- From: Chris Rogers <crogers@google.com>
- Date: Tue, 18 Oct 2011 10:36:43 -0700
- To: Jussi Kalliokoski <jussi.kalliokoski@gmail.com>, public-audio@w3.org
- Message-ID: <CA+EzO0kj+qC+QEZWU9dztB2B-RXH5F2sXigsfdZ2h6QU1e+niQ@mail.gmail.com>
On Mon, Oct 17, 2011 at 11:28 PM, Jussi Kalliokoski < jussi.kalliokoski@gmail.com> wrote: > On Tue, Oct 18, 2011 at 3:47 AM, Chris Rogers <crogers@google.com> wrote: > >> >> >> On Mon, Oct 17, 2011 at 4:23 PM, Olli Pettay <Olli.Pettay@helsinki.fi>wrote: >> >>> On 10/14/2011 03:47 AM, Robert O'Callahan wrote: >>> >>> The big thing it doesn't have is a library of native effects like the >>>> Web Audio API has, although there is infrastructure for specifying named >>>> native effects and attaching effect parameters to streams. I would love >>>> to combine my proposal with the Web Audio effects. >>>> >>> >>> >>> As far as I see Web Audio doesn't actually specify the effects in any >>> way, I mean the algorithms, so having two implementations to do the >>> same thing would be more than lucky. That is not, IMO, something we >>> should expose to the web, at least not in the audio/media core API. >>> >> >> I'm a bit perplexed by this statement. The AudioNodes represent >> established audio building blocks used in audio engineering for decades. >> They have very mathematically precise algorithms. Audio engineering and >> computer music theory has a long tradition, and has been well studied. >> >> Chris >> > > I have to display my ignorance here, as I've yet to see a resource where > you'd have all these effects and their algorithms defined universally. I've > seen a lot of different implementations and even more algorithms for doing > these things, especially filters and reverbs. I haven't heard of a single > universally accepted algorithm for reverberation or spatialization. Makes > sense to say that for example a gain effect is standard, but even then > there's logarithmic gain effects and linear gain effects. The only things > that stand as standards in my mind are FFT and various window functions, > which aren't effects per se. Chris, maybe you can point us to a reference > where these effects are in fact defined in detail? > > Jussi > Convolution [1] [2] is the technique used for reverberation. It's defined with mathematical precision and allows a practically infinite number of reverberation (and other special effects) depending on the impulse response file used. Given a specific impulse response it generates an exact effect. For gain effects, the AudioGainNode can have its gain adjusted according to standard linear/log curves, or with completely arbitrary curves (which are precisely defined as values in an ArrayBuffer). Chris [1] http://en.wikipedia.org/wiki/Convolution [2] http://en.wikipedia.org/wiki/Convolution_reverb
Received on Tuesday, 18 October 2011 17:37:15 UTC