Thank you for the thoughtful feedback.
Advantages over vf_libplacebo’s inverse tone mapping:
1. Algorithmic Differentiation:
My filter is based on a novel local adaptation + inverse tone mapping strategy
specifically tailored to enhance perceptual brightness while preserving spatial
detail.
My implementation uses:
* Local bilateral filtering over luminance for content-adaptive scaling.
* Dynamic inverse tone mapping via (R / (1 - R))^1/n style
reparameterization.
* Chromatic scaling to preserve original hues during dynamic range
expansion.
1. Color Fidelity & HDR Metadata:
* The filter performs color space conversion from BT.709 to BT.2020
explicitly and integrates PQ transfer function encoding with full support for
mastering metadata (mastering_display_primaries, content_light_level, etc.).
* It incorporates localized tone curve shaping, white balance, and
chroma boosting that target HDR presentation aesthetics more directly.
2. Customizability:
* Parameters like sigma_spatial, sigma_range, n, and hdr_max allow users
to tailor the HDR expansion according to scene content or output requirements.
I agree that a GPU-based real-time implementation would be valuable. The
algorithm I've used is highly parallelizable and very well-suited for
implementation as a GPU shader
Get Outlook for Mac <https://aka.ms/GetOutlookForMac>
From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> on behalf of Kacper
Michajlow <kaspe...@gmail.com>
Date: Saturday, 19 July 2025 at 8:18 PM
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] avfilter: add inverse tone mapping
EXTERNAL: Use caution when clicking on links or opening attachments.
On Sat, 19 Jul 2025 at 16:13, Sarthak Indurkhya via ffmpeg-devel <
ffmpeg-devel@ffmpeg.org> wrote:
> Hello FFmpeg developers,
> This patch introduces a new video filter called inversetonemap for FFmpeg.
> The filter performs SDR to HDR conversion by mapping SDR BT.709 video to
> HDR BT.2020 PQ, using local adaptation and inverse tone mapping. The goal
> is to provide a simple, flexible tool for upconverting SDR content for HDR
> displays, with local adaptation, tone curve sensitivity, and chroma
> processing.
>
> Please review.
> Thanks,
> Sarthak
>
>
>
Interesting. Could you describe what are the advantages of the new filter,
compared to existing solutions like vf_libplacebo inverse tone mapping?
Additionally if there is a big gap in libplacebo's inverse tone mapping
quality would you be interested in improving the libplacebo implementation
in addition to this filter? I think there would be a gain in having real
time gpu implementation too.
- Kacper
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