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From: Peng Liang on 18 Jun 2010 11:36
Hi experts,

I want to continuously get the data(speech) from microphone in MATLAB. I know I can use analoginput object. However, it seems only acquire data with limit time. time can be defined. for example, look at the following code:
% Create an analog input object to communicate with the % data acquisition device.
ai = analoginput('winsound');
addchannel(ai, 1);
% Configure the object to acquire 2 seconds of data at 8000 Hz.
Fs = 8000;
duration = 2;
set(ai, 'SampleRate', Fs);
set(ai, 'SamplesPerTrigger', duration*Fs);
% Start the acquisition and retrieve the data.
start(ai);
data = getdata(ai);

delete(ai);
clear ai;

it only can acquire 2 seconds of data with 8000Hz.

I need acquire continuously until I stop data acquisition.

anyone has idea how to achieve continuously data acquisition?

Thank you in advance.
From: Walter Roberson on 18 Jun 2010 13:58
Peng Liang wrote:

> I want to continuously get the data(speech) from microphone in MATLAB. I
> know I can use analoginput object. However, it seems only acquire data
> with limit time. time can be defined. for example, look at the following
> code:
> % Create an analog input object to communicate with the % data
> acquisition device.
> ai = analoginput('winsound');
> addchannel(ai, 1);
> % Configure the object to acquire 2 seconds of data at 8000 Hz.
> Fs = 8000;
> duration = 2;
> set(ai, 'SampleRate', Fs);
> set(ai, 'SamplesPerTrigger', duration*Fs);

That is not by time, that is by number of samples that works out to take that
amount of time.

> % Start the acquisition and retrieve the data.
> start(ai);
> data = getdata(ai);
>
> delete(ai);
> clear ai;
>
> it only can acquire 2 seconds of data with 8000Hz.
>
> I need acquire continuously until I stop data acquisition.
> anyone has idea how to achieve continuously data acquisition?

You cannot get continuous data acquisition, but you can set it to retrigger
and then you loop around getting a buffer-worth and dealing with that buffer.
From: Peng Liang on 18 Jun 2010 15:19
Walter Roberson <roberson(a)hushmail.com> wrote in message <hvgc8o$ehj$3(a)canopus.cc.umanitoba.ca>...
> Peng Liang wrote:
>
> > I want to continuously get the data(speech) from microphone in MATLAB. I
> > know I can use analoginput object. However, it seems only acquire data
> > with limit time. time can be defined. for example, look at the following
> > code:
> > % Create an analog input object to communicate with the % data
> > acquisition device.
> > ai = analoginput('winsound');
> > addchannel(ai, 1);
> > % Configure the object to acquire 2 seconds of data at 8000 Hz.
> > Fs = 8000;
> > duration = 2;
> > set(ai, 'SampleRate', Fs);
> > set(ai, 'SamplesPerTrigger', duration*Fs);
>
> That is not by time, that is by number of samples that works out to take that
> amount of time.
>
> > % Start the acquisition and retrieve the data.
> > start(ai);
> > data = getdata(ai);
> >
> > delete(ai);
> > clear ai;
> >
> > it only can acquire 2 seconds of data with 8000Hz.
> >
> > I need acquire continuously until I stop data acquisition.
> > anyone has idea how to achieve continuously data acquisition?
>
> You cannot get continuous data acquisition, but you can set it to retrigger
> and then you loop around getting a buffer-worth and dealing with that buffer.

Hi Walter,
Could you give more some details? Thank you!
From: Sherryl Radbil on 21 Jun 2010 13:50
Hi Peng Liang,
There is a new demo with Data Acquisition Toolbox in R2010a that shows this.
It is called: Continuous Acquisition Using Analog Input

To see it, in MATLAB R2010a and later execute:

>> showdemo('demoai_continuous')

See especially the section: Continuously Acquire Data until a Particular Condition Occurs

which uses
set(ai,'SamplesPerTrigger',Inf);
to set up the continuous acquisition.
A timer callback is also demonstrated. It looks for a particular condition and then stops the acquisition.

All the best,

Sherryl
From: Peng Liang on 22 Jun 2010 11:49
"Sherryl Radbil" <sherryl.radbil.dontspamme(a)mathworks.com> wrote in message <hvo8og$10p$1(a)fred.mathworks.com>...
> Hi Peng Liang,
> There is a new demo with Data Acquisition Toolbox in R2010a that shows this.
> It is called: Continuous Acquisition Using Analog Input
>
> To see it, in MATLAB R2010a and later execute:
>
> >> showdemo('demoai_continuous')
>
> See especially the section: Continuously Acquire Data until a Particular Condition Occurs
>
> which uses
> set(ai,'SamplesPerTrigger',Inf);
> to set up the continuous acquisition.
> A timer callback is also demonstrated. It looks for a particular condition and then stops the acquisition.
>
> All the best,
>

> Sherryl

Hi Sherryl.

Thank you for the information. unfortunately, I don't have MATLAB R2010a. I am using MATLAB 7.1 version. Is it possible to see that demo somewhere else?

Thank you
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