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 "ss_core.h"
  35 #include "ss_output.h"
  36
  37
  38 /*******************
  39         Data
  40 ********************/
  41
  42 /* master output volume */
  43 float ss_master_volume=1.0;
  44
  45 /* output accounting */
  46 int ss_output_frames=0;
  47 int ss_output_clipped=0;
  48 float ss_output_lowest=0;
  49 float ss_output_highest=0;
  50
  51 /* optimal output volume */
  52 float ss_optimal_volume;
  53
  54 /* driver data */
  55 static void * outdev;
  56
  57 /*
  58         usual channel mapping:
  59
  60         mono: all
  61         stereo: left | right
  62         3 channel: left | right | center
  63         quad: front left | front right | rear left | rear right
  64         4 channel: left | center | right | surround
  65         6 channel: left center | left | center | right center | right | surround
  66 */
  67
  68 /*******************
  69         Code
  70 ********************/
  71
  72 void * ss_outdev_open(char * drvname, char * file, int freq, int n_channels);
  73 void ss_outdev_write(void * drv, short int * frame);
  74 void ss_outdev_close(void * drv);
  75
  76 /**
  77  * ss_output_open - Opens an output device.
  78  * @name: name of the driver
  79  * @filename: name of the file or device
  80  *
  81  * Opens an output device. @name contains the name of the driver
  82  * (i.e. "raw" or "wav"), @filename contains the (optional) name
  83  * of the output file or device (i.e. a filename for "raw" or
  84  * "wav" or "/dev/dsp" for a direct audio device like "oss").
  85  * @Name can be the special pseudo-driver "default"
  86  * to select the most appropriate (usually a platform-specific
  87  * direct output device, or "wav" if no one exists).
  88  * @filename can also be NULL; in that case, a driver dependent,
  89  * default value is used.
  90  *
  91  * The ss_nchannels global variable can be changed on output if
  92  * the driver doesn't support so much channels.
  93  *
  94  * Returns a negative number in case of error, or zero otherwise.
  95  */
  96 int ss_output_open(char * drvname, char * filename)
  97 {
  98         if(strcmp(drvname, "default") == 0)
  99                 drvname=NULL;
 100
 101         /* reset accounting */
 102         ss_output_frames=ss_output_clipped=0;
 103         ss_output_lowest=ss_output_highest=0.0;
 104
 105         return((outdev=ss_outdev_open(drvname,
 106                 filename, ss_frequency, ss_nchannels)) == NULL);
 107 }
 108
 109
 110 void ss_output_init_frame(float samples[])
 111 {
 112         int n;
 113
 114         for(n=0;n < SS_MAX_CHANNELS;n++)
 115                 samples[n] = 0.0;
 116 }
 117
 118
 119 /**
 120  * ss_output_write - Outputs a frame of samples.
 121  * @samples: the frame of samples
 122  *
 123  * Outputs a frame of samples. The output samples are
 124  * intermixed if needed, have the master volume applied and trimmed
 125  * before being sent to the output driver itself.
 126  *
 127  * If the maximum number of channels the output driver supports
 128  * is lower than the global ss_nchannels, they are sequentially intermixed
 129  * (for example, when outputting 4 channel data to a stereo device,
 130  * 0 and 2 channels will go to left and 1 and 3 to right).
 131  *
 132  * Returns a negative value in case of error, or 0 otherwise.
 133  */
 134 int ss_output_write(float samples[])
 135 {
 136         int n, clip, ret=0;
 137         float s;
 138         short int is[SS_MAX_CHANNELS];
 139
 140         /* final corrections */
 141         for(n=clip=0;n < ss_nchannels;n++)
 142         {
 143                 s=samples[n];
 144
 145                 /* store the lowest and highest
 146                    amplitude seen before master volume */
 147                 if(s < ss_output_lowest)
 148                         ss_output_lowest=s;
 149
 150                 if(s > ss_output_highest)
 151                         ss_output_highest=s;
 152
 153                 /* apply master volume */
 154                 s *= ss_master_volume;
 155
 156                 /* clip samples to signed 16 bit boundaries */
 157                 if(s < -32768)
 158                 {
 159                         s=-32768;
 160                         clip++;
 161                 }
 162
 163                 if(s > 32767)
 164                 {
 165                         s=32767;
 166                         clip++;
 167                 }
 168
 169                 /* store in buffer */
 170                 is[n]=(short int) s;
 171         }
 172
 173         /* update accounting */
 174         ss_output_frames++;
 175
 176         if(clip)
 177                 ss_output_clipped++;
 178
 179         /* finally write */
 180         ss_outdev_write(outdev, is);
 181
 182         return(ret);
 183 }
 184
 185
 186 /**
 187  * ss_output_close - Closes the output device.
 188  *
 189  * Closes the output driver.
 190  */
 191 int ss_output_close(void)
 192 {
 193         int r;
 194
 195         ss_outdev_close(outdev);
 196
 197         /* calculate optimal master volume for
 198            zero saturation */
 199         ss_output_lowest=fabs(ss_output_lowest);
 200
 201         ss_optimal_volume = ss_output_lowest > ss_output_highest ?
 202                 32768.0 / ss_output_lowest :
 203                 32767.0 / ss_output_highest;
 204
 205         return(r);
 206 }