nRF5340 Audio - 6 streams broadcasting

RE: nRF5340 Audio - 6 streams broadcasting

uzer123 — Tue, 11 Jun 2024 09:50:12 GMT

Thank you for the detailed and clear answer

RE: nRF5340 Audio - 6 streams broadcasting

dejans — Mon, 10 Jun 2024 11:57:31 GMT

[quote user="uzer123"]

My question is: to enable the 4 BIS streams (in my use case audio quality is not important) you just use the aforementioned flags in prj.conf ? (CONFIG_BT_AUDIO_BROADCAST_24_2_1=y, CONFIG_ENCODER_STACK_SIZE=16384, CONFIG_LC3_ENC_CHAN_MAX=4)

And if this was your only change to the default source code, how do you send the 4 streams to the board?

Can i send 4 mono streams from USB or 2 mono streams through USB and 2 through LINE IN?

[/quote]

Please find below some suggestions from our developers.
Encoding each stream takes around 30% of the CPU time. Therefore, there might not be enough CPU time to encode 4 streams.
Current USB implementation only has 2 (stereo) endpoints. As USB endpoint is synchronous, it is controlled by PC clock. For avoiding the packet loss. synchronization of USB to I2S is required but you would be on your own in potentially achieving this.
With regard to config options, you would need to set CONFIG_BT_CTLR_CONN_ISO_STREAMS=4 and CONFIG_BT_CTLR_SYNC_ISO_STREAM_COUNT=4 in the controller's prj.conf.
In general, in trying to achieve 4 streams, issues might arise due to CPU, USB and clock sources. One could consider trying to find ways to transfer pre-encoded LC3 to the nrf5340 using for example SPI.

Best regards,
Dejan

RE: nRF5340 Audio - 6 streams broadcasting

Tommy_Li — Sat, 08 Jun 2024 06:49:11 GMT

Cool, Looking forward to your progress on lc3 encoed audio streams transferred by UART/SPI.

RE: nRF5340 Audio - 6 streams broadcasting

catalinio — Wed, 08 Feb 2023 08:41:45 GMT

hi uzer123 ,

I'm glad that more people are trying to stream multiple channels, so Nordic could hear us and release a 6-8 streams BLE controller.

I have not input more than 2 audio channels in the Gateway. I've just generated the additional 2 channels (3rd and 4th), with sine-waves. Afik, I2S and USB are each limited to 2 channels, and using both would mean redesigning the application.

Basically, my experiment was to test how many channels can be LC3 encoded and next broadcasted on BLE Audio. In my test, I see that 6 channels is a doable (85% CPU usage, 48kbps bitrate), while 8 streams is a strech-goal.

My next plan is to input on UART/SPI already LC3 encoded audio streams on the Gateway, and next broadcast them, maybe trying the new multi-gateway feature (available in github, not released yet).

As for code modifications, make sure in encoder_thread() there is enough space to handle tmp_pcm_raw_data.

Additionally, in the LC3 wrapper (file: sw_codec_selec.c), make sure LC3 is initialized with 4 channels and in the sw_codec_encode() you design a way to split/concatenate all the 4 channels.

br, catalinio

RE: nRF5340 Audio - 6 streams broadcasting

uzer123 — Tue, 07 Feb 2023 11:05:32 GMT

I am also interested in a similar configuration, so i find it beneficial to write here. From this thread i see that 4 BIS streams is the max supported by the BLE audio controller.

Can i send 4 mono streams from USB or 2 mono streams through USB and 2 through LINE IN?

RE: nRF5340 Audio - 6 streams broadcasting

dejans — Tue, 10 Jan 2023 09:37:47 GMT

Hi,

It is not supported at the moment. For any other information related to future plans and releases please contact your regional sales manager.

Best regards,
Dejan

RE: nRF5340 Audio - 6 streams broadcasting

catalinio — Mon, 09 Jan 2023 15:14:20 GMT

Hi,

Any news on releasing a new BL Controller with 6 or 8 BIS streams?

thanks,

Catalin

RE: nRF5340 Audio - 6 streams broadcasting

dejans — Mon, 19 Dec 2022 11:49:20 GMT

Hi,

As there is theoretical limit for 2M Phy of around 1.4 Mbps, that would enable support for less than 10 streams (with 48 Kbps) with 2 retransmissions each. Even with only 1 retransmission, maximum number of streams would be 14. However, these are only theoretical considerations, since audio controller currently supports maximum 4 BISes.

Best regards,
Dejan

RE: nRF5340 Audio - 6 streams broadcasting

catalinio — Mon, 19 Dec 2022 08:43:50 GMT

Hi,

The main idea is to demonstrate the BLE Audio capabilities of nRF5340; the use-case is: multiple audio-streams will be distributed in a room to multiple listeners, and each will choose their active stream.

For now 2 streams will be from I2S (left and right from audio stereo), while the channels #3 to #6 will be generated sinewaves.

On long-term, minimum 16 channels should be broadcasted; most-likely the LC3 encoding should be done on a more powerful MCU, so nRF5340 will remain just to handle LE Audio stack and decoding (only on the receiving kit).

Would broadcasting 16 BIS (without LC3 encoding, 48kbps each stream (probably 2 retransmissions min), so this is 96KB/sec audio-data for all streams) is achievable for nRF5340 and BLE Audio stack?

Thank you!

RE: nRF5340 Audio - 6 streams broadcasting

dejans — Fri, 16 Dec 2022 13:21:45 GMT

Hi,

If possible, could you provide information why you would need 6 BIS streams and what would they be used for?

Best regards,
Dejan

RE: nRF5340 Audio - 6 streams broadcasting

catalinio — Fri, 16 Dec 2022 09:34:46 GMT

Hi dejans

The first observation is that for either bitrate 32 or 48 kbps there doesn't seem to be a meaningful difference in CPU load (just around 1%).

Also for 32kbps CONFIG_BT_AUDIO_BROADCAST_16_2_1=y was used, while for 48kbps I've enabled CONFIG_BT_AUDIO_BROADCAST_24_2_1=y.

I've always kept CONFIG_ENCODER_STACK_SIZE=16384.

Also DEBUG and LOG was always active, with INFO level.

1. CONFIG_LC3_ENC_CHAN_MAX=4 and streaming 4 channel (2 from I2S stereo and 2 sine-tones 1kHz generated): CPU load is 72%. Streaming is stable for hours.

2. CONFIG_LC3_ENC_CHAN_MAX=6, forcing LC3 encoder to process 6 streams (random data for 2 extra streams), CPU load varies between 77% to 85%.

Trying to compute the time required for a single 10milisec frame to be encoded, I obtain 8milisec (using k_uptime_get_32() before and after).

I see spurious errors from I2S audio_datapath.c module:

GW [00:01:16.567,901] <wrn> audio_datapath: I2S RX overrun. Single msg

GW [00:01:16.568,908] <wrn> audio_datapath: I2S RX continuing stream

Of course, in the second scenario, on BLE only 4 streams are being broadcasted.

I realize the 6 streams broadcasting is a stretched goal, but I'm willing to give it a try on my setup, if a new LE Controller with #6 BIS is released.

Best regards,

Catalin

RE: nRF5340 Audio - 6 streams broadcasting

dejans — Wed, 14 Dec 2022 14:47:41 GMT

Hi,

We are investigating the effects of having more BIS'es. Could you please perform a CPU load check with your settings (see below some of them)? What are the results?

CONFIG_LC3_BITRATE=32000 (and 48000)
CONFIG_LC3_ENC_CHAN_MAX=4 (and 6)
CONFIG_ENCODER_STACK_SIZE=16384

Best regards,
Dejan

RE: nRF5340 Audio - 6 streams broadcasting

catalinio — Tue, 13 Dec 2022 18:21:01 GMT

Thanks, dejans

Is there any chance that the max BIS to be increased to 6 or 8, and a new binary of the controller to be released?

RE: nRF5340 Audio - 6 streams broadcasting

dejans — Tue, 13 Dec 2022 14:50:33 GMT

Hi,

There is a limitation on the controller side to maximum 4 BIS streams.

Best regards,
Dejan

RE: nRF5340 Audio - 6 streams broadcasting

catalinio — Tue, 13 Dec 2022 10:24:37 GMT

Here is the prj.conf

devzone.nordicsemi.com/.../5305.prj_5F00_conf.txt