Off for backwards compatibility.

Bob.
TimTyler wrote on 4/5/2008, 9:45 AM
> 16:9 Project containing standard camcorder
> (TV colorspace, Y=16+) footage in 4:3, hence appearing pillarboxed.
> The background showing through either side of the footage is RGB-black

Do you mean it's anamorphic footage? 16:9 Squeezed into a 4:3 frame?

If so, you can just adjust the way Vegas manages the clip's aspect ratio by right-clicking the clip / Properties / Media / Pixel Aspect / 1.2121

fausseplanete wrote on 4/6/2008, 3:45 AM
@Tim:
The aspect ratio difference / pillarboxing was merely the situation that revealed the issue, not the issue itself. I am familiar with aspect ratio adjustment and cropping etc.

The central issue is transparency. From my point of view, the main ideas to have emerged from the discussion are:
a) How should the Preview display transparency (currently PC-black)? Should it use grey-and-white checks as is conventional elsewhere? Would there be a significant performance hit from this?
b) What should the Broadcast Colors (BC) filter should do with transparency? (currently preserves it). Should it have a checkbox to substitute grey at the user-specified minimum level?

Here's another idea - what should the Renderer should do when rendering transparent pixels to a format that does not support transparency? (currently substitutes PC-Black). Should there be a global option to set any default colour e.g. to allow for chromakeying of the result? Should its default value be TV-Black or Green?
GlennChan wrote on 4/6/2008, 11:59 AM
I think the user should be able to specify that the background should be 16 16 16 RGB with no transparency, since there are certain situations where that is useful (e.g. you don't want to fade to superblack).

Or better yet, Vegas should handle all the levels stuff for the user.