1 files changed, 129 insertions, 0 deletions
diff --git a/audio/filter/af_center.c b/audio/filter/af_center.c
new file mode 100644
index 0000000000..aa9aae8514
--- /dev/null
+++ b/audio/filter/af_center.c
@@ -0,0 +1,129 @@
+/*
+ * 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.
+ *
+ * copyright (c) 2005 Alex Beregszaszi
+ *
+ * This file is part of MPlayer.
+ *
+ * MPlayer is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * MPlayer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with MPlayer; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#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* 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   = ((struct mp_audio*)arg)->rate;
+    af->data->nch    = max(s->ch+1,((struct mp_audio*)arg)->nch);
+    af->data->format = AF_FORMAT_FLOAT_NE;
+    af->data->bps    = 4;
+
+    return af_test_output(af,(struct mp_audio*)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)){
+      mp_msg(MSGT_AFILTER, MSGL_ERR, "[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* af)
+{
+    free(af->data);
+    free(af->setup);
+}
+
+// Filter data through filter
+static struct mp_audio* play(struct af_instance* af, struct mp_audio* data)
+{
+  struct mp_audio*    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 af_open(struct af_instance* af){
+  af_center_t* s;
+  af->control=control;
+  af->uninit=uninit;
+  af->play=play;
+  af->mul=1;
+  af->data=calloc(1,sizeof(struct mp_audio));
+  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
+struct af_info af_info_center = {
+    "Audio filter for adding a center channel",
+    "center",
+    "Alex Beregszaszi",
+    "",
+    AF_FLAGS_NOT_REENTRANT,
+    af_open
+};