Some non-standard A2DP codecs (FastStream/aptX-LL) have "voice duplex
channel" that can be used to provide an A2DP duplex mode.
Add support for duplex channels, accounting for the fact that the two
directions may be encoded with different actual codecs.
This pushes the latency to 256 samples, which still seems to work
Latency of 128 seems to be too small. (NB. the number of input samples
is also the size of packets sent in bytes)
Since pipewire clients usually use powers of two, this may be the
smallest value that makes sense.
Support the low-latency variant of the aptx codec.
The magic mostly seems to be on the device side, since the stream is the
same as standard aptx, but latency is smaller even if stream/packet
sizes are the same.
Sound output latency is noticeably less than with the standard aptx.
Tested on Sennheiser HD 250 / Avantree Aria Pro.
The codec in principle also supports bidirectional duplex streams,
but that is not implemented here.
The codec IDs are user-visible properties.
Some codecs can have multiple endpoints (e.g. different caps struct, or
multiple possible vendor ids), so this detail should not leak to the
user.
This property is exposed on the device Route and forwarded to the
nodes. It then configured the process_latency.ns field, which
influences the reported port latency.
This makes it possible to change the internal port latency on the
sink and source with pavucontrol and tweak the synchronization to
compensate for internal latencies in the device.
Disable flush polling when we don't have data ready to write to the
socket (or socket send failed). This avoids entering into a poll busy
loop, which may result to rtkit killing the process.
Enable SBC-XQ by default, and move it at the end of the codecs list, so
that bluez does not connect to it automatically except when it is the
codec used previously.
When the codec is disabled by quirks, it won't appear in the codecs
list, and so can't be selected by user (and so won't be connected
automatically).
However, since SelectConfiguration does not carry information which
device is in question, we cannot prevent BlueZ connecting to the codec
even if it's disabled for a specific device. If the "impossible" occurs
regardless, we won't reject the connection and the profile will be shown
as the generic "A2DP" one. If the sound is garbled, the user can select
some other profile that works.
If a log message is rate limited, we only need to know about it if we
are actually interested in that log level. We therefore add an argument
to the ratelimit_test function to set the log level of the message
printed if a message is skipped
Change-Id: I5ccd4a78bf7e972fe8b0e7133cd7e08c1e38835f
HF indicator 2 (see [assigned-numbers], Hands-Free Profile) is able to
report battery percentage at 1% intervals (in range [0, 100]), contrary
to the `+XAPL` `+IPHONEACCEV` extension which only supports 10%
increments. This does not guarantee increased granularity however, as
peers may still be limited to imprecise battery measurements internally
or round to coarser percentages.
Supporting both additionally broadens the range of devices for which PW
can report its battery level.
[assigned-numbers]:
https://www.bluetooth.com/specifications/assigned-numbers/
