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LAUNCHXL-CC1352P: The frequency response of mono audio signal is poor, but that of stereo audio signal is good.

Maokun.Liang
Intellectual 515 points
Part Number: LAUNCHXL-CC1352P
Other Parts Discussed in Thread: TLV320AIC3254

Hello, expert，

       We use project C:\ti\simplelink_audio_plugin_3_30_00_06\examples\rtos\CC1352P_2_LAUNCHXL\audio\audiohal_echo for testing. The project is analog audio input. The signal enters cc1352 after AD conversion, and the signal is sent directly from cc1352 to codec for DA conversion.We find that the frequency response of mono audio signal is worse than that of stereo audio signal. We only change one parameter, which is used to select mono and stereo audio signal.We have done experiments to verify that the codec chip has no problem.I would like to ask experts, whether other users have encountered the same problem, whether there is a solution. Figure 1 shows the frequency response of mono audio signal and Figure 2 shows the frequency response of stereo audio signal.

  • 0
    TI__Genius 14845 points

    Hi Maokun, 

    Apologies for the delay. I am trying to find a subject matter expert to help you with your issue. 

    Thanks, 
    Elin

  • 0
    TI__Guru** 101460 points

    Hi,

    This is an interesting observation, thank you for sharing. To be clear, is the issue related to the bandwidth or to the gain?

    Could you please specify how you are doing the tests? Which input are you using on the boosterpack (the microphone, the green input or the black one)? Are you using the same input for STEREO and MONO?

    To finish, my first impression is that an error has been made in the configuration of the codec (this is done in the file TLV320AIC3254.c). It probably worth looking at this :)

    Kind regards,

  • 0 in reply to Clément
    Intellectual 515 points

    Hello, Expert

    I did the experiment again today. The results are as follows:

    1. Only modify the definition of NUM_CHAN as AUDIOHAL_CHANNELS_MONO in the code.Connect the left and right channels of the lineout with a cable, and the audio signal frequency response curve will decrease in advance.If the left and right channels of the lineout are not connected by wires, the frequency response curve of the audio signal is good.

    2. Modify the definition of NUM_CHAN as AUDIOHAL_CHANNELS_MONO and add "AudioHalParams.invertMono= false" to the original code.No matter whether the left and right channels of lineout are disconnected or connected, the frequency response curve is good;

    3. The input side will have no effect whether the left and right channels are connected together or not.

    4.This result is independent of bandwidth and gain. we use green input.Use the same input for STEREO and MONO.

  • 0 in reply to Clément
    Intellectual 515 points

    Maybe it's not a problem.

  • 0 in reply to Elin W
    Intellectual 515 points

    thank you very much.