hoang@rex.cs.tulane.edu (Dzung Hoang) (09/27/89)
In article <1737@draken.nada.kth.se>, d88-jwa@nada.kth.se (Jon W{tte) writes: > The solution is to "fake" a higher sample pitch, causing the CD to > interpolate the samples between the actual samples. The waveform > now looks like this: (4-fold oversampling) . . . > And requres much less steep filters (typically 30 dB/octave) which means > no phase shifting. Good CD players use more bits in the output stage > than is recorded on the CD (i.e. 18 or 20 instead of 16) to get better > resolution in the oversampling if the variation between each sample is > small (i.e. low output) so that they don't have to interpolate 47 -> 48 > as 47 47 47 48 48 but could use 47 47.25 47.5 47.75 48 and thus get a > smoother, cleaner output. My DSP professor discussed CD oversampling and his explanation was different from the above in the details. Oversampling does not directly interpolate the sample values to 47 47.25 47.5, etc. Instead, 0's are inserted as appropriate between samples. The LPF takes care of recovering the signal. There is no distortion at all. Dzung Hoang -- ----------------------------------------------------------------------------- hoang@comus.cs.tulane.edu hoang@rex.cs.tulane.edu hoang@comus.UUCP hoang@rex.UUCP tulane!comus!hoang tulane!rex!hoang -----------------------------------------------------------------------------
jef@Apple.COM (Jonathan Flamm) (09/27/89)
In article <1122@rex.cs.tulane.edu> hoang@rex.UUCP (Dzung Hoang) writes: > My DSP professor discussed CD oversampling and his explanation was >different from the above in the details. Oversampling does not directly >interpolate the sample values to 47 47.25 47.5, etc. Instead, 0's are >inserted as appropriate between samples. The LPF takes care of recovering >the signal. There is no distortion at all. > >Dzung Hoang Actually zeroes are inserted but interpolation is performed using a digital filter -- hence the jargon "digital filtering" so prevelant on CD players. The LPF is done (as usual) in the analog domain and can be accomplished with a much shallower, more linear filter. At least this is what I believed to be true. Jonathan Flamm jef@apple.com