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Nordic Case Info
  • Case ID: 335996
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Popping sounds in Audio transfer

tommy

We are experiencing interruptions in the audio, with noise similar to popping sounds.

When observing the waveform on the spectrum analyzer during the audio interruptions, it appears to be operating with the correct protocol (PDU → ACK → CIE).

We suspect that the interruptions may be occurring because the RX is returning a CIE despite not correctly receiving the data, preventing retries.

Could we get Nordic’s perspective on this issue?
Additionally, is there any other log information that you need?

We will try to get it by SDK.

Figure.pdf

  • 0

    Hi, 

    Please move to the latest NCS like v2.7.0 or v2.8.0 (coming in this week).

    NCS v2.3.0 uses the PCFT controller, which might have minor issues with scheduling. SDC is well implemented and tested.

    Regards,
    Amanda H.

  • 0 in reply to Amanda Hsieh

    Amanda

    Thank you for your quick and clear answer.
    I would appreciate it.

    >NCS v2.3.0 uses the PCFT controller, which might have minor issues with scheduling. SDC is well implemented and tested.

    Could you let us know some more details about the cause and fact of this popping noise?

    How the PCFT controller contribute to it?
    And what is the difference in SDC between 2.3.0 and 2.8.0?

    Since we are under the production phase, would like to validate the effect of this issue.

    BR,

  • 0 in reply to tommy

    Hi, 

    Please let me share more details:

    1. For the popping noise, that might happen if the audio steam is not continuous, and suddenly there's nothing to play cause the energy drop in the speaker so we hear a popping noise
    2. The application should always expect a packet from the controller every 10ms, if the controller doesn't receive a packet from the peer side, then it should indicate the application has a "bad frame", and the application can use PLC (packet loss concealment) from LC3 to generate a frame to avoid the popping noise
    3. However, we do see the PCFT controller (especially the early version like the one in NCS v2.3.0) might have an issue handling this properly. There could be a chance the controller doesn't report the bad frame, so nothing for application to play, leads to the popping noise. 
    4. After NCS v2.6.0, we used our own SDC and deprecated PCFT controller, and also we improve the audio_datapath module a lot which should be able to handle this issue. You could make a trial with the latest NCS to evaluate it.

    Are you using the USB audio interface for the I2S interface? If so, there might be a chance that the USB audio interface is underrun.

    -Amanda H.

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