ADAU1466 - ASRC - is digital filtering involved?

Any form of sample rate conversion, whether synchronous or asynchronous, inherently involves digital filtering, specifically a low-pass (typically linear-phase FIR) filter to prevent aliasing. This is mandatory to ensure that, as long as the input signal of the sample rate conversion has negligible energy outside the passband of the filter, the output of the sample rate conversion represents the same signal.

This filtering is similar to the low-pass filtering (typically both digital and analog) done as part of A/D and D/A conversion, and indeed a sample rate converter can be viewed as an optimized simulation of a DAC (running at input sample rate) followed by an ADC (running at output sample rate), with the output filter of the DAC and the input filter of the ADC combined into one.

I also want to add to matthijs' great response that the ASRCs in our SigmaDSPs are all derived from the work that went into the design of the AD1896. We made some improvements but they were minor. So if you read that datasheet you will have a good idea of how the ASRCs in the SigmaDSP function.

I should also add that these are done in hardware like an accelerator. The sample rate conversion is done outside of the DSP core so no MIPS were used or harmed in the making of the new sample rate. ( a reference to movies saying that no animal were harmed... )

So it does not use any of the core's processing power to do the conversion.

Dave T