MATLAB Answers

0

audioplayer

Asked by Mr Smart on 17 Oct 2011
I made GUI in matlab to play .wav. But I have problem, at callback fcn. I put that code
[y,Fs] = wavread('signalExp01-22KHz.wav');
player=audioplayer(y,Fs);
play(player)
but that`s not work.
But I change like this
[y,Fs] = wavread('signalExp01-22KHz.wav');
sound(y,Fs);
that`s work. But I can`t stop music during playing.

  3 Comments

Walter Roberson
on 17 Oct 2011
What happened when you attempted to use audioplayer ?
Mr Smart on 18 Oct 2011
when I used audio player in GUI.. at callback ... it`s not work.. didn`t hear music.
Daniel Shub
on 18 Oct 2011
How are your planning on stopping the audioplayer? Have you implemented this yet? My guess is that you haven't. I think when you save the handle player so that your can stop the music, you will find that your current function will begin to work. See my answer about variable scope.

Sign in to comment.

2 Answers

Daniel Shub
Answer by Daniel Shub
on 17 Oct 2011
 Accepted Answer

The audioplayer object is "scoped". Once no more references to the handle exist, it stops playing and cleans up itself. See Loren's blog:
You need to save a copy of player someplace, but only long enough to let the sound play. You can use a timer with a callback to keep player in scope, and then have the timer callback delete player when it is done playing.
EDIT
Basically your variable player points to an audioplayer object. When there are no variables in memory that point to that audioplayer object, MATLAB deletes the object. MATLAB automatically takes care of the memory management. Your player variable gets deleted when your callback function exits (again MATLAB is taking care of the memory management). The key then is to either prevent your callback function from exiting until after the playing has finished or make sure a copy of player is "saved" someplace else.
The easiest is probably to replace
play(player)
with
playblocking(player)
A slightly better solution might be to do
play(player);
pause(max(size(y))/Fs);
The playblocking method will potentially block everything including callbacks. The pause method will allow callbacks to be processed. Both these methods, however, will halt the linear flow of the program until after the playback has finished. There are ways around this, but it depends on your program (see my comment to your question).

  3 Comments

Mr Smart on 18 Oct 2011
If you can help...explain detail me how to do it..I don`t know scope.
Daniel Shub
on 18 Oct 2011
See my edit.
Mr Smart on 22 Oct 2011
Thanks , that`s work>> play(player);
pause(max(size(y))/Fs);<<
But I can`t stop and pause song during play,when I click Close Button and Toogle Button.For toogle button>> function togglebutton1_Callback(hObject, eventdata, handles)
[s,Fs] = wavread('signalExp01-22KHz.wav');
player=audioplayer(s,Fs);
play (player);
state=get(handles.togglebutton1,'Value');
if state == 1
set(handles.togglebutton1,'String','Pause');
resume(player);
else
pause(player);
set(handles.togglebutton1,'String','Play');
end <<

Sign in to comment.


Jan
Answer by Jan
on 22 Oct 2011

You can store the AudioPlayer object persistently:
function MyBeep
persistent AP
Play_Data = [sin(1:.6:400), sin(1:.7:400), sin(1:.4:400)]);
AP = audioplayer(Play_Data(:), 22050);
play(AP);
This does not block the execution and allows to stop the sound remotely - with implementing further logic in form of inputs. Drawback: This produces a crashdump when the Matlab session is closed in Matlab 6.5 and 2011b, although there is no problem in e.g. 2009a.
I've tried to use the callback of the AudioPlayer's StopFcn to delete the object after playing, but this let MATLAB crash also. I've reported this to the technical support already.

  1 Comment

Mr Smart on 22 Oct 2011
Thanks for helping Mr.Jan Simon

Sign in to comment.