[FFmpeg-user] Requesting colormatrix advice

Paul B Mahol onemda at gmail.com
Tue Nov 7 12:38:30 EET 2023

On Tue, Nov 7, 2023 at 11:21 AM <markfilipak.imdb at gmail.com> wrote:

> On 11/7/23 04:08, Phil Rhodes via ffmpeg-user wrote:
> >   I have no idea how colour handling in x265 works so I can't really
> advise on specifically how to set it up. Possibly it's documented
> somewhere. One of the problems with this (which comes up in some high end
> post production software quite often) is that it's sometimes not very clear
> whether we're specifying what we expect the input data to be, or what we
> expect it to be converted to.
> I thought only I had that problem. :-)
> > For instance, I'm not sure what's meant by "transfer" in this context.
> Perfect example.
> >> It's 1920x1080. I 'heard' of "studio swing". What is it relative to
> what x265 expects (above)? Do you know?
> > I'm possibly guilty of indulging in jargon here; by "studio swing" I'm
> referring to a reduced data range often from 16-235 for the luminance
> channel.
> The preferred term appears to be 'limited range'.
> >>   I feel a headache coming on. Let's assume ffprobe is correct and
> colormatrix is undefined on the discs
> > What's on the disc will be in Rec. 709.
> I don't think so. If that were true, then what's on disc and what's in the
> MP4 would both play
> accurately and without saturation. I'm pretty sure they're not BT709.
> > I honestly don't know what data ranges blu-rays use.
> Limited. It's silly -- more legacy analog TV hangover -- but it's limited.
> The MPEG folks just can't
> seem to wean themselves away from TV-on-disc.
> > It's often fairly clear if you can look at it and it looks all lifted,
> that'll be why.
> "lifted"?
> > Unfortunately there are a lot of moving parts here.
> I may be naive but I don't think so. X265 has presets that appear to cover
> all commercial media. How
> it covers is apparently a matter of some conjecture. But really, all that
> color adaptation stuff,
> like to accommodate phosphors in CRTs, needs to be done BY THE TV, not by
> the media. There should be
> one set of colors and they should be RGB full range with unlimited gamut.
> The TV makers know what
> the TVs are capable of and can do dot-by-dot fix up.
> You're off the hook, Phil. Thanks for your thoughts. I appreciate them. --
> Mark.

Use setparams filter to properly tag inputs colorspace related metadata.

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