- From: Raymond Toy <rtoy@google.com>
- Date: Mon, 28 Nov 2011 13:47:42 -0800
- To: Alistair MacDonald <al@signedon.com>
- Cc: public-audio@w3.org
- Message-ID: <CAE3TgXEiU7_NNO9whTa+X0X+ZtBRz__1=qemddhZTn4LC+CrWQ@mail.gmail.com>
On Mon, Nov 28, 2011 at 11:39 AM, Alistair MacDonald <al@signedon.com>wrote: > Hi Group, > > While working with the Web Audio API at TPAC I was taking some notes. I > sent these to Chris Rogers and we started discussing this a few weeks back. > > Some of the technical discussion may be very useful / interesting to > people experimenting with the API, so I'm going to forward the thread to > public-audio here. > > At the bottom of the email I have attached the original notes I sent to > Chris. > > Comments/discussion always welcome, > >> >> P O S S I B L E - B U G S >> =========================== >> >> >> >> AudioParam ...RampToValueAtTime( 0, 0 ) >> --------------------------------------- >> >> Exponential ramps do not seem to work properly when starting using "zero" >> values. >> I would expect to hear the sound ramping in from 0 or out to 0, instead >> the >> transition appears to be immediate when it reaches the given time. Much >> like the >> behavior of the setValueAtTime() method. >> > > This is a consequence of the math behind exponential curves. You can > always have an exponentially increasing curve from > value1 -> value2 > > It's not clear from the webaudio docs what an exponential ramp should do, but we could define the ramp to be value1 + (value2-value1)*(1-exp(-t/C)) This will be an exponential ramp starting at value1 and asymptotically approaching value2. Two major differences: - 0 is valid starting point. - We never actually reach value2, but just get closer and closer. Ray
Received on Thursday, 1 December 2011 09:34:11 UTC