From douglas at music.columbia.edu Thu Jan 1 00:00:01 2009 From: douglas at music.columbia.edu (douglas repetto) Date: Thu Jan 1 00:00:06 2009 Subject: [music-dsp] [admin] music-dsp FAQ Message-ID: <20090101050001.1A2B3152AB2@music.columbia.edu> Hi, Just a reminder that if you are new to the list you should read the music-dsp FAQ. It contains answers to both technical _and_ adminstrative questions that often come up on the list. If your question appears in the FAQ it is safe to assume that it has been discussed on the list many times in the past, and you should probably have a look through the list archives before posting your question to the list. http://music.columbia.edu/cmc/music-dsp/musicdspFAQ.html Also of interest to new and not-so-new list members: The music-dsp list archives http://music.columbia.edu/cmc/music-dsp/musicdsparchives.html The music-dsp source code archive http://www.musicdsp.org music-dsp books and reviews http://music.columbia.edu/cmc/music-dsp/dspbooks.html All this and more at: http://music.columbia.edu/cmc/music-dsp Hasta la pasta, douglas (this is an automated message sent out on the 1st and 15th of each month) From stygmate at gmail.com Sun Jan 4 20:52:25 2009 From: stygmate at gmail.com (Benjamin Derei) Date: Sun Jan 4 20:52:46 2009 Subject: [music-dsp] Overlap and save or ... Message-ID: what are the advantages and inconvenients of this two techniques: overlap and save , overlap and add ? Benjamin Derei From rbj at audioimagination.com Sun Jan 4 23:48:17 2009 From: rbj at audioimagination.com (robert bristow-johnson) Date: Sun Jan 4 23:48:33 2009 Subject: [music-dsp] Overlap and save or ... Message-ID: <20090105044817.E32552F8E0@ws6-3.us4.outblaze.com> > ----- Original Message ----- > From: "Benjamin Derei" > To: "A discussion list for music-related DSP" > Subject: [music-dsp] Overlap and save or ... > Date: Mon, 5 Jan 2009 02:52:25 +0100 > > > what are the advantages and inconveniences of these two techniques: overlap > and save , overlap and add ? i think, assuming they have the same FIR length and FFT size (so the frame hop is also the same) they both have the same number of complex multiplies per frame, but the overlap-save does not have the addition needed for the overlapping tails of adjacent frames (but has some copying that the overlap-add doesn't). now if you get real anal about the cost per sample... http://groups.google.com/group/comp.dsp/msg/85f5d2837a47ced2 http://groups.google.com/group/comp.dsp/msg/5af3612b9f0fa5e9 ... then it very well turn out that the optimally efficient choice for the FFT length N (as a function of your FIR length L and the cost function parameters, A,B,C,D) is different for overlap-save vs. overlap-add with the same FIR length L. but i would think that the computational cost for overlap-save would always be less than the counterpart overlap-add. now, maybe in overlap-save there are numerical "echoes" or little residuals of convolving around the likely nasty discontinuity between bins N-1 and 0 even in output samples that are "saved" and with the non-zero part of the impulse response not straddling that discontinuity. i think it's conceivable that, because of roundoff errors in the FFT where tiny numerical consequences of that straddle point propagate into the output samples that you save. that might be an issue if your word length is not good and long. the only time i ever did an overlap-add fast convolution was in college (and it was with the professor's code). on my own, i've only done the overlap-save and it's not too hard to do. i might even be able to scarf up a MATLAB file. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge." From douglas at music.columbia.edu Thu Jan 15 00:00:01 2009 From: douglas at music.columbia.edu (douglas repetto) Date: Thu Jan 15 00:00:05 2009 Subject: [music-dsp] [admin] music-dsp FAQ Message-ID: <20090115050001.4968C1B5BFC@music.columbia.edu> Hi, Just a reminder that if you are new to the list you should read the music-dsp FAQ. It contains answers to both technical _and_ adminstrative questions that often come up on the list. If your question appears in the FAQ it is safe to assume that it has been discussed on the list many times in the past, and you should probably have a look through the list archives before posting your question to the list. http://music.columbia.edu/cmc/music-dsp/musicdspFAQ.html Also of interest to new and not-so-new list members: The music-dsp list archives http://music.columbia.edu/cmc/music-dsp/musicdsparchives.html The music-dsp source code archive http://www.musicdsp.org music-dsp books and reviews http://music.columbia.edu/cmc/music-dsp/dspbooks.html All this and more at: http://music.columbia.edu/cmc/music-dsp Hasta la pasta, douglas (this is an automated message sent out on the 1st and 15th of each month)