receiver does not sync to audio after getting back in range

RE: receiver does not sync to audio after getting back in range

Amanda Hsieh — Wed, 08 Jan 2025 18:06:09 GMT

Hi,

Please try to use the latest NCS v2.9.0 to get the improvement.

-Amanda H.

RE: receiver does not sync to audio after getting back in range

JeraDrson — Sun, 05 Jan 2025 21:11:12 GMT

Ok, so after testing the solution was not correct. It did solve the original issue however sound had glitches and range was worse so I had to reenabled the scan restart by timeout.

So i am back at the beginning.

To summarize:

When LE_AUDIO_EVT_SYNC_LOST is handled in main short before pa_sync_timer expires, the scanning can not be reenabled again.

Compared to the original audio application there is one related change. I added custom advertisement. To be able to receive it I removed bt_le_scan_stop from pa_synced_cb.

RE: receiver does not sync to audio after getting back in range

JeraDrson — Wed, 11 Dec 2024 21:48:05 GMT

Thank you for the reply.

I use 2.6.1.

My current theory is that I needed to add custom advertisment and did not want to stop scanning when pa_synced_cb happens. So I commented the bt_le_scan_stop out from it. However the timeout restart pa_sync_timer is still running. Therefore when the sync is lost the scanning restart may come from the mechanism you described or from the pa_sync_timeout and this may cause the problem.
Does this make sense?

I now tried to disable the timer (with pa_sync_timeout) entirely so the restart happens only after sync lost.

It did not get stuck so far but it is too soon to know yet. Hope this does not cause another issues.

with regards Jeronym

RE: receiver does not sync to audio after getting back in range

Amanda Hsieh — Wed, 11 Dec 2024 15:53:30 GMT

Hi,

When a timeout happens (like we lost the gateway),

The stream_stopped_cb() triggered, with reason "BT_HCI_ERR_CONN_TIMEOUT"
Sending "LE_AUDIO_EVT_SYNC_LOST" event
In streamctrl_broadcast_sink.c, we catch LE_AUDIO_EVT_SYNC_LOST and delete PA sync
Once if the PA sync terminated, the callback for PA sync terminated will be triggered, and BT_MGMT_PA_SYNC_LOST will be sent
Which trigger the scanning automatically

According to this page, The error code -120 returned by this line typically corresponds to EALREADY which means the Operation is already in progress, but this line should already stop scanning before it.

What NCS version are you using? Do you modify the scan_restart_worker function?

Regards,
Amanda H.

RE: receiver does not sync to audio after getting back in range

JeraDrson — Wed, 11 Dec 2024 14:50:42 GMT

Update:
I did more tests. Dependence on temperature and battery did not confirm.

I now think it is now related to the scenario where

LE_AUDIO_EVT_SYNC_LOST is handled in main shortly before the Sync timeout showed in previous message.

My understanding is that in original application the sync timeout was disabled after the first successful sync. However i needed to add custom data advertisement so i commented out the bt_le_scan_stop(); from pa_synced_cb function so my data is passing through. This was in my previous ticket here BL Audio multicast