The nrf5340 audio application's TX function of Gateway

[huma]

Hello

I have implemented the stereo function to the nrf5340 audio application on SDK V2.6.0. i can send stereo audio signal to both of the two headset at the same time or one of them.

But i also have some questions and problems want to figure out.

I found that when i enable the "CONFIG_STREAM_BIDIRECTIONAL", both "frequency" of the "Lc3 codec config for sink" and "Lc3 codec config for source" will be set to 24K, "Octets per frame" will be set to 48000, but if i disable the "CONFIG_STREAM_BIDIRECTIONAL", there is only left "Lc3 codec config for sink", and the frequency will be set to 48K, and the "Octets per frame" will be set to 96000. When the frequency is 24K, the stereo signal data size is 120, when the frequency is 48K, the stereo signal data size is 240.

I guess that resources are automatically allocated here, and after enabling "CONFIG_STREAM_BIDIRECTIONAL" function, it will cause half resources to be used to receive headset signals. Is my guess correct?

But when i want to implement the function that headset can send stereo audio signal to gateway, although it works, because i have to enable the "CONFIG_STREAM_BIDIRECTIONAL", which cause the frequency of lc3 codec config can only up to 24K, that means i can not receive the normal audio signal on the gateway, because the frequency what i want at least up to 48K. Because i want to transmit the music signal not only the mic signal. I have tried to force it to 48K, but the data size still only allocated 120 instead of the 240 I needed.

So i try to disable the TX function of gateway, because i guess maybe if i can only enable the RX function of gateway, the all resources can allocated to it, and I have put in a lot of effort, but there still some problems.

So do you have some official ways to disable the TX function of Gateway?

And i have to say this is our product's user scenarios, so i have to do this work.

Thank you very much and looking forward to your reply!

[Amanda Hsieh]

Hi, 

Would you like to disable the stream from gateway to headset, or headset to gateway?

Regards,
Amanada H.

[huma]

Hello Amanda

Yes, i want to disable the stream from the gateway to the headset but I want to keep stream from the headset to the gateway.

In reality, I'm guessing that when I can only keep the stream from the headset to the gateway, the system will automatically allocate all resources to this path, just like when "CONF_STREAM_SIDIELECTION" is not enabled, all resources will be allocated to the stream from the gateway to the headset.

I'm not sure if my guess is correct. I'm not sure if my guess is correct, but it's worth giving it a try.

Thank you very much and looking forward to your reply!

[Amanda Hsieh]

Hi, 

You can 

1. Since CONFIG_STREAM_BIDIRECTIONAL=y will enable the encoder on headset side and also the decoder on gateway, so please enable it
2. For unciast client, only discover the UNICAST_SERVER_SOURCE
   - ret = unicast_client_discover(msg->conn, UNICAST_SERVER_BIDIR);
   +ret = unicast_client_discover(msg->conn, UNICAST_SERVER_SOURCE);
   https://github.com/nrfconnect/sdk-nrf/blob/5aa5ca0c13de5b6f0c7acf28ef96b307632fb91e/applications/nrf5340_audio/unicast_client/main.c#L397
3. For unicast client in the current code (will improve in later)
   The unicast client will try to allocate the resource for CIG in the start from here
   https://github.com/nrfconnect/sdk-nrf/blob/5aa5ca0c13de5b6f0c7acf28ef96b307632fb91e/applications/nrf5340_audio/src/bluetooth/bt_stream/unicast/unicast_client.c#L1766
   Please try to set the tx_param in here to NULL for a trial
   https://github.com/nrfconnect/sdk-nrf/blob/5aa5ca0c13de5b6f0c7acf28ef96b307632fb91e/applications/nrf5340_audio/src/bluetooth/bt_stream/unicast/unicast_client.c#L1784
   So the gateway will only allocate the time for RX not TX
4. The headset should also expose the support/available context properly
   https://github.com/nrfconnect/sdk-nrf/blob/b83837fb1f9630139b8a372778acc95fc2524073/applications/nrf5340_audio/src/bluetooth/bt_stream/unicast/unicast_server.c#L56

-Amanda H.

[huma]

Hello Amanda

Thank you very much!

I will try it when i back to office. Then will report the result!

Thank you!

[huma]

Hello Amanda,

I have tried following your instructions.

I also enable the "CONFIG_BT_AUDIO_PREF_SAMPLE_RATE_48KHZ=y"

Then the headset device will print:

I found that the size is still 120 and not 240:

So, how can i increase the size to 240? I think may be i also need to modify the headset code.

Thank you very much and looking forward to your reply!

[Amanda Hsieh]

Hi, 

The solution is based on v2.7.0 to disable the TX on the gateway and only keep the streams from the headset to the gateway.

In the default setting, the headset will only send one stream (the left channel) to the gateway.

Would you want to send a stereo audio stream from each headset to the gateway?

-Amanda H.