[FFmpeg-devel] What is the correct way to read Avid ACLR atom?

[Kevin Wheatley]

On Thu, Feb 5, 2015 at 3:55 PM, wm4 <nfxjfg at googlemail.com> wrote:
> Seeing how the patch actually turned out, I'd say it should be in the
> decoder. It's not necessarily mp4 specific, or is it?

In this case I'm exporting the QuickTimes from an Avid Media Composer
so they are DNxHD in .mov, and in .mp4 with both 'RGB' and '709'
settings in Avid speak. From reading the ffmpeg code it looks like
other 'Avid' codecs also use similar atoms inside .mov derivatives,
but I'm not personally aware if any other container format has them.

My question about code style as regards the extradata was me thinking,
if I have read the data and done something with it, it isn't really
'extra' anymore but I'm not very familiar with ffmpeg's coding style
and architecture.

Putting this function in the avformat side of the code allows any
codec to pick it up and looked to be the most contained change, but it
potentially does change the image processing as now it can determine
the encoding range things may get handled differently - this is part
of my goal which is to correctly transport the colour metadata across
a number of different codecs and containers so that appropriate
conversions can be applied.

Kevin