Waveform and queued buffers

[-Tobias-]

Hi,

I have to implement a waveform synthesizer. Finally, it should mix sine waves with different frequencies, and during runtime, these frequencies change. So I have to use queing, I think. The code below produces a nice, clear sound (sine wave) using a single buffer (see commented part). Using multiple buffers and the Queue/Unqueue mechanism as shown, the same simple sine wave sounds rippled/scratchy.

What is the reason for that?

Thanks a lot for your appreciated help,

Tobias

ALuint      uiBuffer;
ALuint      uiBuffers[2];
ALuint      uiSource;  
ALint       iState;
char data[BUFFERSIZE];
char data2[BUFFERSIZE];

// Initialize Framework
        ALFWInit();

        mexPrintf("PlayStatic Test Application\n");

        if (!ALFWInitOpenAL())
        {
                mexPrintf("Failed to initialize OpenAL\n");
                ALFWShutdown();
                return;
        }

        // Generate an AL Buffer
        //alGenBuffers( 1, &uiBuffer );
    alGenBuffers( 2, uiBuffers );


        alSourcei(uiSource, AL_LOOPING, AL_TRUE);
        double pi=3.141592654;
        //for (int z = 0; z< BUFFERSIZE; z++) data[z] = 100*sin((double)z*(2*pi)/1000.0);//+128;//+100*sin(z*(2*pi)/400.0);
   
    double freq = 80;    
    for (int z = 0; z< BUFFERSIZE; z++) data[z] = 100*sin(z*2*pi*freq/SAMPLEFREQ)+128;
    for (int z = 0; z< BUFFERSIZE; z++) data2[z] = 100*sin((BUFFERSIZE+z)*2*pi*freq/SAMPLEFREQ)+128;
       
               
        int i=1;

        //alBufferData(uiBuffer, AL_FORMAT_MONO8, data, sizeof(data), SAMPLEFREQ);    
    alBufferData(uiBuffers[0], AL_FORMAT_MONO8, data, sizeof(data), 11024);
    alBufferData(uiBuffers[1], AL_FORMAT_MONO8, data2, sizeof(data2), 11024);
       

        // Generate a Source to playback the Buffer
    alGenSources( 1, &uiSource );

        // Attach Source to Buffer
        //alSourcei( uiSource, AL_BUFFER, uiBuffer );    
    alSourceQueueBuffers(uiSource,2,uiBuffers);

        // Play Source
        //playIt(uiSource);

        mexPrintf("Playing Source ");
        alSourcePlay( uiSource );

        alGetSourcei( uiSource, AL_SOURCE_STATE, &iState);
        if (iState == AL_PLAYING)
                mexPrintf("confirmed!");

        if ((alGetError()) == AL_NO_ERROR)
                mexPrintf("No Errors!");

[-Tobias-]

Hi,

meanwhile, I switched to the ALUT routines to generate sound which works fine. No I still have the problem to change the queue content - I hear the sound (2 different buffers), but when I try to remove the last played one, I always get the information that there are no processed buffers...

mexPrintf("Initializing OpenAL...");
    if (!alutInit (NULL, NULL))
    {
        mexPrintf("Failed to initialize OpenAL\n");
        return;
    }else
        mexPrintf("done!\n");
   
    uiBuffers[0] = alutCreateBufferWaveform(ALUT_WAVEFORM_SINE, 60.0, 0.0, 0.1);
    uiBuffers[1] = alutCreateBufferWaveform(ALUT_WAVEFORM_SINE, 100.0, 0.0, 0.1);
   
    alGenSources( 1, &uiSource );
   
    alSourceQueueBuffers(uiSource,2,uiBuffers);
    alSourcei(uiSource, AL_LOOPING, AL_TRUE);
    alSourcePlay( uiSource );
   
    Sleep(1000);
   
    alGetSourcei(uiSource, AL_BUFFERS_QUEUED, &processed);
    mexPrintf("Number of loaded buffers: %i\n",processed);
   
    alGetSourcei(uiSource, AL_BUFFERS_PROCESSED, &processed);
    mexPrintf("Number of processed buffers: %i\n",processed);
    while(processed--)
    {
        ALuint buffer;
        mexPrintf("Unqueuing buffers...");
        alSourceUnqueueBuffers(uiSource, 1, &buffer);
        mexPrintf("done!\n");
        mexPrintf("Generate waveform...");
        uiBuffer = alutCreateBufferWaveform(ALUT_WAVEFORM_SINE, 1000.0, 0.0, 0.1);
        mexPrintf("done!\n");
        mexPrintf("Queuing buffers...");
        alSourceQueueBuffers(uiSource, 1, &buffer);
        mexPrintf("done!\n");
    }

Output:
Initializing OpenAL...done!
Number of loaded buffers: 2
Number of processed buffers: 0

What's the problem here?

Thanks a lot and best regards,

Tobias

[Daniel PEACOCK]

Hi Tobias,

The problem is that you have enabled Looping on the Source.   A looped
Source will never set queued buffers as processed because they are
effectively always pending in this scenario.    So, take this line ...

alSourcei(uiSource, AL_LOOPING, AL_TRUE);

out and the buffers will be marked as processed enabling you to unqueue
them.

Dan
Creative Labs (UK) Ltd.

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                                       Re: [Openal-devel] Waveform and    
             10/24/2008 07:09          queued buffers                      
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Hi,

meanwhile, I switched to the ALUT routines to generate sound which works
fine. No I still have the problem to change the queue content - I hear the
sound (2 different buffers), but when I try to remove the last played one,
I
always get the information that there are no processed buffers...

mexPrintf("Initializing OpenAL...");
    if (!alutInit (NULL, NULL))
    {
        mexPrintf("Failed to initialize OpenAL\n");
        return;
    }else
        mexPrintf("done!\n");

    uiBuffers[0] = alutCreateBufferWaveform(ALUT_WAVEFORM_SINE, 60.0, 0.0,
0.1);
    uiBuffers[1] = alutCreateBufferWaveform(ALUT_WAVEFORM_SINE, 100.0, 0.0,
0.1);

    alGenSources( 1, &uiSource );

    alSourceQueueBuffers(uiSource,2,uiBuffers);
    alSourcei(uiSource, AL_LOOPING, AL_TRUE);
    alSourcePlay( uiSource );

    Sleep(1000);

    alGetSourcei(uiSource, AL_BUFFERS_QUEUED, &processed);
    mexPrintf("Number of loaded buffers: %i\n",processed);

    alGetSourcei(uiSource, AL_BUFFERS_PROCESSED, &processed);
    mexPrintf("Number of processed buffers: %i\n",processed);
    while(processed--)
    {
        ALuint buffer;
        mexPrintf("Unqueuing buffers...");
        alSourceUnqueueBuffers(uiSource, 1, &buffer);
        mexPrintf("done!\n");
        mexPrintf("Generate waveform...");
        uiBuffer = alutCreateBufferWaveform(ALUT_WAVEFORM_SINE, 1000.0,
0.0,
0.1);
        mexPrintf("done!\n");
        mexPrintf("Queuing buffers...");
        alSourceQueueBuffers(uiSource, 1, &buffer);
        mexPrintf("done!\n");
    }

Output:
Initializing OpenAL...done!
Number of loaded buffers: 2
Number of processed buffers: 0

What's the problem here?

Thanks a lot and best regards,

Tobias

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