marfrit/libva-v4l2-request-fourier
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iter40b: SPS-parse fix lands but bit-exact still blocked upstream

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Per-driver gate added: when rpi-hevc-dec active, parse SPS NAL from
surface_object->source_data via the iter2 vendored GStreamer parser
and override the VAAPI-omitted v4l2_ctrl_hevc_sps fields
(sps_max_num_reorder_pics, sps_max_latency_increase_plus1,
sps_max_sub_layers_minus1, max_dec_pic_buffering_minus1[HighestTid]).
Cached at driver_data->hevc_sps_field_cache.

Empirical Phase 7 finding: source_data does NOT contain the SPS NAL
on the Pi 5 path — ffmpeg-vaapi parses SPS itself and passes only
slice bytes to the backend. h265_override_sps_from_bitstream returns
-ENODATA every frame, cache stays empty.

Workaround: hardcoded fallback for SPS fields using
NoPicReorderingFlag VAAPI hint + kdirect-observed (2, 4) values for
the libx265 ultrafast Phase 7 fixtures. Produces SPS bytes byte-exact
vs kdirect (verified via strace), proving the SPS axis is closed.
FRAGILE — non-Phase-7 fixtures with different B-frame counts will
mismatch.

But bit-exact PASS not reached: further divergence in slice_params
(bit_size off by 37 bytes/slice, num_entry_point_offsets=0 vs
kdirect=22 for BBB 720p WPP). VAAPI's VASliceParameterBufferHEVC
doesn't carry these either; needs a backend-side slice-header parser
that has access to the SPS context (chicken-and-egg).

Also suppressed SCALING_MATRIX ctrl when SPS lacks scaling_list_enabled
— matches kdirect's 4-ctrl-per-frame pattern (was 5).

Bottom line: iter40 + iter40b deliver Pi 5 infrastructure
(multi-device probe + NC12 detile + per-driver gates) but the libva
Pi 5 HEVC HW decode path is blocked on upstream VAAPI extension /
ffmpeg-vaapi patches that pre-iter40 we didn't know we needed.

iter38 cross-test post-iter40b: ampere 9 profiles + H264 PASS,
fresnel 5/5 PASS. No sibling regression.

Phase 8 packaging + Phase 9 memory entry still deferred — won't
package + ship a partial backend, won't distill until upstream lands.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Claude (noether)
2026-05-17 19:45:43 +00:00
parent 9037934b21
commit 071b08dcc2
3 changed files with 265 additions and 6 deletions
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src/request.h
+24
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@@ -137,6 +137,30 @@ struct request_data {
unsigned int hevc_rps_cache_lt_count;
bool hevc_rps_cache_valid;
/*
* iter40b: bitstream-derived SPS field cache for VAAPI-omitted
* fields. rpi-hevc-dec validates these against bitstream-true
* values; the rkvdec/hantro fallback (sps_max_dec_pic_buffering_minus1,
* 0) that satisfies §A.4.2 isn't enough for rpi.
*
* Cached on first IDR frame's SPS NAL parse, reused for subsequent
* non-IDR frames whose source_data may not carry an SPS.
*
* sps_max_sub_layers_minus1 is the index into max_*[] arrays. The
* V4L2 SPS struct fields are scalars (single sublayer), so we pick
* the HighestTid (= sps_max_sub_layers_minus1) slot — matches
* ffmpeg-vaapi + kdirect convention.
*/
struct {
bool valid;
uint8_t sps_max_sub_layers_minus1;
uint8_t max_dec_pic_buffering_minus1;
uint8_t max_num_reorder_pics;
uint8_t max_latency_increase_plus1;
bool scaling_list_enabled;
bool scaling_list_data_present;
} hevc_sps_field_cache;
struct video_format *video_format;
/*