The 0016 patch declared ff_h264_set_mb_inspect_cb in h264dec.h and
defined it in h264_mb.c, but didn't touch libavcodec/libavcodec.v.
FFmpeg's default version script exports only `av_*`, `avcodec_*`,
`avpriv_*`, and `avsubtitle_free`; everything else is hidden as LOCAL
behind a `*` glob. Result: `nm -D libavcodec.so.62 | grep
ff_h264_set_mb_inspect_cb` returned nothing → dlsym() returned NULL.
Static-link CLI consumer (daedalus_decode_h264) was unaffected
because static linking doesn't care about symbol visibility. The
daedalus-v4l2 daemon shadow_decoder path (PR-Q3a.1) dlopens
libavcodec.so.62 and resolves the callback via dlsym — that needs
the symbol exported.
Fix: add ff_h264_set_mb_inspect_cb to the global list in
libavcodec/libavcodec.v. Single-line addition to the 0016 patch.
Mirrored across the arch/ + debian/ patch trees.
PKGREL bump 14 → 15, changelog entry added (debian side). PKGBUILD
pkgrel bumped on arch side too. No behaviour change to the decode
path: the callback is still opt-in via the H264Context function
pointer; only consumers that have explicitly installed a callback
pay the one-load-one-branch cost per MB.
dejavu-check: this is fixing the existing 0016 observation-hook to
actually work as a dlsym intercept (the architectural shape the
patch was designed for). NOT adding new per-kernel substitution.
Same shape, same patch number, same intent. Just hiding/exporting
plumbing.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Adds 0016-h264-mb-inspect-callback.patch to the FFmpeg fork. Adds an
opt-in callback fired by ff_h264_hl_decode_mb after the existing
pixel work, for tools that need per-MB visibility into H.264 decode.
API:
typedef void (*ff_h264_mb_inspect_cb)(void *opaque,
const struct H264Context *h,
int mb_x, int mb_y);
void ff_h264_set_mb_inspect_cb(AVCodecContext *avctx,
ff_h264_mb_inspect_cb cb, void *opaque);
Two new fields appended to H264Context (internal struct, declared in
h264dec.h not h264.h, no ABI surface to non-libavcodec callers).
Callback fires post-pixel-work for every MB in coded order; receives
const H264Context* so it can inspect any state (slice ctx via
h->slice_ctx, reconstructed pixels via h->cur_pic.f->data[plane],
etc.).
Default (cb==NULL): zero behaviour change, one load + one branch per
MB in the decoder hot path.
Shape distinction: per-MB observation, NOT per-kernel function-pointer
hijack (the 0003-0014 substitution-arc pattern that PR #105 reverted
+ daedalus-fourier PR #37's measurement-correction architecturally
retired). Per-block synchronous Vulkan dispatch from libavcodec is
non-competitive; per-MB CPU-side observation feeding a per-frame
daedalus-decoder batch submit is the right shape (frame-major UMA
dispatch verdict, memory: dejavu).
Used by:
- daedalus-decoder/tools/daedalus_decode_h264 (PR-A1b, follow-up)
- future daedalus-v4l2 daemon refactor
Wired into arch PKGBUILD source[] + prepare() and debian build-deb.sh
patch sequence. pkgrel bumped 12 → 13.
Refs reauktion/daedalus-decoder!12.
marfrit
claude-noether