Merge pull request 'ffmpeg-v4l2-request-fourier: revert ctx flip — PR #36 was a measurement artifact (0015)' (#105) from claude-noether/marfrit-packages:noether/revert-h264-ctx-qpu-capable into main

Reviewed-on: #105

arch/ffmpeg-v4l2-request-fourier/0015-h264-ctx-revert-to-no-qpu.patch

@@ -0,0 +1,73 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Markus Fritsche <mfritsche@reauktion.de>
+Date: Mon, 25 May 2026 22:00:00 +0200
+Subject: [PATCH] avcodec/aarch64/h264: revert ctx flip — daedalus-fourier PR
+ #36 was a measurement artifact
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Reverts the daedalus_ctx_create_no_qpu() → daedalus_ctx_create() flip
+that landed in 0014-h264-ctx-qpu-capable.patch (marfrit-packages PR
+#104).  The flip was justified by daedalus-fourier PR #36 which
+reported a 4.30x QPU-over-CPU win on the 1080p H.264 hot-path sum.
+
+That number was a measurement artifact.  The bench tool's
+v3d_runner.read_spv() did a bare fopen() that resolved relative to
+cwd; when run from the source directory (as in PR #36), the SPVs at
+$builddir/v3d_*.spv were not found, every QPU dispatch returned -1
+fast, and the loop timed the failure path.  Daedalus-fourier PR #37
+fixes the SPV search + bench preflight; corrected numbers from hertz
+(Pi 5 V3D 7.1) show QPU is 12-77x SLOWER than CPU NEON at every
+H.264 hot-path kernel:
+
+  kernel             CPU ns/op  QPU ns/op  winner
+  IDCT 4x4 luma          10.75     217.63  CPU 20.24x
+  IDCT 8x8 luma          29.69     785.94  CPU 26.47x
+  Deblock luma_v         17.63     467.42  CPU 26.51x
+  Deblock luma_h         38.30     498.53  CPU 13.02x
+  qpel mc20 (8x8)        30.17    1300.44  CPU 43.10x
+  qpel mc02 (8x8)        17.69    1363.40  CPU 77.08x
+  qpel mc22 (8x8)        71.60    1948.37  CPU 27.21x
+
+  1080p sum: CPU 5.57 ms vs QPU 123.54 ms — QPU 22x slower.
+
+Until the daedalus QPU dispatch overhead is actually competitive (a
+multi-task effort tracked on the daedalus-fourier side), the
+libavcodec.so substitution must stay on daedalus_ctx_create_no_qpu()
+to avoid pessimizing every host process that loads it
+(firefox-fourier RDD, mpv-fourier, daedalus_v4l2_daemon).
+
+Both H.264 TUs (h264_idct_daedalus.c, h264_qpel_daedalus.c) are
+reverted; the change is a 2-line revert of patch 0014.
+
+Refs reauktion/daedalus-fourier!37 (the retraction PR).
+---
+ libavcodec/aarch64/h264_idct_daedalus.c | 2 +-
+ libavcodec/aarch64/h264_qpel_daedalus.c | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/libavcodec/aarch64/h264_idct_daedalus.c b/libavcodec/aarch64/h264_idct_daedalus.c
+--- a/libavcodec/aarch64/h264_idct_daedalus.c
++++ b/libavcodec/aarch64/h264_idct_daedalus.c
+@@ -32,7 +32,7 @@ static pthread_once_t    g_dctx_once = PTHREAD_ONCE_INIT;
+
+ static void daedalus_ctx_init_once(void)
+ {
+-    g_dctx = daedalus_ctx_create();
++    g_dctx = daedalus_ctx_create_no_qpu();
+ }
+
+ void ff_h264_idct_add_daedalus(uint8_t *dst, int16_t *block, int stride);
+diff --git a/libavcodec/aarch64/h264_qpel_daedalus.c b/libavcodec/aarch64/h264_qpel_daedalus.c
+--- a/libavcodec/aarch64/h264_qpel_daedalus.c
++++ b/libavcodec/aarch64/h264_qpel_daedalus.c
+@@ -38,7 +38,7 @@ static pthread_once_t    g_dctx_once = PTHREAD_ONCE_INIT;
+
+ static void daedalus_ctx_init_once(void)
+ {
+-    g_dctx = daedalus_ctx_create();
++    g_dctx = daedalus_ctx_create_no_qpu();
+ }
+
+ void ff_put_h264_qpel8_mc20_daedalus(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);

arch/ffmpeg-v4l2-request-fourier/PKGBUILD

@@ -24,7 +24,7 @@ _srcname=FFmpeg
 _version='8.1'
 _commit='b57fbbe50c9b2656fad86a1a7eeabfd2b2a50935'  # v4l2-request-n8.1 tip 2026-04-24
 pkgver=8.1.r123329.b57fbbe
-pkgrel=11  # pkgrel=11 — libavcodec.so daedalus ctx flipped no_qpu → qpu-capable (PR #36 bench: QPU 4.30x on 1080p hot-path sum, 2026-05-25)
+pkgrel=12  # pkgrel=12 — REVERT pkgrel=11 ctx flip; daedalus-fourier PR #36 4.30x headline was measurement artifact (PR #37 corrects: QPU 22x SLOWER than CPU)
 epoch=2
 
 # daedalus-fourier pin.  209a421 = PR #2 merge (Phase 8c — public API
@@ -101,8 +101,9 @@ source=("git+https://github.com/Kwiboo/FFmpeg.git#commit=${_commit}"
         '0011-h264-chroma-dc-hadamard-daedalus-fourier.patch'
         '0012-h264-qpel-rest-daedalus-fourier.patch'
         '0013-h264-deblock-chroma-intra-daedalus-fourier.patch'
-        '0014-h264-ctx-qpu-capable.patch')
+        '0014-h264-ctx-qpu-capable.patch'
-sha256sums=('SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP')
+        '0015-h264-ctx-revert-to-no-qpu.patch')
+sha256sums=('SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP')
 
 pkgver() {
   cd "${_srcname}"
@@ -127,6 +128,7 @@ prepare() {
   patch -Np1 -i "${srcdir}/0012-h264-qpel-rest-daedalus-fourier.patch"
   patch -Np1 -i "${srcdir}/0013-h264-deblock-chroma-intra-daedalus-fourier.patch"
   patch -Np1 -i "${srcdir}/0014-h264-ctx-qpu-capable.patch"
+  patch -Np1 -i "${srcdir}/0015-h264-ctx-revert-to-no-qpu.patch"
 }
 
 build() {

debian/ffmpeg-v4l2-request-fourier/0015-h264-ctx-revert-to-no-qpu.patch

@@ -0,0 +1,73 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Markus Fritsche <mfritsche@reauktion.de>
+Date: Mon, 25 May 2026 22:00:00 +0200
+Subject: [PATCH] avcodec/aarch64/h264: revert ctx flip — daedalus-fourier PR
+ #36 was a measurement artifact
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Reverts the daedalus_ctx_create_no_qpu() → daedalus_ctx_create() flip
+that landed in 0014-h264-ctx-qpu-capable.patch (marfrit-packages PR
+#104).  The flip was justified by daedalus-fourier PR #36 which
+reported a 4.30x QPU-over-CPU win on the 1080p H.264 hot-path sum.
+
+That number was a measurement artifact.  The bench tool's
+v3d_runner.read_spv() did a bare fopen() that resolved relative to
+cwd; when run from the source directory (as in PR #36), the SPVs at
+$builddir/v3d_*.spv were not found, every QPU dispatch returned -1
+fast, and the loop timed the failure path.  Daedalus-fourier PR #37
+fixes the SPV search + bench preflight; corrected numbers from hertz
+(Pi 5 V3D 7.1) show QPU is 12-77x SLOWER than CPU NEON at every
+H.264 hot-path kernel:
+
+  kernel             CPU ns/op  QPU ns/op  winner
+  IDCT 4x4 luma          10.75     217.63  CPU 20.24x
+  IDCT 8x8 luma          29.69     785.94  CPU 26.47x
+  Deblock luma_v         17.63     467.42  CPU 26.51x
+  Deblock luma_h         38.30     498.53  CPU 13.02x
+  qpel mc20 (8x8)        30.17    1300.44  CPU 43.10x
+  qpel mc02 (8x8)        17.69    1363.40  CPU 77.08x
+  qpel mc22 (8x8)        71.60    1948.37  CPU 27.21x
+
+  1080p sum: CPU 5.57 ms vs QPU 123.54 ms — QPU 22x slower.
+
+Until the daedalus QPU dispatch overhead is actually competitive (a
+multi-task effort tracked on the daedalus-fourier side), the
+libavcodec.so substitution must stay on daedalus_ctx_create_no_qpu()
+to avoid pessimizing every host process that loads it
+(firefox-fourier RDD, mpv-fourier, daedalus_v4l2_daemon).
+
+Both H.264 TUs (h264_idct_daedalus.c, h264_qpel_daedalus.c) are
+reverted; the change is a 2-line revert of patch 0014.
+
+Refs reauktion/daedalus-fourier!37 (the retraction PR).
+---
+ libavcodec/aarch64/h264_idct_daedalus.c | 2 +-
+ libavcodec/aarch64/h264_qpel_daedalus.c | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/libavcodec/aarch64/h264_idct_daedalus.c b/libavcodec/aarch64/h264_idct_daedalus.c
+--- a/libavcodec/aarch64/h264_idct_daedalus.c
++++ b/libavcodec/aarch64/h264_idct_daedalus.c
+@@ -32,7 +32,7 @@ static pthread_once_t    g_dctx_once = PTHREAD_ONCE_INIT;
+
+ static void daedalus_ctx_init_once(void)
+ {
+-    g_dctx = daedalus_ctx_create();
++    g_dctx = daedalus_ctx_create_no_qpu();
+ }
+
+ void ff_h264_idct_add_daedalus(uint8_t *dst, int16_t *block, int stride);
+diff --git a/libavcodec/aarch64/h264_qpel_daedalus.c b/libavcodec/aarch64/h264_qpel_daedalus.c
+--- a/libavcodec/aarch64/h264_qpel_daedalus.c
++++ b/libavcodec/aarch64/h264_qpel_daedalus.c
+@@ -38,7 +38,7 @@ static pthread_once_t    g_dctx_once = PTHREAD_ONCE_INIT;
+
+ static void daedalus_ctx_init_once(void)
+ {
+-    g_dctx = daedalus_ctx_create();
++    g_dctx = daedalus_ctx_create_no_qpu();
+ }
+
+ void ff_put_h264_qpel8_mc20_daedalus(uint8_t *dst, const uint8_t *src, ptrdiff_t stride);

debian/ffmpeg-v4l2-request-fourier/build-deb.sh

@@ -33,7 +33,7 @@ FFMPEG_VERSION=8.1
 # epoch 2 matches Debian's stock ffmpeg (currently 7:7.1.x in trixie);
 # +rfourier suffix to avoid colliding with upstream/Debian rebuilds.
 PKGVER=2:${FFMPEG_VERSION}+rfourier+gb57fbbe
-PKGREL=11  # pkgrel=11 — libavcodec.so daedalus ctx flipped no_qpu → qpu-capable (PR #36 bench: QPU 4.30x on 1080p hot-path sum, 2026-05-25)
+PKGREL=12  # pkgrel=12 — REVERT pkgrel=11 ctx flip; daedalus-fourier PR #36 4.30x headline was measurement artifact (PR #37 corrects: QPU 22x SLOWER than CPU)
            # (cycle 9 of the daedalus-v4l2#11 step 2 substitution arc; closes
            # the libavcodec.so substitution sequence 6 IDCT4 / 7 IDCT8 /
            # 8 luma-v deblock / 9 qpel mc20).  Pulls daedalus-fourier PR #2
@@ -81,6 +81,7 @@ patch -Np1 -i "$HERE/0011-h264-chroma-dc-hadamard-daedalus-fourier.patch"
 patch -Np1 -i "$HERE/0012-h264-qpel-rest-daedalus-fourier.patch"
 patch -Np1 -i "$HERE/0013-h264-deblock-chroma-intra-daedalus-fourier.patch"
 patch -Np1 -i "$HERE/0014-h264-ctx-qpu-capable.patch"
+patch -Np1 -i "$HERE/0015-h264-ctx-revert-to-no-qpu.patch"
 
 # --- daedalus-fourier: fetch + build static .a with PIC, install to a
 # per-build prefix; libavcodec.so links it into the shared object so