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TLV320AIC3120: Clipping noise issue: Recommended register setting

Shota Mago
Expert 6800 points
Part Number: TLV320AIC3120

Hi team,

My customer has trouble of noise clipping(cracked) when playing back sound recorded with the TLV320AIC3120's microphone input.

They consider to adjust following register setting for recording. 

Is there any suggestion for recommended setting for these registers or any other register which should be optimized?

=======================

Table 7-117. Page 0 / Register 86 (0x56): AGC Control 1                  - p100

Table 7-118. Page 0 / Register 87 (0x57): AGC Control 2                  - p100

Table 7-119. Page 0 / Register 88 (0x58): AGC Maximum Gain               - p101

Table 7-120. Page 0 / Register 89 (0x59): AGC Attack Time                - p101

Table 7-121. Page 0 / Register 90 (0x5A): AGC Decay Time                 - p101

Table 7-122. Page 0 / Register 91 (0x5B): AGC Noise Debounce             - p101

Table 7-122. Page 0 / Register 91 (0x5B): AGC Noise Debounce (continued) - p102

Table 7-123. Page 0 / Register 92 (0x5C): AGC Signal Debounce            - p102

Table 7-124. Page 0 / Register 93 (0x5D): AGC Gain-Applied Reading       - p102

 

Table 7-161. Page-4 Registers              - p111

Table 7-161. Page-4 Registers (continued)  - p112 

Table 7-161. Page-4 Registers (continued)  - p113 

Table 7-161. Page-4 Registers (continued)  - p114 

=======================

Best regards,

Shota Mago

  • 0
    TI__Genius 15985 points

    Hello Mago-san,

    Thank you for reaching out.

    If the issue of clipping is the result of a large spike in the desired audio signal, then the AGC feature is a good place to start. Please see the app note on Using the AGC,DRC and Beep generator Function in TLV320AIC3204/3254/3100/3110/31. Dynamic Range compression (DRC) is another useful feature that would be helpful in processing the input signal (also covered in the app note).

    Let me know if you have any questions.

    Best,
    Andrew

  • 0
    Prodigy 30 points

    Dear Andrew-san

    Nice to meet you, I'm IWASAKI.

    Thank you for your repray.
    The current problem is not noise clipping, but I would like to know the settings for reduce the terrible crackling playback sound. Therefore, I would like to hear more about the setting of "ADC First-Order IIR Filter Coefficients" in register 4. Also, SampleCode's AGC, DRC, and BeepGenerator values are for a sampling frequency of 44.1kHz, but we use a sampling frequency of 12kHz. Can you tell me the "ADC First-Order IIR Filter Coefficients" setting in register 4 at this sampling?

  • 0 in reply to Taichi Iwasaki
    TI__Genius 15985 points

    Hello Iwasaki-san, 

    Thank you for the additional information. I am assuming that the crackling noise is seen at the input of the CODEC. 

    For more information on calculating filter coefficients see the related posts below: 

    1. Tool to calculate the IIR and BiQuad filters coefficients - COEFFICIENT-CALC Calculation tool | TI.com
    2. (+) TLV320AIC3204: First-Order IIR Filter Coefficients for ADC - Audio forum - Audio - TI E2E support forums

    The above links should help calculate the coefficients shown in Table 7-13. ADC First-Order IIR Filter Coefficients

    With Regards to "AGC, DRC, and BeepGenerator values ... for a sampling frequency... of 12kHz",: 

    • The results for these features are dependent on the sample rate (Fs) of given to the CODEC. As a result, the script may not need change from the example, but the values for these features will have to be recalculated for an Fs of 12kHz. 
    • The scripts in the app note will be a good starting point but the specific values will need to be tuned to the application.  

    I hope this helps. Let me know if you have further questions.

    Best,
    Andrew