Decode HDR video into the linear compositor correctly instead of approximating
everything as sRGB/BT.709:
- Read the frame's color_trc and color_primaries in the importer → VideoTransfer
{Gamma,Pq,Hlg} + VideoPrimaries {Bt709,Bt2020} on GpuVideoFrame.
- nv12_blit.wgsl: branch the EOTF — sRGB gamma (SDR), SMPTE2084 PQ (normalized so
203-nit graphics white = 1.0; highlights exceed 1.0), or HLG inverse-OETF
(reference white ≈ 1.0). Then BT.2020→BT.709 primaries in linear light when
wide-gamut, clamping out-of-709 colours.
Establishes the white=1.0 scene-linear convention: SDR content is unchanged
(stays in [0,1]); HDR video carries super-white highlights through compositing.
SDR-output mapping (clip default vs highlight rolloff) is Part 2. HLG's display
OOTF is omitted (scene-referred) — approximate but reasonable for SDR-out.
The NV12→RGB pass hardcoded BT.709, so SD (BT.601) clips had slightly wrong hues.
Read each frame's AVColorSpace in the importer and derive the Y'CbCr→R'G'B'
matrix (BT.709/601/240M/2020; Unspecified guessed by height like swscale/players),
carry the four coefficients on GpuVideoFrame, and apply them in the shader.
- core: GpuVideoFrame.coeffs + ycbcr_coeffs(kr, kb) helper.
- hw_video.rs: map AVColorSpace → (kr, kb) → coeffs.
- nv12_blit{.rs,.wgsl}: uniform grows to 80 bytes (adds a coeffs vec4); the matrix
multiply uses params.coeffs instead of literals.
BT.2020's transfer is still approximated as sRGB. The DRM-modifier-without-SAMPLED case stays a graceful software fallback.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The WGSL struct trailed `full_range: u32` with `_pad: vec3<u32>`, but vec3 has
16-byte alignment so the struct rounded up to 80 bytes while the Rust-side
Nv12Params (BlitTransform + u32 + [u32;3]) is 64 — wgpu rejected the draw
("Buffer is bound with size 64 where the shader expects 80"). Pack the flag as a
single `flags: vec4<u32>` (.x = full_range) so both sides are 64 bytes.
Make the dormant core HW-decode engine live for the preview path:
- hw_video.rs: editor's HwVideoImporter — maps a decoded VAAPI surface to a
DRM-PRIME DMA-BUF and imports it as wgpu NV12 plane textures on the *shared*
device (the only one with the import extensions). install() creates the VAAPI
device and injects it + the importer into the VideoManager.
- main.rs: track whether the shared device is actually in use; only then (Linux,
not LB_NO_SHARED_DEVICE) install hardware decode, using the CreationContext's
shared device + adapter.
- nv12_blit.rs + nv12_blit.wgsl: NV12 plane textures → BT.709 → sRGB-encoded →
linear, written straight into the Rgba16Float HDR layer (no CPU upload). Colour
math mirrors the software path so HW/SW video match; honours full_range.
- stage.rs: the preview Video arm branches on inst.gpu (NV12 blit) vs rgba_data
(existing upload+blit_straight); sets render_hardware_ok = !cpu_renderer so the
CPU fallback still gets software frames.
- video_exporter.rs: sets render_hardware_ok(false) before both compositing
passes — export composites on the encoder's separate device, so a hardware
decoder downloads to CPU instead (export stays software, correct).
- dmabuf.rs: imported plane textures now also carry SAMPLED/TEXTURE_BINDING so
they can be sampled by the NV12 blit (they were render-target-only); into_planes
hands the textures to the longer-lived GpuVideoFrame.
- video.rs: cache-key the GPU/CPU representation on want_gpu (HW-configured AND
render_hardware_ok) so software-only decode keeps a single cache entry.
Preview only this pass; export GPU-residency is the 3c-export follow-up. Untested
at runtime here (no GPU/display in container) — both crates compile.
Skyler Lehmkuhl