On Fri, Mar 6, 2020 at 5:03 AM Kevin Wheatley <kevin.j.wheat...@gmail.com> wrote:
> On Fri, Mar 6, 2020 at 10:19 AM Hendrik Leppkes <h.lepp...@gmail.com> > wrote: > > AVColorTransferCharacteristic should follow ISO/IEC 23001-8 and its > > following standards (ISO/IEC 23091 I believe). Not sure we have a > > solution for specialized variants, but adding one right there would > > collide with the next addition to the standard... > > Agreed, A publicly "aligned twin text" version is available as ITU-T > H.273 https://www.itu.int/rec/T-REC-H.273-201612-I/en shows that value > is 'reserved'. > > Agreed, it felt wrong about adding it where I did, but it was the quickest way illustrate what I was trying to do. I would also suggest that there are a few implementations of the > Cineon log to lin conversion and as such I'd reject it as is. > You will need to pass in the parameters for the various variables > white, black etc. You will also need to add a parameter for the > density per code value constant (0.002 by default convention). > Not all implementations use a gain scaling, though strictly these are > no longer "Cineon" per se, but you will end up with needing various > camera vendor equivalents. This would result in a large proliferation > of equations, which I don't believe are core to the FFmpeg code. > > Agreed and this all could also really be done with a 1dlut video filter but the real issue I'm working around is that the current float->int conversion happens in the exr codec. The currently available apply_trc options clamp at 1.0f (unless I'm mistaken). The full linear range is need to do any logarithmic conversion. I was also thinking ACEScc or ACEScct might be more appropriate instead of cineon. http://j.mp/S-2014-003 http://j.mp/S-2016-001 I also thought of just adding a float pixel format output option to exr sounded like a lot of work and I didn't know where to begin. > You would perhaps be better creating a specialist filter and > implementing it using OCIO (as suggested > https://github.com/AcademySoftwareFoundation/tac/tree/master/gsoc), or > extending the current 3D LUT code to read Cinespace or other 3D LUT > formats that support a pre-shaper and handle the float->integer > conversion that way. > I currently do have a workflow that does something similar to that, but it slower and involves more steps :) > > Kevin > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
