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punktfunk/crates
enricobuehler eb9c5be20d refactor(encode): the VAAPI dmabuf path stops unwinding by hand
`DmabufInner::open` builds four owned objects — a DRM device, a VAAPI device
derived from it, a DRM-PRIME frames context, and a filter graph — and every one of
its eight failure branches unwound them by hand. The same four-line block
(`avfilter_graph_free` + three `av_buffer_unref`s) appeared eight times, once
*inside a macro*, plus a ninth copy in `Drop`. Adding a step to that function meant
remembering to extend the unwind at exactly the right depth; getting it wrong leaks
a device per failed session (the persistent listener accumulates them) or frees one
twice.

All eight are gone. `AvBuffer` already owned the buffer refs; `AvFilterGraph` now
does the same for the graph, so each handle is owned the moment it exists and an
early `bail!` releases whatever was built so far. `open` lost ~40 lines of cleanup
and gained none.

Field order in `DmabufInner` is load-bearing and says so: graph, frames, VAAPI
device, DRM device, then `enc` LAST. Fields drop in declaration order, and that
sequence reproduces the old hand-written `Drop` exactly — including that it ran
ahead of every field, so all four were released before ffmpeg-next dropped the
encoder. Everything here holds its own reference, so refcounting makes any order
sound; the ordering is pinned so a future reorder cannot quietly change what ships.

One subtlety preserved deliberately: the buffersrc parameters take `drm_frames`
BORROWED, not ref'd (`av_buffersrc_parameters_set` takes its own ref). That is now
`drm_frames.as_ptr()` — same borrow, same single owned ref, no new leak.

Verified on .21 (CachyOS, RTX 5070 Ti, FFmpeg 62): `cargo check -p pf-encode
--all-targets` clean at exit 0, `cargo test -p pf-encode` 33 passed / 0 failed, and
`cuda_hw_alloc_drop_cycles` still passes against real CUDA. vaapi.rs now contains
zero `av_buffer_unref` and zero `avfilter_graph_free` calls, down from 40 and 8.
The dmabuf path itself still needs AMD/Intel silicon to exercise end to end.
2026-07-28 21:31:41 +02:00
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