--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/intercom/oss.cpp	Fri Jun 25 09:57:52 2010 +0200
@@ -0,0 +1,90 @@
+/* oss.cpp
+ *
+ * Copyright (C) DFS Deutsche Flugsicherung (2004, 2005). 
+ * All Rights Reserved.
+ *
+ * Open Sound System functions
+ *
+ * Version 0.3
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+/* Error handling */
+#include <assert.h>
+#include <errno.h>
+extern int errno;
+
+/* low level io */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+
+/* OSS, see www.4front-tech.com/pguide/index.html */
+#include <sys/soundcard.h>
+
+#include "oss.h"
+#include "intercomd.h"
+
+int audio_init(char *pathname, int channels_, int mode)
+{
+/* Using OSS is simple in theory. The application just: 
+ * Opens the device.
+ * Optional turns on full duplex
+ * Sets fragment size if necessary
+ * Sets number of channels, sample format and sampling rate
+ * Starts reading and/or writing the device
+ *
+ * Linux ALSA dmix note: To allow dmix simultaneous playback of 
+ * different PCM-out, do not open OSS in full duplex mode. Open two file
+ * descriptors instead.
+ */
+  // fprintf(stderr, "OSS Header SOUND_VERSION = %x\n", SOUND_VERSION);
+
+  int audio_fd = open(pathname, mode);
+  return_if(audio_fd < 0, -1);
+  
+  fprintf(stderr, "audio_init() mode = %d\n", mode);
+  
+  int sound_version = 0;
+  ioctl(audio_fd, OSS_GETVERSION, &sound_version);
+  // fprintf(stderr, "OSS Driver SOUND_VERSION = %x\n", SOUND_VERSION);
+
+  ioctl(audio_fd, SNDCTL_DSP_SETDUPLEX, 0);
+
+  /* The 16 most significant bits (MMMM) determine maximum number of
+   * fragments. By default the driver computes this based on available
+   * buffer space. 
+   * The minimum value is 2 and the maximum depends on the situation. 
+   * Set MMMM=0x7fff if you don't want to limit the number of fragments   
+   */
+  int frag = AUDIOBUFS << 16 | FRAGSIZELD;
+  if (2 == channels_) {
+    ++frag;                     // double FRAGSIZE in stereo mode
+  }
+  int frag_ = frag;
+  ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag);
+  // fprintf(stderr, "SETFRAGMENT=0x%x\n", frag);
+  assert_errno(frag_ == frag);
+
+  int format = FORMAT_OSS;
+  ioctl(audio_fd, SNDCTL_DSP_SETFMT, &format);
+  assert_errno(format == FORMAT_OSS);
+
+  int channels = channels_;
+  ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &channels);
+  assert_errno(channels_ == channels);
+  // fprintf(stderr, "SNDCTL_DSP_CHANNELS=%d\n", channels);
+
+  int rate = RATE;
+  ioctl(audio_fd, SNDCTL_DSP_SPEED, &rate);
+  assert_errno(RATE == rate);
+  // fprintf(stderr, "mode=%d SNDCTL_DSP_SPEED=%d\n", mode, rate);
+
+  fprintf(stderr, "\n");
+  return audio_fd;
+}