marfrit
8c1d9960c4
libva-v4l2-request-fourier (and any V4L2-stateless-API consumer)
passes H.264 SPS/PPS as separate V4L2_CID_STATELESS_H264_{SPS,PPS}
controls; only the slice NAL goes into the OUTPUT buffer. This is
correct per the V4L2 stateless contract. But libavcodec — which
the daedalus daemon uses for actual decode (Option γ) — wants a
self-contained AnnexB stream including SPS+PPS before any slice.
Result on higgs: "non-existing PPS 0 referenced" + decode_slice_
header errors on every H.264 frame, even after LIBVA-1 and -2
routing correctly delivered the request to the daemon.
Fix splits across kernel + daemon, keeping the kernel module as a
thin transport and putting the actual NAL encoding in userspace:
include/daedalus_v4l2_proto.h:
Add struct daedalus_h264_meta (the four v4l2_ctrl_h264_*
structs the kernel collects) and DAEDALUS_REQ_FLAG_H264_META
(set in req.flags when the meta block is present between the
daedalus_req_decode prefix and the slice bitstream).
kernel/daedalus_v4l2_main.c:
Add daedalus_collect_h264_meta() — reads the H.264 ctrl values
from the bound media_request via v4l2_ctrl_find +
ctrl->p_cur.p_h264_*. device_run() calls it on H.264 codec_id,
copies the structs into the REQ_DECODE payload between the
prefix and bitstream, and sets the flag. Payload size is
bounds-checked against DAEDALUS_PROTO_MAX_PAYLOAD so an over-
sized slice + meta fails loud instead of truncating.
daemon/src/bitstream_writer.{c,h}:
New module — MSB-first bit packer with H.264 Exp-Golomb ue(v)
and se(v) coding + rbsp_trailing_bits alignment. Sticky
overflow flag so callers can verify the output buffer wasn't
truncated.
daemon/src/h264_nal_synth.{c,h}:
New module — turns v4l2_ctrl_h264_sps / v4l2_ctrl_h264_pps
into AnnexB-framed NAL units per ITU-T H.264 7.3.2.1 / 7.3.2.2.
Emits emulation prevention bytes (0x03 after every 00 00 in the
EBSP) and the 4-byte start code (0x00000001). Coverage matches
what V4L2 stateless surface gives us: VUI parameters and full
scaling matrices are NOT emitted (V4L2 doesn't carry them — the
seq_scaling_matrix_present_flag is set to 0 and libavcodec uses
flat defaults, which matches the de-facto behaviour of most
H.264 streams libva-v4l2-request drives).
daemon/src/decoder.c:
daedalus_decoder_run_request() now takes an optional
h264_meta parameter. For codec_id == H264 with meta != NULL,
synthesises SPS+PPS NAL units, allocates a combined
[SPS][PPS][slice] buffer (+ AV_INPUT_BUFFER_PADDING_SIZE), and
feeds that to avcodec_send_packet instead of the raw slice.
VP9/AV1 path unchanged (frames are self-contained). Cleanup
now goes through a unified `out:` label so the assembled
buffer is always freed on every exit (including the existing
decoder_open_codec / no-frame / receive_frame failure paths).
daemon/src/chardev_client.c:
handle_req_decode() peels off the optional meta block when the
flag is set, passes it through to the decoder, and updates
the payload-length consistency check (now allows for an extra
sizeof(daedalus_h264_meta) when the flag is on).
Build (boltzmann aarch64): clean compile of all daemon sources,
including bitstream_writer + h264_nal_synth + the refactored
decoder.c. Kernel module compile to be verified via DKMS rebuild
on higgs in the marfrit-packages bump that follows.
Test plan: with this commit + a marfrit-packages daedalus pin
bump, higgs's ffmpeg -hwaccel vaapi -i h264_test.mp4 should
produce a successful decode (vs. the previous "non-existing PPS 0
referenced" failure). The daemon log should show:
decoder: opened h264 context
decoder: h264 prepended SPS=NB PPS=MB slice=KB
decoder: OK 320x240 fmt=0 (yuv420p) fnv1a=0x...
VP9 / AV1 behaviour unchanged — they don't carry meta and the
existing per-frame self-describing path still applies.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
45 lines
1.6 KiB
C
45 lines
1.6 KiB
C
/* SPDX-License-Identifier: BSD-2-Clause */
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/*
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* h264_nal_synth.h — synthesise AnnexB SPS + PPS NAL units from the
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* v4l2_ctrl_h264_sps / v4l2_ctrl_h264_pps structures the libva driver
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* sets via V4L2 stateless controls and the daedalus kernel module
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* forwards over the chardev as struct daedalus_h264_meta.
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*
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* libavcodec needs SPS+PPS NAL units BEFORE any slice NAL to bind
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* the slice's pic_parameter_set_id reference; libva-v4l2-request
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* passes only the slice in the OUTPUT buffer (per the V4L2 stateless
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* H.264 contract). The daemon bridges by reconstructing SPS+PPS
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* NAL bytes from the structured controls and prepending them to the
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* bitstream the daemon hands libavcodec.
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*
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* Output is AnnexB-framed: 0x00 0x00 0x00 0x01 start code + NAL.
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* Emulation prevention (insert 0x03 after any 0x00 0x00 in the RBSP)
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* is handled by this module so the consumer can concatenate raw.
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*/
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#ifndef DAEDALUS_H264_NAL_SYNTH_H
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#define DAEDALUS_H264_NAL_SYNTH_H
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#include <stddef.h>
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#include <stdint.h>
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#include <linux/v4l2-controls.h>
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/*
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* Encode an AnnexB SPS NAL into out[]. Returns the number of bytes
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* written, or 0 on overflow / malformed input. out_cap must be at
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* least 256 bytes to handle worst-case SPS with full offset_for_ref_
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* frame[] cycle.
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*/
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size_t h264_synth_sps(const struct v4l2_ctrl_h264_sps *sps,
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uint8_t *out, size_t out_cap);
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/*
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* Encode an AnnexB PPS NAL into out[]. Returns the number of bytes
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* written, or 0 on overflow. out_cap should be at least 64 bytes;
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* PPS NALs are small.
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*/
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size_t h264_synth_pps(const struct v4l2_ctrl_h264_pps *pps,
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uint8_t *out, size_t out_cap);
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#endif /* DAEDALUS_H264_NAL_SYNTH_H */
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