gpu_vram_bytes() now chains per vendor/platform:
- NVIDIA everywhere: nvidia-smi (shipped by the NVIDIA driver on every
OS) — the NVDEC path's primary device.
- AMD/Intel on Linux: the DRM mem_info_vram_total/used sysfs attributes
(amdgpu, i915, Xe). Free = total - used; the first non-zero card wins
(an iGPU without dedicated vram reports 0 and is skipped). The walk is
now testable via an injectable sysfs root; a card missing the attrs is
skipped, never aborts the walk.
- Apple Silicon: unified memory — no separate vram exists; the RAM/4
budget IS the correct bound for decode surfaces and render targets, so
no query (an explicit vram budget would double-count the same pool).
- Windows AMD/Intel: no portable CLI; DXGI QueryVideoMemoryInfo is the
real API but wgpu 25 does not expose it. Falling back to the RAM
policy is safe-side (under-sized pool loses throughput, never OOMs the
device).
Tests: the sysfs walk (fixture with a missing-attr card, a 0-total
iGPU and a discrete winner) and the per-worker budget scaling (1080p
baseline, 4K ~4x, 60 fps over-provision).
Mike-Solar
8de9af705e