[FFmpeg-user] convert from bt601 to bt709

[Bob Maple]

On 6/6/2014 12:46 AM, Carl Eugen Hoyos wrote:

> Imo, that's mostly because so far, nobody has uploaded 
> a RGB image which is not full-scale.

Where would you like one?  I can provide an unlimited number of them
(they are pretty easily made.)  I can collect together all kinds of
samples when I get to the office tomorrow.

I found some references to -color_range but browsing quickly through the
source it seems only hooked up to a few specific codecs.

On 6/6/2014 12:28 AM, tim nicholson wrote:

> ISTR that if you give ffmpeg RGB it assumes its full range

That's what I've found;  Giving it 10-bit RGB DPX files already at 709
levels (64-940 and 709 color matrix) and going to DNxHD it was scaling
the levels again, as if the input was full range.

> it also by default converts using 601 matrices.

That's probably true as well; 601 and 709 are kinda close, and my test
images weren't particularly saturated so the shift I was seeing was not
dramatic.

I could make things worse though using -vf colormatrix=bt601:bt709 :)

Ignoring the overall range scaling, not using colormatrix in this
instance gets pretty close -- maybe only as close as is possible for
RGB->YUV->RGB (since I was inevitably looking at the results as RGB) but
I'll have to revisit in the morning because I don't completely remember
-- my number of test compression files last night was getting out of
control :)

Bob