filter for adding a center channel, adding a high pass filter would be nice

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@14750 b3059339-0415-0410-9bf9-f77b7e298cf2

libaf/Makefile

@@ -5,7 +5,7 @@ LIBNAME = libaf.a
 SRCS=af.c af_dummy.c af_delay.c af_channels.c af_format.c af_resample.c \
 window.c filter.c af_volume.c af_equalizer.c af_tools.c af_comp.c af_gate.c \
 af_pan.c af_surround.c af_sub.c af_export.c af_volnorm.c af_extrastereo.c \
-af_lavcresample.c af_sweep.c af_hrtf.c format.c $(OPTIONAL_SRCS)
+af_lavcresample.c af_sweep.c af_hrtf.c format.c af_center.c $(OPTIONAL_SRCS)
 
 OBJS=$(SRCS:.c=.o)
 

libaf/af_center.c

@@ -0,0 +1,117 @@
+/*
+    (C) Alex Beregszaszi
+    License: GPL
+    
+    This filter adds a center channel to the audio stream by
+    averaging the left and right channel.
+    There are two runtime controls one for setting which channel to
+    insert the center-audio into called AF_CONTROL_SUB_CH.
+
+    FIXME: implement a high-pass filter for better results.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> 
+
+#include "af.h"
+
+// Data for specific instances of this filter
+typedef struct af_center_s
+{
+  int ch;		// Channel number which to insert the filtered data
+}af_center_t;
+
+// Initialization and runtime control
+static int control(struct af_instance_s* af, int cmd, void* arg)
+{
+  af_center_t* s   = af->setup; 
+
+  switch(cmd){
+  case AF_CONTROL_REINIT:{
+    // Sanity check
+    if(!arg) return AF_ERROR;
+
+    af->data->rate   = ((af_data_t*)arg)->rate;
+    af->data->nch    = max(s->ch+1,((af_data_t*)arg)->nch);
+    af->data->format = AF_FORMAT_FLOAT_NE;
+    af->data->bps    = 4;
+
+    return af_test_output(af,(af_data_t*)arg);
+  }
+  case AF_CONTROL_COMMAND_LINE:{
+    int   ch=1;
+    sscanf(arg,"%i", &ch);
+    return control(af,AF_CONTROL_CENTER_CH | AF_CONTROL_SET, &ch);
+  }
+  case AF_CONTROL_CENTER_CH | AF_CONTROL_SET: // Requires reinit
+    // Sanity check
+    if((*(int*)arg >= AF_NCH) || (*(int*)arg < 0)){
+      af_msg(AF_MSG_ERROR,"[sub] Center channel number must be between "
+	     " 0 and %i current value is %i\n", AF_NCH-1, *(int*)arg);
+      return AF_ERROR;
+    }
+    s->ch = *(int*)arg;
+    return AF_OK;
+  case AF_CONTROL_CENTER_CH | AF_CONTROL_GET:
+    *(int*)arg = s->ch;
+    return AF_OK;
+  }
+  return AF_UNKNOWN;
+}
+
+// Deallocate memory 
+static void uninit(struct af_instance_s* af)
+{
+  if(af->data)
+    free(af->data);
+  if(af->setup)
+    free(af->setup);
+}
+
+// Filter data through filter
+static af_data_t* play(struct af_instance_s* af, af_data_t* data)
+{
+  af_data_t*    c   = data;	 // Current working data
+  af_center_t*  s   = af->setup; // Setup for this instance
+  float*   	a   = c->audio;	 // Audio data
+  int		len = c->len/4;	 // Number of samples in current audio block 
+  int		nch = c->nch;	 // Number of channels
+  int		ch  = s->ch;	 // Channel in which to insert the center audio
+  register int  i;
+
+  // Run filter
+  for(i=0;i<len;i+=nch){
+    // Average left and right
+    a[i+ch] = (a[i]/2) + (a[i+1]/2);
+  }
+
+  return c;
+}
+
+// Allocate memory and set function pointers
+static int open(af_instance_t* af){
+  af_center_t* s;
+  af->control=control;
+  af->uninit=uninit;
+  af->play=play;
+  af->mul.n=1;
+  af->mul.d=1;
+  af->data=calloc(1,sizeof(af_data_t));
+  af->setup=s=calloc(1,sizeof(af_center_t));
+  if(af->data == NULL || af->setup == NULL)
+    return AF_ERROR;
+  // Set default values
+  s->ch = 1;  	 // Channel nr 2
+  return AF_OK;
+}
+
+// Description of this filter
+af_info_t af_info_center = {
+    "Audio filter for adding a center channel",
+    "center",
+    "Alex Beregszaszi",
+    "",
+    AF_FLAGS_NOT_REENTRANT,
+    open
+};

libaf/control.h

@@ -218,4 +218,10 @@ typedef struct af_control_ext_s{
 // ExtraStereo Multiplier
 #define AF_CONTROL_ES_MUL		0x00002100 | AF_CONTROL_FILTER_SPECIFIC
 
+
+// Center
+
+// Channel number which to inster the filtered data, arg in int*
+#define AF_CONTROL_CENTER_CH		0x00002200 | AF_CONTROL_FILTER_SPECIFIC
+
 #endif /*__af_control_h */