BL Audio multicast

RE: BL Audio multicast

AHaug — Thu, 11 Jul 2024 14:05:11 GMT

Alright,

Thank you for verifying.

Kind regards,
Andreas

RE: BL Audio multicast

JeraDrson — Thu, 11 Jul 2024 13:52:41 GMT

I do not know if my solution is the correct way to do it but it works. So you can close it for now. If encounter problems I will make new case.

Thank you for now

RE: BL Audio multicast

AHaug — Thu, 11 Jul 2024 13:46:37 GMT

Hi,

Karl is no longer available, and your case were not picked up before now. From your latest reply it looks that your query has been resolved? Is that correct?

If not, could you create a new case that describes the remaining issues you have with implementing your firmware?

Kind regards,
Andreas

RE: BL Audio multicast

JeraDrson — Thu, 11 Jul 2024 12:02:25 GMT

I found out the is bt_le_scan_stop function call in pa_synced_cb, after commenting this out it seems my data is being received correctly.

RE: BL Audio multicast

JeraDrson — Mon, 08 Jul 2024 12:06:12 GMT

Hello, could you please provide some example how to receive? Thank you

RE: BL Audio multicast

JeraDrson — Thu, 04 Jul 2024 09:59:09 GMT

Hi,

I implemented the solution on the TX side. The device is advertising the mask based on the buttons(manufacturer data, mask).

However i am not sure how to scan for the advertised data correctly. I can see the packet is received because scan_check_broadcast_source is called with my data. However when the audio is streaming it probably disables the callback. Therefore i usually receive the data only once after the device boots.

I than tried to add another very similar callback to bt_mgmt_scan_for_broadcast_start using bt_le_scan_cb_registe , however i only receive the data once more.

Could you please point me to some example or advice me how can I receive the advertisement at all times?

Thank you

Jeronym

RE: BL Audio multicast

Karl Ylvisaker — Thu, 27 Jun 2024 14:14:28 GMT

Hello Jeronym,

[quote user="JeraDrson"]

The privacy is not an issue in this application. Therefore we would try the solution with broadcasting the mask.

Could you please give me some advice regarding this solution? Could we encode the mask to some stream information? Or the second audio channel? Or create some non audio broadcast channel?

[/quote]

Great, that sounds like a good idea! Please do not hesitate to ask or open a new ticket if you should encounter any other issues or questions when you give this a try!

You can set up regular advertising alongside the broadcast to broadcast the mask - this way you do not have to create an implementation that continuously scans the received audio to extract the mask.
For simplicity in the beginning you can basically set up an advertisement that contains a number, and have each device know their own identity number in order to know if they should listen in to the secondary broadcast or not.

In the next step you can then have all the peripheral devices advertise their own ID's on a buttonpress (such as during setup for the practice) so that the central can know 'who is available'.

And for the final version perhaps you would like to use NFC or something similar to 'scan' into the training session, so that the head coach easily can know who is in the session and what their peripheral ID they are using.

There are many ways you can achieve this, and you might already have a plan for something other than my suggestion above, in which can you can disregard it - this was just the first I envisioned based on the understanding I have of your targeted use-case.

Best regards,
Karl

RE: BL Audio multicast

JeraDrson — Thu, 27 Jun 2024 13:04:32 GMT

Thank you for the answer. The privacy is not an issue in this application. Therefore we would try the solution with broadcasting the mask.

Could you please give me some advice regarding this solution? Could we encode the mask to some stream information? Or the second audio channel? Or create some non audio broadcast channel?

regards

Jeronym

RE: BL Audio multicast

Karl Ylvisaker — Wed, 26 Jun 2024 11:18:28 GMT

Hello,

No problem at all, I am happy to help!

I am glad to read that you have already got the encrypted broadcast up and running!

Will the audio need to be private if they are speaking to single students, or could it be an option to transmit the mask (open for anyone to pick up) to indicate which student who should listen into the secondary transmit meant for the single student?

One solution would indeed be to have a connection to each of the students, and then indicate over the regular BLE link that they will receive a one-on-on conversation, which then also would be private.
The main drawback with this would be that a connection needs to be handled at all times even when idle, and this will consume a lot of power on the peripheral side if you require this to be over a long distance so that the TX power of the peripheral also will be at maximum value.

The drawback to a broadcast only solution would be privacy of the one-to-one transfers, and the central's ability to know if anyone is actually listening. I.e it could go into a 'one on one' broadcast without getting any acknowledgement back that the peer is actually present and listening.

Best regards,
Karl

RE: BL Audio multicast

JeraDrson — Wed, 26 Jun 2024 07:54:28 GMT

Hello, thank you for the answer.

I tried the passkey and it works, I want to use it to so multiple instructors can operate in one area with their own group of students.

However I need the instructor to be able to choose who in h is group will he talk to individually. Sometimes he wants to speak to single student, sometimes a group and sometimes all his students. Is this also possible?

Maybe many separate connections just to tell what students should receive the broadcast audio, or maybe use second broadcast channel and only transmit some mask to indicate what listener should enable the audio?

RE: BL Audio multicast

Karl Ylvisaker — Wed, 26 Jun 2024 07:40:01 GMT

Hello Jeronym,

Thank you for your extreme patience with this.

[quote user=""]

We would need to pair the source device with all the listening devices so no one else can listen to the audio.

We would use BL audio broadcast to stream the audio.

There would be BLE connections with every listener, so the source device could notify every single listener to connect/disconnect the audio.

Is our solution correct or is there a better way?

[/quote]

Thank you for your scenario overview. I have got some good news for you - all this is possible already, without needing a connection to every device! :)
You are correct that you can use the broadcast audio feature of LE Audio for this, and in addition, you can encrypt the broadcast with a passkey so that only the students/listeners with this passkey can listen into the broadcast.
If you would like for the range to be as large as possible you could also use a Front End Module with your device, to increase the TX output power to +10 or +20 dBm (depending on regulatory requirements in the region you will sell the device).

You could give this a try by enabling the broadcast encryption and setting the passkey using these kconfigs.

Please give this a try, and do not hesitate to let me know if you run into any issues or questions! :)

Best regards,
Karl