[kelnos]

The issue is that hardware decoding is a hodgepodge of various vendor-specific interfaces. Projects like VA-API try to put a nice frontend onto them so applications don't have to care about the hardware, but ultimately that just means twice the work needs to be done to add support for new hardware, and to maintain existing hardware.

If kernel developers writing drivers for hardware video acceleration were to build to a standard set of kernel interfaces, then userspace would just have one interface to work with, simplifying things and reducing overall effort.

[robert_foss]

Good description.

Furthermore stateless H.264 decoders are a specific subset of hardware decoders that, like the name implies, don't maintain any state by themselves.