Aaron Newcomb wrote:
On 8/27/07, Graham Evans <[EMAIL PROTECTED]> wrote:
I just checked ... you use component Y'CbCrA 8-bit 4:4:4:4 in a
quicktime container for YUVA-8 bit color model or use Uncompressed RGBA
for the RGBA-8bit color model. These are the only formats which I have
succeeded with so far to properly save alpha channel footage with no
glitches.
Make sure you specify the right color model in the Format dialog
otherwise the resulting render is black or chaotic with no warning why.
I use this technique to render out chromakey footage. As well as using
chromakey HSV (often in several layers) I mask out stray chromakey
glitches (such as when you use a too small back-cloth), blur zoom on the
chromakey effects for nice smooth anti-alias style edge and apply any
other simple corrections which will save me work later. Then I render.
Using the pre-rendered footage I can now begin editing with all speed
and no effects cluttering up the timeline.
So, what happens if you don't do this first? Is the playback just to
slow and timeline too cluttered to be useful in getting the effect
right? Just curious.
That's right - playback gets slower, the timeline gets cluttered, and
the projects themselves can grow fragile compared to rendered out
material. The key is making sure you are confident you won't need to go
backward and tweak a control... Or alternatively you keep that part of
the project as a separate sub-project in case you do need to go back and
tweak.
There is an option in the Video menu "Render effect" which does
intermediate rendering in a much more limited way. Personally I don't
use this option. Doing it manually gives you much more power and get a
better understanding of how all the pieces work.
Intermediate render steps are also a part of the ardour workflow - which
has many parallels to cinelerra. Ardour has 'Render' options in
right-click menus as well as other manual ways of doing this.
You are basically breaking a complex project down into a sequence of
manageable steps.
all the best - look forward to seeing your next episode
Graham
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