On Wed, Feb 1, 2017 at 1:42 PM, Kieran O Leary <kieran.o.le...@gmail.com> wrote: > Hello, > > I'm cc'ing Vittorio as I don't think that he's subscribed to the list but > he's contributed to dpxenc.c and recent colorspace filters. The same with > Kate Murray from the Library of Congress who knows a lot more about DPX than > me. Apologies if this is inappropriate. > > I mostly based this patch on other ffmpeg encoders, such as pncenc.c. I'm > not really a C coder, I'm a moving image archivist who needs to be able to > specify colour metadata in DPX for various workflows. Please excuse my > ignorance/mistakes. > > This patch adds documentation and two command line options for the DPX > encoder: > -trc (Transfer Characteristics) and -clr (Colorimetric Specification), which > set colour metadata values in a DPX file. Currently these are hardcoded to > always be 2, aka Linear. Ticket #6023 is related to this, but there have > also been many mailing list posts about this issue: > https://ffmpeg.org/pipermail/ffmpeg-user/2015-March/025630.html > https://ffmpeg.org/pipermail/ffmpeg-user/2015-December/029456.html > > I've kept the default values as 2 (Linear) as this is what was originally in > dpxenc, but I'm not sure of the value of this really. I think that there's > more value in a default of 0 (User-defined) which would just leave the > values unspecified. Or perhaps no value at all! The initial default of 2 for > colorimetric was potentially useless as 2 is listed as 'Not applicable' for > colorimetric specification in SMPTE 268M-2003. > > The values for each of these options are the integers listed in the SMPTE > standards doc: > https://web.archive.org/web/20050706060025/http://www.smpte.org/smpte_store/standards/pdf/s268m.pdf > > Initially I just had one argument that set the Transfer Characteristic and > Colorimetric Specification to the same value, but perhaps some use cases > could require that these values be different? I'm not sure if they ever > would. I have never seen real world files that suggest this but I can edit > this if it seems weird. > > Some of the values from 0-12 are listed as 'Not applicable' for the > colorimetric specification, but I didn't know how to specify just those > numbers (0-1, 4-10) in the patch. Perhaps it's OK to leave it as is, > otherwise hopefully someone can point me to similar code that I can learn > from. Again, apologies for my ignorance. >
Hey Kieran, I think the code looks fine. I am just wondering if we should also offer the possibility to set these flags from the standard context options (-color_trc and others). I'm aware that not all values match or are valid but maybe a small conversion table or extending the main table could be a viable approach. Similarly this could be done for the decoder so that color properties are not lost during a dpx->dpx conversion maybe. -- Vittorio _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel