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 "annhell.h"
  35
  36 /*******************
  37         Data
  38 ********************/
  39
  40 /* master output volume */
  41 float ss_master_volume=0.5;
  42
  43 /* output accounting */
  44 int ss_output_clipped=0;
  45 float ss_output_lowest=0;
  46 float ss_output_highest=0;
  47
  48 /* optimal output volume */
  49 float ss_optimal_volume;
  50
  51 /* driver data */
  52 static void * outdev;
  53
  54 /*
  55         usual channel mapping:
  56
  57         mono: all
  58         stereo: left | right
  59         3 channel: left | right | center
  60         quad: front left | front right | rear left | rear right
  61         4 channel: left | center | right | surround
  62         6 channel: left center | left | center | right center | right | surround
  63 */
  64
  65 /*******************
  66         Code
  67 ********************/
  68
  69 void * ss_outdev_open(char * drvname, char * file, int freq, int n_channels);
  70 void ss_outdev_write(void * drv, short int * frame);
  71 void ss_outdev_close(void * drv);
  72
  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. "oss" or "wav"), @filename contains the (optional) name
  81  * of the output file or device (i.e. a filename
  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  * Returns zero if the output device was correctly open, or
  90  * nonzero otherwise.
  91  */
  92 int ss_output_open(char * drvname, char * filename)
  93 {
  94         if(strcmp(drvname, "default") == 0)
  95                 drvname=NULL;
  96
  97         /* reset accounting */
  98         ss_output_clipped=0;
  99         ss_output_lowest=ss_output_highest=0.0;
 100
 101         return((outdev=ss_outdev_open(drvname,
 102                 filename, ss_frequency, ss_nchannels)) == NULL);
 103 }
 104
 105
 106 /**
 107  * ss_output_init_frame - Inits a frame
 108  * @frame: the frame
 109  *
 110  * Inits a frame, setting all samples to zero.
 111  */
 112 void ss_output_init_frame(float frame[])
 113 {
 114         int n;
 115
 116         for(n=0;n < SS_MAX_CHANNELS;n++)
 117                 frame[n] = 0.0;
 118 }
 119
 120
 121 /**
 122  * ss_output_write - Outputs a frame of samples.
 123  * @frame: the frame of samples
 124  *
 125  * Outputs a frame of samples. The output samples are
 126  * intermixed if needed, have the master volume applied and trimmed
 127  * before being sent to the output driver itself.
 128  *
 129  * If the maximum number of channels the output driver supports
 130  * is lower than the global ss_nchannels, they are sequentially intermixed
 131  * (for example, when outputting 4 channel data to a stereo device,
 132  * 0 and 2 channels will go to left and 1 and 3 to right).
 133  *
 134  * Returns a negative value in case of error, or 0 otherwise.
 135  */
 136 int ss_output_write(float frame[])
 137 {
 138         int n, clip, ret=0;
 139         float s;
 140         short int is[SS_MAX_CHANNELS];
 141
 142         /* final corrections */
 143         for(n=clip=0;n < ss_nchannels;n++)
 144         {
 145                 s=frame[n];
 146
 147                 /* store the lowest and highest
 148                    amplitude seen before master volume */
 149                 if(s < ss_output_lowest)
 150                         ss_output_lowest=s;
 151
 152                 if(s > ss_output_highest)
 153                         ss_output_highest=s;
 154
 155                 /* apply master volume */
 156                 s *= ss_master_volume;
 157
 158                 /* clip samples to signed 16 bit boundaries */
 159                 if(s < -32768)
 160                 {
 161                         s=-32768;
 162                         clip++;
 163                 }
 164
 165                 if(s > 32767)
 166                 {
 167                         s=32767;
 168                         clip++;
 169                 }
 170
 171                 /* store in buffer */
 172                 is[n]=(short int) s;
 173         }
 174
 175         if(clip)
 176                 ss_output_clipped++;
 177
 178         /* finally write */
 179         ss_outdev_write(outdev, is);
 180
 181         return(ret);
 182 }
 183
 184
 185 /**
 186  * ss_output_close - Closes the output device.
 187  *
 188  * Closes the output driver.
 189  */
 190 void ss_output_close(void)
 191 {
 192         ss_outdev_close(outdev);
 193
 194         /* calculate optimal master volume for
 195            zero saturation */
 196         ss_output_lowest=fabs(ss_output_lowest);
 197
 198         ss_optimal_volume = ss_output_lowest > ss_output_highest ?
 199                 32768.0 / ss_output_lowest :
 200                 32767.0 / ss_output_highest;
 201 }