What's USB, synchronous and asynchronous, implicit feedback, WDM and CoreAudio?
'Universal Serial Bus' (USB) is an external peripheral interface standard for data transmission. USB 1.1 and USB 2.0 'full speed' operate at 12Mbps and provides up to 8 uncompressed audio channels at 48kHz / 16bit.
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USB2.0 'high speed' (480Mbps), USB3.0 'superspeed' (5Gbps), USB3.1 'superspeed+' (10Gbps) and USB3.2 (20Gbps) offer higher samplerates, bitrates, lower latency and more audio channels.
So called synchronous designs derive the samplerates from the USB clock. This increases the compatibility. e.g. it works with any smartphone etc. On the downside the audio samplerate contains more jitter, as there's on-purpose jitter on the USB clock from 'clock spreading' technologies.
Asynchronous designs use samplerates from crystals, external masterclocks or audio PLLs. If not in implicit mode, an additional USB feedback endpoint reports the rounded current samplerate, relative to the USB frame clock.
Implicit feedback means the driver uses the number of sample frames in the input stream's packets to construct the packets for output streams. No feedback endpoint is required and perfect syncronisation is ensured. This had always been the concept of Ploytec drivers.
Polytec Sound Cards & Media Devices Drivers
Windows WDM 'Windows Driver Model' audio is a basic standard, even supported by Windows Mediaplayer.
Mac OS X and iOS provide an advanced Audio and MIDI system called Core Audio, being part of the operating system. Many USB audio interfaces are 'class compliant', work out of the box on the Mac and don't need additional drivers.
Still, for interfaces needing a driver, Ploytec supplies a USB Audio HAL-plugin driver for Mac OS X.