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root/cebix/Frodo4/Src/SID_linux.h
Revision: 1.7
Committed: 2010-04-22T09:09:28Z (12 years, 7 months ago) by cebix
Content type: text/plain
Branch: MAIN
CVS Tags: HEAD
Changes since 1.6: +1 -88 lines
Log Message:
use SDL for sound

File Contents

# Content
1 /*
2 * SID_linux.h - 6581 emulation, Linux specific stuff
3 *
4 * Frodo Copyright (C) Christian Bauer
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 */
20
21 #include <unistd.h>
22 #include <fcntl.h>
23 #include <sys/ioctl.h>
24 #include <linux/soundcard.h>
25
26
27 /*
28 * Initialization
29 */
30
31 void DigitalRenderer::init_sound(void)
32 {
33 int arg;
34 unsigned long format;
35
36 ready = false;
37 devfd = open("/dev/dsp", O_WRONLY);
38 if (devfd < 0)
39 return;
40
41 ioctl(devfd, SNDCTL_DSP_GETFMTS, &format);
42 if (!(format & AFMT_S16_LE))
43 return;
44 format = AFMT_S16_LE;
45 ioctl(devfd, SNDCTL_DSP_SETFMT, &format);
46
47 // Buffer size: 2^9 == 512 bytes. Note that too large buffers will not work
48 // very well: The speed of the C64 is slowed down to an average speed of
49 // 100% by the blocking write() call in EmulateLine(). If you use a buffer
50 // of, say 4096 bytes, that will happen only about every 4 frames, which
51 // means that the emulation runs much faster in some frames, and much
52 // slower in others.
53 // On really fast machines, it might make sense to use an even smaller
54 // buffer size.
55 arg = 0x00100009;
56 ioctl(devfd, SNDCTL_DSP_SETFRAGMENT, &arg);
57 arg = 0;
58 ioctl(devfd, SNDCTL_DSP_STEREO, &arg);
59 arg = 44100;
60 ioctl(devfd, SNDCTL_DSP_SPEED, &arg);
61 ioctl(devfd, SOUND_PCM_READ_RATE, &arg);
62 if (arg < 43000 || arg > 45000)
63 return;
64
65 ioctl(devfd, SNDCTL_DSP_GETBLKSIZE, &sndbufsize);
66 sound_buffer = new int16[sndbufsize];
67 ready = true;
68 }
69
70
71 /*
72 * Destructor
73 */
74
75 DigitalRenderer::~DigitalRenderer()
76 {
77 if (devfd >= 0)
78 close(devfd);
79 }
80
81
82 /*
83 * Pause sound output
84 */
85
86 void DigitalRenderer::Pause(void)
87 {
88 }
89
90
91 /*
92 * Resume sound output
93 */
94
95 void DigitalRenderer::Resume(void)
96 {
97 }
98
99
100 /*
101 * Fill buffer, sample volume (for sampled voice)
102 */
103
104 void DigitalRenderer::EmulateLine(void)
105 {
106 static int divisor = 0;
107 static int to_output = 0;
108 static int buffer_pos = 0;
109
110 if (!ready)
111 return;
112
113 sample_buf[sample_in_ptr] = volume;
114 sample_in_ptr = (sample_in_ptr + 1) % SAMPLE_BUF_SIZE;
115
116 // Now see how many samples have to be added for this line
117 divisor += SAMPLE_FREQ;
118 while (divisor >= 0)
119 divisor -= TOTAL_RASTERS*SCREEN_FREQ, to_output++;
120
121 // Calculate the sound data only when we have enough to fill
122 // the buffer entirely
123 if ((buffer_pos + to_output) >= sndbufsize) {
124 int datalen = sndbufsize - buffer_pos;
125 to_output -= datalen;
126 calc_buffer(sound_buffer + buffer_pos, datalen*2);
127 write(devfd, sound_buffer, sndbufsize*2);
128 buffer_pos = 0;
129 }
130 }