I pinpointed the problem and wrote a small program
to illustrate the problem.
When compiling the program given below with:
gcc -DUSE_DSP_SETFMT=0 troep.c
it runs fine.
But, when compiling it with:
gcc -DUSE_DSP_SETFMT=1 troep.c
It stops rather quickly with reading data.
Example output of the latter:
~>a.out
Fragment size: 1024
Number of fragments: 32767
Number of channels: 1
Sample rate: 22050
Read 1024 bytes.
Number of full fragments that can be read or written without blocking: 0
Total number of fragments allocated for buffering: 2
Size of a fragment in bytes: 1024
Number of bytes that can be read or written immediately without blocking: 0
#fragments, #bytes: 0, 0
#fragments, #bytes: 1, 1632
Read 1024 bytes.
#fragments, #bytes: 2, 2048
Read 1024 bytes.
#fragments, #bytes: 1, 1024
Read 1024 bytes.
#fragments, #bytes: 0, 0
#fragments, #bytes: 0, 0
#fragments, #bytes: 0, 0
...etc
--
Carlo Wood <[EMAIL PROTECTED]>
The program:
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <linux/soundcard.h>
#include <time.h>
int main(void)
{
int res;
char buf[1024];
int fd = open("/dev/dsp", O_RDONLY);
if (fd == -1)
{
perror("open");
exit(1);
}
res = 0x7fff000a;
if (ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &res) == -1)
{
perror("ioctl");
exit(1);
}
printf("Fragment size: %d\n", 1 << (res & 0xffff));
printf("Number of fragments: %d\n", res >> 16);
#if USE_DSP_SETFMT
res = AFMT_S16_LE;
if (ioctl(fd, SNDCTL_DSP_SETFMT, &res) == -1)
{
perror("ioctl");
exit(1);
}
#endif
res = 0; // Not stereo (1 channel).
if (ioctl(fd, SNDCTL_DSP_STEREO, &res) == -1)
{
perror("ioctl");
exit(1);
}
printf("Number of channels: %d\n", res ? 2 : 1);
res = 22050;
if (ioctl(fd, SOUND_PCM_READ_RATE, 0xbfffdcfc) == -1)
{
perror("ioctl");
exit(1);
}
printf("Sample rate: %d\n", res);
ssize_t rlen = read(fd, buf, sizeof(buf));
if (rlen <= 0)
{
perror("read");
exit(1);
}
printf("Read %d bytes.\n", rlen);
audio_buf_info info;
if (ioctl(fd, SNDCTL_DSP_GETISPACE, &info) == -1)
{
perror("read");
exit(1);
}
printf("Number of full fragments that can be read or written without blocking:
%d\n", info.fragments);
printf("Total number of fragments allocated for buffering: %d\n", info.fragstotal);
printf("Size of a fragment in bytes: %d\n", info.fragsize);
printf("Number of bytes that can be read or written immediately without blocking:
%d\n", info.bytes);
int i;
for (i = 0; i < 100; ++i)
{
if (ioctl(fd, SNDCTL_DSP_GETISPACE, &info) == -1)
{
perror("read");
exit(1);
}
printf("#fragments, #bytes: %d, %d\n", info.fragments, info.bytes);
if (info.fragments > 0)
{
ssize_t rlen = read(fd, buf, sizeof(buf));
if (rlen <= 0)
{
perror("read");
exit(1);
}
printf("Read %d bytes.\n", rlen);
}
static struct timespec naptime = { 0, 100000000 };
nanosleep(&naptime, 0);
}
close(fd);
return 0;
}
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