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Phase 8c: H.264 luma qpel mc20 through public API

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Extends daedalus-fourier with daedalus_recipe_dispatch_h264_qpel_mc20
so libavcodec.so can route H264QpelContext.put_h264_qpel_pixels_tab[1][2]
through the recipe layer instead of ff_put_h264_qpel8_mc20_neon directly.

API additions (header + library):
  - daedalus_h264_qpel_meta { dst_off, src_off }
  - daedalus_dispatch_h264_qpel_mc20(ctx, sub, dst, src, stride,
                                     n_blocks, meta)
  - daedalus_recipe_dispatch_h264_qpel_mc20(...)  (AUTO wrapper)
  - DAEDALUS_KERNEL_H264_QPEL_MC20 = 9 in the recipe-query enum
  - daedalus_recipe_substrate_for() returns CPU NEON for cycle 9

The 6-tap horizontal half-pel filter signature matches FFmpeg's
H264QpelContext convention exactly: dst and src share a single stride
and src already points at output column 0 (filter reads cols -2..+3).
Single-stride API to make the marfrit-packages FFmpeg shim a
straight pointer-pass; no buffer rearrangement.

Verdict per docs/k9_h264qpel_mc20.md: CPU NEON.  Per-block 7.6 ns
gives 135x margin over 30 fps 1080p; QPU dispatch floor at ~250 ns
makes any V3D shader strictly worse.  Recipe table reflects that —
the recipe_dispatch entry is a one-line forward to the CPU path.

CMakeLists changes:
  - h264qpel_neon.S added to the daedalus_core static lib (only the
    bench targets owned it before; now the public API needs it too)
  - tests/h264_qpel8_mc20_ref.c added to the test_api_h264 target

Phase 8a/8b smoke gains a 4th case (test_qpel_mc20): 1024/1024
bytes bit-exact via daedalus_recipe_dispatch_h264_qpel_mc20.

Refs reauktion/daedalus-v4l2#11 — substitution arc step 2 cycle 9.
This commit is contained in:
Claude (noether)
2026-05-23 03:25:24 +02:00
parent d87239d817
commit 8fdef27a7d
4 changed files with 116 additions and 0 deletions
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tests/test_api_h264.c
+45
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@@ -18,6 +18,8 @@ extern void daedalus_h264_idct_add_ref(uint8_t *dst, int16_t *block, ptrdiff_t s
extern void daedalus_h264_idct8_add_ref(uint8_t *dst, int16_t *block, ptrdiff_t stride);
extern void daedalus_h264_v_loop_filter_luma_ref(uint8_t *pix, ptrdiff_t stride,
int alpha, int beta, int8_t tc0[4]);
extern void daedalus_put_h264_qpel8_mc20_ref(uint8_t *dst, const uint8_t *src,
ptrdiff_t stride);
static uint64_t xs_state = 0xa11264ULL;
static inline uint64_t xs(void) {
@@ -143,6 +145,46 @@ static int test_deblock(void)
return diff == 0 ? 0 : 1;
}
static int test_qpel_mc20(void)
{
/* Cycle 9 — one 8x8 block per 16-wide row-tile, 8 tiles. Each tile
* holds rows 0..7; src[c-2..c+3] read via SRC_COL offset matches the
* cycle-9 bench convention so the same C reference and NEON .S can
* be compared. */
enum { N = 8, TILE_STRIDE = 16, TILE_ROWS = 8,
TILE_BYTES = TILE_ROWS * TILE_STRIDE, TOTAL = N * TILE_BYTES,
SRC_COL = 3 };
daedalus_ctx *ctx = daedalus_ctx_create();
if (!ctx) return 1;
uint8_t src[TOTAL], dst[TOTAL], dst_ref[TOTAL];
daedalus_h264_qpel_meta meta[N];
for (int i = 0; i < TOTAL; i++) src[i] = (uint8_t)(xs() & 0xff);
memset(dst, 0, sizeof(dst));
memset(dst_ref, 0, sizeof(dst_ref));
for (int i = 0; i < N; i++) {
meta[i].src_off = (uint32_t)(i * TILE_BYTES + SRC_COL);
meta[i].dst_off = (uint32_t)(i * TILE_BYTES + SRC_COL);
}
for (int i = 0; i < N; i++)
daedalus_put_h264_qpel8_mc20_ref(dst_ref + meta[i].dst_off,
src + meta[i].src_off,
TILE_STRIDE);
int rc = daedalus_recipe_dispatch_h264_qpel_mc20(ctx, dst, src,
TILE_STRIDE, N, meta);
if (rc) { fprintf(stderr, "qpel_mc20 dispatch rc=%d\n", rc); return 1; }
int diff = 0;
for (int i = 0; i < TOTAL; i++) if (dst[i] != dst_ref[i]) diff++;
printf(" H.264 qpel mc20: %d/%d bytes bit-exact (%.4f%%)\n",
TOTAL - diff, TOTAL, 100.0 * (TOTAL - diff) / TOTAL);
daedalus_ctx_destroy(ctx);
return diff == 0 ? 0 : 1;
}
int main(void)
{
printf("=== Phase 8a API smoke: H.264 kernels via recipe dispatch ===\n");
@@ -152,10 +194,13 @@ int main(void)
(int) daedalus_recipe_substrate_for(DAEDALUS_KERNEL_H264_IDCT8));
printf(" H264_DEBLOCK_LV recipe substrate: %d\n",
(int) daedalus_recipe_substrate_for(DAEDALUS_KERNEL_H264_DEBLOCK_LV));
printf(" H264_QPEL_MC20 recipe substrate: %d\n",
(int) daedalus_recipe_substrate_for(DAEDALUS_KERNEL_H264_QPEL_MC20));
int fail = 0;
fail |= test_idct4();
fail |= test_idct8();
fail |= test_deblock();
fail |= test_qpel_mc20();
return fail;
}