Our current AES67 sender setup requires that that PTP driver drive the
entire graph. This adds support for allowing the AES67 RTP sink to be
driven by an arbitrary driver, while still using the PTP driver for
sending data on the network.
When aes67.driver-group is specified a pw_filter is created with no
ports, node.always-process = true and node.group set to the
aes67.driver-group. When set to PTP, this gives us process callbacks at
the PTP rate which we use to get the current PTP time in the RTP sender
by interpolating the clock snapshots from the pw-filter.
Implementation ideas from Wim Taymans. Co-authored with Sanchayan Maity.
For a detailed reference, refer the following papers by Fons Adriaensen.
- Using a DLL to filter time
(https://kokkinizita.linuxaudio.org/papers/usingdll.pdf)
- Controlling adaptive resampling
(http://kokkinizita.linuxaudio.org/papers/adapt-resamp.pdf)
Make a rtprio-server and rtprio-client option. Leave the server
priority by default to 88 but lower client priority to 83. JACK
does something similar by setting clients to rtprio-server - 5.
Make module-rt use the client priority by default and bump the server
priority explicitly in the config file.
Leave the pulse-server to the default rtprio-client, there is no reason
to lower this any further because it is really just a regular client.
Bump the ffado packetizer thread to rtprio-server + 5 because that is
also what JACK does.
88 is still much higher than the value of 60 that JACK uses in
Fedora but now this is at least configurable.
Move some of the tracking code for the DLL to where it is used.
Add resync.ms (default 10) option at which we give up rate adjusting
and instead do a hard resync. This results in a jump in the position
of the graph clock.
It's better for PHC identification in multi-NIC systems. PHC numbering might be dependent on the probe order yet no bugs was observed. Still recommend this for more comfortable configuration.
Also added some guidance on what must be changed
As reported in #3217, PTP driver has to have the highest priority for packets to arrive in time
Everything connected to AES67 should be clocked by the Grandmaster clock
