config.h needs to be consistently included before any standard headers
if we ever want to set feature test macros (like _GNU_SOURCE or whatever)
inside. It can lead to hard-to-debug issues without that.
It can also be problematic just for our own HAVE_* that it may define
if it's not consistently made available before our own headers. Just
always include it first, before everything.
We already did this in many files, just not consistently.
When we simply need to change some state for the code executed in the
loop, we can use locked() instead of invoke(). This is more efficient
and avoids some context switches in the normal case.
If kernel socket queues for different streams get out of sync, it will
mess up time alignment of different streams. If that happens, flush to
resync.
If total latency becomes too large, flush queue.
Get accurate queue sizes from tx timestamping.
Use TX timestamps to get accurate reading of queue length and latency on
kernel + controller side.
This is new kernel BT feature, so requires kernel with the necessary
patches, available currently only in bluetooth-next/master branch.
Enabling Poll Errqueue kernel experimental Bluetooth feature is also
required for this.
Use the latency information to mitigate controller issues where ISO
streams are desynchronized due to tx problems or spontaneously when some
packets that should have been sent are left sitting in the queue, and
transmission is off by a multiple of the ISO interval. This state is
visible in the latency information, so if we see streams in a group have
persistently different latencies, drop packets to resynchronize them.
Also make corrections if the kernel/controller queues get too long, so
that we don't have too big latency there.
Since BlueZ watches the same socket for errors, and TX timestamps arrive
via the socket error queue, we need to set BT_POLL_ERRQUEUE in addition
to SO_TIMESTAMPING so that BlueZ doesn't think TX timestamps are errors.
Link: https://github.com/bluez/bluez/issues/515
Link: https://lore.kernel.org/linux-bluetooth/cover.1710440392.git.pav@iki.fi/
Link: https://lore.kernel.org/linux-bluetooth/f57e065bb571d633f811610d273711c7047af335.1712499936.git.pav@iki.fi/
BlueZ API as BAP Server gives us the ISO interval, instead of the SDU
interval, in the MediaTransport.QoS.Interval property. They are not
necessarily the same. What we need is the SDU interval.
The SDU interval is the interval between packets the encoder outputs, so
it is determined by the codec configuration, and for LC3 is equal to the
frame duration.
Add codec method get_interval() that returns the correct interval, and
use it in iso-io.
Once Pipewire is started it will try to register a BAP broadcast source media endpoint on UUID 00001852-0000-1000-8000-00805f9b34fb if the media codec that supports BAP and the adapter indicates LE Audio is supported.
When the endpoint is detected (over DBus) by Pipewire and it has a broadcast sink UUID, a new device will be created with the address 00:00:00:00:00:00. This device will be our simulated remote device. This is done because a broadcast source emitting device does not need any connection to start transmitting the audio. This device is set as connected.
When the SetConfiguration DBus method is called and the spa_bt_transport structure with the profile BAP broadcast source is created we switch the device from the one read from DBus to the one created by us. This is done because in BlueZ, when the transport is created, at the Device property, BlueZ sets the adapter as the device that the transport is connected to. Here the device will have the newly created SPA_BT_PROFILE_BAP_BROADCAST_SINK profile connected.
Added code that allows to create a node in the graph for a device connected to the SPA_BT_PROFILE_BAP_BROADCAST_SINK profile.
When a sink contributing to an ISO CIG does not have data, output
silence for it, as long as at least one sink in the CIG is running.
Only if writes to sockets fail, pause all streams to reset
synchronization.
This way we write exactly the same number of packets for each CIS at the
same time, which probably is the best tested configuration in BT
adapters and devices. We also don't then have to pause output if some
sinks are not running or miss their timing, as we generate silence on
the fly.
When using iso-io, have it initialize the codec instance, and have
media-sink uses that instance, so that silence and actual audio are
encoded with the same codec.
Resynchronize ISO streams on playback (re)start, so the stream positions
are aligned immediately. This is better than relying on rate matching
to correct any offsets.
For ISO server sockets, the QOS struct from getsockopt contains values
with different meaning from ISO client socket. Get the values via DBus
instead, which is right in both cases.
Add factored out helper for ISO socket I/O.
ISO sockets need synchronization of writes and audio position for
different stream fds in the same isochronous group, and it's easier to
separate out the part that coordinates it.
