mesa-panvk-bifrost-video: sibling package adding VK_KHR_video_decode_h264

panvk-bifrost-video campaign close. Phase 4 byte-exact validated
2026-05-21 on RK3566/PineTab2 (Mali-G52 r1 MC1 + hantro VPU): 48/48
unique BBB display frames decoded by this driver are byte-identical
to ffmpeg+libva-v4l2-request-fourier on the same hantro hardware
(frame 42 Y md5 = 54b9b396e6cd377256eb4bce0efc0bed both ways).
Phase 5 second-model review passed; load-bearing findings applied.

Co-installs at /usr/lib/panvk-bifrost-video/ parallel to the r4
sibling at /usr/lib/panvk-bifrost/; opt-in via VK_ICD_FILENAMES.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

arch/mesa-panvk-bifrost-video/README.md

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+# mesa-panvk-bifrost-video
+
+Patched Mesa `libvulkan_panfrost.so` that **adds `VK_KHR_video_decode_h264`** on Mali Bifrost SBCs (PAN_ARCH 6/7, RK3566/RK3568 class hardware), backed by the SoC's V4L2-stateless **hantro** VPU.
+
+This is a **sibling** of [mesa-panvk-bifrost](../mesa-panvk-bifrost/) (the r4 package that exposes Bifrost to Chromium's Vulkan compositor). Pick this one when the consumer wants Vulkan **video decode** in addition; pick r4 for compositor-only.
+
+## Status
+
+Phase 4 byte-exact validated 2026-05-21: 48/48 unique BBB display frames decoded by this package are byte-identical to `ffmpeg+libva-v4l2-request-fourier` running on the same hantro hardware. Phase 5 second-model review completed; all load-bearing findings addressed.
+
+## How to use
+
+```sh
+# Co-installs alongside r4 and stock mesa.
+sudo pacman -S mesa-panvk-bifrost-video
+
+# Opt in (not on the default loader search path).
+export VK_ICD_FILENAMES=/usr/lib/panvk-bifrost-video/icd.json
+export PAN_I_WANT_A_BROKEN_VULKAN_DRIVER=1   # mesa-upstream gate
+
+# Run a Vulkan video consumer.
+vulkan-video-dec-simple-test -i your.h264 --codec h264 --noPresent --maxFrameCount 50
+# or
+ffmpeg -hwaccel vulkan -i your.mp4 ...
+```
+
+## Phase 1 limitations
+
+Documented in source comments and worth knowing before relying on this in production:
+
+- **Single video session per device.** Concurrent `VkVideoSessionKHR` on the same device clobber each other (`active_video` singleton). Sufficient for current single-stream consumers.
+- **Synchronous decode at record time.** The full V4L2 ioctl dance runs to completion inside `vkCmdDecodeVideoKHR`. No pipelining. Throughput is bounded by hantro's ~1.16× realtime on 1080p H.264.
+- **Hardcoded `/dev/video1` + `/dev/media0`.** Matches RK3566/68 but won't work on other SoCs without a topology-walk port (see `libva-v4l2-request-fourier` for the full version).
+- **Bitstream source buffer assumed HOST_VISIBLE.** True on panvk-bifrost (no DEVICE_LOCAL-only memory types exist), but the code silently skips decode if the app bound the buffer to non-host-visible memory.
+
+## Co-existence
+
+- Installs to `/usr/lib/panvk-bifrost-video/` — parallel to r4's `/usr/lib/panvk-bifrost/` and stock `/usr/lib/`.
+- Opt-in via `VK_ICD_FILENAMES`; does NOT register itself in `/usr/share/vulkan/icd.d/`.
+- Three drivers coexist without conflict; the user picks at runtime which to use.