fn dxgi_device_manager() -> Option<IMFDXGIDeviceManager>Expand description
D3D11 device + DXGI device manager for hardware-accelerated decode (DXVA). Built once per process;
every source reader attaches to the same manager. None when the adapter/driver can’t do it — callers
fall back to the source reader’s normal software decode, so this is purely a speed opt-in.