Raspberry Pi 5 + Chromium hardware video decode question

pi5-chromium-hw-decode-gist.md

Raspberry Pi 5 + Chromium Hardware Decode: Is This Possible?

Problem Summary

I’m investigating hardware-accelerated video decode on Raspberry Pi 5 using Chromium (Wayland). The goal is smooth playback (no frame drops) and a Chromium-based UI. So far, Chromium appears to run software-only for video decode/compositing on Pi 5, despite extensive flag and VA-API attempts.

Environment

• Hardware: Raspberry Pi 5 (BCM2712)
• OS/Display: Wayland (Sway/Wlroots)
• Browser: Chromium (aarch64)
• GPU: V3D
• Decoder API: V4L2 stateless (rpivid)

What We Know (Current Findings)

• Pi 5 appears to expose HEVC-only hardware decode via V4L2 stateless (rpivid). H.264 hardware decode is not available.
• Chromium’s chrome://gpu shows Video Decode: Software only.
• CDP Media diagnostics report FFmpegVideoDecoder (software decode).
• video.canPlayType('video/mp4; codecs="hvc1"') and MediaSource.isTypeSupported(...) return not supported for HEVC in current Chromium build.

Attempts So Far

• Enabled Chromium features/flags:
  • VaapiVideoDecoder, VaapiIgnoreDriverChecks, V4L2VideoDecoder, V4L2StatelessVideoDecoder, VaapiVideoDecodeLinuxGL, UseMultiPlaneFormatForHardwareVideo, Vulkan, DefaultANGLEVulkan, PlatformHEVCDecoderSupport, etc.
• Forced VA-API V4L2 backend via LIBVA_DRIVER_NAME=v4l2 and LIBVA_DRIVERS_PATH=....
• Tested libva-v4l2 (mxsrc fork): loads but reports no profiles/entrypoints on Pi 5.
• Attempted to build libva-v4l2-request (bootlin) but it fails against modern kernel headers.

Hypothesis

Pi 5 hardware decode is HEVC-only, but Chromium on Linux does not accept HEVC without a custom build (proprietary codecs + platform decoder enabled). If Chromium can’t be built to accept HEVC on aarch64, then hardware decode may be unavailable in Chromium on Pi 5.

What I’m Looking For

• Has anyone successfully enabled HEVC playback in Chromium on Raspberry Pi 5?
• Are there known patches or build flags to enable HEVC/platform decoding on aarch64 Chromium?
• Any references to Chromium builds with V4L2 stateless HEVC decode working on Pi 5?

Potential Solutions / Workarounds (in priority order)

1. Custom Chromium build with proprietary codecs + HEVC enabled (and platform decoder wired in). If canPlayType flips and CDP Media shows a platform decoder, this is likely the best path.
2. Alternate Chromium builds (e.g., downstream patches) that explicitly enable V4L2/HEVC.
3. Pipeline split (still Chromium UI): keep Chromium for UI but offload video playback to a native player only if Chromium cannot do HEVC (last resort).

Related Links / Issues

• HEVC / proprietary codecs on Chromium:
  • ungoogled-software/ungoogled-chromium#2752
  • uazo/cromite#710
  • chromiumembedded/cef#3559
• V4L2 decoding support in Chromium builds:
  • saiarcot895/chromium-ubuntu-build#65
• Pi 5 / HEVC decode discussions:
  • Screenly/Anthias#2450
  • FDH2/UxPlay#358
• VA-API / driver stack notes:
  • bootlin/libva-v4l2-request#42
  • NixOS/nixpkgs#299773

Minimal Checks

• chrome://gpu shows Video Decode: Hardware accelerated.
• chrome://media-internals shows a hardware/platform decoder (not FFmpeg).
• MediaSource.isTypeSupported('video/mp4; codecs="hvc1.1.6.L93.B0"') returns true.

Additional Details / Observations

• Pi 5 decode block: Pi 5 removed the legacy H.264 decoder block; hardware decode appears to be HEVC‑only (rpivid / V4L2 stateless). If Chromium can’t accept HEVC, hardware decode is effectively unavailable.
• VA-API backend status: libva-v4l2 loads but reports no profiles/entrypoints on Pi 5. This suggests the V4L2 -> VA-API shim may not expose HEVC yet (or needs specific device paths/patches).
• V4L2 device signals: /dev/video19 reports S265 (HEVC parsed slices). rpivid_hevc kernel module is loaded; no H.264 module appears.
• Chromium diagnostics: chrome://gpu consistently reports “Video Decode: Software only” even with VaapiIgnoreDriverChecks and V4L2StatelessVideoDecoder enabled. CDP Media uses FFmpegVideoDecoder.
• HEVC support in Chromium: video.canPlayType and MediaSource.isTypeSupported return empty for HEVC in current builds, implying missing proprietary codecs/platform decode wiring.
• If HEVC can be enabled: We’d expect canPlayType to flip to probably/maybe, chrome://media-internals to show a platform decoder, and chrome://gpu to report hardware decode.

If you’ve seen this working (or know why it can’t), please share links/patches/build flags.