- From: Chuck Adams <cadams@fender.com>
- Date: Fri, 23 Mar 2012 13:18:22 -0700
- To: "Raymond Toy" <rtoy@google.com>, "Jussi Kalliokoski" <jussi.kalliokoski@gmail.com>
- Cc: "Wei, James" <james.wei@intel.com>, <public-audio@w3.org>
- Message-ID: <BA7323721D505F41BA5E5464FB3361AD059E3FD6@exchangeus.inside.fender>
Power of two isn't an arbitrary limit in the FFT, it's a fundamental piece of what makes it the Fast Fourier Transform. If you want an arbitrary number then you can't use the FFT algorithm, you need the discrete Fourier transform or the like. Chuck Adams Director - Fender R&D Fender Musical Instruments 17600 N. Perimeter Drive, Suite 100 Scottsdale, AZ 85255 (480) 845 5229 cadams@fender.com From: Raymond Toy [mailto:rtoy@google.com] Sent: Friday, March 23, 2012 9:34 AM To: Jussi Kalliokoski Cc: Wei, James; public-audio@w3.org Subject: Re: fftSize requirement for RealtimeAnalyserNode On Thu, Mar 22, 2012 at 4:36 PM, Jussi Kalliokoski <jussi.kalliokoski@gmail.com> wrote: On Thu, Mar 22, 2012 at 11:27 PM, Raymond Toy <rtoy@google.com> wrote: Do you have a specific need for a non-power of two analysis? I'm just curious. It just seems like an arbitrary limit. Most of the time, you probably want to set the length in seconds, not samples, and then you won't get a power-of-two. Yes, I'll agree that it's an arbitrary limit. And, yes, seconds (or more lilkely, fractions of a second) is probably more useful and scales better if the sample rate changes. Also, FFTW uses the GPL license, so if the browser is also not GPL, there are potential legal issues. This is where you go ask a lawyer. There are other ones as well (kissfft is BSD 3-clause for example, IIRC), but I don't think the licensing of certain FFT implementations is a valid argument to base the spec on. No, but you mentioned using FFTW in particular which has some licensing issues. Also, the algorithm isn't complex, you could implement it without a library. Agreed. But getting a fast one is complex. Thanks for the info, Ray CONFIDENTIALITY NOTICE: This e-mail and any accompanying documents contain confidential information intended for a specific individual purpose. This information is private and protected by law. If you are not the intended recipient, you are hereby notified that any disclosure, copying or distribution, or the taking of any action based on the contents of this information, is strictly prohibited. If you have received this transmission in error, please delete it. Thank you.
Received on Friday, 23 March 2012 20:18:54 UTC