[FFmpeg-devel] dcp encoding + new pixel format request/sponsorship

Paul B Mahol onemda at gmail.com
Tue Jan 22 16:08:35 CET 2013

On 1/22/13, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> Michael Bradshaw <mjbshaw <at> gmail.com> writes:
>> > Is there any reason to add a 12 bit per component format
>> > instead of using the 16 bit one and telling the encoder
>> > it should discard 4 bit?
>> Out of curiosity, how would that work? Which 4 bits do you discard?
> I believe when we "scale" from 16 to 8 bits, we simply discard
> the 8 least significant bit, the same can be done for the
> 16 -> 12 case.

FYI, contributor from Libav, with irc nick Buxiness is hacking on j2k
code is also working on XYZ.

>> openjpeg itself can, in theory, save 12-bit RGB, but lavc
>> would provide frames in 16-bit RGB; simply discarding bits
>> would give improper results. A proper/scaling 16-bit to
>> 12-bit conversion would need to be done, and it
>> hardly seems like the encoder is the right place to put that.
> It would simplify things to do it like that.
>> We also wouldn't be able to decode it without a 12-bit pixel format.
> The decoder would simply shift the most significant 4 bits
> into the least significant bits and set bits_per_coded_sample
> to 12.
> Is "Digital Cinema" JPEG 2000?

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