https://web.archive.org/web/20170822225433/http://www.mysterybox.us/blog/20…
====
As slightly more concerning consideration, however, is the availability of
high quality 12+ bit codecs for use in intermediate files. Obviously any
codec using 8 bits / channel only are out of the question for HDR masters
or intermediates, since 10 bits are required by all HDR standards. 10 bit
encoding is completely fine for mastering space, and codecs like ProRes
422, DNxHR HQX/444, 10 bit DPX, or any of the many proprietary
‘uncompressed’ 10 bit formats you’ll find with most NLEs and color
correction softwares should all work effectively.
However, if you’re considering which codecs to use as intermediates for HDR
work, especially if you’re planning on an SDR down-grade from these
intermediates, 12 bits per channel as a minimum is important. I don’t want
to get sidetracked into the math behind it, but just a straight cross
conversion from PQ HDR into SDR loses about ½ bit of precision in data
scaling, and another ¼ - ½ bit precision in redistributing the values to
the gamma 2.4 curve, leaving a little more 1 bit of precision available for
readjusting the contrast curve (these are not uniform values). So, to end
up with an error-free 10 bit master (say, for UHD broadcast) you need to
encode 12 bits of precision into your HDR intermediate.
ProRes 4444 / 4444 (XQ), DNxHR 444, 12 bit DPX, Cineform RGB 12 bit, 16 bit
TIFFs, or OpenEXR (Half Precision) are all suitable intermediate codecs,**
though it’s important to double check all of your downstream applications
to make sure that whichever you pick will work later. Similarly, any of
these codecs should be suitable for mastering, with the possibility of
creating a cross converted grade from the master later.
====
hm, so even if swscale from rgba32f timeline to libavcodec still buggy we
can just use cingg's built-in tiff/exr output, I guess?
Strangely for now those blogs are not linked to site?
I found link while looking inside HDR.zip provided at doom9 forums
https://spaces.hightail.com/space/nEaXy
91 Mb!
