On-glass A/B on the Ryzen 7000 iGPU (1080p120 HDR P010, hevc_amf,
PUNKTFUNK_PERF stage split): the system-memory readback costs the encode
thread 2.7-2.9 ms p50 (6.6 ms p99) per frame in submit; the zero-copy D3D11
pool path does the same work in 0.26 ms p50 (0.5 ms p99) — and on an iGPU the
readback also burns the shared memory bandwidth the game needs. The docs-site
already promised "on by default ... D3D11 on Windows" since the Linux flip
(2f9e61d was Linux-only); the Windows code now delivers it.
PUNKTFUNK_ZEROCOPY becomes a tri-state override: unset defers to a per-vendor
default in zerocopy_enabled(vendor) — ON for AMF (validated above; open
failures still fall back to system-memory readback), OFF for QSV until it is
validated on Intel glass (the fallback only catches *setup* errors; a QSV
derive that opens but maps wrong would corrupt silently, so probe-never-assume
applies). Explicit values force either way: 0|false|off|no = readback,
anything else = zero-copy, so the old presence-style =1 keeps working.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehler
8fb126482e