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Urgent: please help me. Audio Codec on OMAP-L137

Jack Kilbey
Intellectual 450 points
Other Parts Discussed in Thread: TLV320AIC3106, OMAP-L137

Hi,

I am working on Audio Codec (TLV320AIC3106) that is available on OMAP-L137 board. The input of the codec via "Line in" input is a clean sinusoid wave  without any noise. I read the data from codec in ARM and write the same data to "Line out" by PCM library. The output is very noisy in spite of clean input. I tried to set the parameters of the codec by "amixer" instruction to decrease the noise but the output did not changed. Although I tried any scenario, but the noise was the same. I read the codec datasheet many times but I could not find any thing. I thought the effects (de-emphasis, 3-D, ...) may be the main reason of this chaos so I changed the co-efficient of them by amixer instruction to set their transfer functions H(z)=1.

Is there any other way to disable this effects?

Why is the output very noisy?

I am confused. I really do not know why the output is noisy?!!!!! :-(

  • 0
    TI__Mastermind 43955 points

    Hi Jack,

    Moving your post to Multimedia software codec forum to get appropriate response.

     

    Regards,

    Shankari.

  • 0 in reply to Shankari G
    Intellectual 830 points

    This noise is OUT-BAND noise!

    Your scope works in the bandwidth more than 20 kHz. But pdf on TLV320AIC3106 guarantees the SNR in the bandwidth 20 kHz.

    If you connect HP output of You board with input of a Sound Card of PC and on this PC launch any virtual scope (as audiotester, for example), you will see CLEAR SIGNAL.

    SO: if DAC TLV320AIC3106 drives some devices, which are sensitive to signals in bandwidth more then 20 kHz, the output signal of codec must be filtered by analog LPF with cutoff frequency 20 kHz.

    Is it helps? Becomes output signal clearer if you limit the bandwidth of analyser to 20 kHz?

    Best Regards Vitalii