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h264: qpel avg anchors (avg_mc20/02/22, biprediction support)

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Begins the avg_ qpel buildout for B-slice biprediction.  Each avg_
form computes the same half-pel formula as its put_ sibling, then
L2-averages the result with the existing dst contents — the caller
pre-loads dst with the list0 prediction; the avg_ call adds list1
per H.264 §8.4.2.3.1.

Scope (3 anchors, sets the pattern for the remaining 13 avg_
variants):
  - 3 new kernel enums (AVG_MC20=31, AVG_MC02=32, AVG_MC22=33) → CPU.
  - 3 NEON externs for the vendored ff_avg_h264_qpel8_{mc20,mc02,mc22}_neon.
  - 3 CPU dispatches via existing DEFINE_QPEL_CPU_DISPATCH macro
    (the macro is type-agnostic so it didn't need changes for avg_).
  - 3 public dispatches via DEFINE_QPEL_DISPATCH macro.
  - 3 recipe wrappers via DEFINE_QPEL_RECIPE macro.
  - tests/h264_qpel8_avg_anchors_ref.c — per-cell helpers + L2 avg.
  - Test harness: run_avg_qpel() seeds dst with random content so
    the L2 averaging is actually exercised (not just put_-style
    overwrite that would silently pass).

Verified on hertz:

  $ ./build/test_api_h264 | tail -3
    H.264 qpel avg_mc20: 2048/2048 bytes bit-exact (100.0000%)
    H.264 qpel avg_mc02: 2048/2048 bytes bit-exact (100.0000%)
    H.264 qpel avg_mc22: 2048/2048 bytes bit-exact (100.0000%)

  All 3 anchors bit-exact PASS first try.

Why anchors only in this PR: the avg_ pattern is uniform across all
16 positions (each is just "put_ result + L2 with dst").  Landing
the anchors first confirms the macro pattern works for both put_
and avg_; the remaining 13 (avg_mc10/30/01/03 + avg_mc11..33) follow
the same template in a follow-up PR.

State of the qpel matrix after this PR:
  put_ : 15 of 16 positions ✓ (mc00 is integer copy, no wrapper)
  avg_ :  3 of 16 positions ✓ (mc20, mc02, mc22 anchors)
        13 follow-up positions
This commit is contained in:
Claude (noether)
2026-05-25 08:35:25 +02:00
parent 76e3076670
commit 1113953f97
5 changed files with 182 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
CMakeLists.txt
+1
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@@ -527,6 +527,7 @@ add_executable(test_api_h264
tests/h264_qpel8_mc22_ref.c
tests/h264_qpel8_quarter_axis_ref.c
tests/h264_qpel8_diag_ref.c
tests/h264_qpel8_avg_anchors_ref.c
)
target_link_libraries(test_api_h264 PRIVATE daedalus_core)
target_compile_options(test_api_h264 PRIVATE -O2)
include/daedalus.h
+24
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@@ -511,6 +511,27 @@ DECLARE_QPEL_DIAG(mc33)
#undef DECLARE_QPEL_DIAG
/* H.264 luma qpel avg_ biprediction anchors — 3 half-pel positions
* (the put_ result is L2-averaged into the existing dst buffer per
* H.264 §8.4.2.3.1). Caller is responsible for pre-loading dst with
* the list0 prediction; the avg_ call adds list1.
*
* Same single-stride convention as put_; CPU NEON only for now.
*/
#define DECLARE_QPEL_AVG(name) \
int daedalus_recipe_dispatch_h264_qpel_ ## name(daedalus_ctx *ctx, \
uint8_t *dst, const uint8_t *src, size_t stride, \
size_t n_blocks, const daedalus_h264_qpel_meta *meta); \
int daedalus_dispatch_h264_qpel_ ## name(daedalus_ctx *ctx, daedalus_substrate sub, \
uint8_t *dst, const uint8_t *src, size_t stride, \
size_t n_blocks, const daedalus_h264_qpel_meta *meta);
DECLARE_QPEL_AVG(avg_mc20)
DECLARE_QPEL_AVG(avg_mc02)
DECLARE_QPEL_AVG(avg_mc22)
#undef DECLARE_QPEL_AVG
/* -------------------------------------------------------------------
* Recipe query — what does the API recommend for each kernel?
* ----------------------------------------------------------------- */
@@ -545,6 +566,9 @@ typedef enum {
DAEDALUS_KERNEL_H264_QPEL_MC31 = 28,
DAEDALUS_KERNEL_H264_QPEL_MC32 = 29,
DAEDALUS_KERNEL_H264_QPEL_MC33 = 30,
DAEDALUS_KERNEL_H264_QPEL_AVG_MC20 = 31,
DAEDALUS_KERNEL_H264_QPEL_AVG_MC02 = 32,
DAEDALUS_KERNEL_H264_QPEL_AVG_MC22 = 33,
} daedalus_kernel;
daedalus_substrate daedalus_recipe_substrate_for(daedalus_kernel k);
src/daedalus_core.c
+18
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@@ -152,6 +152,9 @@ daedalus_substrate daedalus_recipe_substrate_for(daedalus_kernel k)
case DAEDALUS_KERNEL_H264_QPEL_MC31: return DAEDALUS_SUBSTRATE_CPU; /* diagonal ¾¼ */
case DAEDALUS_KERNEL_H264_QPEL_MC32: return DAEDALUS_SUBSTRATE_CPU; /* diagonal ¾½ */
case DAEDALUS_KERNEL_H264_QPEL_MC33: return DAEDALUS_SUBSTRATE_CPU; /* diagonal ¾¾ */
case DAEDALUS_KERNEL_H264_QPEL_AVG_MC20: return DAEDALUS_SUBSTRATE_CPU; /* biprediction anchors */
case DAEDALUS_KERNEL_H264_QPEL_AVG_MC02: return DAEDALUS_SUBSTRATE_CPU;
case DAEDALUS_KERNEL_H264_QPEL_AVG_MC22: return DAEDALUS_SUBSTRATE_CPU;
}
return DAEDALUS_SUBSTRATE_CPU;
}
@@ -212,6 +215,9 @@ extern void ff_put_h264_qpel8_mc23_neon(uint8_t *dst, const uint8_t *src, ptrdif
extern void ff_put_h264_qpel8_mc31_neon(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void ff_put_h264_qpel8_mc32_neon(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void ff_put_h264_qpel8_mc33_neon(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void ff_avg_h264_qpel8_mc20_neon(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void ff_avg_h264_qpel8_mc02_neon(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void ff_avg_h264_qpel8_mc22_neon(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
/* -------------------- CPU dispatch implementations -------------- */
@@ -493,6 +499,12 @@ DEFINE_QPEL_CPU_DISPATCH(mc31, ff_put_h264_qpel8_mc31_neon)
DEFINE_QPEL_CPU_DISPATCH(mc32, ff_put_h264_qpel8_mc32_neon)
DEFINE_QPEL_CPU_DISPATCH(mc33, ff_put_h264_qpel8_mc33_neon)
/* avg_ biprediction variants — same dispatch shape as put_, just
* different NEON entry that L2-averages with the existing dst. */
DEFINE_QPEL_CPU_DISPATCH(avg_mc20, ff_avg_h264_qpel8_mc20_neon)
DEFINE_QPEL_CPU_DISPATCH(avg_mc02, ff_avg_h264_qpel8_mc02_neon)
DEFINE_QPEL_CPU_DISPATCH(avg_mc22, ff_avg_h264_qpel8_mc22_neon)
#undef DEFINE_QPEL_CPU_DISPATCH
/* -------------------- IDCT QPU dispatch (cycle 1 v4 shader) ---- */
@@ -1521,6 +1533,9 @@ DEFINE_QPEL_DISPATCH(mc23, DAEDALUS_KERNEL_H264_QPEL_MC23)
DEFINE_QPEL_DISPATCH(mc31, DAEDALUS_KERNEL_H264_QPEL_MC31)
DEFINE_QPEL_DISPATCH(mc32, DAEDALUS_KERNEL_H264_QPEL_MC32)
DEFINE_QPEL_DISPATCH(mc33, DAEDALUS_KERNEL_H264_QPEL_MC33)
DEFINE_QPEL_DISPATCH(avg_mc20, DAEDALUS_KERNEL_H264_QPEL_AVG_MC20)
DEFINE_QPEL_DISPATCH(avg_mc02, DAEDALUS_KERNEL_H264_QPEL_AVG_MC02)
DEFINE_QPEL_DISPATCH(avg_mc22, DAEDALUS_KERNEL_H264_QPEL_AVG_MC22)
#undef DEFINE_QPEL_DISPATCH
@@ -1680,5 +1695,8 @@ DEFINE_QPEL_RECIPE(mc23)
DEFINE_QPEL_RECIPE(mc31)
DEFINE_QPEL_RECIPE(mc32)
DEFINE_QPEL_RECIPE(mc33)
DEFINE_QPEL_RECIPE(avg_mc20)
DEFINE_QPEL_RECIPE(avg_mc02)
DEFINE_QPEL_RECIPE(avg_mc22)
#undef DEFINE_QPEL_RECIPE
tests/h264_qpel8_avg_anchors_ref.c
+79
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@@ -0,0 +1,79 @@
/*
* Standalone bit-exact C references for the avg_ qpel anchors —
* the biprediction "average against existing dst" form of mc20,
* mc02, mc22. Used in B-slices where two qpel-interpolated samples
* (one from list0, one from list1) are averaged per H.264 §8.4.2.3.
*
* Each kernel computes the same half-pel formula as the put_ form,
* then averages with dst[r,c] via L2 ((dst + put_val + 1) >> 1).
* The dst buffer carries the list0 prediction on entry; the avg_
* call adds the list1 contribution.
*
* Mirror FFmpeg's `ff_avg_h264_qpel8_{mc20,mc02,mc22}_neon` in
* external/ffmpeg-snapshot/libavcodec/aarch64/h264qpel_neon.S
* (same `\type=avg` expansion as the put_ functions).
*
* 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; }
static inline uint8_t avg2(uint8_t a, uint8_t b) { return (uint8_t)((a + b + 1) >> 1); }
/* Same per-cell helpers as the diag/quarter-axis refs. Duplicated
* here (rather than extern'd) so this TU compiles standalone. */
static inline uint8_t hpel_h(const uint8_t *s, int r, int c, ptrdiff_t stride)
{
int v = (int) s[r*stride + c-2] - 5 * (int) s[r*stride + c-1]
+ 20 * (int) s[r*stride + c] + 20 * (int) s[r*stride + c+1]
- 5 * (int) s[r*stride + c+2] + (int) s[r*stride + c+3]
+ 16;
return (uint8_t) clip_u8(v >> 5);
}
static inline uint8_t hpel_v(const uint8_t *s, int r, int c, ptrdiff_t stride)
{
int v = (int) s[(r-2)*stride + c] - 5 * (int) s[(r-1)*stride + c]
+ 20 * (int) s[r*stride + c] + 20 * (int) s[(r+1)*stride + c]
- 5 * (int) s[(r+2)*stride + c] + (int) s[(r+3)*stride + c]
+ 16;
return (uint8_t) clip_u8(v >> 5);
}
void daedalus_avg_h264_qpel8_mc20_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)
{
for (int r = 0; r < 8; r++)
for (int c = 0; c < 8; c++)
dst[r*stride + c] = avg2(dst[r*stride + c], hpel_h(src, r, c, stride));
}
void daedalus_avg_h264_qpel8_mc02_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)
{
for (int r = 0; r < 8; r++)
for (int c = 0; c < 8; c++)
dst[r*stride + c] = avg2(dst[r*stride + c], hpel_v(src, r, c, stride));
}
void daedalus_avg_h264_qpel8_mc22_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride)
{
/* Per-cell mc22: same 13-row int16 tmp[] computation as the
* put_ reference, then L2 with dst. */
int16_t tmp[13][8];
for (int rr = 0; rr < 13; rr++) {
int src_row = rr - 2;
const uint8_t *s = src + src_row * 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];
tmp[rr][c] = (int16_t) v;
}
}
for (int r = 0; r < 8; r++)
for (int c = 0; c < 8; c++) {
int v = tmp[r+0][c] - 5*tmp[r+1][c] + 20*tmp[r+2][c]
+ 20*tmp[r+3][c] - 5*tmp[r+4][c] + tmp[r+5][c] + 512;
uint8_t p = (uint8_t) clip_u8(v >> 10);
dst[r*stride + c] = avg2(dst[r*stride + c], p);
}
}
tests/test_api_h264.c
+60
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@@ -52,6 +52,9 @@ extern void daedalus_put_h264_qpel8_mc23_ref(uint8_t *dst, const uint8_t *src, p
extern void daedalus_put_h264_qpel8_mc31_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void daedalus_put_h264_qpel8_mc32_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void daedalus_put_h264_qpel8_mc33_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void daedalus_avg_h264_qpel8_mc20_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void daedalus_avg_h264_qpel8_mc02_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void daedalus_avg_h264_qpel8_mc22_ref(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void daedalus_put_h264_qpel8_mc20_ref(uint8_t *dst, const uint8_t *src,
ptrdiff_t stride);
@@ -583,6 +586,62 @@ static int test_qpel_diag_all(void)
return fail;
}
/* Avg-form harness: pre-loads dst + dst_ref with the same random
* content so we can verify the L2 averaging is happening (not just
* put_-style overwrite). If the dispatch incorrectly overwrote
* dst, the bit-exact compare would still catch the mismatch against
* the avg_ reference. */
static int run_avg_qpel(const char *name,
qpel_ref_fn ref, qpel_dispatch_fn dispatch)
{
enum { N = 8, TILE_STRIDE = 16, TILE_ROWS = 16,
TILE_BYTES = TILE_ROWS * TILE_STRIDE, TOTAL = N * TILE_BYTES,
SRC_ROW = 3, 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];
/* Two random buffers: src for the qpel input, dst seeded with
* different random content as the "list0 prediction" — both
* dst and dst_ref get the SAME seed so the avg compare is fair. */
for (int i = 0; i < TOTAL; i++) src[i] = (uint8_t)(xs() & 0xff);
for (int i = 0; i < TOTAL; i++) {
uint8_t v = (uint8_t)(xs() & 0xff);
dst[i] = dst_ref[i] = v;
}
for (int i = 0; i < N; i++) {
meta[i].src_off = (uint32_t)(i * TILE_BYTES + SRC_ROW * TILE_STRIDE + SRC_COL);
meta[i].dst_off = (uint32_t)(i * TILE_BYTES + SRC_ROW * TILE_STRIDE + SRC_COL);
}
for (int i = 0; i < N; i++)
ref(dst_ref + meta[i].dst_off, src + meta[i].src_off, TILE_STRIDE);
int rc = dispatch(ctx, dst, src, TILE_STRIDE, N, meta);
if (rc) { fprintf(stderr, "%s dispatch rc=%d\n", name, rc); return 1; }
int diff = 0;
for (int i = 0; i < TOTAL; i++) if (dst[i] != dst_ref[i]) diff++;
printf(" H.264 qpel %s: %d/%d bytes bit-exact (%.4f%%)\n",
name, TOTAL - diff, TOTAL, 100.0 * (TOTAL - diff) / TOTAL);
daedalus_ctx_destroy(ctx);
return diff == 0 ? 0 : 1;
}
static int test_qpel_avg_anchors(void)
{
int fail = 0;
fail |= run_avg_qpel("avg_mc20", daedalus_avg_h264_qpel8_mc20_ref,
daedalus_recipe_dispatch_h264_qpel_avg_mc20);
fail |= run_avg_qpel("avg_mc02", daedalus_avg_h264_qpel8_mc02_ref,
daedalus_recipe_dispatch_h264_qpel_avg_mc02);
fail |= run_avg_qpel("avg_mc22", daedalus_avg_h264_qpel8_mc22_ref,
daedalus_recipe_dispatch_h264_qpel_avg_mc22);
return fail;
}
int main(void)
{
printf("=== Phase 8a API smoke: H.264 kernels via recipe dispatch ===\n");
@@ -617,5 +676,6 @@ int main(void)
fail |= test_qpel_mc22();
fail |= test_qpel_quarter_axis_all();
fail |= test_qpel_diag_all();
fail |= test_qpel_avg_anchors();
return fail;
}