# Phase 8 close — iter14: Brave VAAPI engagement attempt — **investigation, not delivery**

**Result:** STRUCTURAL WALL hit. Lower-stack proven green; Brave/Chromium ARM64 binary doesn't have VAAPI compiled into its dispatch. iter14 ends as a documented dead-end so future iterations don't repeat the bounce.

## What iter14 actually proved

### 1. libva-v4l2-request-fourier + hantro-vpu chain is END-TO-END GREEN

Standalone test with ffmpeg-v4l2-request-fourier:

```
$ LIBVA_DRIVER_NAME=v4l2_request ffmpeg -hwaccel v4l2request \
    -i /home/mfritsche/fourier-test/bbb_1080p30_h264.mp4 -t 5 -f null -
[...]
[AVHWFramesContext @ ...] Using V4L2 media driver hantro-vpu (7.0.0) for S264
frame=  120 fps= 28 q=-0.0 Lsize=N/A time=00:00:05.00 bitrate=N/A speed=1.16x
```

```
$ lsof /dev/video1
COMMAND   PID      USER  FD   TYPE DEVICE
ffmpeg  15261 mfritsche mem    CHR   81,1  /dev/video1
ffmpeg  15261 mfritsche   5u   CHR   81,1  /dev/video1

$ lsof /dev/media0
COMMAND   PID      USER FD   TYPE DEVICE
ffmpeg  15261 mfritsche 4u   CHR  242,0  /dev/media0
```

ffmpeg explicitly opens `/dev/video1` (hantro-vpu) + `/dev/media0` (media controller), announces the hantro driver name, and decodes 1080p30 H.264 at **1.16× realtime** with ~25% of total quad-A55 CPU (bulk from audio re-encode + format conversion, not video decode). The hardware decoder is engaged.

### 2. Brave / Chromium ARM64 packages don't compile VAAPI into dispatch

Three signals converged:

a) chrome://gpu "Video Acceleration Information" panel shows **empty** Decoding and Encoding sections, even with `--enable-features=Vulkan,AcceleratedVideoDecodeLinuxGL,AcceleratedVideoDecodeLinuxZeroCopyGL,VaapiVideoDecoder,VaapiIgnoreDriverChecks,V4L2VideoDecoder` and `LIBVA_DRIVER_NAME=v4l2_request` env.

b) chrome://media-internals reports `Cannot select VaapiVideoDecoder for video decoding. status=DecoderStatus::Codes::kUnsupportedConfig → Selected FFmpegVideoDecoder` — VaapiVideoDecoder factory exists but rejects every config because its internal supported-profiles set is empty (libva was never queried).

c) Direct `/proc/<gpu-pid>/maps` inspection: the GPU process has **zero libva libraries loaded**. No `libva.so.2`, no `v4l2_request_drv_video.so`. VaapiWrapper code paths are never invoked.

The Arch upstream chromium PKGBUILD (which informs the Brave binary's build flavour) does not set `use_vaapi=true` in its GN flags, and Chromium's GN defaults `use_vaapi=false` on aarch64. Linux ARM64 chromium-family browsers shipped in package repos are universally built without VAAPI in dispatch.

## What iter14 ruled out

- ✗ Not a libva backend bug — vainfo + ffmpeg-fourier confirm v4l2_request is healthy
- ✗ Not a hardware bug — hantro-vpu engages fine
- ✗ Not a flag-combo bug — all known Brave/Chromium VAAPI feature flags tried; LIBVA_DRIVER_NAME set; `--no-zygote` used to bypass env-stripping; `VaapiIgnoreDriverChecks` enabled; nothing changes the empty dispatch
- ✗ Not an ANGLE-Vulkan bug — iter13 confirmed ANGLE-Vulkan engages on PanVk-Bifrost
- ✗ Not env-stripping across process boundary — libva isn't loaded in ANY child process either, not just stripped along the way

## What iter14 leaves open

**For a future "VAAPI in chromium on PanVk-Bifrost" goal:** the path forward is **building chromium from source for aarch64 with `use_vaapi=true` and `use_v4l2_codec=true`**, packaged as e.g. `chromium-vaapi-bifrost` in marfrit-packages. This is **multi-hour aarch64 CI work** (chromium aarch64 build is 6-12 hours even with distcc) and a substantial PKGBUILD undertaking. Not in scope for this iteration.

iter13 close stands: the Vulkan compositor + ANGLE-Vulkan stack delivers everything the original campaign charter asked for. HW video decode in Brave was always a stretch beyond charter scope (operator framing on iter11 open: "is the vulkan output used for video display? yup").

## Decision

iter14 closes as **investigation complete; structural wall documented**. Anyone returning to "make Brave do VAAPI HW decode" should start from this doc, NOT redo the flag-combo exhaustion that iter11/12/14 each independently bounced off.

— claude-noether, 2026-05-20