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	#include <stdio.h>
 1 
	#include <stdio.h>
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	#include <stdlib.h>
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	#include <stdlib.h>
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 3 
	#include <errno.h>
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 4 
	#include <poll.h>
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	#include <alsa/asoundlib.h>
 5 
	#include <alsa/asoundlib.h>
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 6 
 
5 
	int rate = 44100;
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6 
	int exact_rate;
 7 
	int exact_rate;
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 8 
	int rate = 44100;
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 9 
	snd_pcm_t *playback_handle;
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 10 
	short buf[4096];
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11 
 
- 
 
 12 
	FILE *random;
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 13 
 
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 14
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 15 
	int
8 
	main (int argc, char *argv[])
 16 
	playback_callback (snd_pcm_sframes_t nframes)
9 
	{
 17 
	{
10 
		int i;
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		int err;
 18 
		int err;
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 19 
 
- 
 
 20 
		printf ("playback callback called with %u frames\n", nframes);
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 21 
 
- 
 
 22 
		fread(buf,1,4096,random);
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 23
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 24 
		/* ... fill buf with data ... */
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 25
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 26 
		if ((err = snd_pcm_writei (playback_handle, buf, nframes)) < 0) {
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 27 
			fprintf (stderr, "write failed (%s)\n", snd_strerror (err));
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 28 
		}
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 29
12 
		short buf[128];
 30 
		return err;
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 31 
	}
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 32
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	main (int argc, char *argv[])
- 
 
 34 
	{
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 35
13 
		snd_pcm_t *capture_handle;
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		random = fopen("/dev/urandom","r");
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 37 
 
14 
		snd_pcm_hw_params_t *hw_params;
 38 
		snd_pcm_hw_params_t *hw_params;
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 39 
		snd_pcm_sw_params_t *sw_params;
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 40 
		snd_pcm_sframes_t frames_to_deliver;
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 41 
		int nfds;
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 42 
		int err;
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 43 
		struct pollfd *pfds;
15
44
16 
		if ((err = snd_pcm_open (&capture_handle, argv[1], SND_PCM_STREAM_CAPTURE, 0)) < 0) {
 45 
		if ((err = snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
17 
			fprintf (stderr, "cannot open audio device %s (%s)\n",
46 
			fprintf (stderr, "cannot open audio device %s (%s)\n",
18 
				 argv[1],
 47 
				 argv[1],
19 
				 snd_strerror (err));
 48 
				 snd_strerror (err));
20 
			exit (1);
 49 
			exit (1);
21 
		}
 50 
		}
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24 
			fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
 53 
			fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
25 
				 snd_strerror (err));
 54 
				 snd_strerror (err));
26 
			exit (1);
 55 
			exit (1);
27 
		}
 56 
		}
28
57
29 
		if ((err = snd_pcm_hw_params_any (capture_handle, hw_params)) < 0) {
 58 
		if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) {
30 
			fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
 59 
			fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
31 
				 snd_strerror (err));
 60 
				 snd_strerror (err));
32 
			exit (1);
 61 
			exit (1);
33 
		}
 62 
		}
34
63
35 
		if ((err = snd_pcm_hw_params_set_access (capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
 64 
		if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
36 
			fprintf (stderr, "cannot set access type (%s)\n",
 65 
			fprintf (stderr, "cannot set access type (%s)\n",
37 
				 snd_strerror (err));
 66 
				 snd_strerror (err));
38 
			exit (1);
 67 
			exit (1);
39 
		}
 68 
		}
40
69
41 
		if ((err = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
 70 
		if ((err = snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
42 
			fprintf (stderr, "cannot set sample format (%s)\n",
 71 
			fprintf (stderr, "cannot set sample format (%s)\n",
43 
				 snd_strerror (err));
 72 
				 snd_strerror (err));
44 
			exit (1);
 73 
			exit (1);
45 
		}
 74 
		}
46
75 
 
47 
		exact_rate = rate;
 76 
		exact_rate = rate;
48 
		if ((err = snd_pcm_hw_params_set_rate_near (capture_handle, hw_params, &exact_rate, 0)) < 0) {
 77 
		if ((err = snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, &exact_rate, 0)) < 0) {
49 
			fprintf (stderr, "cannot set sample rate (%s)\n",
 78 
			fprintf (stderr, "cannot set sample rate (%s)\n",
50 
				 snd_strerror (err));
 79 
				 snd_strerror (err));
51 
			exit (1);
 80 
			exit (1);
52 
		}
 81 
		}
53
82 
 
- 
 
 83
54 
		if ((err = snd_pcm_hw_params_set_channels (capture_handle, hw_params, 2)) < 0) {
 84 
		if ((err = snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2)) < 0) {
55 
			fprintf (stderr, "cannot set channel count (%s)\n",
 85 
			fprintf (stderr, "cannot set channel count (%s)\n",
56 
				 snd_strerror (err));
 86 
				 snd_strerror (err));
57 
			exit (1);
 87 
			exit (1);
58 
		}
 88 
		}
59
89
60 
		if ((err = snd_pcm_hw_params (capture_handle, hw_params)) < 0) {
 90 
		if ((err = snd_pcm_hw_params (playback_handle, hw_params)) < 0) {
61 
			fprintf (stderr, "cannot set parameters (%s)\n",
 91 
			fprintf (stderr, "cannot set parameters (%s)\n",
62 
				 snd_strerror (err));
 92 
				 snd_strerror (err));
63 
			exit (1);
 93 
			exit (1);
64 
		}
 94 
		}
65
95
66 
		snd_pcm_hw_params_free (hw_params);
 96 
		snd_pcm_hw_params_free (hw_params);
67
97
- 
 
 98 
		/* tell ALSA to wake us up whenever 4096 or more frames
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 99 
		   of playback data can be delivered. Also, tell
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 100 
		   ALSA that we'll start the device ourselves.
- 
 
 101 
		*/
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 102
68 
		if ((err = snd_pcm_prepare (capture_handle)) < 0) {
 103 
		if ((err = snd_pcm_sw_params_malloc (&sw_params)) < 0) {
69 
			fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
 104 
			fprintf (stderr, "cannot allocate software parameters structure (%s)\n",
70 
				 snd_strerror (err));
 105 
				 snd_strerror (err));
71 
			exit (1);
 106 
			exit (1);
72 
		}
 107 
		}
73
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74 
		for (i = 0; i < 10; ++i) {
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75 
			if ((err = snd_pcm_readi (capture_handle, buf, 128)) != 128) {
 108 
		if ((err = snd_pcm_sw_params_current (playback_handle, sw_params)) < 0) {
76 
				fprintf (stderr, "read from audio interface failed (%s)\n",
 109 
			fprintf (stderr, "cannot initialize software parameters structure (%s)\n",
77 
					 snd_strerror (err));
 110 
				 snd_strerror (err));
78 
				exit (1);
 111 
			exit (1);
79 
			}
 112 
		}
80 
			/*if ((err = snd_pcm_writei (capture_handle, buf, 128)) != 128) {
 113 
		if ((err = snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096)) < 0) {
81 
				fprintf (stderr, "write to audio interface failed (%s)\n",
 114 
			fprintf (stderr, "cannot set minimum available count (%s)\n",
82 
					 snd_strerror (err));
 115 
				 snd_strerror (err));
83 
				exit (1);
 116 
			exit (1);
84 
			}*/
 - 
 
85 
		}
 117 
		}
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 118 
		if ((err = snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 0U)) < 0) {
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 119 
			fprintf (stderr, "cannot set start mode (%s)\n",
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 120 
				 snd_strerror (err));
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 121 
			exit (1);
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 122 
		}
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 123 
		if ((err = snd_pcm_sw_params (playback_handle, sw_params)) < 0) {
- 
 
 124 
			fprintf (stderr, "cannot set software parameters (%s)\n",
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 125 
				 snd_strerror (err));
- 
 
 126 
			exit (1);
- 
 
 127 
		}
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 128
- 
 
 129 
		/* the interface will interrupt the kernel every 4096 frames, and ALSA
- 
 
 130 
		   will wake up this program very soon after that.
- 
 
 131 
		*/
- 
 
 132
- 
 
 133 
		if ((err = snd_pcm_prepare (playback_handle)) < 0) {
- 
 
 134 
			fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
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 135 
				 snd_strerror (err));
- 
 
 136 
			exit (1);
- 
 
 137 
		}
- 
 
 138
- 
 
 139 
		while (1) {
86 
 
 140
- 
 
 141 
			/* wait till the interface is ready for data, or 1 second
- 
 
 142 
			   has elapsed.
- 
 
 143 
			*/
87
144
- 
 
 145 
			if ((err = snd_pcm_wait (playback_handle, 1000)) < 0) {
- 
 
 146 
			        fprintf (stderr, "poll failed (%s)\n", strerror (errno));
- 
 
 147 
			        break;
- 
 
 148 
			}
- 
 
 149
- 
 
 150 
			/* find out how much space is available for playback data */
- 
 
 151
- 
 
 152 
			if ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) < 0) {
- 
 
 153 
				if (frames_to_deliver == -EPIPE) {
- 
 
 154 
					fprintf (stderr, "an xrun occured\n");
- 
 
 155 
					break;
- 
 
 156 
				} else {
- 
 
 157 
					fprintf (stderr, "unknown ALSA avail update return value (%d)\n",
- 
 
 158 
						 frames_to_deliver);
- 
 
 159 
					break;
- 
 
 160 
				}
- 
 
 161 
			}
- 
 
 162
- 
 
 163 
			frames_to_deliver = frames_to_deliver > 4096 ? 4096 : frames_to_deliver;
- 
 
 164
- 
 
 165 
			/* deliver the data */
- 
 
 166
- 
 
 167 
			if (playback_callback (frames_to_deliver) != frames_to_deliver) {
- 
 
 168 
			        fprintf (stderr, "playback callback failed\n");
- 
 
 169 
				break;
- 
 
 170 
			}
- 
 
 171 
		}
- 
 
 172
88 
		snd_pcm_close (capture_handle);
 173 
		snd_pcm_close (playback_handle);
- 
 
 174 
		fclose(random);
89 
		exit (0);
 175 
		exit (0);
90 
	}
 176 
	}
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 177