Convert HDR Video to SDR
Upload an HDR clip — it's tone-mapped down to standard-dynamic-range in your browser, so it plays with correct color and brightness anywhere. Nothing is uploaded.
About this tool
HDR video is mastered for wide-gamut BT.2020 color and a high peak brightness using
a PQ (smpte2084) or HLG (arib-std-b67) transfer curve. Play that same file on an
ordinary standard-dynamic-range screen — or drop it into an editor or a website
that doesn't understand HDR — and it renders gray, dim, over-dark, or washed-out,
because the SDR display reads the HDR signal as if it were plain BT.709. This tool
tone-maps the clip down to SDR BT.709 / yuv420p so it looks right everywhere.
It runs a fixed, order-sensitive ffmpeg zscale + tonemap filter chain: linearize
the source transfer → convert to float RGB → gamut-map to BT.709 → tone-map the
luminance with your chosen curve → re-encode the BT.709 transfer at limited (tv)
range → 8-bit 4:2:0. Everything runs in your browser via WebAssembly ffmpeg — the
file is never uploaded.
Controls
- Tone-map curve — Hable is the filmic default every HDR→SDR guide recommends; it preserves highlight and shadow detail with natural contrast. Mobius keeps more midtone saturation. Reinhard is a flatter, brighter global operator. Linear and Clip are the simplest (and can dim or blow out highlights).
- Peak luminance (nits) — the target display's nominal peak white. 100 is the reference SDR white point and the right default; raise it only if you're mastering for a brighter SDR target.
- Highlight desaturation —
0keeps highlight color (recommended). A small value (e.g.0.5) grays very bright areas to tame neon/clipped highlights. - Output format — MP4 (H.264 + AAC) for maximum compatibility, or WebM (VP9 + Opus). Quality is 1-100 and maps to the encoder's CRF (75 ≈ high-quality delivery; lower = smaller file).
Worked examples
- A phone HDR clip that looks washed-out on your laptop: keep every default —
Hable, peak 100, desat 0, MP4, quality 75. The filter chain becomes
zscale=t=linear:npl=100,...,tonemap=tonemap=hable:desat=0,...,format=yuv420pand you get a natural-looking SDR MP4. - Punchier grade for social: pick Mobius and quality 80 to hold more midtone saturation.
- For the web with alpha-free VP9: switch Output format to WebM — the exact same tone-map runs, only the codec changes to VP9/Opus.
FAQ
Why does my HDR video look gray or dim on a normal screen?
Because the file carries an HDR transfer curve (PQ or HLG) and BT.2020 wide-gamut color, but a standard-dynamic-range display decodes it as ordinary BT.709. The bright, wide-gamut signal gets squashed into the SDR range with no tone-mapping, so highlights flatten and midtones look washed-out or dark. Tone-mapping remaps the luminance and gamut into BT.709 so the picture looks correct.
Which tone-map curve should I pick?
Start with Hable — it's a filmic S-curve that keeps highlight and shadow detail with natural contrast, and it's the default in almost every HDR→SDR guide. Try Mobius if you want punchier, more saturated midtones, or Reinhard for a flatter, brighter look. Linear and Clip are the simplest operators; Clip hard-clips bright highlights (sharpest but can blow them out), Linear just scales luminance.
What does "peak luminance (nits)" do?
It's the nominal peak brightness of the SDR target you're mapping to — the reference white the tone-map curve rolls the HDR highlights down toward. 100 nits is the standard SDR white point and the right value for almost everyone. Raising it targets a brighter SDR display and leaves highlights a little brighter (and closer to clipping).
What can I put in, and what comes out?
Input can be any HDR (or SDR) video your browser can decode — MP4/MOV/MKV with PQ or HLG HDR, BT.2020. Output is MP4 (H.264 + AAC) by default, or WebM (VP9 + Opus) — both SDR BT.709 / 8-bit 4:2:0, playable on any ordinary screen. Audio is re-encoded, not dropped.
Limits
- Runs entirely in your browser via WebAssembly ffmpeg; large inputs are bounded by your browser's memory, and very long or high-resolution clips encode slowly on the CPU.
- Tone-mapping is one-way — it maps HDR down to SDR and can't recover HDR from an SDR source. The tone-map curve and peak are heuristics, not a per-shot color grade.
- Output is always 8-bit SDR BT.709 (
yuv420p); it does not preserve HDR metadata or 10-bit color. Only MP4 and WebM containers are written.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool video-hdr-to-sdr 'url=https://example.com/input' 'tonemap=hable' 'peak=100' 'desat=0' 'format=mp4' 'quality=75'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/video-hdr-to-sdr/?url=https://example.com/input&tonemap=hable&peak=100&desat=0&format=mp4&quality=75Machine-readable descriptor: tool.json — title + parameters JSON Schema for agents.