3 Ann Hell Ex Machina - Music Software
4 Copyright (C) 2003/2005 Angel Ortega <angel@triptico.com>
6 ss_output.c - Softsynth output interface
8 This program is free software; you can redistribute it and/or
9 modify it under the terms of the GNU General Public License
10 as published by the Free Software Foundation; either version 2
11 of the License, or (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
22 http://www.triptico.com
42 /* master output volume */
43 sample_t ss_master_volume
=0.5;
45 /* output accounting */
46 int ss_output_clipped
=0;
47 sample_t ss_output_lowest
=0;
48 sample_t ss_output_highest
=0;
50 /* optimal output volume */
51 sample_t ss_optimal_volume
;
57 usual channel mapping:
61 3 channel: left | right | center
62 quad: front left | front right | rear left | rear right
63 4 channel: left | center | right | surround
64 6 channel: left center | left | center | right center | right | surround
71 void * ss_outdev_open(char * drvname
, char * file
, int freq
, int n_channels
);
72 void ss_outdev_write(void * drv
, short int * frame
);
73 void * ss_outdev_close(void * drv
);
76 static void close_on_signal(int sig_num
)
77 /* SIGINT (and other) signal handler */
79 /* close output device */
80 outdev
=ss_outdev_close(outdev
);
88 * ss_output_open - Opens an output device.
89 * @name: name of the driver
90 * @filename: name of the file or device
92 * Opens an output device. @name contains the name of the driver
93 * (i.e. "oss" or "wav"), @filename contains the (optional) name
94 * of the output file or device (i.e. a filename
95 * "wav" or "/dev/dsp" for a direct audio device like "oss").
96 * @Name can be the special pseudo-driver "default"
97 * to select the most appropriate (usually a platform-specific
98 * direct output device, or "wav" if no one exists).
99 * @filename can also be NULL; in that case, a driver dependent,
100 * default value is used.
102 * Returns zero if the output device was correctly open, or
105 int ss_output_open(char * drvname
, char * filename
)
107 if(strcmp(drvname
, "default") == 0)
110 /* reset accounting */
112 ss_output_lowest
=ss_output_highest
=0.0;
114 /* close the device on unexpected signals */
115 signal(SIGINT
, close_on_signal
);
117 return((outdev
=ss_outdev_open(drvname
,
118 filename
, ss_frequency
, ss_nchannels
)) == NULL
);
123 * ss_output_init_frame - Inits a frame
126 * Inits a frame, setting all samples to zero.
128 void ss_output_init_frame(sample_t frame
[])
132 for(n
=0;n
< SS_MAX_CHANNELS
;n
++)
138 * ss_output_write - Outputs a frame of samples.
139 * @frame: the frame of samples
141 * Outputs a frame of samples. The output samples are
142 * intermixed if needed, have the master volume applied and trimmed
143 * before being sent to the output driver itself.
145 * If the maximum number of channels the output driver supports
146 * is lower than the global ss_nchannels, they are sequentially intermixed
147 * (for example, when outputting 4 channel data to a stereo device,
148 * 0 and 2 channels will go to left and 1 and 3 to right).
150 * Returns a negative value in case of error, or 0 otherwise.
152 int ss_output_write(sample_t frame
[])
156 short int is
[SS_MAX_CHANNELS
];
158 /* final corrections */
159 for(n
=clip
=0;n
< ss_nchannels
;n
++)
163 /* store the lowest and highest
164 amplitude seen before master volume */
165 if(s
< ss_output_lowest
)
168 if(s
> ss_output_highest
)
171 /* apply master volume */
172 s
*= ss_master_volume
;
174 /* clip samples to signed 16 bit boundaries */
187 /* store in buffer */
195 ss_outdev_write(outdev
, is
);
202 * ss_output_close - Closes the output device.
204 * Closes the output driver.
206 void ss_output_close(void)
208 /* back to default signal behaviour */
209 signal(SIGINT
, SIG_DFL
);
211 /* close the device */
212 outdev
=ss_outdev_close(outdev
);
214 /* calculate optimal master volume for
216 ss_output_lowest
=fabs(ss_output_lowest
);
218 ss_optimal_volume
= ss_output_lowest
> ss_output_highest
?
219 32768.0 / ss_output_lowest
:
220 32767.0 / ss_output_highest
;