[FFmpeg-devel] SDR->HDR tone mapping algorithm?

[Harish Krupo]

Hi Vittorio,

Vittorio Giovara <vittorio.giovara at gmail.com> writes:

> On Fri, Feb 8, 2019 at 3:22 AM Harish Krupo <harish.krupo.kps at intel.com>
> wrote:
>
>> Hello,
>>
>> We are in the process of implementing HDR rendering support in the
>> Weston display compositor [1] (HDR discussion here [2]). When HDR
>> and SDR surfaces like a video buffer and a subtitle buffer are presented
>> together, the composition would take place as follows:
>> - If the display does not support HDR metadata:
>>   in-coming HDR surfaces would be tone mapped using opengl to SDR and
>>   blended with the other SDR surfaces. We are currently using the Hable
>>   operator for tone mapping.
>> - If the display supports setting HDR metadata:
>>   SDR surfaces would be tone mapped to HDR and blended with HDR surfaces.
>>
>> The literature available for SDR->HDR tone mapping varies from simple
>> linear expansion of luminance to CNN based approaches. We wanted to know
>> your recommendations for an acceptable algorithm for SDR->HDR tone mapping.
>>
>> Any help is greatly appreciated!
>>
>> [1] https://gitlab.freedesktop.org/wayland/weston
>> [2]
>> https://lists.freedesktop.org/archives/wayland-devel/2019-January/039809.html
>>
>> Thank you
>> Regards
>> Harish Krupo
>>
>
> In *theory* the tonemapping functions should be reversible, so if you use
> vf_tonemap or vf_tonemap_opencl and properly expand the range via zimg
> (vf_zscale) before compression it should work fine. However I have never
> tried it myself, so I cannot guarantee that those filters will work as is.
> Of course haasn from the libplacebo project might have better suggestions,
> so you should really reach out to him.

Thanks, will try reversing the algorithms. Sure, will contact Haasn.

Regards
Harish Krupo