Add a flag A2DP_CODEC_FLAG_SINK to incidate a sink endpoint.
Also enum_config and caps_preference_cmp may need to know whether the
codec is being configured for SRC or SNK. Also add the flags argument to
init_props.
Bump codec API version.
Codecs may need to fragment a single encoder frame across multiple
packets that are sent consecutively.
Allow codec->encode() to set need_flush=NEED_FLUSH_FRAGMENT, so that
sink should immediately call start_encode + encode with NULL input data,
to produce the next packet.
Previously, other return values than need_flush=1 were unused, so no
need to bump codec ABI for this.
Make easier to package A2DP codecs separately, by splitting each to a
separate SPA plugin. Adjust the code to not use a global variable for
the codec list.
The A2DP SPA interface API is in the bluez5 private headers, and not
exposed in installed SPA headers, as it's too close to the
implementation.
We don't currently implement encoding for the duplex channel
for these codecs, so they are not fully functional as A2DP sinks,
and their main use is anyway with headphones.
Also, the number of endpoints in BlueZ appears to be limited, and
appears to be counted across all adapters. Unclear whether this comes
from AVDTP limitation, but currently plugging in a second BT adapter
causes the second media application registration to fail. This change
reduces the number of endpoints enough so that registration succeeds for
two adapters.
There doesn't seem to be a way to control the A2DP duplex microphone
HW volume gain, and devices sometimes have very low mic volumes.
Work around this by boosting the software volume scale by +20 dB. If it
causes clipping, the user can just reduce the volume to bring SW gain
below 1.0.
