Hi,
We are running audio loop back application on DM6446 using AIC23 codec, but
we are able to here some noise with the song.
Following point elaborates type and form of noise
1. Noise is of crackling type when heard.
2. The noise is not continuous. It is very much random in nature.
3. It is being heard in both the channels
Following are the things that we did in order to remove it.
1. Experiment : We Configured AIC23 registers with below configuration
ADDRESS REGISTER
Register address
Register Description
Register Value
0000000
Left line input channel volume control
0x17
0000001
Right line input channel volume control
0x17
0000010
Left channel headphone volume control
0x1F9
0000011
Right channel headphone volume control
0x1F9
0000100
Analog audio path control
0x12
0000101
Digital audio path control
0x01
0000110
Power down control
0x00
0000111
Digital audio interface format
0x12
0001000
Sample rate control
0x18
0001001
Digital interface activation
0x01
0001111
Reset register
0x00
Pls note that AIC23 is configured as
slave and McBSP is Master.
Also, Clock Mode is NORMAL Mode.
Result: No improvement
2. Experiment: Configured AIC23 in Bypass mode by setting Bypass bit
in Analog audio path Control to 1
Results: Was able to play song successfully without any crackling
noise.
3. Experiment: Checked receive buffer in driver for any garbage value.
The noise can be very well observed in the buffer at driver level only.
Reslult: the receive buffer contains noise which depicts that noise is
originated well at the lower levels.
4. Experiment: Clock settings
Result: BCLK - 1MHz for 32K stereo mode
LRCIN - 32 KHz
LRCOUT- 32 KHz
MCLK- 12.288 MHz
Note: When executing Player application(reading a file and playing it at
respective sampling rate), it is observed that noise does not exists.
It will be great if you can help me to reduce the noise.
Thank you in advanced.
Thanks,
[Sneha Shah]
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