I downloaded the kindle source for my pw4 and searched it for the code for the mixersink without success. This led me to pull the strings for that library binary where I unfortunately found:
Code:
EINK-specific Mixer GStreamer sink
Proprietary
eink
http://www.amazon.com/
audio/x-raw-int, rate = (int) [ 1, MAX ], channels = (int) { 1, 2 }
So much for source code. This does appear to be exactly what is needed to feed an audio stream to and have it wind up output to the bluetooth headset or, looking at strings in another of the active processes, an OTG USB connected audio output.
The lsof shows the stdin,stdout and stderr handles and an open /var/run/playermgr.pid file plus four sockets, three FIFO pipes and the audible file being played. These must form the interface to the mixer sink and the player GUI displayed on the pw4 and its controls.
Is there at this point a reasonable source code reconstructor that could allow deducing which of these are actually the mixer sink interface? Is there a debug tool that would allow tracing all calls to the library?
Once again I wonder if I have the skills to track down what is necessary make use of this mixer sink library interface and code an alternative front end to feed other audio to it.
Dave