Hi Ron, let me try a little on this one. > I guess the process of copying audio and data from CD > doesn't introduce any opportunity to compromise the > sonic quality of the source. Am I right or wrong? Right, if it's done digitally and correctly. > Is what I am seeing clipping This is almost a philosophical question :-) Not knowing Rezound, I assume that it simply checks whether the sample values are just about to max out. For 16 bits, you have a range of -32768 to +32767, so the program might blink the red light for samples below -30000 or above +30000, for example. Rezound can not actually know if the signal has clipped - maybe it's recorded beautifully at full dynamic range. Of course, you can look at the waveform to see if it's flat on the peaks, but maybe it was meant to be that way - there are many strange musical aesthetics out there - the computer can not know. So to answer your question: The red light does not technically show clipping within the digital domain, but I would say that it is a strong indication that you did have clipping somewhere in your analogue path way back then. > Perhaps someone could provide a technical explanation > of clipping or a link to a definition. Hm, this is really quite simple, something like limiting of the signal due to the amplitude exceeding the dynamic range. If your original, full-scale samples x are clipped in a system with a range of -1 to +1, the clipped signal y will be y=-1 for x<-1 y=x for -1<=x<=1 y=1 for x>1 > What tools do you use for eliminating clipping that > already exists in a source? I don't care at all about > preventing the problem. Clipping means information loss, and you can not in general reconstruct the signal. There are all kinds of clever tricks to try to round off clipping, but they will always be fudges and not total cures. > For the moment I am using the Rezound Arbitrary Fir > Filter to identify the hz where the clips occur ?? clipping will affect all frequencies. Of course, depending upon your signal, the audible effect of this will be more serious on some frequencies. In general, clipping will add energy on high frequencies (for a pure sinusoid it will add harmonics). > performing a decibal cut on the problem range. Yes, it's not a bad idea to bandstop-filter bands which sound particularly nasty. > Reguardless of how detailed I get, there's > an audible consequence to eliminating the clips. Yep! > What's interesting about this specific set of clips is > that they are mostly inaudible. The clipping occurs > around 10kHz -> 15kHz and are almost all within the > high hat. This is a little strange. Althoug clipping generally adds high-frequency content (and can be dampened a little by a low-pass filter, effectively rounding off those nasty sharp bends in the curve), I would expect some goo below 10 kHz. Maybe it's masked by your music. > *how Rezound is configured to conclude that there are > clips See above > *should measuring for these types of problems be user > configurable or does a technical specification define > when a clip occurs ? > *can engineers safely ignore inaudible clips and tell > their clients ... not to worry Ha ha, they do all the time :-) > Is a Fir filter a good tool for addressing the problem > of digital clips or is there something better? There are special, "intelligent" tools out there (can anyone help us with names?), but no miracle cure. > Are there alternative Fir filter algorithms that > produce better results than the one being used in > Rezound? I haven't a clue what Rezound uses. Me neither, and there are all kinds of fir filters, but I doubt if any would be better at solving your problem. Dr. Oyvind Hammer Dinosaur researcher etc. University of Oslo
