ss_output.c

   1 /*
   2
   3     Ann Hell Ex Machina - Music Software
   4     Copyright (C) 2003/2005 Angel Ortega <angel@triptico.com>
   5
   6     ss_output.c - Softsynth output interface
   7
   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.
  12
  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.
  17
  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.
  21
  22     http://www.triptico.com
  23
  24 */
  25
  26 #include "config.h"
  27
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <unistd.h>
  31 #include <string.h>
  32 #include <math.h>
  33
  34 #include <signal.h>
  35
  36 #include "annhell.h"
  37
  38 /*******************
  39         Data
  40 ********************/
  41
  42 /* master output volume */
  43 sample_t ss_master_volume = 0.5;
  44
  45 /* output accounting */
  46 int ss_output_clipped = 0;
  47 sample_t ss_output_lowest = 0;
  48 sample_t ss_output_highest = 0;
  49
  50 /* optimal output volume */
  51 sample_t ss_optimal_volume;
  52
  53 /* driver data */
  54 static void * outdev;
  55
  56 /*
  57         usual channel mapping:
  58
  59         mono: all
  60         stereo: left | right
  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
  65 */
  66
  67 /*******************
  68         Code
  69 ********************/
  70
  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);
  74
  75
  76 static void close_on_signal(int sig_num)
  77 /* SIGINT (and other) signal handler */
  78 {
  79         /* close output device */
  80         outdev = ss_outdev_close(outdev);
  81
  82         /* exit */
  83         exit(0);
  84 }
  85
  86
  87 /**
  88  * ss_output_open - Opens an output device.
  89  * @name: name of the driver
  90  * @filename: name of the file or device
  91  *
  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.
 101  *
 102  * Returns zero if the output device was correctly open, or
 103  * nonzero otherwise.
 104  */
 105 int ss_output_open(char * drvname, char * filename)
 106 {
 107         if(strcmp(drvname, "default") == 0)
 108                 drvname = NULL;
 109
 110         /* reset accounting */
 111         ss_output_clipped = 0;
 112         ss_output_lowest = ss_output_highest = 0.0;
 113
 114         /* close the device on unexpected signals */
 115         signal(SIGINT, close_on_signal);
 116
 117         return((outdev = ss_outdev_open(drvname,
 118                 filename, ss_frequency, ss_nchannels)) == NULL);
 119 }
 120
 121
 122 /**
 123  * ss_output_init_frame - Inits a frame
 124  * @frame: the frame
 125  *
 126  * Inits a frame, setting all samples to zero.
 127  */
 128 void ss_output_init_frame(sample_t frame[])
 129 {
 130         int n;
 131
 132         for(n = 0;n < SS_MAX_CHANNELS;n++)
 133                 frame[n] = 0.0;
 134 }
 135
 136
 137 /**
 138  * ss_output_write - Outputs a frame of samples.
 139  * @frame: the frame of samples
 140  *
 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.
 144  *
 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).
 149  *
 150  * Returns a negative value in case of error, or 0 otherwise.
 151  */
 152 int ss_output_write(sample_t frame[])
 153 {
 154         int n, clip, ret = 0;
 155         sample_t s;
 156         short int is[SS_MAX_CHANNELS];
 157
 158         /* final corrections */
 159         for(n = clip = 0;n < ss_nchannels;n++)
 160         {
 161                 s = frame[n];
 162
 163                 /* store the lowest and highest
 164                    amplitude seen before master volume */
 165                 if(s < ss_output_lowest)
 166                         ss_output_lowest = s;
 167
 168                 if(s > ss_output_highest)
 169                         ss_output_highest = s;
 170
 171                 /* apply master volume */
 172                 s *= ss_master_volume;
 173
 174                 /* clip samples to signed 16 bit boundaries */
 175                 if(s < -32768)
 176                 {
 177                         s = -32768;
 178                         clip++;
 179                 }
 180
 181                 if(s > 32767)
 182                 {
 183                         s = 32767;
 184                         clip++;
 185                 }
 186
 187                 /* store in buffer */
 188                 is[n] = (short int) s;
 189         }
 190
 191         if(clip)
 192                 ss_output_clipped++;
 193
 194         /* finally write */
 195         ss_outdev_write(outdev, is);
 196
 197         return(ret);
 198 }
 199
 200
 201 /**
 202  * ss_output_close - Closes the output device.
 203  *
 204  * Closes the output driver.
 205  */
 206 void ss_output_close(void)
 207 {
 208         /* back to default signal behaviour */
 209         signal(SIGINT, SIG_DFL);
 210
 211         /* close the device */
 212         outdev = ss_outdev_close(outdev);
 213
 214         /* calculate optimal master volume for
 215            zero saturation */
 216         ss_output_lowest = fabs(ss_output_lowest);
 217
 218         ss_optimal_volume = ss_output_lowest > ss_output_highest ?
 219                 32768.0 / ss_output_lowest :
 220                 32767.0 / ss_output_highest;
 221 }