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 /* output filehandle */
  55 static int ss_of;
  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 int ss_outdev(char * drv, char * file, int freq, int n_channels);
  73
  74 /**
  75  * ss_output_open - Opens an output device.
  76  * @name: name of the driver
  77  * @filename: name of the file or device
  78  *
  79  * Opens an output device. @name contains the name of the driver
  80  * (i.e. "raw" or "wav"), @filename contains the (optional) name
  81  * of the output file or device (i.e. a filename for "raw" or
  82  * "wav" or "/dev/dsp" for a direct audio device like "oss").
  83  * @Name can be the special pseudo-driver "default"
  84  * to select the most appropriate (usually a platform-specific
  85  * direct output device, or "wav" if no one exists).
  86  * @filename can also be NULL; in that case, a driver dependent,
  87  * default value is used.
  88  *
  89  * The _n_channels global variable can be changed on output if
  90  * the driver doesn't support so much channels.
  91  *
  92  * Returns a negative number in case of error, or zero otherwise.
  93  */
  94 int ss_output_open(char * drvname, char * filename)
  95 {
  96         if(strcmp(drvname, "default") == 0)
  97                 drvname=NULL;
  98
  99         /* reset accounting */
 100         ss_output_frames=ss_output_clipped=0;
 101         ss_output_lowest=ss_output_highest=0.0;
 102
 103         ss_of=ss_outdev(drvname, filename, ss_frequency, ss_nchannels);
 104
 105         return(0);
 106 }
 107
 108
 109 void ss_output_init_frame(float samples[])
 110 {
 111         int n;
 112
 113         for(n=0;n < SS_MAX_CHANNELS;n++)
 114                 samples[n] = 0.0;
 115 }
 116
 117
 118 /**
 119  * ss_output_write - Outputs a frame of samples.
 120  * @samples: the frame of samples
 121  *
 122  * Outputs a frame of samples. The output samples are
 123  * intermixed if needed, have the master volume applied and trimmed
 124  * before being sent to the output driver itself.
 125  *
 126  * If the maximum number of channels the output driver supports
 127  * is lower than the global _n_channels, they are sequentially intermixed
 128  * (for example, when outputting 4 channel data to a stereo device,
 129  * 0 and 2 channels will go to left and 1 and 3 to right).
 130  *
 131  * Returns a negative value in case of error, or 0 otherwise.
 132  */
 133 int ss_output_write(float samples[])
 134 {
 135         int n, clip, ret=0;
 136         float s;
 137         short int is[SS_MAX_CHANNELS];
 138
 139         /* final corrections */
 140         for(n=clip=0;n < ss_nchannels;n++)
 141         {
 142                 s=samples[n];
 143
 144                 /* store the lowest and highest
 145                    amplitude seen before master volume */
 146                 if(s < ss_output_lowest)
 147                         ss_output_lowest=s;
 148
 149                 if(s > ss_output_highest)
 150                         ss_output_highest=s;
 151
 152                 /* apply master volume */
 153                 s *= ss_master_volume;
 154
 155                 /* clip samples to signed 16 bit boundaries */
 156                 if(s < -32768)
 157                 {
 158                         s=-32768;
 159                         clip++;
 160                 }
 161
 162                 if(s > 32767)
 163                 {
 164                         s=32767;
 165                         clip++;
 166                 }
 167
 168                 /* store in buffer */
 169                 is[n]=(short int) s;
 170         }
 171
 172         /* update accounting */
 173         ss_output_frames++;
 174
 175         if(clip)
 176                 ss_output_clipped++;
 177
 178         /* finally write */
 179         write(ss_of, is, ss_nchannels * sizeof(short int));
 180 /*      write(ss_of, is, 256);*/
 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         close(ss_of);
 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 }