Re: Testing with lossless codecs
Re: Testing with lossless codecs
- Subject: Re: Testing with lossless codecs
- From: Andreas Wittenstein <email@hidden>
- Date: Mon, 10 Aug 2009 20:37:35 -0700
Brian,
Animation and None are 8-bit RGB[A] codecs. If you need an RGB[A]
QuickTime codec with 10 bits of precision per channel, try Sheer
RGB[A] 10bf.
http://www.bitjazz.com/sheervideo/
It's only free for the first 20 days of use, but it's truly lossless,
it's really fast, and it's cross-platform.
Andreas Wittenstein
BitJazz Inc.
http://www.bitjazz.com/
On 2009 Aug 10, at 12:44 , Brian Gardner wrote:
Thanks, Darrin.
There appears to be no way to test my plugins using
a lossless QuickTime codec.
I tried the Difference matte technique you suggested to test a
number of QuickTime codecs, including the Animation codec.
None of them were lossless. Actually, it's kind of scary
that QuickTime does not have a single codec that is completely
lossless...
even the "uncompressed" were lossy.
I used a 10 bit DPX 1920x1080p 24.0 fps sequence as source footage,
which I've just received from a recent music video shoot, shot on a
stage.
The goal is to convert it into a single QuickTime ".mov" file,
with lossless compression (or even no compression). I couldn't
achieve that goal.
Here are the codecs that I tested:
Animation (at best setting) - truncates off the bottom 2 bits (10
bit - > 8 bit), which is lossy.
None - Exact same results as Animation. 8-bit only. truncated bottom
2 bits. Lossy.
(Differencing the Animation and None codecs to each other gives
0's-- exact match.)
FCP Uncompressed 422 10 bit - differences at all edges (to be
expected, 444->422 issue)
DNxHD 10 bit 709 - Noisiest of these codecs. (Noisy into top 8
bits.) Blocking artifacts,
especially in the vertically oriented direction.
Lossy.
Apple Pro Res HQ - slightly noisier than FCP Uncompressed 422, but
similar 444->422 lossy results.
Apple Pro Res 4444 codec - least lossy of the codecs I tested.
Appears to have saved full 10 bits.
(Did not just truncate down to 8. Possibly can do
16->16 bit?) Noisy in bottom bits, though. Lossy.
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.
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.)
When I layer two copies of the SAME resulting ProRes 4444 video on
top of each other,
and toggle visibility of the top layer On & Off -- they do not match!
There is a brightness/contrast difference, which appears to be
stemming from the alpha.
For my 10 bit 444 source video, Pro Res 4444 was less lossy than
"Uncompressed", "None", and "Animation".
"Lossless" QT codecs appear to only be lossless for 8 bit video, not
anything above 8 bits.
Ditto for 444 video ... where even "Uncompressed" is quite lossy.
Both were rather jarring surprises.
-- Brian
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