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fix(encode): RGB-direct probe — accept cosited-even chroma siting (what VCN EFC actually offers)

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On-glass B0 result from the 780M (RADV PHOENIX, host Mesa 26.0.4): the
probe returned no-709-narrow-midpoint because RADV advertises
xChromaOffsets = COSITED_EVEN only — the VCN EFC does canonical H.26x
left-cosited x-chroma, while the requirement was written to bit-match our
2x2-average (midpoint) shader. The delta is a half-pel chroma-x phase,
imperceptible and unsignalled in our bitstream; EFC's siting is arguably
the more correct one. Accept either siting bit per axis (model + range
stay exact: 709 narrow); B1 will pass the preferred available bit.

With this the 780M probes rgb_direct=available; both GPU smoke tests
(H265 + AV1) pass on that box against host Mesa 26.0.4 — the first
real-RADV validation of the poll fix, the quality-level control, and B0.
(Container mesa alone can't run the H265 smoke: Fedora ships RADV with
H264/H265 encode compiled out — AV1 only. Use the host ICD via
VK_ICD_FILENAMES on Atomic boxes.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
enricobuehler
2026-07-20 19:44:33 +02:00
committed by enricobuehler
co-authored by Claude Opus 4.8
parent d833cff470
commit d5a0f5012b
1 changed files with 10 additions and 3 deletions
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crates/pf-encode/src/enc/linux/vulkan_video.rs
+10 -3
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@@ -2572,12 +2572,19 @@ unsafe fn probe_rgb_direct(
if r != vk::Result::SUCCESS {
return "no-rgb-profile(caps)";
}
// Colour model + range must match the shader exactly (709 narrow). Chroma siting is looser
// BY ON-GLASS FINDING (RADV 26.0.4 / 780M): the VCN EFC advertises x=COSITED_EVEN only —
// the canonical H.26x left-cosited siting — while our 2x2-average shader is midpoint. The
// difference is a half-pel chroma-x phase, imperceptible (and EFC's is arguably the more
// correct one since nothing in our bitstream signals siting). Accept either bit per axis;
// B1 passes the preferred available bit (midpoint if offered, else cosited-even).
let any_siting = vrgb::CHROMA_OFFSET_MIDPOINT | vrgb::CHROMA_OFFSET_COSITED_EVEN;
if rgb_caps.rgb_models & vrgb::MODEL_YCBCR_709 == 0
|| rgb_caps.rgb_ranges & vrgb::RANGE_NARROW == 0
|| rgb_caps.x_chroma_offsets & vrgb::CHROMA_OFFSET_MIDPOINT == 0
|| rgb_caps.y_chroma_offsets & vrgb::CHROMA_OFFSET_MIDPOINT == 0
|| rgb_caps.x_chroma_offsets & any_siting == 0
|| rgb_caps.y_chroma_offsets & any_siting == 0
{
return "no-709-narrow-midpoint";
return "no-709-narrow";
}
// 4. The encode-src format set under this profile must offer BGRA with DRM-modifier tiling —
// the capture hands LINEAR BGRx dmabufs (fourcc XR24), which import as B8G8R8A8_UNORM.