declip.exe win32 (CuteStudio Ltd)
Reply #3 – 2007-08-09 09:32:05
Thanks Dynamic, it's very useful to have some feedback on this article as it is quire near 'written once' status. Nyquist This may be down to my ignorance, but this problem still puzzles me: 22.05kHz, assuming we have a perfect clock and perfect sinusoidal waveform, how do we represent a (for instance) 1024 level waveform? It peaks at +512 and -512, which is fine. But what if that signal is really a slightly phase shifted one (30 degrees perhaps) which IIRC was originally at +1024 and -1024 peaks. In the digital domain it may look like a perfect 22.05kHz signal but who is to say it is not a different amplitude at a slightly different phase? Going from 96kHz to 44.1 (eg) has to deal with this, integrating may simply create an average amplitude and phase which will still not be the same as the original.Grainy sound The Dynamic range is extremely bad wording on my part, what I'm trying to say here is that the linear and log scale conversion causes problems with the 16bit CDs for quiet passages (not an issue with modern pop!). For instance, if you have a trailing cymbal sound that goes to -50dB below the normal music level then that sound will use 0.003162 of the DAC scale. If the RMS loudness of the music was -6dB below full scale (0dB) anyway (i.e. the CD is not clipped) then the actual 16bit level will be -56dB or 0.001585 of 65536 levels = 103.87456 levels. This corresponds to slightly less than roughly to 7bits of resolution, in the 24bit world you'd still have almost 15bits at this level. Maybe grainy is the wrong word - but you run out of bits very fast on quiet areas, I know dither can help in the midrange but 16bits is still rather tight compared to analog. Maybe it's just the vinyl hiss but for me vinyl always sounds 'softer' or 'sweeter' on very quiet parts than the CD.Down-converting I agree that the music can still be respectable here, certainly CDs made by Hi-Fi manufacturers seem to be pretty good, although I'm not a personal fan of dither as I can't see it doing much to help the high frequencies.Dark side of the music Industry I'm disappointed that Dark Side of The Moon has been squashed - if Floyd gets squashed on the new 'high quality' iTunes then that's game over for everything. Most annoying.MP3 compression[] MP3s and compression - don't know how I said dynamic compression for MP3, typo/editing artifact - corrected! It probably came from the view that if a CD is compressed and clipped anyway, an MP3 will hardly sound any worse. Thanks for the comments, I'll amend the page accordingly (still not sure about the phase differenciation of a 22.05kHz tone though )