Re: [Audacity-devel] Equalizer problem - Fixed (mostly)
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From: <xip...@xi...> - 2005-07-08 05:48:19
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On Thu, Jul 07, 2005 at 09:12:49PM -0400, Mar...@ao... wrote: > I agree with everything that has been said about IEEE754 should be good > enough for audio samples but that is not the issue here. I said it is the core > of the FFT that is the problem, further to that it is the bit that does the > DIT (decimation in time) butterflies and more specifically the way in which the > twiddle factors are calculated. So we *do* have a bad FFT? Even when there are so many reliable canned ones! I guess that makes at least four flaws. :-) I wrote the C DRFT in Netlib (well, not really; it's derived from the Fortran version) and gave a more modern copy of that FFT to Dominic last summer when he was trying to decide if FFTW's licensing issues were worth it. I thought that meant Audacity was already using either my FFT or FFTW... I was apparently wrong. Anyway, both behave respectably. Given that the full complex->complex FFT is a waste as the time domain signal is always real, we should simply replace it with a new drop-in. > than float? I suspect on modern machines it is very little. And who wants > to use a longer window than 16384? That's about 0.4 seconds of blurring > already! It's not blurring, it's applying a larger sinc kernel. That's a good thing, not bad :-) > Sorry for the rather long post, but I reserve the right to make > further long posts in the future! Feel free! This was a good one. Monty |