Strange behavior of ADAU144x

Hi TomY,

It looks like you are using different sample rates on the input and output. Without sample rate converters, this will not be possible. It is important to note that sample rate converters use digital filters in order to properly process data, so the output stream of an ASRC will not be a bit-accurate match of the input data stream; the filters will have an effect on the data and introduce slight delay and some differences on the order of a few LSBs. This is true of any ASRC, not just the ones inside the ADAU144x. That being said, if you test the ASRCs with any audio source, you should see performance somewhere in the neighborhood of 140 dB SNR and -130 dB THD+N, which out-perform the audio converters by a great margin and should be acceptable in any audio system.

I hope this answers your question.

Hi, BrettG

Thank you for your reply.

It looks like you are using different sample rates on the input and

output.

Without sample rate converters, this will not be possible.

It is important to note that sample rate converters use digital filters

in order to properly process data,

so the output stream of an ASRC will not be a bit-accurate match of the

input data stream;

the filters will have an effect on the data and introduce slight delay

and some differences on the order of a few LSBs.

Yes, it is difference sample rate between Input and Output.

So, I know that the routing should be done via ASRC.

And I could understand that the input data and the output data is not be a

bit-accurate match by ASRC digital filter.

However, I am seeing the phenomenon that the data breaks by the different

of Input format.

For the details, please refer to the sheet "20120528" of the attachment

file.

And one more, could you comment about

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Re: Strange behavior of ADAU144x

created by BrettG in SigmaDSP Processors and Development Tools - View the

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Hi TomY,

It looks like you are using different sample rates on the input and

output. Without sample rate converters, this will not be possible. It is

important to note that sample rate converters use digital filters in order

to properly process data, so the output stream of an ASRC will not be a

bit-accurate match of the input data stream; the filters will have an

effect on the data and introduce slight delay and some differences on the

order of a few LSBs. This is true of any ASRC, not just the ones inside

the ADAU144x. That being said, if you test the ASRCs with any audio

source, you should see performance somewhere in the neighborhood of 140 dB

SNR and -130 dB THD+N, which out-perform the audio converters by a great

margin and should be acceptable in any audio system.

I hope this answers your question.

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Hi TomY,

When you change the input format to left-justified, are you also configuring the ADAU144x's serial port registers for left-justified mode? I have attempted to use left-justified on the evaluation board (using the Audio Precision PSIA as an I2S source), and the data is correctly appearing at the DAC output.

Hi, BrettG

Thank you for your reply.

As I talked as follows, the input format was not correct in this behavior.
https://ez.analog.com/message/52323#52323

I'll confirm the behavior using correct input format (64Fs), again.

Best Regards,

TomY

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