Range of CONFIG_LC3_BITRATE

[gocchan]

Hi, 

I am evaluating the nRF5340 Audio DK and measuring while adjusting the audio bitrate.

I found the following 3 symbols definition for bitrate.

CONFIG_LC3_BITRATE=96000 (Default)

CONFIG_LC3_BITRATE_MAX=124000

CONFIG_LC3_BITRATE_MIN=32000

I tried setting it to 124000 in prj.conf and writing it to both the gateway and the headset, but it seems that the headset cannot receive or play the broadcast.

# nRF5340 Audio
CONFIG_NRF5340_AUDIO=y
CONFIG_AUDIO_DEV=1
CONFIG_TRANSPORT_BIS=y
CONFIG_TRANSPORT_CIS=n
CONFIG_AUDIO_SOURCE_USB=n
CONFIG_AUDIO_SOURCE_I2S=y
CONFIG_AUDIO_FRAME_DURATION_7_5_MS=n
CONFIG_AUDIO_FRAME_DURATION_10_MS=y
CONFIG_LC3_BITRATE=124000

If I set it to 112000 or 32000 it works fine.

Is there a way to run at 124000 bps or higher?

I use 2 PCA10121 (1.0.0) boards, NCS 2.1.2 and sample code "nrf5340_audio".

Regards, 

Gotoda

[Didrik Rokhaug]

Hi,

Could you share the log from the boards when using 124000?

Best regards,

Didrik

[gocchan]

*** Booting Zephyr OS build v3.1.99-ncs1-1  ***.
.GW [00:00:00.254,302] .[0m<inf> audio_sync_timer: Audio sync timer initialized.[0m.
.GW [00:00:00.254,760] .[0m<dbg> nrf5340_audio_dk_nrf5340_cpuapp: core_config: Setting gpiote latency to low power.[0m.
.GW [00:00:00.254,821] .[0m<dbg> nrf5340_audio_dk_nrf5340_cpuapp: remoteproc_mgr_boot: Network MCU released..[0m.
.GW [00:00:00.259,674] .[0m<inf> fw_info: .[0;32m.
.. nRF5340 Audio nRF5340 Audio DK cpuapp ...    .
.. NCS Version: 2.1.2 ...    .
.. Cmake run : Thu Nov 17 11:23:26 2022.[0m.[0m.
.GW [00:00:00.259,704] .[0m<inf> fw_info: ------- DEBUG BUILD -------.[0m.
.GW [00:00:00.259,704] .[0m<inf> fw_info: .[0;36m.
.. Compiled for GATEWAY device.[0m.[0m.
.GW [00:00:00.270,294] .[0m<inf> board_version: .[0;32mCompatible board/HW version found: 1.0.0.[0m.[0m.
.GW [00:00:02.316,101] .[0m<inf> ble: MAC: C1:40:B2:B1:24:8C (random).[0m.
.GW [00:00:02.316,345] .[0m<inf> ble: Controller version: 3303.[0m.
.GW [00:00:02.452,941] .[0m<inf> bis_gateway: Broadcast source 0x20009c88 started.[0m.
.GW [00:00:02.453,216] .[0m<inf> bis_gateway: Broadcast source 0x20009cac started.[0m.
.GW [00:00:02.477,813] .[1;33m<wrn> bt_hci_core: opcode 0x2061 status 0x0c.[0m.
.GW [00:00:02.491,058] .[1;33m<wrn> audio_datapath: I2S RX overrun. Single msg.[0m.
.GW [00:00:02.492,065] .[1;33m<wrn> audio_datapath: I2S RX continuing stream.[0m.
.GW [00:00:02.492,065] .[0m<inf> audio_datapath: Drft comp state: CALIB.[0m.
.GW [00:00:02.592,071] .[0m<inf> audio_datapath: Drft comp state: OFFSET.[0m.
.
.
.GW [00:01:08.231,292] .[0m<inf> audio_datapath: Drft comp state: LOCKED.[0m.
.

[gocchan]

I sent it by mistake.

I captured the LOG_INF() message and attached it.

Gateway:

*** Booting Zephyr OS build v3.1.99-ncs1-1  ***.
.GW [00:00:00.254,302] .[0m<inf> audio_sync_timer: Audio sync timer initialized.[0m.
.GW [00:00:00.254,760] .[0m<dbg> nrf5340_audio_dk_nrf5340_cpuapp: core_config: Setting gpiote latency to low power.[0m.
.GW [00:00:00.254,821] .[0m<dbg> nrf5340_audio_dk_nrf5340_cpuapp: remoteproc_mgr_boot: Network MCU released..[0m.
.GW [00:00:00.259,674] .[0m<inf> fw_info: .[0;32m.
.. nRF5340 Audio nRF5340 Audio DK cpuapp ...    .
.. NCS Version: 2.1.2 ...    .
.. Cmake run : Thu Nov 17 11:23:26 2022.[0m.[0m.
.GW [00:00:00.259,704] .[0m<inf> fw_info: ------- DEBUG BUILD -------.[0m.
.GW [00:00:00.259,704] .[0m<inf> fw_info: .[0;36m.
.. Compiled for GATEWAY device.[0m.[0m.
.GW [00:00:00.270,294] .[0m<inf> board_version: .[0;32mCompatible board/HW version found: 1.0.0.[0m.[0m.
.GW [00:00:02.316,101] .[0m<inf> ble: MAC: C1:40:B2:B1:24:8C (random).[0m.
.GW [00:00:02.316,345] .[0m<inf> ble: Controller version: 3303.[0m.
.GW [00:00:02.452,941] .[0m<inf> bis_gateway: Broadcast source 0x20009c88 started.[0m.
.GW [00:00:02.453,216] .[0m<inf> bis_gateway: Broadcast source 0x20009cac started.[0m.
.GW [00:00:02.477,813] .[1;33m<wrn> bt_hci_core: opcode 0x2061 status 0x0c.[0m.
.GW [00:00:02.491,058] .[1;33m<wrn> audio_datapath: I2S RX overrun. Single msg.[0m.
.GW [00:00:02.492,065] .[1;33m<wrn> audio_datapath: I2S RX continuing stream.[0m.
.GW [00:00:02.492,065] .[0m<inf> audio_datapath: Drft comp state: CALIB.[0m.
.GW [00:00:02.592,071] .[0m<inf> audio_datapath: Drft comp state: OFFSET.[0m.
.
.
.GW [00:01:08.231,292] .[0m<inf> audio_datapath: Drft comp state: LOCKED.[0m.
.

Headset:

*** Booting Zephyr OS build v3.1.99-ncs1-1  ***.
.HL [00:00:00.254,302] .[0m<inf> audio_sync_timer: Audio sync timer initialized.[0m.
.HL [00:00:00.255,035] .[0m<dbg> nrf5340_audio_dk_nrf5340_cpuapp: core_config: Setting gpiote latency to low power.[0m.
.HL [00:00:00.255,065] .[0m<dbg> nrf5340_audio_dk_nrf5340_cpuapp: remoteproc_mgr_boot: Network MCU released..[0m.
.HL [00:00:00.259,979] .[0m<inf> fw_info: .[0;32m.
.. nRF5340 Audio nRF5340 Audio DK cpuapp ...    .
.. NCS Version: 2.1.2 ...    .
.. Cmake run : Thu Nov 17 11:14:24 2022.[0m.[0m.
.HL [00:00:00.259,979] .[0m<inf> fw_info: ------- DEBUG BUILD -------.[0m.
.HL [00:00:00.260,009] .[0m<inf> fw_info: .[0;36m.
.. HEADSET <no ch selected> defaulting to AUDIO_CH_L .[0m.[0m.
.HL [00:00:00.260,009] .[0m<inf> fw_info: .[0;36m.
.. HEADSET left device.[0m.[0m.
.HL [00:00:00.270,599] .[0m<inf> board_version: .[0;32mCompatible board/HW version found: 1.0.0.[0m.[0m.
.HL [00:00:02.315,307] .[1;33m<wrn> bt_hci_core: Controller to host flow control not supported.[0m.
.HL [00:00:02.444,152] .[0m<inf> ble: MAC: C5:1E:EC:9B:FC:5B (random).[0m.
.HL [00:00:02.444,335] .[0m<inf> ble: Controller version: 3303.[0m.
.HL [00:00:02.539,428] .[0m<inf> bis_headset: Scanning for broadcast sources.[0m.
.

Regards

Gotoda

[Didrik Rokhaug]

Thanks. I have asked our developers to take a look.

I'll come back to you when I get a reply from them.

[Didrik Rokhaug]

By default, the sample uses a retransmission time of 4. This means that there isn't enough bandwidth for a bitrate of 124kbps.

However, I believe you can reduce the number of retransmits here (the 4u), to make it work: https://github.com/nrfconnect/sdk-nrf/blob/main/applications/nrf5340_audio/src/bluetooth/le_audio.h#L65