Re: Testing with lossless codecs
Re: Testing with lossless codecs
- Subject: Re: Testing with lossless codecs
- From: Peter Chou <email@hidden>
- Date: Tue, 11 Aug 2009 12:53:30 -0700
Hi Brian,
Regarding:
NOTE: The Apple Pro Res 4444 codec has a bug, in that it does not
appear to do
the right thing if it is given an image that does not have an alpha
channel.
When the codec receives a buffer in ARGB format to be compressed, it
has no way of knowing if the non-opaque values in the "A" channel
should be preserved or ignored, unless you explicitly tell the codec
to ignore them (see below). I have heard before that there is a
problem with alpha in DPXs written by certain systems. A workaround
for this if you happen to be using Shake is to select "autoAlpha" on
the FileIn and set its value to 1.
And there is no option in the codec UI to automatically add a fully
opaque alpha channel.
(It would be very nice to have that option.)
It's subtle, but there actually IS an option in the codec UI to do
this. It follows the standard QuickTime convention of using "Millions
of Colors+" (note the trailing plus sign) to indicate "with alpha" and
"Millions of Colors" (no trailing plus) to indicate "without alpha".
If you set the Depth popup menu to "Millions of Colors", the codec
will ignore the incoming alpha channel and produce a fully opaque one
upon decode.
-Peter
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