about bap_broadcast_sink example

[heavyjo]

here is 2 question for this example. (v2.9.0)

as i looking for this example, there are some limitations like belows.

• One BIG, one of the two BIS streams (selectable).

then i have a question, is it a hardware limitation? or just fw limitation?

and this example used a 16bit resolution.
could i changed that bit resolution to 24bit? 

[Maria Gilje]

Hello,

I will start with a slight clarification on the sample: the bap_broadcast_sink sample (zephyr/samples/bluetooth/bap_broadcast_sink) is not the same as the nRF5340 Aduio: Broadcast sink application (nrf/applications/nrf5340_audio/broadcast_sink).

and this example used a 16bit resolution.
could i changed that bit resolution to 24bit? 

The answer to this question may differ depending on which sample you are using, so please clarify if you mean to use the nRF5340 Audio application or the Broadcast Audio Sink Zephyr sample.

• One BIG, one of the two BIS streams (selectable).

then i have a question, is it a hardware limitation? or just fw limitation?

I am fairly certain that this is an application limitation, so I will double check this and reply properly when you clarify which sample you are asking about.

Best regards,

Maria

[heavyjo]

i'm sorry that confuse you.
i'm using first one, (zephyr/samples/bluetooth/bap_broadcast_sink). 

[Maria Gilje]

Hello,

Thank you for clarifying.

Maria Gilje said:

I am fairly certain that this is an application limitation, so I will double check this and reply properly when you clarify which sample you are asking about.

It is indeed an application limitation. The hardware limitation is in terms of CPU power, as the incoming streams need to be decoded. Our measurements estimates about 15% CPU load to decode one BIS.

could i changed that bit resolution to 24bit? 

You could. Do note that the LC3 codec acceps 24 bit samples, but truncates them to 16bit.

Best regards,

Maria

[heavyjo]

The Galaxy S23 Ultra Auracast broadcast, based on data analysis, uses a 40ms Presentation Delay (PD), LC3 codec, and two streams. From the Codec_Specific_Configuration[0], we can determine that it operates at 48kHz with a 10ms frame duration, but the channel information is not explicitly stated. However, the channel information is present within the stream details.

Using this Auracast broadcast, I configured the SINK with the following settings:
static const struct bt_audio_codec_cap codec_cap = BT_AUDIO_CODEC_CAP_LC3(
BT_AUDIO_CODEC_CAP_FREQ_24KHZ | BT_AUDIO_CODEC_CAP_FREQ_48KHZ | BT_AUDIO_CODEC_CAP_FREQ_96KHZ,
BT_AUDIO_CODEC_CAP_DURATION_10,
BT_AUDIO_CODEC_CAP_CHAN_COUNT_SUPPORT(2),
60u, 120u, // (1) BT_AUDIO_CODEC_CAP_DURATION_10
CONFIG_MAX_CODEC_FRAMES_PER_SDU,
(BT_AUDIO_CONTEXT_TYPE_MEDIA | BT_AUDIO_CONTEXT_TYPE_CONVERSATIONAL));

With this configuration, I attempted to receive the SINK audio through the example code. However, the RIGHT channel is not received at all, while the LEFT channel stream is received to some extent.

It does not appear to be a decoding issue, as removing the decoding process still does not resolve the problem—the right channel is simply not received.

Below is the reception log:
Stream 0x20003868: received 134000 total ISO packets: Valid 0 | Error 134000 | Loss 0
Stream 0x20001470: received 140000 total ISO packets: Valid 70767 | Error 69233 | Loss 0

[heavyjo]

I'm using nrf5340_audio_dk board & ncs2.9.0 & ( zephyr/samples/bluetooth/bap_broadcast_sink )

[heavyjo]

it works on 48khz mono.