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1 /* oss.cpp
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2 *
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3 * Copyright (C) DFS Deutsche Flugsicherung (2004, 2005).
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4 * All Rights Reserved.
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5 *
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6 * Open Sound System functions
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7 *
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8 * Version 0.3
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9 */
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10
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11 #include <stdio.h>
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12 #include <stdlib.h>
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13 #include <string.h>
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14 #include <math.h>
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15
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16 /* Error handling */
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17 #include <assert.h>
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18 #include <errno.h>
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19 extern int errno;
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20
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21 /* low level io */
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22 #include <sys/types.h>
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23 #include <sys/stat.h>
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24 #include <fcntl.h>
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25 #include <sys/ioctl.h>
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26
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27 /* OSS, see www.4front-tech.com/pguide/index.html */
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28 #include <sys/soundcard.h>
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29
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30 #include "oss.h"
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31 #include "intercomd.h"
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32
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33 int audio_init(char *pathname, int channels_, int mode)
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34 {
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35 /* Using OSS is simple in theory. The application just:
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36 * Opens the device.
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37 * Optional turns on full duplex
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38 * Sets fragment size if necessary
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39 * Sets number of channels, sample format and sampling rate
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40 * Starts reading and/or writing the device
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41 *
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42 * Linux ALSA dmix note: To allow dmix simultaneous playback of
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43 * different PCM-out, do not open OSS in full duplex mode. Open two file
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44 * descriptors instead.
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45 */
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46 // fprintf(stderr, "OSS Header SOUND_VERSION = %x\n", SOUND_VERSION);
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47
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48 int audio_fd = open(pathname, mode);
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49 return_if(audio_fd < 0, -1);
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50
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51 fprintf(stderr, "audio_init() mode = %d\n", mode);
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52
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53 int sound_version = 0;
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54 ioctl(audio_fd, OSS_GETVERSION, &sound_version);
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55 // fprintf(stderr, "OSS Driver SOUND_VERSION = %x\n", SOUND_VERSION);
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56
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57 ioctl(audio_fd, SNDCTL_DSP_SETDUPLEX, 0);
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58
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59 /* The 16 most significant bits (MMMM) determine maximum number of
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60 * fragments. By default the driver computes this based on available
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61 * buffer space.
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62 * The minimum value is 2 and the maximum depends on the situation.
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63 * Set MMMM=0x7fff if you don't want to limit the number of fragments
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64 */
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65 int frag = AUDIOBUFS << 16 | FRAGSIZELD;
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66 if (2 == channels_) {
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67 ++frag; // double FRAGSIZE in stereo mode
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68 }
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69 int frag_ = frag;
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70 ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag);
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71 // fprintf(stderr, "SETFRAGMENT=0x%x\n", frag);
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72 assert_errno(frag_ == frag);
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73
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74 int format = FORMAT_OSS;
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75 ioctl(audio_fd, SNDCTL_DSP_SETFMT, &format);
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76 assert_errno(format == FORMAT_OSS);
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77
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78 int channels = channels_;
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79 ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &channels);
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80 assert_errno(channels_ == channels);
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81 // fprintf(stderr, "SNDCTL_DSP_CHANNELS=%d\n", channels);
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82
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83 int rate = RATE;
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84 ioctl(audio_fd, SNDCTL_DSP_SPEED, &rate);
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85 assert_errno(RATE == rate);
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86 // fprintf(stderr, "mode=%d SNDCTL_DSP_SPEED=%d\n", mode, rate);
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87
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88 fprintf(stderr, "\n");
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89 return audio_fd;
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90 }
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