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  • Case ID: 327098
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Are there any ISO packets thransferred when the BIS gateway pauses playback?

Tommy_Li

Dear All,

I need your help to clarify some LE Audio protocol related concepts.

For the BIS use cases. When the PC pause the playback, after that, are there any ISO packets transfered by the BIS gateway.

or some empty iso packets? 

And I want to know is there any plan for the Nordic to upgrade the nrf sniffer tool to support LE Audio related features.

Best Regards.

Tommy.

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  • 0

    Hello Tommy,

    Having had a quick look at our audio app, pausing the stream leads to bt_cap_initiator_broadcast_audio_stop() which I think stops the stream. Are you thinking of this in more of a general sense? Like if having a BIS stream stopped implies that there are no ISO packets?

    And I want to know is there any plan for the Nordic to upgrade the nrf sniffer tool to support LE Audio related features.

    That is unfortunately what I would call a question about upcoming plans. I unfortunately can't comment on this myself, but if you contact your local RSM he might be able to talk about this. Let me know if you do not know who your local RSM is, so that I can give you his contact info. Though as of now the sniffer software that we provide does not support this.

    Regards,

    Elfving

  • 0 in reply to Elfving

    Hi Elfving,

    Thanks for your reply.

    Then function you mentioned above is triggered by the broadcast_source_stop which is triggered by the  BUTTON_PAUSE_EVENT(play/pause btn on the audio dk) 

    In my case, for the broadcast gateway side,  I connected it to the PC through the USB port.

    The broadcast geteway device functioned as  a usb audio device.

    When I palyed a song using a media player on the PC, the sound was played back normally from the broadcast headset side.

    At this moment, I press the pause button on the media player (not the audio dk board), the function you mentioned will not be triggered.

    I just wonder whether there is audio data transfered from the PC to the broadcast gateway board.

    and Whether there is ios packet transfered from Broadcast gateway side to the Boradcast headset side.

    The reason why i ask this question is when i tested the lc3 playback from the sdcard on the broadcast headside side.

    I need let the broadcast headset side synchronize to the broadcast gateway side.

    And then i can play the lc3 on the broadcast headset side normally.

    When i investigated the code, i found that there was a pcm mix action between iso packets and pcm data which was decoded from the lc3 read from sdcard.

     

    and i found that although the broadcast gateway side didn't play anything, the broadcast headset side can play lc3 normally.

    It meant that the sd_card_playback_mix_with_stream function was called periodically.

    It meant that the ble_fifo_rx buffer will be filled with ios packets from the controller periodically, even though the broadcast gateway side didn't play anything.

    and it made me confused.

    Best Regards.

    Tommy.

  • +1 in reply to Tommy_Li

    Sorry about the wait Tommy,

    I asked the relevant R&D team just to be sure. The BIS gateway won't send ISO packets contains PCM with "0"s if there's no stream playing from PC. Here is a sniffer trace showing this: 

    The payload size of the BIS ISO packets is "0". Same device, but after we press "play/pause" for stop sending BIS ISO packets we get this.

    So there's no ISO, but only EXT-ADV and PER-ADV packets.

    For SD card mix and play feature, that is in receiver side, if the receiver is in play state, then user can enter command for triggering "play lc3" from file, and that will trigger the decoding, then mixing to I2S buffer.

    Regards,

    Elfving

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  • +1 in reply to Tommy_Li

    Sorry about the wait Tommy,

    I asked the relevant R&D team just to be sure. The BIS gateway won't send ISO packets contains PCM with "0"s if there's no stream playing from PC. Here is a sniffer trace showing this: 

    The payload size of the BIS ISO packets is "0". Same device, but after we press "play/pause" for stop sending BIS ISO packets we get this.

    So there's no ISO, but only EXT-ADV and PER-ADV packets.

    For SD card mix and play feature, that is in receiver side, if the receiver is in play state, then user can enter command for triggering "play lc3" from file, and that will trigger the decoding, then mixing to I2S buffer.

    Regards,

    Elfving

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