It is a proprietary audio interface for transferring compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controller, to a compatible computer monitor, video projector, digital television, or digital audio device. HDMI is a digital replacement for analog video standards.
nanoAVR is the miniDSP Home Theater Series of 8-channel HDMI audio processors for home theater tuning. Bass management and parametric EQ, or Dirac Live® digital room correction (nanoAVR HD/HDA/DL).
(Source: wikipedia.org)