Information about input color space

[Ilya87]

Summary of the bug: ffmpeg even with -loglevel debug provides no data about input colorspace that will be used later by encoder.
How to reproduce:

% ffmpeg -loglevel 5 -i bd.mkv
ffmpeg version 4.1
built on Antergos Linux
Using the command -vf colorspace=all=bt601-6-625:iall=bt601-6-625 I found out that ffmpeg treats input video as BT.601 (I compared first screenshot made with -frames:v 1 default.png with screenshot made using this filter). Why not BT.709? Where does ffmpeg get the information?

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[Elon Musk]

It guess input colorspace if it is not properly marked. Look at setparams filter how to force input colorspace for filters.

[Ilya87]

It's good about correct guess, but I think that this info (even it is guessed) should be shown using debug or other command.

[Ilya87]

The input is blu-ray part, can it have bt.601?

[Elon Musk]

Dunno, you can see which colorspace frame use with showinfo filter.

[Ilya87]

Replying to richardpl:

Dunno, you can see which colorspace frame use with showinfo filter.

In description I see it shows pixel format, not colorspace

[Elon Musk]

Because your ffmpeg is older than mine, update it ASAP.

[Elon Musk]

And documentation is not in sync.

[Elon Musk]

ffmpeg -i bd.mkv -vf showinfo -f null -

You need 4.1 or newer.

[Ilya87]

I have 4.1 and it says color_range:unknown color_space:unknown color_primaries:unknown color_trc:unknown

But guessed is BT.601

[Elon Musk]

Yes, use: ffmpeg -i bd.mkv -vf setparams=colorspace=bt709,rest_of_filtering ....

[Ilya87]

I still don't understand why I should set bt709 and maybe it's a bug already if ffmpeg chooses incorrect input color space?

[Elon Musk]

Nope, your input just lacks necessary metadata either in container or in video.

[Ilya87]

In this case ffmpeg must explicitly declare that color space is guessed and may be incorrect and it is recommended to set it manually.

[Balling]

blu-ray part, can it have bt.601?

Both AVC and HEVC support BT.601 matrix, but no, Blu-rays are all BT.709.

Ffmpeg swscale defaults to BT.601 limited.