nrf5340 stereo output using external codec on SDK 2.6.1

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Tue, 10 Dec 2024 12:10:55 GMT

Hi,

You can refer to this branch cis_stereo_audio_sink. This is demo branch which is provided without warranty or guarantee to be working. You would need to add a mechanism on CIS gateway for restricting scanning and connecting to more than one headset.

Best regards,
Dejan

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Mon, 17 Jun 2024 10:06:45 GMT

Hi,

Please find below some suggestions from our developers.
It is possible to send both left and right data in a single ISO stream by stacking both left and right data in the same SDU. After encoding on the sender side, the data would be combined. Data would later be split on the receiving side. The downside of this is that it is rather uncommon and packets over the air might get too large potentially causing retransmissions due to CRC errors.
If the packets in the same CIG/BIG are sent with the same SDU reference, the receiving side would also perceive it like that. If you have one peripheral receiving 2 CISes, you should receive the same timestamp as long as they are in the same CIG. If the streams are sent with the same timestamp, then they should be in sync. You can send Left and Right in separate CISes to the same peripheral. On the receiving side, you can check if timestamps are the same and if they are that means that the streams are in sync (as they should be). If the timestamps happen to be different then this would need to be handled by the application.

Best regards,
Dejan

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Fri, 14 Jun 2024 18:43:19 GMT

Hi,

I am sorry for a delayed reply. I have not yet got internal response. I will reach out to developers on Monday. I will get back to you hopefully during next week.

Thank you for your patience.

Best regards,
Dejan

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Fri, 07 Jun 2024 11:21:18 GMT

Hi,

I have asked internally for some clarifications. I will get back to you during next week.

Best regards,
Dejan

RE: nrf5340 stereo output using external codec on SDK 2.6.1

EchoCharlieWhiskey — Mon, 03 Jun 2024 16:21:38 GMT

In NRF5340: CIS Groups, and Streams: Stereo headset + stereo gateway + NUS?, you (dejans ) suggested I move to the new SDK though I described what I wanted in terms of strereo. Additionally, you said

"An audio stream is unidirectional stream which means there can be up to 2 audio streams in a single CIS. Each of the 2 audio streams could go different way as CIS can be bidirectional. It is possible to have multiple audio channels in a single audio stream. In other words, it is possible to have stereo in a single audio stream."

So I'm having some trouble understanding your current answer which seems to contradict that. I do not want to have two mono streams that need to be sync'd on my single device, I need it to be one stereo stream. How do I do that?

Thank you,

ECW

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Tue, 28 May 2024 08:08:07 GMT

Hi,

I had a discussion with our developers. Below are some relevant points.

[quote user="elecia"]how should a CIS stereo stream from the gateway to the headset (with an external codec) work for SDK 2.6.1?[/quote]

At the moment our application supports only mono bidirectional. However, you should be able to do either stereo in one BIS to the headset or 2 mono BIS to the headset, but this would require some code changes.

[quote user="elecia"]having stereo in unicast mode is a common application. Does a white paper exist?[/quote]

There is currently no such white paper. We are aiming at implementing full support for this.

The error that you see is what is expected. You could try to print sizes and compare values. You would need to split the data yourself and decode it. Please note that the tone module is mono by design. Even if this approach works, you would still see mono data on I2S.
The suggestion is to first start with mono stream and duplicate the data after it has been received. Audio part of it can then be modified so that one gets 2 mono outputs, Then, changes can happen on the BLE and sending side.

Best regards,
Dejan

RE: nrf5340 stereo output using external codec on SDK 2.6.1

EchoCharlieWhiskey — Fri, 24 May 2024 16:44:35 GMT

My code aside, how should a CIS stereo stream from the gateway to the headset (with an external codec) work for SDK 2.6.1? Note that I also want a mono stream from the headset to the gateway and I have only one headset.

(And yes, my modifications above were for the unicast_server and unicast_client example code in 2.6.1, recompiling both gateway and headset.)

Also, from the forums here, having stereo in unicast mode is a common application. Does a white paper exist?

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Fri, 24 May 2024 11:14:25 GMT

Hi,

Could you specify all changes which you made when you used NCS v2.5.1 and when everything was working as expected?

When providing code changes you mentioned unicast_server and unicast_client. Did you modify these samples on the headset and gateway side?

Best regards,
Dejan

RE: nrf5340 stereo output using external codec on SDK 2.6.1

EchoCharlieWhiskey — Thu, 23 May 2024 21:00:42 GMT

Yes.

RE: nrf5340 stereo output using external codec on SDK 2.6.1

dejans — Thu, 23 May 2024 11:46:43 GMT

Hi,

Are all mentioned configuration and code changes specified for NCS v2.6.1?

Best regards,
Dejan