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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
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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);