Re: graphics over video question

[Andi Loor <andiloor(at)algonet.se>]

Yes, this is what I think. YUV 0 level is far below RGB 0 level, as soon 
as there is a RGB conversion involved then the level gets limited.
All the best
Andi



Jef Huey wrote:

> Andi,
>
> Source was digitzed from a NTSC Digibeta deck.  That is not RGB.  
> While the levels on tape were non-standard (0 level black when viewed 
> through an encoder on composite scopes) they are valid in the 601 world.
>
> Now what you may be saying is that by putting the graphics effect 
> directly on the video clip, I was - in effect - forcing a YUV to RGB 
> to YUV conversion.   Is that what happened here?   And the fact that 
> putting text on 0 alpha black on another layer was a simple composite 
> which could happen in YUV space without conversion might be the answer?
>
> While the ability of the DS to work in both worlds (YUV and RGB) sort 
> of at the same time can be a plus, I feel there needs to be better 
> documentation as to exactly what actions will trigger the transcode.  
> I have asked for a list before and recieved a "Why do you want to 
> know?" response.
>
> Thanks for giving this question a shot.
>
> Jef
>
>
>
> Andi Loor wrote:
>
> > Hi Jef,
> > I think what you experienced is due to the difference between RGB and 
> > Component colour space. O ire is what can be called Super Black, it's 
> > blacker than black. This only excists in Component video. Switching 
> > to RGB colour space everything below black is limited and cut off. 
> > Working in DS you have a choice of telling the system in what colour 
> > space the graphic is created before import - this goes for graphic 
> > files. Tape is allways brought in as Component video. Some effects in 
> > DS work in RGB and because of this levels outside RGB colour space 
> > are limited to RGB levels.
> > Andi
> >
> >
> > Jef Huey wrote:
> >
> > > v7.6 qfe1 NTSC SD
> > >
> > > Had a silly issue the other day.  Found a workaround.  Now trying to 
> > > figure out why.
> > >
> > > Client brought in a completed "master" on Digibeta.   Due to lack of 
> > > skill on their part the show was mastered to the Digibeta with the 
> > > black levels of ONLY the black elements (black between scenes, black 
> > > in the letterbox matting added in edit, etc.) at 0ire not 7.5ire as 
> > > would be expected.  Not the black levels of actual video.  Due to a 
> > > variety of reasons they did not want me to fix this, only add an 
> > > extra title at the end.   Since all the black in the run out was 
> > > 0ire, no problem I thought.  I digitized some of that Black, put it 
> > > in  the timeline, added a Graphic tool to it and BAM, the black 
> > > levels were pushed to 7.5.
> > > Scratch head.
> > >
> > > Take off Graphic tool, put a Generated Black on V2, alpha to 0, add 
> > > Graphic Tool, and black level stays at 0ire.  Type text, output and 
> > > session is done.
> > >
> > > So, now ....
> > >
> > > What happened?
> > >
> > >
> > > Jef
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--
Andi Loor
www.andiloor.se

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