nrf5340 audio:LE audio Stream stopped.INSUFFICIENT_RESOURCES

[Reskyllr]

We have an nrf5340 audio application, and there were no problems with the previous development.
But when I want to extend the CIS function, especially when enabling bidirectional transmission, an error occurs, but I cannot determine the reason.
00> HL [00:11:23.514,648] <inf> cis_gateway: Stream 0x20003744 stopped. Reason 13
00> HL [00:11:23.514,648] <wrn> cis_gateway: Unknown stream
00> HL [00:11:23.514,678] <inf> cis_gateway: Stream 0x20003524 stopped. Reason 13
00> HL [00:11:23.515,625] <wrn> cis_gateway: Unknown stream

Reason 13 is BT_HCI_ERR_INSUFFICIENT_RESOURCES.
What causes this error? If bidirectional transmission is not started, it works normally.
What I want to know most is what causes this error.

Thanks,

Reskyllr

[dejans]

Hi,

Support for bidirectional streams to or from 2 headsets was added in NCS v2.3.0. Have you selected CONFIG_STREAM_BIDIRECTIONAL=y in your project configuration?

Could you please provide information on what you try to achieve?

Best regards,
Dejan

[Reskyllr]

Hi dejans,

Yes, I added CONFIG_STREAM_BIDIRECTIONAL=y, I want to use CIS intercom functionality, but that's not my main goal.
I want to know what causes BT_HCI_ERR_INSUFFICIENT_RESOURCES.
Because there is another situation where the same error occurs:
I expanded the SDU size to 240 (used to transmit stereo sound) in BIS mode, and everything worked fine.
When I want to do the same work in CIS mode, Stream stop: Reason 13(BT_HCI_ERR_INSUFFICIENT_RESOURCES) appears.
If you restore the SDU size to 120 (mono transmission), it works normally.
But when adding CONFIG_STREAM_BIDIRECTIONAL=y, the same error (BT_HCI_ERR_INSUFFICIENT_RESOURCES) occurred again.

You don't need to understand it, I just want to know the cause of this error and how to fix it.
Thanks,
Reskyllr

[dejans]

Hi Reskyllr,

Which NCS version do you use?

Best regards,
Dejan

[Reskyllr]

2.4.0

[dejans]

Hi Reskyllr,

I have asked internally about supported bitrate/SDU values. I'll get back to you when I get this information, hopefully till the end of this week.

Best regards,
Dejan

[Reskyllr]

Hi dejans,

Thank you very much, I will wait.

Best regards,

Reskyllr

[dejans]

Hi Reskyllr,

I am sorry for delayed reply. I was out of the office.

We have tested bidirectional streams with bitrate 48000 which seems to be working for both USB and I2S input on the gateway. These are relevant configuration options:

CONFIG_STREAM_BIDIRECTIONAL=y
CONFIG_BT_AUDIO_BITRATE_UNICAST_SINK=48000
CONFIG_BT_AUDIO_BITRATE_UNICAST_SRC=48000

The highest bidirectional stream bitrate is 64000 bits/s (SDU size of 80). For unidirectional streams, bitrate could go up to 96000. The lowest bitrate is 32000 and it is given by CONFIG_LC3_BITRATE_MIN.

Best regards,
Dejan

[Reskyllr]

Hi dejans,
Thanks so much for testing, I now understand where its upper limit is.

Reskyllr