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Audio equilizer on dskc6713

Gajendra Kanjikar
Prodigy 200 points
Other Parts Discussed in Thread: CCSTUDIO

hello. I am trying to implement a simple equilizer using three FIR filter -LPF, BPF and a HPF, on DSK6713 board using ccstudio v4.1.

The output audio I am getting is very noisy. I have generated filter coeffients using MATLAB. Here I have taken the sampli g frrequency to be 8k(for audio we take 44.1k). To start with I have put same input value to both the output channel i.e.,

l_output=l_input;

r_output=l_input;

The filter I have used is- FIR  equiripple, length=95.

When this program is being executed the ouput very noisy.

I would want to know what changes or points I should take in to considerations and what steps I need to take for the same.?

Your guidance would be very helpful       

Thanks in Advance

Here is the program -- 

 

*******************************************

 

#include

"C:\DSP\support\dsk6713.h"

#include

"C:\DSP\support\dsk6713_aic23.h"

#include

"stdlib.h"

#include

"math.h"

signed

int LPF_FIR_FILTER(float * h, signed int x);

signed

int FIR_FILTER(float * h, signed int x);

/*======================Filter coefficients for HPF==================*/

float

hpf_filter_coeff[] = {

-7.766913568768e-008,-9.900075428318e-008,3.080638964617e-007,8.794016247218e-007,

1.466105703614e-007,-2.727840495866e-006,-4.287748458356e-006,1.653975184879e-006,

1.343035552033e-005,1.393248613103e-005,-1.29494295252e-005,-4.792298807515e-005,

-3.385124117307e-005,5.583557349189e-005,0.0001374757463951,6.273970385775e-005,

-0.0001808335056419,-0.0003344524927968,-8.091876775644e-005,0.0004851618558757,

0.0007123341267946,2.824867858417e-005,-0.001131781408246,-0.001355991569058,

0.0002265270932089, 0.002364817437227, 0.002340122925688,-0.0009231574104267,

-0.004520961841846,-0.003698698120553, 0.002456578471041, 0.008050662131954,

0.005394101018351,-0.005457414095261, -0.01360120918768,-0.007298509665367,

0.01100837028542, 0.0223357072597, 0.00919910229859, -0.02142160819756,

-0.03721888296544, -0.01083194027653, 0.04401891383592, 0.07027814768834,

0.01193876307694, -0.1294732120043, -0.2806604136014, 0.654335881523,

-0.2806604136014, -0.1294732120043, 0.01193876307694, 0.07027814768834,

0.04401891383592, -0.01083194027653, -0.03721888296544, -0.02142160819756,

0.00919910229859, 0.0223357072597, 0.01100837028542,-0.007298509665367,

-0.01360120918768,-0.005457414095261, 0.005394101018351, 0.008050662131954,

0.002456578471041,-0.003698698120553,-0.004520961841846,-0.0009231574104267,

0.002340122925688, 0.002364817437227,0.0002265270932089,-0.001355991569058,

-0.001131781408246,2.824867858417e-005,0.0007123341267946,0.0004851618558757,

-8.091876775644e-005,-0.0003344524927968,-0.0001808335056419,6.273970385775e-005,

0.0001374757463951,5.583557349189e-005,-3.385124117307e-005,-4.792298807515e-005,

-1.29494295252e-005,1.393248613103e-005,1.343035552033e-005,1.653975184879e-006,

-4.287748458356e-006,-2.727840495866e-006,1.466105703614e-007,8.794016247218e-007,

3.080638964617e-007,-9.900075428318e-008,-7.766913568768e-008

};

/******************** filter coefficient for BPF********************/

float

bpf_filter_coeff[]= {

-0.006537049892988, -0.00101208566238,-0.0008631507053782,-0.0005495352514237,

-6.756668096198e-005,0.0005670380368977, 0.001326683358643, 0.002172645528609,

0.003054169964298, 0.003906847322553, 0.004666813430797, 0.005265488073615,

0.005640574492745, 0.005734972817922, 0.005510251480791, 0.004941306418854,

0.004028105944829, 0.002789236994392, 0.001270548884404,-0.0004642689154306,

-0.002327323061019,-0.004219805910315,-0.006029272984756,-0.007645202552779,

-0.008957950902011,-0.009874490389723, -0.01031667003304, -0.01023582652631,

-0.009608019794076,-0.008444236405394,-0.006784471358844,-0.004704956659893,

-0.0023057540843,0.0002869999489705, 0.002934425614991, 0.005491927339289,

0.007822443920869, 0.009792616061499, 0.01127858486869, 0.01221076200141,

0.01252925507263, 0.01221076200141, 0.01127858486869, 0.009792616061499,

0.007822443920869, 0.005491927339289, 0.002934425614991,0.0002869999489705,

-0.0023057540843,-0.004704956659893,-0.006784471358844,-0.008444236405394,

-0.009608019794076, -0.01023582652631, -0.01031667003304,-0.009874490389723,

-0.008957950902011,-0.007645202552779,-0.006029272984756,-0.004219805910315,

-0.002327323061019,-0.0004642689154306, 0.001270548884404, 0.002789236994392,

0.004028105944829, 0.004941306418854, 0.005510251480791, 0.005734972817922,

0.005640574492745, 0.005265488073615, 0.004666813430797, 0.003906847322553,

0.003054169964298, 0.002172645528609, 0.001326683358643,0.0005670380368977,

-6.756668096198e-005,-0.0005495352514237,-0.0008631507053782, -0.00101208566238,

-0.006537049892988

};

/*LPF coeff.*/

float

lpf_filter_coeff[]= {

2.334696805708e-008,-9.151950455956e-009,-2.780212797993e-008,-2.096266138452e-009,

2.737020404238e-008,-2.008316301565e-008,-1.182691890808e-007,-1.026271019745e-008,

5.0374790089e-007,7.796086425549e-007,-6.604602529232e-007,-3.532052789177e-006,

-2.867884858737e-006,6.43636366798e-006,1.632947128282e-005,3.821209750149e-006,

-3.621591938371e-005,-5.27357292705e-005,2.163092776587e-005,0.0001420263204344,

0.0001132482722209,-0.0001700046151373,-0.0004118453462941,-0.0001058255788768,

0.0006719033608461,0.0008882061515017,-0.0003109131030571,-0.001877683496101,

-0.001321429195181, 0.001878985090081, 0.004004549887244,0.0007771776518274,

-0.005664367063949,-0.006546957771539, 0.00268735441146, 0.01253627138426,

0.007476336480221, -0.01205209987099, -0.02230471651372,-0.002341674248763,

0.03165514635351, 0.03309889258194, -0.01873350186391, -0.07329291090865,

-0.04170537346808, 0.1079409274233, 0.2938449921914, 0.378339866313,

0.2938449921914, 0.1079409274233, -0.04170537346808, -0.07329291090865,

-0.01873350186391, 0.03309889258194, 0.03165514635351,-0.002341674248763,

-0.02230471651372, -0.01205209987099, 0.007476336480221, 0.01253627138426,

0.00268735441146,-0.006546957771539,-0.005664367063949,0.0007771776518274,

0.004004549887244, 0.001878985090081,-0.001321429195181,-0.001877683496101,

-0.0003109131030571,0.0008882061515017,0.0006719033608461,-0.0001058255788768,

-0.0004118453462941,-0.0001700046151373,0.0001132482722209,0.0001420263204344,

2.163092776587e-005,-5.27357292705e-005,-3.621591938371e-005,3.821209750149e-006,

1.632947128282e-005,6.43636366798e-006,-2.867884858737e-006,-3.532052789177e-006,

-6.604602529232e-007,7.796086425549e-007, 5.0374790089e-007,-1.026271019745e-008,

-1.182691890808e-007,-2.008316301565e-008,2.737020404238e-008,-2.096266138452e-009,

-2.780212797993e-008,-9.151950455956e-009,2.334696805708e-008

};

/*===========================================================*/

DSK6713_AIC23_Config configg = { \

0x0017,

/* 0 DSK6713_AIC23_LEFTINVOL Left line input channel volume */ \

0x0017,

/* 1 DSK6713_AIC23_RIGHTINVOL Right line input channel volume */\

0x00d8,

/* 2 DSK6713_AIC23_LEFTHPVOL Left channel headphone volume */ \

0x00d8,

/* 3 DSK6713_AIC23_RIGHTHPVOL Right channel headphone volume */ \

0x0011,

/* 4 DSK6713_AIC23_ANAPATH Analog audio path control */ \

0x0000,

/* 5 DSK6713_AIC23_DIGPATH Digital audio path control */ \

0x0000,

/* 6 DSK6713_AIC23_POWERDOWN Power down control */ \

0x0043,

/* 7 DSK6713_AIC23_DIGIF Digital audio interface format */ \

0x0081,

/* 8 DSK6713_AIC23_SAMPLERATE Sample rate control */ \

0x0001

/* 9 DSK6713_AIC23_DIGACT Digital interface activation */ \

};

void

main()

{

DSK6713_AIC23_CodecHandle hCodec;

Uint32 l_input, r_input,l_output, r_output,lpf_l_input,bpf_l_input,hpf_l_input;

/* Initialize the board support library, must be called first */

DSK6713_init();

/* Start the codec */

hCodec = DSK6713_AIC23_openCodec(0, &configg);

DSK6713_AIC23_setFreq(hCodec,6);

//***********************************************************

while(1)

{

/* Read a sample to the left channel */

while (!DSK6713_AIC23_read(hCodec, &l_input));

/* Read a sample to the right channel */

while (!DSK6713_AIC23_read(hCodec, &r_input));

/*#############################################################*/

lpf_l_input = FIR_FILTER(lpf_filter_coeff ,l_input);

// low frequencies

bpf_l_input = FIR_FILTER(&bpf_filter_coeff ,l_input);

//middle frequencies

hpf_l_input = FIR_FILTER(hpf_filter_coeff ,l_input);

//high frequencies

l_input=(hpf_l_input)+(hpf_l_input)+(bpf_l_input);

/*#############################################################*/

l_output=l_input;

r_output=l_input;

/*==========setting the gain===========*/

DSK6713_AIC23_outGain(hCodec, 0x79);

//========================================//

/* Send a sample to the left channel */

while (!DSK6713_AIC23_write(hCodec, l_output));

/* Send a sample to the right channel */

while (!DSK6713_AIC23_write(hCodec, r_output));

}

/* Close the codec */

DSK6713_AIC23_closeCodec(hCodec);

}

//************************************************************

signed

int FIR_FILTER(float * h, signed intx)

{

int in_buffer[95];

int

i=0;

signed

long output=0;

in_buffer[0] = x;

/* new input at buffer[0] */

for

(i=95;i>0;i--)

in_buffer[i] = in_buffer[i-1];

/* shuffle the buffer */

for

(i=0;i<95;i++)

output = output + h[i] * in_buffer[i];

return

(output);

}

*******************************************

  • 0
    TI__Guru* 84110 points

    Gajendra,

    If you replace the FIR filter with just a pure pass-through, do you get noisy output on your audio or is it clean?

    Regards,
    RandyP

  • 0 in reply to RandyP
    Prodigy 200 points

    When I have just a pure pass-through, the audio is very clear without noise( at 8khz sampling freq.). 

    But when I increase  sampling frequency from 8khz to 48khz it is giving a little noise. 

  • 0 in reply to Gajendra Kanjikar
    TI__Guru* 84110 points

    Gajendra,

    This is good that you have eliminated some of the possible problem points. It is always good practice to move in small steps and test the results at each point along the way.

    You have stated two different audio sampling frequencies, 44.1kHz and 48kHz. It should not matter in the long run, but details are important when you are building a system. The sampling frequency makes a big difference in the cut-off frequencies for your filters, so the sampling frequency is important to the sound of the results.

    Since you are talking about sampling rates at 8kHz, 44.1kHz, and 48kHz, I am not sure which is required for your project or which your filters are designed for. But you now have two possible directions to debug:

    1. Why do you get noisy output at the higher sampling frequencies?

    For this, look at the configuration of the ADC and DAC to find if there are any changes needed to support the higher frequencies. Then look at the input data buffers to find out where the noise is coming from. You may want to create a sine wave in the output buffer to hear if you get noise on the output when the output buffer has clean data; try different frequencies to be sure. You may want to use that clean sinewave output as input to the DSK then look at the input buffer to see if the input data is as clean as you expect.

    2. Get your filters working.

    Once you have fixed the bypass paths so that the input/output paths are working 100%, then you can start debugging your filters. Start with one at a time. Since they are FIR filters, start with a unity pulse (or slightly less than 1.0 to avoid overflow) and see if your code is causing problems. Shorten the length of the filter to see if the processing time is causing problems. If you have processing-time problems, make sure you are using the compiler's optimization settings, like the Release build configuration, but the Debug configuration may make it easier to do your debug if you can avoid that for now.

    Take small steps in building your system and debug it at each step to get things working right.

    Regards,
    RandyP

  • 0 in reply to RandyP
    Prodigy 200 points

    Thanks for reply Randy

                I think, the it would be good if implement audio equilizer using ping pong buffer implementation. But I am not very sure how to start from.

     It would be very helpful if you provide any link for that or useful information for the same.

     Thanks in Advance

  • 0 in reply to Gajendra Kanjikar
    TI__Guru* 84110 points

    Have you looked in the EDMA Reference Guide or the CSL examples?

    You may also learn a lot from the archived training classes. Search the TI Wiki Pages for "C6713 workshop" (no quotes).

    Regards,
    RandyP