Resample between 2 unsyncronised sources

I have been working on a live mixer for some time. Using a Dante network card and asio drivers I need to output audio locally so would like to output the result usb device for monitoring. SInce the clocks are not synchronized I am looking at the resampling audio class and use it like zita-resampler.

The resampling ratio will calculated based all call back timing so the 2 device drivers. But I am unclear how to setup the audio source. The source is simply a data buffer provided to the asio callback. It seems this data should be provided to the AudioSource so the resampler can provide the data to getNextAudioBlock for the output device callback.

If this is correct, how is the data provided to the AudioSource. Or am I completely off track here?