On Mon, 28 May 2007 15:32:16 -0400 "Ashlesha Shintre" ashlesha.shintre@gmail.com wrote:

Hi,

In my asynchronous playback program, the hardware stops asking for any data and the program gets stuck after one call to the callback function. I have pasted the program below -- please let me know if something is wrong -

Thanks, Ashlesha.

/* Reading wav file into a buffer and then trying to play it */

...

#include <stdio.h> #include </usr/include/alsa/asoundlib.h> #include </usr/include/alsa/pcm.h> #include <sys/types.h> #include <unistd.h> #include <fcntl.h>

#define SIZE 128

short int *buffer; int ind=10, fd1; static snd_pcm_t *handle; static char *device = "default"; /* playback device */ snd_output_t *output = NULL; static short int *wto, *rfrom, buflen;

void MyCallback(snd_async_handler_t *pcm_callback);

int main() { int i,j,n,length,count,a,err,k=0; char c; snd_pcm_sframes_t frames; snd_async_handler_t *pcm_callback;

if((fd1=open("SA2.WAV",O_RDONLY,0))==-1)
    printf("error opening wav file\n");

count=0;
while(count++<40)
    a=read(fd1,&c,sizeof(char));

a=read(fd1,&length,sizeof(int));

n=length/SIZE;

printf("length = %d\n",length);

buflen = 4*SIZE;
buffer = (short int *) malloc (buflen*sizeof(short int));

wto = NULL;
rfrom = &buffer[0];

count=0;
a=1;
while(count<buflen && a>0)
    a=read(fd1,&buffer[count++],sizeof(short int));
if(a<0)
    printf("error in reading from wav file\n");

if((err = snd_pcm_open(&handle, device,

SND_PCM_STREAM_PLAYBACK, 0)) < 0) { printf("error opening device: %s\n",snd_strerror(err)); return -1; }

if((err = snd_pcm_set_params(handle,
                            SND_PCM_FORMAT_S16_LE,
                            SND_PCM_ACCESS_RW_INTERLEAVED,
                            1,
                            16000,
                            1,
                            1000)) < 0) {   /* 2 sec */
        printf("Playback open error: %s\n", snd_strerror(err));
        return -2;
}
printf("n=%d\n",n);
for (i=0; i<50; i++)
{
    printf("i=%d\n",i);
    frames = snd_pcm_writei(handle, rfrom, SIZE);
    if(frames < 0)              // underrun
        {
            printf("underrun recovery\n");
            frames = snd_pcm_recover(handle, frames,0);
            if(frames < 0){
                printf("error in recovery\n");
                return -3;
                }
        }
    if(frames >0 && frames < SIZE)
        printf("expected to write %d, wrote %d\n",SIZE,frames);
    printf("distance between ptrs before reinit is %d\n",rfrom

• wto); if(rfrom < &buffer[buflen-1]) { wto = rfrom; rfrom = rfrom + SIZE; } else { printf("rfm at the end, rfrom -buffer[buflen-1]

=%d\n",(*rfrom - buffer[buflen-1])); wto = rfrom; rfrom = &buffer[0]; } for(k=0; k<SIZE; k++) { a=read(fd1,(wto+k),sizeof(short int)); if(a<0) printf("error in reading from wav file k = %d\n"); } printf("buffer[i*SIZE] - rfrom = %d\n",(buffer[(i+1)*SIZE] - *rfrom));

}

/* Async Handler */

// err = snd_async_add_pcm_handler(&pcm_callback,handle,MyCallback,buffer); err = snd_async_add_pcm_handler(&pcm_callback,handle,MyCallback,NULL); if(err<0) printf("add pcm handler error = %d\n%s\n",err,snd_strerror(err));

err = snd_pcm_start(handle);
if(err<0)
    printf("error in starting snd pcm start err

:%s\n",snd_strerror(err));

while (1) { if(wto == NULL) break; sleep(1);

I think you should be filling the buffer in this loop instead of in the callback function below.

...

     }

err = snd_pcm_close(handle);
if(err<0)
    printf("error in closing pcm device:

%s\n",snd_strerror(err)); close(fd1); return 0; }

void MyCallback(snd_async_handler_t *pcm_callback) {

snd_pcm_t *pcm_handle = snd_async_handler_get_pcm(pcm_callback);
snd_pcm_sframes_t avail;
int count,a;
snd_pcm_uframes_t period_size = 64;
snd_pcm_sframes_t frames;
//short int *bufferin =

snd_async_handler_get_callback_private(pcm_callback);

while((avail=snd_pcm_avail_update(pcm_handle)) >= period_size)
    {
        printf("available frames = %d\n",avail);
        frames = snd_pcm_writei(pcm_handle, rfrom, SIZE);
        if(frames < 0)              // underrun
        {
            printf("underrun recovery\n");
            frames = snd_pcm_prepare(pcm_handle);
            printf("error from snd_pcm_prepare is:

%d\n",frames); if(frames < 0){ printf("error in recovery\n"); // break; } }

        if(frames >0 && frames < SIZE)
            printf("expected to write %d, wrote

%d\n",SIZE,frames); count = 0; a=1; while(count<SIZE && a>0){ a=read(fd1,(wto+count),sizeof(short int)); //write to the buffer from file ++count; } printf("count = %d\n",count); if(a <0){ //EOF wto = NULL; printf("end of file reached\n"); break; } else{ if(rfrom < &buffer[buflen-1]) { wto = wto+count; rfrom = rfrom + SIZE; } else { wto = wto + count; rfrom = &buffer[0]; } //location of where to start writing from next } ++ind; }

    printf("going out of callback, ind = %d\n",ind);

}

---

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Could you post the output of all the printfs when the program runs, and describe the behavior. I read what you read above as saying that it hangs. The printf output will indicate where it is hanging.