Subject: Re: onset detection From: DeLiang Wang <dwang@xxxxxxxx> Date: Thu, 27 Dec 2007 10:04:16 -0500 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>The CASA book edited by Guy Brown and myself (Wiley/IEEE Press, 2006) has a general discussion on onset and offset detection and its connection to edge detection in image analysis (Chapter 3). Holiday greetings, DeLiang Wang Andrew McGuiness wrote: >Thanks, Bob. I had another look at your ""Smooth" Rhythms" paper and found it quite interesting. >In fact, the negative-going zero crossing of the 2nd derivative of energy is just the highest >point of the peak of the 1st derivative (ie. the 'steepest slope' that I mentioned in the second >par of my post: "Having found the general area of the onset, the script looks for the > steepest point in the energy curve of the upper partials of the sound, to identify the precise >point of onset." Your method will work fine on smooth energy curves with one peak per onset, but >not for fine discrimination on an audio file which is a bit messy (say, one instrument in a >drumkit, recorded in an ensemble situation). I was pleased to find that you located the P-center >at the peak of the 1st derivative though. > > > > >>Andy, >> >> For a counter example, you might look at an old paper of mine, =20= >> >>=93Smooth=94 Rhythms as Probes of Entrainment,=94 _Music Perception_ 10 =20= >> >>(1993): 503-508 (<http://faculty-web.at.northwestern.edu/music/=20 >>gjerdingen/Papers/PubPapers/SmoothRhythms.pdf>). There the perceived =20 >>onsets occur at positive-to-negative zero crossings of the second =20 >>derivative of energy. This would be in a region of all positive =20 >>slope, if I'm not misunderstanding your method. >> >>Best wishes for the Holidays, >>Bob Gjerdingen >>Northwestern Univ. School of Music= >> >> >> > >hi Nick - Of course I had already looked (although briefly) at the Mirex stuff, but it didn't meet >my needs. I needed a finer-grained discrimination than 50 milliseconds. On the other hand, I don't >need to find onsets in real time (as you did with your work) and I can put up with a few false >positives (which I can remove by hand). You're prob right, though, about there not being a simple >relation between onset and PAT - I just thought there might have been something I hadn't come >across yet. > >Andy > > >>------------------------------ >> >>Date: Wed, 26 Dec 2007 19:06:50 +0000 >>From: Nick Collins <nc272@xxxxxxxx> >>Subject: Re: onset detection >> >>Hi Andy, >> >>You'll probably want to look into the large literature on onset detection >>algorithms, perhaps starting from the MIREX competitions? >> >>I've linked the most recent here: >> >>http://www.music-ir.org/mirex/2007/index.php/Audio_Onset_Detection_Results >> >>Onset detection based on overall energy change over 100 msec blocks is not >>necessarily a very general strategy. Further, p-centre is potentially a >>rather complicated phenomena with a further literature and not to be >>confounded with physical onset detection. Not sure you'll find a simple >>relation between perceptual and physical onset based on a simple single >>band energy change detection function, especially over a variety of >>timbres. >> >>best, >>Nick >> >> >> >>--On 26 December 2007 11:31:05 -0600 robert gjerdingen >><r-gjerdingen@xxxxxxxx> wrote: >> >> >> >>>On Dec 25, 2007, at 5:57 AM, Andrew McGuiness wrote: >>> >>> >>> >>>>First, the script looks for negative slope in the energy curve of >>>>the sound, with energy calculate by averaging 100 millisecond >>>>blocks, to eliminate very local fluctuations. If the sound file is >>>>recorded clean, with no spill, this works well to identify the >>>>general area of the onset. >>>> >>>> >>>> >>------------------------------ >> >>End of AUDITORY Digest - 25 Dec 2007 to 26 Dec 2007 (#2007-295) >>*************************************************************** >> >> >> > > > > Make the switch to the world's best email. Get the new Yahoo!7 Mail now. www.yahoo7.com.au/worldsbestemail > > > > -- ------------------------------------------------------------ Prof. DeLiang Wang Department of Computer Science and Engineering The Ohio State University 2015 Neil Ave. Columbus, OH 43210-1277, U.S.A. Phone: 614-292-6827 (OFFICE); 614-292-7402 (LAB) Fax: 614-292-2911 URL: http://www.cse.ohio-state.edu/~dwang