• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 32 subscribers
  • Views 614 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AIC3204 processing delay

Charles Oram
Intellectual 330 points
Other Parts Discussed in Thread: TLV320AIC3204

Hi,

I am using the TLV320AIC3204 codec in an application where I need to accurately detect the time of arrival of an audio signal. At 44.1 kHz sampling rate I seem to get a 0.5ms delay from starting to transmit the data to the audio signal appearing on the line out and a 0.5ms delay at the ADC (audio signal arriving at the MIC to available at McBSP receive register). At 32kHz sampling rate I get a 2ms delay from starting to transmit the data to the audio signal appearing on the line out and a 1.5ms delay at the ADC.

Can anyone tell me what exact delay I should expect to get? I expect that it should be related to the sampling rate, oversampling rate and maybe which signal processing clocks are enabled (I've got DOSR=128 and AOSR=128, PTM_R4, PRB_P1 and PRB_R1).

 

regards,

Charles

  • 0
    TI__Mastermind 46195 points

    Hello Charles,

    The delay you are observing is dominated by the group delay of the decimation (for ADC) or interpolation (for DAC) FIR filters. This delay is a function of both the sample rate and the decimation/interpolation filter that is selected. For example, ADC Filter A has a group delay of 17/Fs, as shown in page 51 of http://focus.ti.com/lit/ds/symlink/tlv320aic3204.pdf. This results in a decimation filter delay = 17/44.1k = 0.39ms.

    Regards,

    J-

     

  • 0 in reply to J-
    Intellectual 330 points

    Hi J,

    Thanks, I hadn't read the datasheet carefully enough to spot that figure in those tables.

    - Charles

  • 0 in reply to J-
    Genius 3735 points


    I am experiencing the same problems as Charles.  I also see a 2 ms delay between the commanded DAC output and when it actually appears at the output.  As far as I understand, this does NOT match the group delay specified for the interpolation filters.  Charles was using Filter A with a 32 kHz sample rate; he should have seen a 21 sample delay or 0.656 ms.  I am using Filter C with a 96 kHz sample rate; I expect to see 13 sample delay or 0.135 ms delay.  Instead I am seeing more like 192 samples of delay.

    Are there any recommendations on how to reduce this?  It is an application-killer.

     

  • 0 in reply to Bill Finger
    Prodigy 20 points

    I'm having a similar problem, though I've not worked too hard to fix the problem yet.  What is the smallest group delay we should expect to be able to get with this device when sampling at 48 KHz?  I'm currently getting 1ms from input to output on the C5515 eZDSP Stick (920-930 micro seconds to be exact) but would like to drop this to 100 micro seconds or lower if possible.