C - simultaneous audio input and output using portaudio and callback function

0
votes

I am trying to make a full duplex audio program that detects audio input from the mic and direct it to the speaker in real time using portaudio library and callback function but I keep getting errors. I tried to open a full input output stream then starting the read from the mic and send the captured data to a callback function that will start the streaming of audio to the speaker Can anyone help me with this ?? Here is the errors:

ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
Output device # 14.
Output LL: 0.00870748 s
Output HL: 0.0348299 s
Now recording!!
An error occured while using the portaudio stream
Error number: -9988
Error message: Invalid stream pointer
An error occured while using the portaudio stream
Error number: -9988
Error message: Invalid stream pointer
An error occured while using the portaudio stream
Error number: -9977
Error message: Can't read from a callback stream

and this is my code:


#include "diffusion.c"
#include "confusion.c"
#include "portaudio.h"
#include "wave_file.c"

/* #define SAMPLE_RATE  (17932) // Test failure to open with this value. */
#define SAMPLE_RATE  (44100)
#define FRAMES_PER_BUFFER (0)
#define NUM_SECONDS     (2)
#define NUM_CHANNELS    (2)
/* #define DITHER_FLAG     (paDitherOff)  */
#define DITHER_FLAG     (0) /**/

#define WRITE_TO_WAVE_FILE  (1)

/* define sample format. */

#define PA_SAMPLE_TYPE  paInt16
typedef short SAMPLE;
#define SAMPLE_SILENCE  (0)
#define PRINTF_S_FORMAT "%d"


PaStreamParameters inputParameters, outputParameters;
    PaStream *stream;
    PaError err;
    SAMPLE *recordedSamples, *recordedSamples2;
    int i;
    int totalFrames;
    int numSamples;
    int numBytes;

static int playCallback (const void *input,
                                      void *output,
                                      unsigned long frameCount,
                                      const PaStreamCallbackTimeInfo* timeInfo,
                                      PaStreamCallbackFlags statusFlags,
                                      void *userData
 ) 
{


    err = Pa_StartStream( stream );
    if( err != paNoError ) goto error;
    printf("Now recording!!\n"); fflush(stdout);

    err = Pa_WriteStream( stream, userData, totalFrames );
    if( err != paNoError ) goto error;
    
    err = Pa_CloseStream( stream );
    if( err != paNoError ) goto error;
    free( userData );
    return paContinue;

error:
    fprintf( stderr, "An error occured while using the portaudio stream\n" );
    fprintf( stderr, "Error number: %d\n", err );
    fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
    return paContinue;
}





int main(void);
int main(void)
{
    PaStreamParameters inputParameters, outputParameters;
    PaStream *stream;
    PaError err;
    SAMPLE *recordedSamples, *recordedSamples2;
    int i;
    int totalFrames;
    int numSamples;
    int numBytes;
    
    printf("patest_read_record.c\n"); fflush(stdout);
    totalFrames = NUM_SECONDS * SAMPLE_RATE; /* Record for a few seconds. */
    numSamples = totalFrames * NUM_CHANNELS;

    numBytes = numSamples * sizeof(SAMPLE);
    recordedSamples = (SAMPLE *) malloc( numBytes );
    if( recordedSamples == NULL )
    {
        printf("Could not allocate record array.\n");
        exit(1);
    }
    for( i=0; i<numSamples; i++ ) recordedSamples[i] = 0;

    err = Pa_Initialize();
    if( err != paNoError ) goto error;

    inputParameters.device = Pa_GetDefaultInputDevice(); /* default input device */
    if (inputParameters.device == paNoDevice) {
      fprintf(stderr,"Error: No default input device.\n");
      goto error;
    }
    inputParameters.channelCount = NUM_CHANNELS;
    inputParameters.sampleFormat = PA_SAMPLE_TYPE;
    inputParameters.suggestedLatency = Pa_GetDeviceInfo( inputParameters.device )->defaultLowInputLatency;
    inputParameters.hostApiSpecificStreamInfo = NULL;

    outputParameters.device = Pa_GetDefaultOutputDevice(); /* default output device */
    printf( "Output device # %d.\n", outputParameters.device );
    printf( "Output LL: %g s\n", Pa_GetDeviceInfo( outputParameters.device )->defaultLowOutputLatency );
    printf( "Output HL: %g s\n", Pa_GetDeviceInfo( outputParameters.device )->defaultHighOutputLatency );
    outputParameters.channelCount = NUM_CHANNELS;
    outputParameters.sampleFormat = PA_SAMPLE_TYPE;
    outputParameters.suggestedLatency = Pa_GetDeviceInfo( outputParameters.device )->defaultHighOutputLatency;
    outputParameters.hostApiSpecificStreamInfo = NULL;

    /* Record some audio. -------------------------------------------- */
    err = Pa_OpenStream(
              &stream,
              &inputParameters,
              &outputParameters,                  /* &outputParameters, */
              SAMPLE_RATE,
              paFramesPerBufferUnspecified,
              paClipOff,      /* we won't output out of range samples so don't bother clipping them */
              playCallback, /* no callback, use blocking API */
              recordedSamples ); /* no callback, so no callback userData */
    if( err != paNoError ) goto error;

    err = Pa_StartStream( stream );
    if( err != paNoError ) goto error;
    printf("Now recording!!\n"); fflush(stdout);

    err = Pa_ReadStream( stream, recordedSamples, totalFrames );
    if( err != paNoError ) goto error;
    
    err = Pa_CloseStream( stream );
    if( err != paNoError ) goto error;
     /* save the recorded data in a wave file " recording.wav ".  -------------------------- */
    saveInWaveFile(recordedSamples, totalFrames, "recording.wav");
    for (int i =0; i< numSamples ; i++){
        recordedSamples2[i] = recordedSamples[i];
    }

    free( recordedSamples );
    Pa_Terminate();
    return 0;

error:
    Pa_Terminate();
    fprintf( stderr, "An error occured while using the portaudio stream\n" );
    fprintf( stderr, "Error number: %d\n", err );
    fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
    return -1;
}
2
caudiocallbackreal-timeportaudio

2 Answers

0
votes

First make sure that the default input and output devices are correct. You can do that by first running the pa_devs.c example in the examples folder to print a list of enabled audio devices connected to the computer. Once you have identified the correct devices, replace the lines with the device number e.g.

inputParameters.device = Pa_GetDefaultInputDevice();

for

inputParameters.device = <device number (e.g. 11)>;

and

outputParameters.device = Pa_GetDefaultOutputDevice();

for

outputParameters.device = <device number (e.g. 11)>;

Another avenue you can try is the example called paex_read_write_wire.c. This should achieve the same functionality you're talking about however uses a blocking approach rather than the callback function you have used in your code.

0
votes

I can not test it now, but it should play (monitor) the input buffer (the microphone):

static int patestCallback( const void *inputBuffer, void *outputBuffer,
                       unsigned long framesPerBuffer,
                       const PaStreamCallbackTimeInfo* timeInfo,
                       PaStreamCallbackFlags statusFlags,
                       void *userData )
{
    paTestData *data = (paTestData*)userData; 
    float *out = (float*)outputBuffer;
    unsigned int i;
    float *in = (float*)inputBuffer;

    for( i=0; i<framesPerBuffer; i++ )
    {
         out++ = in++;  /* left */
         out++ = in++;  /* right*/
    }
    return 0;
}