[FFmpeg-user] [Cin] FranceBB's LUT collection

[Andrew Randrianasulu]

On Sun, May 18, 2025 at 2:37 AM Mark Filipak <markfilipak.imdb at gmail.com> wrote:
>
> On 16/05/2025 21.48, Andrew Randrianasulu wrote:
> > сб, 17 мая 2025 г., 04:32 Mark Filipak <markfilipak.imdb at gmail.com>:
> ...
> >> https://www.cinelerra-gg.org/forum/help-video/francebb-luts-for-space-color-conversions/
> >>
> >> Color transfer by LUT, wonderful!
> >> ...
> >> What do you have for '-vf'?
> >
> > With  bash shell on Slackware 15.0  it works like this from home directory:
> >
> > -vf
> > lut3d=file=/home/guest/botva/src/src/LUTs/HLG_BT2020_to_Linear_BT709.cube
>
> I tried a few 'cubes'. I was unsure which 'cubes' to use based solely on their names -- for example,
> what does 'linear' mean in this context

As far as I understand "linear" here means linear light, without any
gamma curve applied, mostly for  further processing?


 -- but I eventually settled on the following:
>
> set _BT2100_HDR_PQ_to__BT709_=^
> lut3d=file='BT2100_HDR_PQ_to_BT2020_SDR.cube'^,lut3d=file='BT2020_to_BT709.cube'
> ...
>   -filter_complex^
>   "[0:v]%_UHD_TO_HD_%,%_BT2100_HDR_PQ_to__BT709_%,format=yuv420p[v]"^
>   -map "[v]"^
> ...
>
> The result required extensive contrast-brightness-saturation tweaking, so I obviously don't have the
> right formula. Would you care to comment, Andrew?

Well, I mostly played around inside cinelerra-gg, so my experience
probably not directly transferable to ffmpeg's CLI,
but I also noticed I need either Histogram Beizer plugin, or
brightness/contrast after just naively applying tonemap alone.

I guess zscale + tonemap or libplacebo do more things automagically
for different input sources ...

>
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