HDCD decoding

HDCD encodes the equivalent of 20 bits worth of data in a 16-bit digital audio signal by using custom dithering, audio filters, and some reversible amplitude and gain encoding (cit. en.wikipedia.org/wiki/High_Defi … le_Digital)

The problem is that when ripping HDCDs the PCM samples of 16 bit are stored in the file as they are, undecoded. Most DACs do not recognise the special HDCD encoding, thus not giving the user the extra dynamic promised by the HDCD format. Even worse the peaks are clipped and the sound sligtly distorted (see audiomisc.co.uk/HFN/HDCD/Enigma.html)

A nice feature for Volumio would be to recognize such format and perform the HDCD decoding on the fly, thus sending the “uncompressed” PCM stream 20/44.1 to the DAC.

It would be very nice feature, many country music CD’s from 1991-2005 use this format. Without decoding they sound flat and harsh. Be aware that there are CD’s with HDCD flag ON but no compression features used.