Extrastereo plugin: increases linearly the difference between left and right

channels (as the XMMS extrastereo plugin) which has some of "live" effect (use
it to hear what I mean)

ex: mplayer media.avi -aop list=extrastereo[:mul=3.4]
The default coefficient (mul) is a float number that defaults to 2.5.  If you
set it to 0.0, you will have a mono sound (average of both channels), if you
set it to 1.0, you will have unchanged sound.

A patch for DOCS/sound.html is about to be sent to Gabucino.


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@4928 b3059339-0415-0410-9bf9-f77b7e298cf2

cfg-mplayer.h

@@ -107,6 +107,7 @@ struct config ao_plugin_conf[]={
 	{"format", &ao_plugin_cfg.pl_format_type, CONF_TYPE_INT, CONF_MIN, 0, 0, NULL},
 	{"fout", &ao_plugin_cfg.pl_resample_fout, CONF_TYPE_INT, CONF_MIN, 0, 0, NULL},
 	{"volume", &ao_plugin_cfg.pl_volume_volume, CONF_TYPE_INT, CONF_RANGE, 0, 255, NULL},
+	{"mul", &ao_plugin_cfg.pl_extrastereo_mul, CONF_TYPE_FLOAT, CONF_MIN, 0, 0, NULL},
 	{NULL, NULL, 0, 0, 0, 0, NULL}
 };
 

libao2/Makefile

@@ -4,7 +4,7 @@ include config.mak
 LIBNAME = libao2.a
 
 # TODO: moveout ao_sdl.c so it's only used when SDL is detected
-SRCS=afmt.c audio_out.c ao_mpegpes.c ao_null.c ao_pcm.c ao_plugin.c pl_delay.c pl_format.c pl_surround.c remez.c pl_resample.c pl_volume.c $(OPTIONAL_SRCS)
+SRCS=afmt.c audio_out.c ao_mpegpes.c ao_null.c ao_pcm.c ao_plugin.c pl_delay.c pl_format.c pl_surround.c remez.c pl_resample.c pl_volume.c pl_extrastereo.c $(OPTIONAL_SRCS)
 
 OBJS=$(SRCS:.c=.o)
 

libao2/audio_plugin.h

@@ -36,6 +36,7 @@ typedef struct ao_plugin_cfg_s
   int pl_delay_len;	// Number of samples to delay sound output
   int pl_resample_fout;	// Output frequency from resampling
   int pl_volume_volume; // Initial volume setting
+  float pl_extrastereo_mul; // Stereo enhancer multiplier
 } ao_plugin_cfg_t;
 
 extern ao_plugin_cfg_t ao_plugin_cfg;
@@ -46,19 +47,21 @@ extern ao_plugin_cfg_t ao_plugin_cfg;
  AFMT_S16_LE, \
  0, \
  48000, \
- 255 \
+ 255, \
+ 2.5 \
 };
 
 // This block should not be available in the pl_xxxx files
 // due to compilation issues
 #ifndef PLUGIN
-#define NPL 5+1 // Number of PLugins ( +1 list ends with NULL )
+#define NPL 6+1 // Number of PLugins ( +1 list ends with NULL )
 // List of plugins 
 extern ao_plugin_functions_t audio_plugin_delay;
 extern ao_plugin_functions_t audio_plugin_format; 
 extern ao_plugin_functions_t audio_plugin_surround;
 extern ao_plugin_functions_t audio_plugin_resample;
 extern ao_plugin_functions_t audio_plugin_volume;
+extern ao_plugin_functions_t audio_plugin_extrastereo;
 
 
 #define AO_PLUGINS { \
@@ -67,6 +70,7 @@ extern ao_plugin_functions_t audio_plugin_volume;
    &audio_plugin_surround, \
    &audio_plugin_resample, \
    &audio_plugin_volume, \
+   &audio_plugin_extrastereo, \
    NULL \
 }
 #endif /* PLUGIN */

libao2/pl_extrastereo.c

@@ -0,0 +1,121 @@
+/* Extrastereo effect plugin
+ * (linearly increases difference between L&R channels)
+ * 
+ * Current limitations:
+ *  - only AFMT_S16_LE is supported currently
+ *
+ * License: GPLv2 (as a mix of pl_volume.c and 
+ *          xmms:stereo_plugin/stereo.c)
+ * 
+ * Author: pl <p_l@gmx.fr> (c) 2002 and beyond...
+ * */
+
+#define PLUGIN
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <inttypes.h>
+
+#include "audio_out.h"
+#include "audio_plugin.h"
+#include "audio_plugin_internal.h"
+#include "afmt.h"
+
+static ao_info_t info = {
+        "Extra stereo plugin",
+        "extrastereo",
+        "pl <p_l@gmx.fr>",
+        ""
+};
+
+LIBAO_PLUGIN_EXTERN(extrastereo)
+
+// local data
+static struct {
+  float    mul;         // intensity
+  int      inuse;     	// This plugin is in use TRUE, FALSE
+  int      format;	// sample format
+} pl_extrastereo = {2.5, 0, 0};
+
+
+// to set/get/query special features/parameters
+static int control(int cmd,int arg){
+  switch(cmd){
+  case AOCONTROL_PLUGIN_SET_LEN:
+    return CONTROL_OK;
+  }
+  return CONTROL_UNKNOWN;
+}
+
+// open & setup audio device
+// return: 1=success 0=fail
+static int init(){
+  switch(ao_plugin_data.format){
+  case(AFMT_S16_LE):
+    break;
+  default:
+    fprintf(stderr,"[pl_extrastereo] Audio format not yet suported \n");
+    return 0;
+  }
+
+  pl_extrastereo.mul=ao_plugin_cfg.pl_extrastereo_mul;
+  pl_extrastereo.format=ao_plugin_data.format;
+  pl_extrastereo.inuse=1;
+
+  printf("[pl_extrastereo] Extra stereo plugin in use (multiplier=%2.2f).\n",
+           pl_extrastereo.mul);
+  return 1;
+}
+
+// close plugin
+static void uninit(){
+  pl_extrastereo.inuse=0;
+}
+
+// empty buffers
+static void reset(){
+}
+
+// processes 'ao_plugin_data.len' bytes of 'data'
+// called for every block of data
+static int play(){
+
+  switch(pl_extrastereo.format){
+  case(AFMT_S16_LE): {
+
+    int16_t* data=(int16_t*)ao_plugin_data.data;
+    int len=ao_plugin_data.len / 2; // 16 bits samples
+
+    float mul = pl_extrastereo.mul;
+    int32_t i, avg, ltmp, rtmp;
+
+    for (i=0; i < len ; i += 2) {
+
+      avg = (data[i] + data[i + 1]) / 2;
+
+      ltmp = avg + (int) (mul * (data[i] - avg));
+      rtmp = avg + (int) (mul * (data[i + 1] - avg));
+
+      if (ltmp < -32768) {
+        ltmp = -32768;
+      } else if (ltmp > 32767) {
+        ltmp = 32767;
+      }
+
+      if (rtmp < -32768) {
+        rtmp = -32768;
+      } else if (rtmp > 32767) {
+        rtmp = 32767;
+      }
+
+      data[i] = ltmp;
+      data[i + 1] = rtmp;
+    }
+    break;
+  }
+  default:
+    return 0;
+  }
+  return 1;
+}
+