Audio Howto

From OESF

Zaurus audio development howto: by L.J. Potter

To get brief audio device info: run this command from the console:

 # cat /dev/sndstat

The VERY easiest way to play sound is to use use cat command such as this:

 # cat myNewSound >/dev/dsp

or in a program, use system()

system( "cat myNewSound >/dev/dsp");

The VERY easiest way to record sound is to use use cat command such as this:

 # cat /dev/dsp1 >myNewSound

or in a program, use system()

system( "cat /dev/dsp1 >myNewSound");

This is not the most elegant way to do this.

---

The next easiest way to play audio is to use QSound: The benefits are that you should be able to play more than one sound at a time. (*) NOTE: there is no QSound::record()

 #include <qsound.h>
 #include <qpe/resource.h>
  

QSound

:play( Resource::findSound("ohdear") );

(*) NOTE: There is a bug on the Zaurus with QSound not being able to play sounds shorter than about 8k.

---

or if you can use Qtopia's Sound class to loop sounds: (there's no docs, so grab the qtopia cvs at sourceforge and look in the source)

 #include <qpe/sound.h>
 #include <qpe/resource.h>

Sound

:soundAlarm();

or something like:

Sound mySound( Resource

:findSound("ohdear") );

mySound.playLoop();

mySound.stop();

(*) NOTE: There is a bug on the Zaurus with QSound not being able to play sounds shorter than about 8k.

---

!Using oss with the Zaurus: !Playing sounds:

 #include <sys/ioctl.h>
 #include <linux/soundcard.h>

int speed = 44100;

int channels = 2;

int format = AFMT_S16_LE; // or AFMT_U8, but has buggy output on the Z

int dsp=0;

signed short soundBuffer[1024];

dsp = 

:open("/dev/dsp", O_WRONLY);

if( dsp == -1) {

perror("open(\"/dev/dsp\")");

return;

}

 // this is assuming you know what the format of the wav file is.
 // otherwise you'd have to read the header file first.

if( ioctl( dsp, SNDCTL_DSP_SETFMT , &format)==-1) {

perror("ioctl(\"SNDCTL_DSP_SETFMT\")");

return -1;

}

if( ioctl( dsp, SNDCTL_DSP_CHANNELS , &channels)==-1) {

perror("ioctl(\"SNDCTL_DSP_CHANNELS\")");

return -1;

}

if( ioctl( dsp, SNDCTL_DSP_SPEED , &speed)==-1) {

perror("ioctl(\"SNDCTL_DSP_SPEED\")");

return -1;

}

QFile track( "/opt/!QtPalmtop/sounds/somesound.wav" );

if( !track.open( IO_!ReadOnly )) {

QMessageBox:message("Sounds","There was an error opening the wav file");

return -1;

}

int oldStyleFileHandle = track.handle();

int length;

while( !track.atEnd()) {

length = ::read( oldStyleFileHandle, soundBuffer, 1024 ); //read from the file

 ::write( dsp, soundBuffer, length); //write to the device

}

 

:close (dsp);

track.close();

---

!To record:

 #include <sys/ioctl.h>
 #include <linux/soundcard.h>

int speed = 22050;

int channels = 1;

// *NOTE* the Zaurus input is ONLY mono !!

int format = AFMT_S16_LE;

int dsp=0;

signed short soundBuffer[1024];

dsp = 

:open("/dev/dsp1", O_RDONLY);

// *NOTE* the Zaurus has a nonstandard input

// so /dev/dsp1 must be opened when

// recording

if( dsp == -1) {

perror("open(\"/dev/dsp\")");

return;

}

// this is assuming you know what the format of the wav file is.

// otherwise you'd have to read the header file first.

if( ioctl( dsp, SNDCTL_DSP_SETFMT , &format)==-1) {

perror("ioctl(\"SNDCTL_DSP_SETFMT\")");

return -1;

}

if( ioctl( dsp, SNDCTL_DSP_CHANNELS , &channels)==-1) {

perror("ioctl(\"SNDCTL_DSP_CHANNELS\")");

return -1;

}

if( ioctl( dsp, SNDCTL_DSP_SPEED , &speed)==-1) {

perror("ioctl(\"SNDCTL_DSP_SPEED\")");

return -1;

}

QFile track( "/opt/!QtPalmtop/sounds/myNewSound.wav" );

if( !track.open( IO_!WriteOnly | IO_Truncate )) {

QMessageBox:message("Sounds","There was an error opening the wav file");

return -1;

}

int oldStyleFileHandle = track.handle();

int length;

while( 1) { // or some other way to stop this crazy thing

length = 

:read( dsp, soundBuffer, 1024 ); //read from the file

 ::write( oldStyleFileHandle, soundBuffer, length); //write to the device

}

 

:close (dsp);

track.close();

// to make a standard wav file, you would need to write

// a header before you start writing from the device, and then

// write to the header after you finish

For more information about programming OSS, visit: http://www.opensound.com

This page was last updated: May 21 2003 06:25:12.