V4L2 Media Controller Request API
summary
V4L2 Media Controller Request API provides per-frame controls tied to a media request FD so user space can set volatile parameters and receive exact per-frame metadata for stateless codecs, mem‑to‑mem postprocessors and complex ISP pipelines. Workflow: ioctl on /dev/media to allocate a request FD, set controls on that FD, queue buffer with request FD and cue the request, poll completion then use G-ctrl to read metadata. Userland adopters include Vulkan video extensions, Intel VA API and GStreamer. Current limits: mem‑to‑mem requests work on the output side; capture devices need kernel changes.
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chapters (8)
- 0:00V4L2 Media Controller Request API intro
- 1:46Limitations of V4L2 control
- 3:59Use cases for request API
- 8:35How request API works
- 12:28API workflow example
- 16:22Restrictions and device behavior
- 18:29Stateless codecs example
- 19:54Status and future work
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