marfrit
3e4e6e8eae
libva-v4l2-request-fourier flushes a stub packet into the V4L2
OUTPUT_MPLANE queue at playback-pause boundaries. The payload is
shorter than any parseable H.264 NAL (3-byte start code + 1-byte
NAL header = 4 bytes minimum); avcodec_send_packet returns
AVERROR_INVALIDDATA (-1094995529), which propagated to the kernel
as a decode failure. Firefox then marked H.264-via-VAAPI as
broken for the session and routed every subsequent frame to
libmozavcodec SW — pause never recovered to HW.
At the REQ_DECODE entry in chardev_client.c::handle_req_decode,
short-circuit any bitstream below the minimum-parseable threshold:
log INFO, skip daedalus_decoder_run_request, and reply RESP_FRAME
with status=DAEDALUS_DECODE_NO_FRAME so libva's V4L2 surface pool
stays healthy and Firefox doesn't see a failure.
Repro: Pi CM5 trixie, daedalus-v4l2 0.1.0+r41 + ffmpeg-v4l2-
request-fourier 2:8.1+rfourier+gb57fbbe-9, Firefox YouTube avc1.
Play → daemon decodes at ~46 fps. Pause ≥ 1s. Resume → daemon
silent; sudo journalctl -u daedalus-v4l2 --since '10s' | grep -c
'decoder: OK' = 0. Last entry before silence:
REQ_DECODE cookie=N codec=3 bitstream=3 bytes ...
[h264 @ ...] no frame!
[ERR] decoder: avcodec_send_packet failed: -1094995529
After this fix the 3-byte sentinel logs as 'tiny bitstream 3
bytes — dropping as no-op' and the libavcodec context is
untouched; the next real REQ_DECODE proceeds normally.
Scope NOT covered (intentionally deferred):
- A more general "tolerate AVERROR_INVALIDDATA mid-stream" path.
Worth doing later but masks unrelated bugs.
- Investigating WHY libva sends the 3-byte sentinel on pause.
Likely an upstream libva-v4l2-request-fourier issue; tracked
separately if this filter is not enough.
Wire protocol unchanged. No DAEDALUS_PROTO_VERSION bump.
daedalus-v4l2
V4L2 stateless decoder for the Raspberry Pi 5 / CM5, backed by the
daedalus-fourier kernel library (VP9 + AV1 CDEF + H.264 video
decode kernels on VideoCore VII compute + ARM NEON).
Status: scaffold (2026-05-18). Architecture locked per daedalus-fourier session memory; implementation not yet begun.
What this is
Sibling repo to daedalus-fourier (the kernel library; cycles 1-9 closed).
A two-piece userspace + kernel-module stack that exposes a V4L2
stateless decoder interface (/dev/videoNN) so that
libva-v4l2-request-fourier → firefox-fourier /
chromium-fourier can drive it the same way they drive existing
hardware-decode pipelines on Pi 5 / RK3588.
+-----------------------------------------------------------+
| firefox-fourier / chromium-fourier (existing) |
+-----------------------------------------------------------+
| VA-API |
+-----------------------------------------------------------+
| libva-v4l2-request-fourier (existing, sibling project) |
+-----------------------------------------------------------+
| V4L2 stateless ioctl uAPI |
+-----------------------------------------------------------+
| daedalus-v4l2 kernel module (`kernel/`) |
| - registers /dev/videoNN |
| - parses V4L2 stateless ioctls (VP9/AV1/H.264 controls) |
| - forwards bitstream + controls to userspace daemon |
| via chardev or netlink |
+-----------------------------------------------------------+
| daedalus-v4l2 userspace daemon (`daemon/`) |
| - takes bitstream blobs + per-slice controls |
| - drives FFmpeg parsers via dlopen (Option γ) |
| - dispatches per-block ops via daedalus-fourier |
| public API (daedalus_dispatch_*) |
| - posts decoded frames back to kernel module |
+-----------------------------------------------------------+
| daedalus-fourier kernel library (sibling project) |
| - exports include/daedalus.h public API |
| - per-kernel CPU NEON + opportunistic V3D QPU dispatch |
| - 9 closed cycles across VP9, AV1 CDEF, H.264 |
+-----------------------------------------------------------+
| V3D 7.1 (Mesa userspace v3dv) + ARM NEON (BCM2712) |
+-----------------------------------------------------------+
Why this architecture (Option B + γ + sibling)
Locked by user 2026-05-18 from 3 options in
daedalus-fourier/docs/phase8_scoping.md:
- Option B over A (userspace v4l2loopback): real
/dev/videoNN, proper DRM PRIME / dmabuf for browser zero-copy. - Option γ: dlopen FFmpeg as parser at runtime. No vendoring, fastest to v1.
- Sibling repo: per
project_consumer_targetconvention, V4L2-side work lives outside daedalus-fourier so the kernel-library has a clean API boundary.
Status
Initial scaffold only. See docs/architecture.md for the
deeper design and docs/roadmap.md for the
sub-phase breakdown.
Repo layout
kernel/— Linux kernel module (V4L2 device registration + ioctl handling + userspace chardev bridge). Out-of-tree.daemon/— userspace decoder daemon (linkslibdaedalus_core.afrom sibling daedalus-fourier; uses dlopen for FFmpeg parser).include/— shared headers between kernel and daemon.docs/— architecture + roadmap.
License
Kernel module: GPLv2 (required for kernel-tree compatibility). Userspace daemon: BSD-2-Clause (matches daedalus-fourier).