Hi,
Thanks for the link you emailed earlier. I tried writing my own code, based
on the how to in the alsa wiki. I have attached that code with this email.
The problem it faces is a buffer underrun every alternate time, i try
writing to the device.
In my code, to take care of underruns, I do the following:
period_size=64;
buffer is a short int array which is 16000 in length.
every alternate call to snd_pcm_writei is successful but only write in the
vicinity of 1350 frames, instead of size which is initialised to length of
buffer.
Now, in the code below, the snd_pcm_recover function prints a message
indicating a buffer under-run has occured, however, it returns a 0,
indicating success in recovery from the error!
I am not sure how to deal with this -- is there a problem with my ALSA
libraries?
Sorry about the length of this email and thanks again,
Ashlesha.
while(size>(2*period_size))
{
frames = snd_pcm_writei (pcm_handle, buffer, size);
printf("frames returned is %d\n",frames);
if (frames>0)
temp=frames;
if (frames == -32){
frames = snd_pcm_recover(pcm_handle, frames, 0);
printf("recover returned %d\n",frames);
}
if (frames < 0){
printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
return -1;
}
printf("%d frames written\n",frames);
if(temp>0)
size=size-temp;
}
/* My code using the ALSA Asynchronous playback wiki */
#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 126976
/*Global Variables */
int err;
const char *device_name = "default";
int main()
{
snd_pcm_t *pcm_handle;
unsigned int rrate = 16000;
int fd1,count,bytesread=1,a,err,frames,i,size=SIZE,temp;
short int buffer[SIZE];
char d;
char errstr[50];
snd_pcm_uframes_t buffer_size = 1024;
snd_pcm_uframes_t period_size = 64;
snd_pcm_hw_params_t *hw_params;
snd_pcm_sw_params_t *sw_params;
if((fd1=open("orig.wav",O_RDONLY,0))==-1) {
printf("error opening file\n");
return -1;
}
for(count=0;count<44;count++)
{
a=read(fd1,&d,sizeof(char)); //first 40 bytes of the wav file
}
count=0;
while(bytesread >0 && count<SIZE)
bytesread = read( fd1 , &buffer[count++], sizeof( short int ) );
printf("no. of samples @16000Hz are %d\n",count); // count is the size of the wave file
printf("bytesread = %d\n",bytesread);
if((err = snd_pcm_open (&pcm_handle, device_name, SND_PCM_STREAM_PLAYBACK, 0))!=0)
{
printf("err in pcm open\n");
printf("errstr is %s\n",snd_strerror (err));
return -1;
}
if((err=snd_pcm_hw_params_malloc (&hw_params))!=0){
printf("malloc err\n");
printf("errstr is %s\n",snd_strerror (err));
return -1;
}
if ((err = snd_pcm_set_params( pcm_handle,
SND_PCM_FORMAT_S16_LE,
SND_PCM_ACCESS_RW_INTERLEAVED,
1,
16000,
1,
100)) < 0) {
printf("Playback open error: %s\n", snd_strerror(err));
exit(EXIT_FAILURE);
}
if ((err=snd_pcm_prepare (pcm_handle))<0){
printf("pcm prepare error %d\n",err);
printf("errstr is %s\n",snd_strerror (err));
}
frames=0;
size=SIZE;
temp=0;
while(size>(2*period_size))
{
frames = snd_pcm_writei (pcm_handle, buffer, size);
printf("frames returned is %d\n",frames);
if (frames>0)
temp=frames;
if (frames == -32){
frames = snd_pcm_recover(pcm_handle, frames, 0);
printf("recover returned %d\n",frames);
}
if (frames < 0){
printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
return -1;
}
printf("%d frames written\n",frames);
if(temp>0)
size=size-temp;
}
snd_pcm_close (pcm_handle);
return 0;
}
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