Trying to wrap my head around something I thought was right but apparently is
not. A few questions about RGB vs 709
This is material destined to be compressed into MP4s, WMVs and FLVs via Sorenson
for desktop or internet display.
When exporting material from an Avid timeline containing video digitized via DNX
HD or similar, what should I select as the export video level in the main export
settings dialog box 601/709 or RGB?
My past assumption was RGB but when doing so video with shadow detail gets very
noisy and contains marco blocking in the shadows post compression. When I export
this as 601/709 and work a little voodoo with filters in Sorenson to restore the
black level for computer based viewing I get a much better result.
This isn't all the time, just with material which is a little noisy due to
things like Varicam's propensity to get a little challenged in the "grays". It
definitely still looks good and more than acceptable when viewed 709 or via
blu-ray or DVD on a video monitor. Just very poor when exported via RGB and
compressed.
I don't think Composer is really remapping 709 levels (including crushed blacks)
to RGB as much as it is chopping and stretching. Which poses a problem as that
eliminates picture data.
Exporting 601/709 is no big deal and it would be GREAT to do so as that file
would serve as a nice backup or source for DVDs too, BUT there is no easy way to
tell Sorenson or many other compression programs that the source is at 601/709
levels. Rather, it takes a bunch of un scientific twiddling with black
restoration, gamma, contrast and other things to eyeball a proper solution.
Also, there are some options available to assist in some codecs which are not
available in others.
Am I missing something here? Anyone making these adjustments in more reliable
fashion? Is there a source level setting I am missing or filter to remap?
Lastly. When having to transcode on export due to AMA material things get one
step deeper. There is no "same as source", so I set the codec to DNX HD in the
QUICKTIME settings box to 601/709 because I believe that the codec wants to know
what it is receiving at that stage. But in the Avid export setting dialog box I
have been setting this to RGB as I believe this is where you tell the codec what
you want it to create.
Do I have the functions of those dialog boxes right?
Any other wisdom?
Christopher Magid
RTVF
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