vp8dec: add deadline option

Submitted by Cecill Etheredge (ijsf)

Link to original bug (#747534)

Description

Created attachment 301163
Patch that adds deadline option to gstvp8dec

This patch adds support for a "deadline" option in vp8dec, similar to that in gstvp8dec.

This option is required to force the deadline to real-time (VPX_DL_REALTIME) in applications where real-time video is essential, e.g. in OpenWebRTC.

I have tested and verified that the calculated deadline is actually 0 in the case of OpenWebRTC, and should be 1. By adding this option, the deadline can be overruled from the application end.

Patch 301163, "Patch that adds deadline option to gstvp8dec":
ijsf_gstvp8dec_deadline.patch