Project 2 Hints

The sound file is here
Test the audio device by writing the audio file to /dev/audio,
# cat pp.au > /dev/audio
If you cannot hear anything from your headset, adjust volumes using the volume control applet(upper right corner of the screen) on the GNOME desktop(audioctl will not be provided).
Please be advised that writing to /dev/audio is only allowed when you are working from the console (you cannot write to /dev/audio with ssh.)
If there's any problem with the sound system, report me EARLY!
An example code for sound output
#include #include int main() { int fi, fo, n,i; char buf[256]; fi = open("pp.au", O_RDONLY); fo = open("/dev/audio", O_WRONLY | O_NONBLOCK); for (i=0; i<300; ++i) { read(fi, buf, sizeof(buf)); n = write(fo, buf, sizeof(buf)); printf("%d\n", n); usleep(25000); } return 1; } You may notice that /dev/audio is opened with non-blocking mode since we don't want the program blocks while playing sound; since we are using only one process/thread the program should receive and process packets (also feedback).
This example code writes 256 bytes to /dev/audio each time. 25ms of usleep duration can be interpreted as your sigalarm interval. This example sounds quite well. However, if you increase the usleep duration you can hear some pause in playback. Likewise, if you decrease the usleep duration the playback skips some data so that it makes some scratch noise.