[alsa-devel] hardware not asking for more data using asyn call back
stan
stanl at cox.net
Tue May 29 00:43:00 CEST 2007
On Mon, 28 May 2007 15:32:16 -0400
"Ashlesha Shintre" <ashlesha.shintre at 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.
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