marfrit
5c8b09349c
Last unmeasured H.264 kernel. mc20 picked as representative (horizontal half-pel, 6-tap filter; canonical for the H.264 luma qpel family). M1 PASS 10000/10000 first try, M3 = 131.477 Mblock/s on a single core (7.6 ns/block), 135x the 1080p30 floor. Per the cycles 6+7 lightweight-kernel rationale, Phase 4 deferred: QPU dispatch floor (~250 ns/block) is 33x above the NEON per-block cost; R9 ≈ 0.03 deep RED. No realistic QPU offload value. Generalization: all H.264 luma MC variants (mc02, mc11, mc22, etc.) will share this verdict. No need to measure each variant individually. H.264 NEON is dramatically faster than VP9 NEON across the board: - IDCT 4x4: 175 vs N/A (no VP9 analog) - IDCT 8x8: 151 vs 8.2 Mblock/s (18x faster) - MC 6/8-tap: 131 vs 7.0 (19x faster) - Deblock: 92 vs 48 Medge/s (2x faster) H.264 deployment recipe: all CPU NEON except deblock (opportunistic QPU). On a Pi 5 running H.264-only, the QPU is mostly idle. Cycles 1-9 complete. Public API exposes all 9. Next: daedalus-v4l2 sibling repo per locked Phase 8 architecture (B + γ + sibling), then README polish. - external/ffmpeg-snapshot/libavcodec/aarch64/h264qpel_neon.S vendored (1467 lines, all qpel variants) - tests/h264_qpel8_mc20_ref.c: 40-line C ref (clip255 of 6-tap convolution) - tests/bench_neon_h264qpel_mc20.c: M1 + M3 bench - docs/k9_h264qpel_mc20.md: cycle 9 closure with comparison matrix Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
40 lines
1.3 KiB
C
40 lines
1.3 KiB
C
/*
|
||
* Standalone bit-exact C reference for H.264 luma qpel 8×8 mc20
|
||
* (horizontal half-pel, "put" variant). 6-tap filter:
|
||
*
|
||
* dst[r,c] = clip255( (s[r,c-2] - 5*s[r,c-1] + 20*s[r,c]
|
||
* + 20*s[r,c+1] - 5*s[r,c+2] + s[r,c+3]
|
||
* + 16) >> 5 )
|
||
*
|
||
* Mirrors FFmpeg `ff_put_h264_qpel8_mc20_neon` (in
|
||
* external/ffmpeg-snapshot/libavcodec/aarch64/h264qpel_neon.S
|
||
* line 595, which tail-calls put_h264_qpel8_h_lowpass_neon).
|
||
*
|
||
* Signature:
|
||
* void(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
|
||
*
|
||
* Both dst and src use the SAME stride. src points at the
|
||
* leftmost output column (col 0); filter reads cols -2..+3.
|
||
*
|
||
* License: LGPL-2.1-or-later.
|
||
*/
|
||
#include <stdint.h>
|
||
#include <stddef.h>
|
||
|
||
static inline int clip_u8(int v) { return v < 0 ? 0 : v > 255 ? 255 : v; }
|
||
|
||
void daedalus_put_h264_qpel8_mc20_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)
|
||
{
|
||
for (int r = 0; r < 8; r++) {
|
||
const uint8_t *s = src + r * stride;
|
||
uint8_t *d = dst + r * stride;
|
||
for (int c = 0; c < 8; c++) {
|
||
int v = (int) s[c - 2] - 5 * (int) s[c - 1]
|
||
+ 20 * (int) s[c] + 20 * (int) s[c + 1]
|
||
- 5 * (int) s[c + 2] + (int) s[c + 3]
|
||
+ 16;
|
||
d[c] = (uint8_t) clip_u8(v >> 5);
|
||
}
|
||
}
|
||
}
|