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forgectrl: NEON demosaic - 15 fps, sensor-limited

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NEON kernel for the YUV420 superpixel convert (vld2q deinterleave, rounding-halving greens, mlal/rshrn luma, pairwise-add chroma block sums), bit-identical to the scalar path and proven so on a live frame via the FORGECTRL_NEON_CHECK one-shot memcmp. Convert 75 to 18 ms; the stream now runs at the OV5648 frame rate. Motion coexistence re-proven at 15 fps (clamped 0).
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ScottW514
2026-08-03 13:46:08 -04:00
parent d75ff717ac
commit 421909a6a8
4 changed files with 192 additions and 9 deletions
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docs/BRINGUP.md
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@@ -156,8 +156,9 @@ The cameras share the hardware video-mux; the NEWEST request wins it
The per-camera lamp (`pic/lid_led` / `head/white_led`) is raised to
`FORGECTRL_LAMP` (default 132) while capturing and restored on idle.
Bench (2026-08-03, on the board): stream **7.9 fps** sustained at
1296×972 (VPU encode; 3.2 fps on the software fallback);
Bench (2026-08-03, on the board): stream **15.0 fps** sustained at
1296×972 (NEON demosaic + VPU encode; 3.2 fps on the full software
fallback);
full-res snapshot 2.4 s warm / 2.7 s cold (cold includes the pipeline
bring-up); two parallel same-camera clients share the frame rate; idle
teardown observed. Borrow verified: head snapshot 200 during a lid
@@ -190,9 +191,18 @@ encode 7 ms**. Two hard-won facts:
needed) with quality via V4L2_CID_JPEG_COMPRESSION_QUALITY.
libjpeg remains the automatic fallback (`FORGECTRL_NO_VPU=1` forces
it) and the snapshot path; `/cam/status` reports `"encoder"`.
Remaining headroom: the scalar convert dominates — NEON would push
toward the sensor/CSI limit. If motion contention ever shows clamps
during streaming, a stream-fps cap knob is the easy relief valve.
**NEON demosaic: DONE 2026-08-03 — 15.0 fps, sensor-limited.** The
YUV420 superpixel convert has a NEON kernel (vld2q deinterleave,
vrhaddq greens, vmlal/vrshrn luma, vpaddlq block sums for chroma;
`FORGECTRL_NO_NEON=1` forces scalar): convert 75 → 18 ms, per-frame
copy 34 + convert 18 + encode 7 ≈ 59 ms against the sensor's 66 ms
frame period. The NEON and scalar paths are bit-identical — proven on
a live frame via `FORGECTRL_NEON_CHECK=1` (one-shot memcmp, logs
IDENTICAL). Motion coexistence re-proven at 15 fps: jogs with an
active stream show clamped 0, max behind 7.2 ms (~4 % of the 200 ms
queue) — the worst-case contention signature so far; if real jobs
ever clamp, a stream-fps cap knob is the relief valve.
The IPU cannot help with demosaic (its IC is CSC/scale only — the
`imx-csc-scaler` at /dev/video8 matters only for a future full-res
stream). Not yet done: lens calibration / bed alignment (the