Patrick Dixon;130951 Wrote: > This is completely wrong - Upsampling/oversampling doesn't invent any > data! Interpolation is actually a filtering process which removes the > repeat spectra that are created by the upsampling/oversampling process. This thread seems to have developed in all kinds of directions since I last dropped in, but I wanted to try and clarify the point I was trying to make about the difference between oversampling and upsampling, and which Patrick has disagreed with.
1. Oversampling, as the term is generally used, is the process of adding extra data points (usually zeros) between the real data points. This has the effect of moving the repeat spectra higher up the frequency range, so they can be removed with a much gentler post-DAC filter. I think nobody is in dispute over this. 2. Upsampling, as the term is generally used, similarly involves adding extra data points. But instead of the normal zeros used in oversampling, interpolation is used. If that upsampled signal is then subsequently filtered in the same way as an oversampled one, the outcome is the same. But it is my understanding that this is *not* what is done. >From what I've read about upsamplers, the whole purpose is to use the results to feed a DAC running at the higher sampling rate, and to *retain* the additional high frequencies. If this is not the intention, then I have to ask what is the point of upsampling rather than oversampling? If you filter the results in the same way, it doesn't matter what the extra data points are. But if upsampled signals are indeed used to feed higher speed DACs, and the higher frequencies are retained, then I stand by my original point that the high frequency content (over and above that which would have been produced from a "normal" D/A process) is bogus. -- cliveb Performers -> dozens of mixers and effects -> clipped/hypercompressed mastering -> you think a few extra ps of jitter matters? ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=26685 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
