Playrec - Forum

What you want to do is possible, you will just need to be slightly clever in how you do it!

The Playrec command 'play' returns a unique page number that is associated with the frame of audio that you supplied.  The 'isFinished' command can take an optional parameter which is a page number.  When a page number is supplied it tells you whether that page (or frame as you're calling them) of samples has finished.  The 'block' command is similar in that it can be made to wait until a particular page has finished rather than all pages queued up.

Here's a rough flow to get you going:

1) Send multiple frames to Playrec one after the other (don't wait for them to complete).  As you are only playing this can be any number (maybe try 10 or so initially), just make sure it's large enough to avoid glitches (found through trial and error!).  Keep a record of the page number returned for each frame.

2) Display the graph for the first frame of samples

3) Wait for the first page to complete (this is why you need to keep track of the page numbers returned!).

4) Send Playrec the next frame of samples continuing from where you got to, again keeping a record of the page number returned.

5) Loop back to (2) but this time display the graph for the second frame of samples.

Note how you're displaying graphs for frames you sent to Playrec a little while previously.  Playrec needs to have the next frame of samples before the previous frame finishes to avoid audible glitches...but this doesn't mean you have to display the graph for that frame!

If you look at the play_wav.m file in the example scripts download then this shows how to play a wav file using multiple pages. It waits for the first page in the list of pages sent to Playrec to finish before sending another one to add to the end of the list.  You could potentially use this file as a starting point, modifying it as follows:

    if(length(pageNumList) > pageBufCount)
        if(runMaxSpeed)
            while(playrec('isFinished', pageNumList(1)) == 0)
            end
        else       
            playrec('block', pageNumList(1));
        end

        pageNumList = pageNumList(2:end);

<Add your code here to display the graphs.  The first time this code is run you should display the graph for the SECOND frame - the first frame should be displayed before the outer for loop starts.  The next time the code is run it should display the graph for the 3rd frame and so on.>

    end

I hope this helps - please let me know how you get on.