Somebody should edit the wiki entry, because it's really wrong... The details of HDCD have been released, and because it's a patented process, the details are available to anybody with the desire to get a copy of the patent!
In a nutshell, HDCD is a dynamic compressor, in the same vein as DBX or (to a slightly lesser extent) Dolby. The basic idea is the same, compress the dynamic range of the music for the recording media, then expand it during playback. The net result is lower distortion at amplitude extreme's, and a better signal to noise ratio. The biggest difference between HDCD and things like DBX, is that the de-compressor (or decoder) is controlled by a seperate control signal, not the amplitude of the signal itself. This was always DBX and Dolby's problem. If the playback amplitudes weren't properly calibrated, the whole system was thrown off. In the case of HDCD, the control signal is buried into the noise floor created by the dithering algorithm used when converting from 20 bits to 16. That's why a properly ripped HDCD retains the HDCD encoding. The control signal is buried in the LSB of the noise floor, you won't hear it, but a decoder that's looking for it's specific signature, will read it. The compression curves of HDCD were chosen as a compromise, to maximize the improvement in sound quality when properly decoded, but NOT to sound overly compressed when played back without proper decoding. Inspite of this, some producers like the compressed sound, and use the encoders hoping no one will actually use the decoder! Happy listening! Dave -- DCtoDaylight ------------------------------------------------------------------------ DCtoDaylight's Profile: http://forums.slimdevices.com/member.php?userid=7284 View this thread: http://forums.slimdevices.com/showthread.php?t=32967 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
