opusenc: review misleading "audio-type" property, possibly add "signal-type" property

Submitted by Marcin Lewandowski

Link to original bug (#771261)

Description

Created attachment 335319
patch that adds new property signal-type to opusenc

Currently, opusenc has no setting that can be used to call OPUS_SET_SIGNAL ctl.

The attached patch adds new property signal-type to opusenc.

Patch 335319, "patch that adds new property signal-type to opusenc":
0001-opusenc-Added-signal-type-property-that-maps-to-OPUS.patch