marfrit/fourier
1
0
Fork 0
Code Issues 1 Pull Requests Actions Packages Projects Releases Wiki Activity

ohm task (b.2): neither system ffmpeg nor Chromium's V4L2 decoder reachable

Browse Source 
Followup to the user's "can Brave use our ffmpeg instead?" question.
Both alternatives investigated, both dead ends:

- System ffmpeg path: Chromium/Brave link a vendored ffmpeg. Even the
  use_system_ffmpeg builds use system libavcodec only as a pure SW decoder
  (FfmpegVideoDecoder — no hw_device_ctx / hwaccel wiring). Our
  ffmpeg-v4l2-request-git would be used as SW. No HW speedup.
- Chromium's own V4L2VideoDecoder: class IS compiled into brave-bin
  (strings /opt/brave-bin/brave | grep V4L2VideoDecoder hits), but the
  factory is ChromeOS-gated. Feature flag strings UseChromeOSDirectVideoDecoder
  / V4L2FlatStatelessVideoDecoder / V4L2FlatVideoDecoder do NOT appear as
  strings in the binary — only AcceleratedVideoDecodeLinuxGL does, and
  that's the VA-API gate, not a V4L2 gate. Setting those flags on the
  cmdline is a no-op on this build.

Conclusion: unlocking browser HW decode on ohm requires either (a) Chromium
rebuilt with V4L2 decoder factory extended to Linux non-ChromeOS, (b) a
multiplanar-capable libva-v4l2-request, or (c) a new chromium-on-Linux HW
decode path that hasn't shipped yet.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Markus Fritsche
2026-04-24 20:57:20 +00:00
parent 7301067108
commit 7517fb7e9b
1 changed files with 17 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
README.md
+17
View File
@@ -252,6 +252,23 @@ Non-browser HW decode (GStreamer `v4l2codecs`, FFmpeg via
ohm is a useful starting point for anyone who wants to pick up the
multiplanar port.
#### Why not "Brave via our system ffmpeg" or Chromium's own V4L2 decoder?
- **System ffmpeg is not a decoder source for Chromium/Brave.** Chromium
links a vendored ffmpeg fork; even the Arch-style `use_system_ffmpeg`
builds use system `libavcodec` only as a pure software decoder
(`FfmpegVideoDecoder`), with no `hw_device_ctx` / hwaccel wiring.
Installing our `ffmpeg-v4l2-request-git` would not give Brave HW decode.
- **Chromium's own `V4L2VideoDecoder` class is compiled into `brave-bin`**
(verified via `strings`) but gated behind ChromeOS-only runtime factory
checks. `UseChromeOSDirectVideoDecoder` / `V4L2FlatStatelessVideoDecoder`
feature flag names do **not** appear as strings in the brave-bin binary
— only `AcceleratedVideoDecodeLinuxGL` does, which is a VA-API gate, not
a V4L2 gate. Enabling those flags at the command line is a no-op on this
build. Unlocking V4L2 on Linux Brave would require either (a) a Chromium
rebuild with different buildflags, or (b) upstream patches to extend the
V4L2 decoder factory to Linux non-ChromeOS targets.
### Acceptance criterion
**1080p @ 30 fps, no dropped frames.** Applies to every device and every