gst/audiofx/audiopanorama.c - mtk-gst-plugins-good-debian - Git at Google

 /*
  * GStreamer
  * Copyright (C) 2006 Stefan Kost <ensonic@users.sf.net>
  * Copyright (C) 2006 Sebastian Dröge <slomo@circular-chaos.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library 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
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public
  * License along with this library; if not, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */

 /**
  * SECTION:element-audiopanorama
  *
  * Stereo panorama effect with controllable pan position. One can choose between the default psychoacoustic panning method,
  * which keeps the same perceived loudness, and a simple panning method that just controls the volume on one channel.
  *
  * <refsect2>
  * <title>Example launch line</title>
  * |[
  * gst-launch audiotestsrc wave=saw ! audiopanorama panorama=-1.00 ! alsasink
  * gst-launch filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiopanorama panorama=-1.00 ! alsasink
  * gst-launch audiotestsrc wave=saw ! audioconvert ! audiopanorama panorama=-1.00 ! audioconvert ! alsasink
  * gst-launch audiotestsrc wave=saw ! audioconvert ! audiopanorama method=simple panorama=-0.50 ! audioconvert ! alsasink
  * ]|
  * </refsect2>
  */

 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif

 #include <string.h>

 #include <gst/gst.h>
 #include <gst/base/gstbasetransform.h>

 #include "audiopanorama.h"

 #define GST_CAT_DEFAULT gst_audio_panorama_debug
 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

 /* Filter signals and args */
 enum
 {
   /* FILL ME */
   LAST_SIGNAL
 };

 enum
 {
   PROP_0,
   PROP_PANORAMA,
   PROP_METHOD
 };

 enum
 {
   METHOD_PSYCHOACOUSTIC = 0,
   METHOD_SIMPLE,
   NUM_METHODS
 };

 #define GST_TYPE_AUDIO_PANORAMA_METHOD (gst_audio_panorama_method_get_type ())
 static GType
 gst_audio_panorama_method_get_type (void)
 {
   static GType gtype = 0;

   if (gtype == 0) {
     static const GEnumValue values[] = {
       {METHOD_PSYCHOACOUSTIC, "Psychoacoustic Panning (default)",
           "psychoacoustic"},
       {METHOD_SIMPLE, "Simple Panning", "simple"},
       {0, NULL, NULL}
     };

     gtype = g_enum_register_static ("GstAudioPanoramaMethod", values);
   }
   return gtype;
 }

 static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
     GST_PAD_SINK,
     GST_PAD_ALWAYS,
     GST_STATIC_CAPS ("audio/x-raw, "
         "format = (string) { " GST_AUDIO_NE (F32) ", " GST_AUDIO_NE (S16) "}, "
         "rate = (int) [ 1, MAX ], " "channels = (int) 1, "
         "layout = (string) interleaved;"
         "audio/x-raw, "
         "format = (string) { " GST_AUDIO_NE (F32) ", " GST_AUDIO_NE (S16) "}, "
         "rate = (int) [ 1, MAX ], " "channels = (int) 2, "
         "layout = (string) interleaved, " "channel-mask = (bitmask) 0x3")
     );

 static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
     GST_PAD_SRC,
     GST_PAD_ALWAYS,
     GST_STATIC_CAPS ("audio/x-raw, "
         "format = (string) { " GST_AUDIO_NE (S32) ", " GST_AUDIO_NE (S16) "}, "
         "rate = (int) [ 1, MAX ], " "channels = (int) 2, "
         "layout = (string) interleaved, " "channel-mask = (bitmask)0x3")
     );

 G_DEFINE_TYPE (GstAudioPanorama, gst_audio_panorama, GST_TYPE_BASE_TRANSFORM);

 static void gst_audio_panorama_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec);
 static void gst_audio_panorama_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec);

 static gboolean gst_audio_panorama_get_unit_size (GstBaseTransform * base,
     GstCaps * caps, gsize * size);
 static GstCaps *gst_audio_panorama_transform_caps (GstBaseTransform * base,
     GstPadDirection direction, GstCaps * caps, GstCaps * filter);
 static gboolean gst_audio_panorama_set_caps (GstBaseTransform * base,
     GstCaps * incaps, GstCaps * outcaps);

 static void gst_audio_panorama_transform_m2s_int (GstAudioPanorama * filter,
     gint16 * idata, gint16 * odata, guint num_samples);
 static void gst_audio_panorama_transform_s2s_int (GstAudioPanorama * filter,
     gint16 * idata, gint16 * odata, guint num_samples);
 static void gst_audio_panorama_transform_m2s_float (GstAudioPanorama * filter,
     gfloat * idata, gfloat * odata, guint num_samples);
 static void gst_audio_panorama_transform_s2s_float (GstAudioPanorama * filter,
     gfloat * idata, gfloat * odata, guint num_samples);

 static void gst_audio_panorama_transform_m2s_int_simple (GstAudioPanorama *
     filter, gint16 * idata, gint16 * odata, guint num_samples);
 static void gst_audio_panorama_transform_s2s_int_simple (GstAudioPanorama *
     filter, gint16 * idata, gint16 * odata, guint num_samples);
 static void gst_audio_panorama_transform_m2s_float_simple (GstAudioPanorama *
     filter, gfloat * idata, gfloat * odata, guint num_samples);
 static void gst_audio_panorama_transform_s2s_float_simple (GstAudioPanorama *
     filter, gfloat * idata, gfloat * odata, guint num_samples);

 static GstFlowReturn gst_audio_panorama_transform (GstBaseTransform * base,
     GstBuffer * inbuf, GstBuffer * outbuf);


 /* Table with processing functions: [channels][format][method] */
 static GstAudioPanoramaProcessFunc panorama_process_functions[2][2][2] = {
   {
         {(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_m2s_int,
               (GstAudioPanoramaProcessFunc)
             gst_audio_panorama_transform_m2s_int_simple},
         {(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_m2s_float,
               (GstAudioPanoramaProcessFunc)
             gst_audio_panorama_transform_m2s_float_simple}
       },
   {
         {(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_s2s_int,
               (GstAudioPanoramaProcessFunc)
             gst_audio_panorama_transform_s2s_int_simple},
         {(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_s2s_float,
               (GstAudioPanoramaProcessFunc)
             gst_audio_panorama_transform_s2s_float_simple}
       }
 };

 /* GObject vmethod implementations */

 static void
 gst_audio_panorama_class_init (GstAudioPanoramaClass * klass)
 {
   GObjectClass *gobject_class;
   GstElementClass *gstelement_class;

   GST_DEBUG_CATEGORY_INIT (gst_audio_panorama_debug, "audiopanorama", 0,
       "audiopanorama element");

   gobject_class = (GObjectClass *) klass;
   gstelement_class = (GstElementClass *) klass;

   gobject_class->set_property = gst_audio_panorama_set_property;
   gobject_class->get_property = gst_audio_panorama_get_property;

   g_object_class_install_property (gobject_class, PROP_PANORAMA,
       g_param_spec_float ("panorama", "Panorama",
           "Position in stereo panorama (-1.0 left -> 1.0 right)", -1.0, 1.0,
           0.0,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));
   /**
    * GstAudioPanorama:method
    *
    * Panning method: psychoacoustic mode keeps the same perceived loudness,
    * while simple mode just controls the volume of one channel. It's merely
    * a matter of taste which method should be chosen.
    *
    * Since: 0.10.6
    **/
   g_object_class_install_property (gobject_class, PROP_METHOD,
       g_param_spec_enum ("method", "Panning method",
           "Psychoacoustic mode keeps same perceived loudness, "
           "simple mode just controls volume of one channel.",
           GST_TYPE_AUDIO_PANORAMA_METHOD, METHOD_PSYCHOACOUSTIC,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

   gst_element_class_set_static_metadata (gstelement_class, "Stereo positioning",
       "Filter/Effect/Audio",
       "Positions audio streams in the stereo panorama",
       "Stefan Kost <ensonic@users.sf.net>");

   gst_element_class_add_pad_template (gstelement_class,
       gst_static_pad_template_get (&src_template));
   gst_element_class_add_pad_template (gstelement_class,
       gst_static_pad_template_get (&sink_template));

   GST_BASE_TRANSFORM_CLASS (klass)->get_unit_size =
       GST_DEBUG_FUNCPTR (gst_audio_panorama_get_unit_size);
   GST_BASE_TRANSFORM_CLASS (klass)->transform_caps =
       GST_DEBUG_FUNCPTR (gst_audio_panorama_transform_caps);
   GST_BASE_TRANSFORM_CLASS (klass)->set_caps =
       GST_DEBUG_FUNCPTR (gst_audio_panorama_set_caps);
   GST_BASE_TRANSFORM_CLASS (klass)->transform =
       GST_DEBUG_FUNCPTR (gst_audio_panorama_transform);
 }

 static void
 gst_audio_panorama_init (GstAudioPanorama * filter)
 {

   filter->panorama = 0;
   filter->method = METHOD_PSYCHOACOUSTIC;
   gst_audio_info_init (&filter->info);
   filter->process = NULL;

   gst_base_transform_set_gap_aware (GST_BASE_TRANSFORM (filter), TRUE);
 }

 static gboolean
 gst_audio_panorama_set_process_function (GstAudioPanorama * filter,
     GstAudioInfo * info)
 {
   gint channel_index, format_index, method_index;
   const GstAudioFormatInfo *finfo = info->finfo;

   /* set processing function */
   channel_index = GST_AUDIO_INFO_CHANNELS (info) - 1;
   if (channel_index > 1 || channel_index < 0) {
     filter->process = NULL;
     return FALSE;
   }

   format_index = GST_AUDIO_FORMAT_INFO_IS_FLOAT (finfo) ? 1 : 0;

   method_index = filter->method;
   if (method_index >= NUM_METHODS || method_index < 0)
     method_index = METHOD_PSYCHOACOUSTIC;

   filter->process =
       panorama_process_functions[channel_index][format_index][method_index];
   return TRUE;
 }

 static void
 gst_audio_panorama_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec)
 {
   GstAudioPanorama *filter = GST_AUDIO_PANORAMA (object);

   switch (prop_id) {
     case PROP_PANORAMA:
       filter->panorama = g_value_get_float (value);
       break;
     case PROP_METHOD:
       filter->method = g_value_get_enum (value);
       gst_audio_panorama_set_process_function (filter, &filter->info);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 static void
 gst_audio_panorama_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec)
 {
   GstAudioPanorama *filter = GST_AUDIO_PANORAMA (object);

   switch (prop_id) {
     case PROP_PANORAMA:
       g_value_set_float (value, filter->panorama);
       break;
     case PROP_METHOD:
       g_value_set_enum (value, filter->method);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 /* GstBaseTransform vmethod implementations */

 static gboolean
 gst_audio_panorama_get_unit_size (GstBaseTransform * base, GstCaps * caps,
     gsize * size)
 {
   GstAudioInfo info;

   g_assert (size);

   if (!gst_audio_info_from_caps (&info, caps))
     return FALSE;

   *size = GST_AUDIO_INFO_BPF (&info);

   return TRUE;
 }

 static GstCaps *
 gst_audio_panorama_transform_caps (GstBaseTransform * base,
     GstPadDirection direction, GstCaps * caps, GstCaps * filter)
 {
   GstCaps *res;
   GstStructure *structure;

   /* transform caps gives one single caps so we can just replace
    * the channel property with our range. */
   res = gst_caps_copy (caps);
   structure = gst_caps_get_structure (res, 0);
   if (direction == GST_PAD_SRC) {
     GST_INFO ("allow 1-2 channels");
     gst_structure_set (structure, "channels", GST_TYPE_INT_RANGE, 1, 2, NULL);
   } else {
     GST_INFO ("allow 2 channels");
     gst_structure_set (structure, "channels", G_TYPE_INT, 2, NULL);
   }

   return res;
 }

 static gboolean
 gst_audio_panorama_set_caps (GstBaseTransform * base, GstCaps * incaps,
     GstCaps * outcaps)
 {
   GstAudioPanorama *filter = GST_AUDIO_PANORAMA (base);
   GstAudioInfo info;

   /*GST_INFO ("incaps are %" GST_PTR_FORMAT, incaps); */
   if (!gst_audio_info_from_caps (&info, incaps))
     goto no_format;

   GST_DEBUG ("try to process %d input with %d channels",
       GST_AUDIO_INFO_FORMAT (&info), GST_AUDIO_INFO_CHANNELS (&info));

   if (!gst_audio_panorama_set_process_function (filter, &info))
     goto no_format;

   filter->info = info;

   return TRUE;

 no_format:
   {
     GST_DEBUG ("invalid caps");
     return FALSE;
   }
 }

 /* psychoacoustic processing functions */
 static void
 gst_audio_panorama_transform_m2s_int (GstAudioPanorama * filter, gint16 * idata,
     gint16 * odata, guint num_samples)
 {
   guint i;
   gdouble val;
   glong lval, rval;
   gdouble rpan, lpan;

   /* pan:  -1.0  0.0  1.0
    * lpan:  1.0  0.5  0.0
    * rpan:  0.0  0.5  1.0
    *
    * FIXME: we should use -3db (1/sqtr(2)) for 50:50
    */
   rpan = (gdouble) (filter->panorama + 1.0) / 2.0;
   lpan = 1.0 - rpan;

   for (i = 0; i < num_samples; i++) {
     val = (gdouble) * idata++;

     lval = (glong) (val * lpan);
     rval = (glong) (val * rpan);

     *odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
     *odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
   }
 }

 static void
 gst_audio_panorama_transform_s2s_int (GstAudioPanorama * filter, gint16 * idata,
     gint16 * odata, guint num_samples)
 {
   guint i;
   glong lval, rval;
   gdouble lival, rival;
   gdouble lrpan, llpan, rrpan, rlpan;

   /* pan:  -1.0  0.0  1.0
    * llpan: 1.0  1.0  0.0
    * lrpan: 1.0  0.0  0.0
    * rrpan: 0.0  1.0  1.0
    * rlpan: 0.0  0.0  1.0
    */
   if (filter->panorama > 0) {
     rlpan = (gdouble) filter->panorama;
     llpan = 1.0 - rlpan;
     lrpan = 0.0;
     rrpan = 1.0;
   } else {
     rrpan = (gdouble) (1.0 + filter->panorama);
     lrpan = 1.0 - rrpan;
     rlpan = 0.0;
     llpan = 1.0;
   }

   for (i = 0; i < num_samples; i++) {
     lival = (gdouble) * idata++;
     rival = (gdouble) * idata++;

     lval = lival * llpan + rival * lrpan;
     rval = lival * rlpan + rival * rrpan;

     *odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
     *odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
   }
 }

 static void
 gst_audio_panorama_transform_m2s_float (GstAudioPanorama * filter,
     gfloat * idata, gfloat * odata, guint num_samples)
 {
   guint i;
   gfloat val;
   gdouble rpan, lpan;

   /* pan:  -1.0  0.0  1.0
    * lpan:  1.0  0.5  0.0
    * rpan:  0.0  0.5  1.0
    *
    * FIXME: we should use -3db (1/sqtr(2)) for 50:50
    */
   rpan = (gdouble) (filter->panorama + 1.0) / 2.0;
   lpan = 1.0 - rpan;

   for (i = 0; i < num_samples; i++) {
     val = *idata++;

     *odata++ = val * lpan;
     *odata++ = val * rpan;
   }
 }

 static void
 gst_audio_panorama_transform_s2s_float (GstAudioPanorama * filter,
     gfloat * idata, gfloat * odata, guint num_samples)
 {
   guint i;
   gfloat lival, rival;
   gdouble lrpan, llpan, rrpan, rlpan;

   /* pan:  -1.0  0.0  1.0
    * llpan: 1.0  1.0  0.0
    * lrpan: 1.0  0.0  0.0
    * rrpan: 0.0  1.0  1.0
    * rlpan: 0.0  0.0  1.0
    */
   if (filter->panorama > 0) {
     rlpan = (gdouble) filter->panorama;
     llpan = 1.0 - rlpan;
     lrpan = 0.0;
     rrpan = 1.0;
   } else {
     rrpan = (gdouble) (1.0 + filter->panorama);
     lrpan = 1.0 - rrpan;
     rlpan = 0.0;
     llpan = 1.0;
   }

   for (i = 0; i < num_samples; i++) {
     lival = *idata++;
     rival = *idata++;

     *odata++ = lival * llpan + rival * lrpan;
     *odata++ = lival * rlpan + rival * rrpan;
   }
 }

 /* simple processing functions */
 static void
 gst_audio_panorama_transform_m2s_int_simple (GstAudioPanorama * filter,
     gint16 * idata, gint16 * odata, guint num_samples)
 {
   guint i;
   gdouble pan;
   glong lval, rval;

   if (filter->panorama > 0.0) {
     pan = 1.0 - filter->panorama;
     for (i = 0; i < num_samples; i++) {
       rval = *idata++;
       lval = (glong) ((gdouble) rval * pan);

       *odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
       *odata++ = (gint16) rval;
     }
   } else {
     pan = 1.0 + filter->panorama;
     for (i = 0; i < num_samples; i++) {
       lval = *idata++;
       rval = (glong) ((gdouble) lval * pan);

       *odata++ = (gint16) lval;
       *odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
     }
   }
 }

 static void
 gst_audio_panorama_transform_s2s_int_simple (GstAudioPanorama * filter,
     gint16 * idata, gint16 * odata, guint num_samples)
 {
   guint i;
   glong lval, rval;
   gdouble lival, rival, pan;

   if (filter->panorama > 0.0) {
     pan = 1.0 - filter->panorama;
     for (i = 0; i < num_samples; i++) {
       lival = (gdouble) * idata++;
       rival = (gdouble) * idata++;

       lval = (glong) (lival * pan);
       rval = (glong) rival;

       *odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
       *odata++ = (gint16) rval;
     }
   } else {
     pan = 1.0 + filter->panorama;
     for (i = 0; i < num_samples; i++) {
       lival = (gdouble) * idata++;
       rival = (gdouble) * idata++;

       lval = (glong) lival;
       rval = (glong) (rival * pan);

       *odata++ = (gint16) lval;
       *odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
     }
   }
 }

 static void
 gst_audio_panorama_transform_m2s_float_simple (GstAudioPanorama * filter,
     gfloat * idata, gfloat * odata, guint num_samples)
 {
   guint i;
   gfloat val, pan;

   if (filter->panorama > 0.0) {
     pan = 1.0 - filter->panorama;
     for (i = 0; i < num_samples; i++) {
       val = *idata++;

       *odata++ = val * pan;
       *odata++ = val;
     }
   } else {
     pan = 1.0 + filter->panorama;
     for (i = 0; i < num_samples; i++) {
       val = *idata++;

       *odata++ = val;
       *odata++ = val * pan;
     }
   }
 }

 static void
 gst_audio_panorama_transform_s2s_float_simple (GstAudioPanorama * filter,
     gfloat * idata, gfloat * odata, guint num_samples)
 {
   guint i;
   gfloat lival, rival, pan;

   if (filter->panorama > 0.0) {
     pan = 1.0 - filter->panorama;
     for (i = 0; i < num_samples; i++) {
       lival = *idata++;
       rival = *idata++;

       *odata++ = lival * pan;
       *odata++ = rival;
     }
   } else {
     pan = 1.0 + filter->panorama;
     for (i = 0; i < num_samples; i++) {
       lival = *idata++;
       rival = *idata++;

       *odata++ = lival;
       *odata++ = rival * pan;
     }
   }
 }

 /* this function does the actual processing
  */
 static GstFlowReturn
 gst_audio_panorama_transform (GstBaseTransform * base, GstBuffer * inbuf,
     GstBuffer * outbuf)
 {
   GstAudioPanorama *filter = GST_AUDIO_PANORAMA (base);
   GstClockTime timestamp, stream_time;
   GstMapInfo inmap, outmap;

   timestamp = GST_BUFFER_TIMESTAMP (inbuf);
   stream_time =
       gst_segment_to_stream_time (&base->segment, GST_FORMAT_TIME, timestamp);

   GST_DEBUG_OBJECT (filter, "sync to %" GST_TIME_FORMAT,
       GST_TIME_ARGS (timestamp));

   if (GST_CLOCK_TIME_IS_VALID (stream_time))
     gst_object_sync_values (GST_OBJECT (filter), stream_time);

   gst_buffer_map (inbuf, &inmap, GST_MAP_READ);
   gst_buffer_map (outbuf, &outmap, GST_MAP_WRITE);

   if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (inbuf, GST_BUFFER_FLAG_GAP))) {
     GST_BUFFER_FLAG_SET (outbuf, GST_BUFFER_FLAG_GAP);
     memset (outmap.data, 0, outmap.size);
   } else {
     /* output always stereo, input mono or stereo,
      * and info describes input format */
     guint num_samples = outmap.size / (2 * GST_AUDIO_INFO_BPS (&filter->info));

     filter->process (filter, inmap.data, outmap.data, num_samples);
   }

   gst_buffer_unmap (inbuf, &inmap);
   gst_buffer_unmap (outbuf, &outmap);

   return GST_FLOW_OK;
 }
	/*
	* GStreamer
	* Copyright (C) 2006 Stefan Kost <ensonic@users.sf.net>
	* Copyright (C) 2006 Sebastian Dröge <slomo@circular-chaos.org>
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Library General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library 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
	* Library General Public License for more details.
	*
	* You should have received a copy of the GNU Library General Public
	* License along with this library; if not, write to the
	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	* Boston, MA 02111-1307, USA.
	*/

	/**
	* SECTION:element-audiopanorama
	*
	* Stereo panorama effect with controllable pan position. One can choose between the default psychoacoustic panning method,
	* which keeps the same perceived loudness, and a simple panning method that just controls the volume on one channel.
	*
	* <refsect2>
	* <title>Example launch line</title>
	* \|[
	* gst-launch audiotestsrc wave=saw ! audiopanorama panorama=-1.00 ! alsasink
	* gst-launch filesrc location="melo1.ogg" ! oggdemux ! vorbisdec ! audioconvert ! audiopanorama panorama=-1.00 ! alsasink
	* gst-launch audiotestsrc wave=saw ! audioconvert ! audiopanorama panorama=-1.00 ! audioconvert ! alsasink
	* gst-launch audiotestsrc wave=saw ! audioconvert ! audiopanorama method=simple panorama=-0.50 ! audioconvert ! alsasink
	* ]\|
	* </refsect2>
	*/

	#ifdef HAVE_CONFIG_H
	#include "config.h"
	#endif

	#include <string.h>

	#include <gst/gst.h>
	#include <gst/base/gstbasetransform.h>

	#include "audiopanorama.h"

	#define GST_CAT_DEFAULT gst_audio_panorama_debug
	GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

	/* Filter signals and args */
	enum
	{
	/* FILL ME */
	LAST_SIGNAL
	};

	enum
	{
	PROP_0,
	PROP_PANORAMA,
	PROP_METHOD
	};

	enum
	{
	METHOD_PSYCHOACOUSTIC = 0,
	METHOD_SIMPLE,
	NUM_METHODS
	};

	#define GST_TYPE_AUDIO_PANORAMA_METHOD (gst_audio_panorama_method_get_type ())
	static GType
	gst_audio_panorama_method_get_type (void)
	{
	static GType gtype = 0;

	if (gtype == 0) {
	static const GEnumValue values[] = {
	{METHOD_PSYCHOACOUSTIC, "Psychoacoustic Panning (default)",
	"psychoacoustic"},
	{METHOD_SIMPLE, "Simple Panning", "simple"},
	{0, NULL, NULL}
	};

	gtype = g_enum_register_static ("GstAudioPanoramaMethod", values);
	}
	return gtype;
	}

	static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
	GST_PAD_SINK,
	GST_PAD_ALWAYS,
	GST_STATIC_CAPS ("audio/x-raw, "
	"format = (string) { " GST_AUDIO_NE (F32) ", " GST_AUDIO_NE (S16) "}, "
	"rate = (int) [ 1, MAX ], " "channels = (int) 1, "
	"layout = (string) interleaved;"
	"audio/x-raw, "
	"format = (string) { " GST_AUDIO_NE (F32) ", " GST_AUDIO_NE (S16) "}, "
	"rate = (int) [ 1, MAX ], " "channels = (int) 2, "
	"layout = (string) interleaved, " "channel-mask = (bitmask) 0x3")
	);

	static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
	GST_PAD_SRC,
	GST_PAD_ALWAYS,
	GST_STATIC_CAPS ("audio/x-raw, "
	"format = (string) { " GST_AUDIO_NE (S32) ", " GST_AUDIO_NE (S16) "}, "
	"rate = (int) [ 1, MAX ], " "channels = (int) 2, "
	"layout = (string) interleaved, " "channel-mask = (bitmask)0x3")
	);

	G_DEFINE_TYPE (GstAudioPanorama, gst_audio_panorama, GST_TYPE_BASE_TRANSFORM);

	static void gst_audio_panorama_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec);
	static void gst_audio_panorama_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec);

	static gboolean gst_audio_panorama_get_unit_size (GstBaseTransform * base,
	GstCaps * caps, gsize * size);
	static GstCaps gst_audio_panorama_transform_caps (GstBaseTransform base,
	GstPadDirection direction, GstCaps * caps, GstCaps * filter);
	static gboolean gst_audio_panorama_set_caps (GstBaseTransform * base,
	GstCaps * incaps, GstCaps * outcaps);

	static void gst_audio_panorama_transform_m2s_int (GstAudioPanorama * filter,
	gint16 * idata, gint16 * odata, guint num_samples);
	static void gst_audio_panorama_transform_s2s_int (GstAudioPanorama * filter,
	gint16 * idata, gint16 * odata, guint num_samples);
	static void gst_audio_panorama_transform_m2s_float (GstAudioPanorama * filter,
	gfloat * idata, gfloat * odata, guint num_samples);
	static void gst_audio_panorama_transform_s2s_float (GstAudioPanorama * filter,
	gfloat * idata, gfloat * odata, guint num_samples);

	static void gst_audio_panorama_transform_m2s_int_simple (GstAudioPanorama *
	filter, gint16 * idata, gint16 * odata, guint num_samples);
	static void gst_audio_panorama_transform_s2s_int_simple (GstAudioPanorama *
	filter, gint16 * idata, gint16 * odata, guint num_samples);
	static void gst_audio_panorama_transform_m2s_float_simple (GstAudioPanorama *
	filter, gfloat * idata, gfloat * odata, guint num_samples);
	static void gst_audio_panorama_transform_s2s_float_simple (GstAudioPanorama *
	filter, gfloat * idata, gfloat * odata, guint num_samples);

	static GstFlowReturn gst_audio_panorama_transform (GstBaseTransform * base,
	GstBuffer * inbuf, GstBuffer * outbuf);


	/* Table with processing functions: [channels][format][method] */
	static GstAudioPanoramaProcessFunc panorama_process_functions[2][2][2] = {
	{
	{(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_m2s_int,
	(GstAudioPanoramaProcessFunc)
	gst_audio_panorama_transform_m2s_int_simple},
	{(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_m2s_float,
	(GstAudioPanoramaProcessFunc)
	gst_audio_panorama_transform_m2s_float_simple}
	},
	{
	{(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_s2s_int,
	(GstAudioPanoramaProcessFunc)
	gst_audio_panorama_transform_s2s_int_simple},
	{(GstAudioPanoramaProcessFunc) gst_audio_panorama_transform_s2s_float,
	(GstAudioPanoramaProcessFunc)
	gst_audio_panorama_transform_s2s_float_simple}
	}
	};

	/* GObject vmethod implementations */

	static void
	gst_audio_panorama_class_init (GstAudioPanoramaClass * klass)
	{
	GObjectClass *gobject_class;
	GstElementClass *gstelement_class;

	GST_DEBUG_CATEGORY_INIT (gst_audio_panorama_debug, "audiopanorama", 0,
	"audiopanorama element");

	gobject_class = (GObjectClass *) klass;
	gstelement_class = (GstElementClass *) klass;

	gobject_class->set_property = gst_audio_panorama_set_property;
	gobject_class->get_property = gst_audio_panorama_get_property;

	g_object_class_install_property (gobject_class, PROP_PANORAMA,
	g_param_spec_float ("panorama", "Panorama",
	"Position in stereo panorama (-1.0 left -> 1.0 right)", -1.0, 1.0,
	0.0,
	G_PARAM_READWRITE \| GST_PARAM_CONTROLLABLE \| G_PARAM_STATIC_STRINGS));
	/**
	* GstAudioPanorama:method
	*
	* Panning method: psychoacoustic mode keeps the same perceived loudness,
	* while simple mode just controls the volume of one channel. It's merely
	* a matter of taste which method should be chosen.
	*
	* Since: 0.10.6
	**/
	g_object_class_install_property (gobject_class, PROP_METHOD,
	g_param_spec_enum ("method", "Panning method",
	"Psychoacoustic mode keeps same perceived loudness, "
	"simple mode just controls volume of one channel.",
	GST_TYPE_AUDIO_PANORAMA_METHOD, METHOD_PSYCHOACOUSTIC,
	G_PARAM_READWRITE \| G_PARAM_STATIC_STRINGS));

	gst_element_class_set_static_metadata (gstelement_class, "Stereo positioning",
	"Filter/Effect/Audio",
	"Positions audio streams in the stereo panorama",
	"Stefan Kost <ensonic@users.sf.net>");

	gst_element_class_add_pad_template (gstelement_class,
	gst_static_pad_template_get (&src_template));
	gst_element_class_add_pad_template (gstelement_class,
	gst_static_pad_template_get (&sink_template));

	GST_BASE_TRANSFORM_CLASS (klass)->get_unit_size =
	GST_DEBUG_FUNCPTR (gst_audio_panorama_get_unit_size);
	GST_BASE_TRANSFORM_CLASS (klass)->transform_caps =
	GST_DEBUG_FUNCPTR (gst_audio_panorama_transform_caps);
	GST_BASE_TRANSFORM_CLASS (klass)->set_caps =
	GST_DEBUG_FUNCPTR (gst_audio_panorama_set_caps);
	GST_BASE_TRANSFORM_CLASS (klass)->transform =
	GST_DEBUG_FUNCPTR (gst_audio_panorama_transform);
	}

	static void
	gst_audio_panorama_init (GstAudioPanorama * filter)
	{

	filter->panorama = 0;
	filter->method = METHOD_PSYCHOACOUSTIC;
	gst_audio_info_init (&filter->info);
	filter->process = NULL;

	gst_base_transform_set_gap_aware (GST_BASE_TRANSFORM (filter), TRUE);
	}

	static gboolean
	gst_audio_panorama_set_process_function (GstAudioPanorama * filter,
	GstAudioInfo * info)
	{
	gint channel_index, format_index, method_index;
	const GstAudioFormatInfo *finfo = info->finfo;

	/* set processing function */
	channel_index = GST_AUDIO_INFO_CHANNELS (info) - 1;
	if (channel_index > 1 \|\| channel_index < 0) {
	filter->process = NULL;
	return FALSE;
	}

	format_index = GST_AUDIO_FORMAT_INFO_IS_FLOAT (finfo) ? 1 : 0;

	method_index = filter->method;
	if (method_index >= NUM_METHODS \|\| method_index < 0)
	method_index = METHOD_PSYCHOACOUSTIC;

	filter->process =
	panorama_process_functions[channel_index][format_index][method_index];
	return TRUE;
	}

	static void
	gst_audio_panorama_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec)
	{
	GstAudioPanorama *filter = GST_AUDIO_PANORAMA (object);

	switch (prop_id) {
	case PROP_PANORAMA:
	filter->panorama = g_value_get_float (value);
	break;
	case PROP_METHOD:
	filter->method = g_value_get_enum (value);
	gst_audio_panorama_set_process_function (filter, &filter->info);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	static void
	gst_audio_panorama_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec)
	{
	GstAudioPanorama *filter = GST_AUDIO_PANORAMA (object);

	switch (prop_id) {
	case PROP_PANORAMA:
	g_value_set_float (value, filter->panorama);
	break;
	case PROP_METHOD:
	g_value_set_enum (value, filter->method);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	/* GstBaseTransform vmethod implementations */

	static gboolean
	gst_audio_panorama_get_unit_size (GstBaseTransform * base, GstCaps * caps,
	gsize * size)
	{
	GstAudioInfo info;

	g_assert (size);

	if (!gst_audio_info_from_caps (&info, caps))
	return FALSE;

	*size = GST_AUDIO_INFO_BPF (&info);

	return TRUE;
	}

	static GstCaps *
	gst_audio_panorama_transform_caps (GstBaseTransform * base,
	GstPadDirection direction, GstCaps * caps, GstCaps * filter)
	{
	GstCaps *res;
	GstStructure *structure;

	/* transform caps gives one single caps so we can just replace
	* the channel property with our range. */
	res = gst_caps_copy (caps);
	structure = gst_caps_get_structure (res, 0);
	if (direction == GST_PAD_SRC) {
	GST_INFO ("allow 1-2 channels");
	gst_structure_set (structure, "channels", GST_TYPE_INT_RANGE, 1, 2, NULL);
	} else {
	GST_INFO ("allow 2 channels");
	gst_structure_set (structure, "channels", G_TYPE_INT, 2, NULL);
	}

	return res;
	}

	static gboolean
	gst_audio_panorama_set_caps (GstBaseTransform * base, GstCaps * incaps,
	GstCaps * outcaps)
	{
	GstAudioPanorama *filter = GST_AUDIO_PANORAMA (base);
	GstAudioInfo info;

	/GST_INFO ("incaps are %" GST_PTR_FORMAT, incaps); /
	if (!gst_audio_info_from_caps (&info, incaps))
	goto no_format;

	GST_DEBUG ("try to process %d input with %d channels",
	GST_AUDIO_INFO_FORMAT (&info), GST_AUDIO_INFO_CHANNELS (&info));

	if (!gst_audio_panorama_set_process_function (filter, &info))
	goto no_format;

	filter->info = info;

	return TRUE;

	no_format:
	{
	GST_DEBUG ("invalid caps");
	return FALSE;
	}
	}

	/* psychoacoustic processing functions */
	static void
	gst_audio_panorama_transform_m2s_int (GstAudioPanorama * filter, gint16 * idata,
	gint16 * odata, guint num_samples)
	{
	guint i;
	gdouble val;
	glong lval, rval;
	gdouble rpan, lpan;

	/* pan: -1.0 0.0 1.0
	* lpan: 1.0 0.5 0.0
	* rpan: 0.0 0.5 1.0
	*
	* FIXME: we should use -3db (1/sqtr(2)) for 50:50
	*/
	rpan = (gdouble) (filter->panorama + 1.0) / 2.0;
	lpan = 1.0 - rpan;

	for (i = 0; i < num_samples; i++) {
	val = (gdouble) * idata++;

	lval = (glong) (val * lpan);
	rval = (glong) (val * rpan);

	*odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
	*odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
	}
	}

	static void
	gst_audio_panorama_transform_s2s_int (GstAudioPanorama * filter, gint16 * idata,
	gint16 * odata, guint num_samples)
	{
	guint i;
	glong lval, rval;
	gdouble lival, rival;
	gdouble lrpan, llpan, rrpan, rlpan;

	/* pan: -1.0 0.0 1.0
	* llpan: 1.0 1.0 0.0
	* lrpan: 1.0 0.0 0.0
	* rrpan: 0.0 1.0 1.0
	* rlpan: 0.0 0.0 1.0
	*/
	if (filter->panorama > 0) {
	rlpan = (gdouble) filter->panorama;
	llpan = 1.0 - rlpan;
	lrpan = 0.0;
	rrpan = 1.0;
	} else {
	rrpan = (gdouble) (1.0 + filter->panorama);
	lrpan = 1.0 - rrpan;
	rlpan = 0.0;
	llpan = 1.0;
	}

	for (i = 0; i < num_samples; i++) {
	lival = (gdouble) * idata++;
	rival = (gdouble) * idata++;

	lval = lival * llpan + rival * lrpan;
	rval = lival * rlpan + rival * rrpan;

	*odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
	*odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
	}
	}

	static void
	gst_audio_panorama_transform_m2s_float (GstAudioPanorama * filter,
	gfloat * idata, gfloat * odata, guint num_samples)
	{
	guint i;
	gfloat val;
	gdouble rpan, lpan;

	/* pan: -1.0 0.0 1.0
	* lpan: 1.0 0.5 0.0
	* rpan: 0.0 0.5 1.0
	*
	* FIXME: we should use -3db (1/sqtr(2)) for 50:50
	*/
	rpan = (gdouble) (filter->panorama + 1.0) / 2.0;
	lpan = 1.0 - rpan;

	for (i = 0; i < num_samples; i++) {
	val = *idata++;

	odata++ = val lpan;
	odata++ = val rpan;
	}
	}

	static void
	gst_audio_panorama_transform_s2s_float (GstAudioPanorama * filter,
	gfloat * idata, gfloat * odata, guint num_samples)
	{
	guint i;
	gfloat lival, rival;
	gdouble lrpan, llpan, rrpan, rlpan;

	/* pan: -1.0 0.0 1.0
	* llpan: 1.0 1.0 0.0
	* lrpan: 1.0 0.0 0.0
	* rrpan: 0.0 1.0 1.0
	* rlpan: 0.0 0.0 1.0
	*/
	if (filter->panorama > 0) {
	rlpan = (gdouble) filter->panorama;
	llpan = 1.0 - rlpan;
	lrpan = 0.0;
	rrpan = 1.0;
	} else {
	rrpan = (gdouble) (1.0 + filter->panorama);
	lrpan = 1.0 - rrpan;
	rlpan = 0.0;
	llpan = 1.0;
	}

	for (i = 0; i < num_samples; i++) {
	lival = *idata++;
	rival = *idata++;

	odata++ = lival llpan + rival * lrpan;
	odata++ = lival rlpan + rival * rrpan;
	}
	}

	/* simple processing functions */
	static void
	gst_audio_panorama_transform_m2s_int_simple (GstAudioPanorama * filter,
	gint16 * idata, gint16 * odata, guint num_samples)
	{
	guint i;
	gdouble pan;
	glong lval, rval;

	if (filter->panorama > 0.0) {
	pan = 1.0 - filter->panorama;
	for (i = 0; i < num_samples; i++) {
	rval = *idata++;
	lval = (glong) ((gdouble) rval * pan);

	*odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
	*odata++ = (gint16) rval;
	}
	} else {
	pan = 1.0 + filter->panorama;
	for (i = 0; i < num_samples; i++) {
	lval = *idata++;
	rval = (glong) ((gdouble) lval * pan);

	*odata++ = (gint16) lval;
	*odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
	}
	}
	}

	static void
	gst_audio_panorama_transform_s2s_int_simple (GstAudioPanorama * filter,
	gint16 * idata, gint16 * odata, guint num_samples)
	{
	guint i;
	glong lval, rval;
	gdouble lival, rival, pan;

	if (filter->panorama > 0.0) {
	pan = 1.0 - filter->panorama;
	for (i = 0; i < num_samples; i++) {
	lival = (gdouble) * idata++;
	rival = (gdouble) * idata++;

	lval = (glong) (lival * pan);
	rval = (glong) rival;

	*odata++ = (gint16) CLAMP (lval, G_MININT16, G_MAXINT16);
	*odata++ = (gint16) rval;
	}
	} else {
	pan = 1.0 + filter->panorama;
	for (i = 0; i < num_samples; i++) {
	lival = (gdouble) * idata++;
	rival = (gdouble) * idata++;

	lval = (glong) lival;
	rval = (glong) (rival * pan);

	*odata++ = (gint16) lval;
	*odata++ = (gint16) CLAMP (rval, G_MININT16, G_MAXINT16);
	}
	}
	}

	static void
	gst_audio_panorama_transform_m2s_float_simple (GstAudioPanorama * filter,
	gfloat * idata, gfloat * odata, guint num_samples)
	{
	guint i;
	gfloat val, pan;

	if (filter->panorama > 0.0) {
	pan = 1.0 - filter->panorama;
	for (i = 0; i < num_samples; i++) {
	val = *idata++;

	odata++ = val pan;
	*odata++ = val;
	}
	} else {
	pan = 1.0 + filter->panorama;
	for (i = 0; i < num_samples; i++) {
	val = *idata++;

	*odata++ = val;
	odata++ = val pan;
	}
	}
	}

	static void
	gst_audio_panorama_transform_s2s_float_simple (GstAudioPanorama * filter,
	gfloat * idata, gfloat * odata, guint num_samples)
	{
	guint i;
	gfloat lival, rival, pan;

	if (filter->panorama > 0.0) {
	pan = 1.0 - filter->panorama;
	for (i = 0; i < num_samples; i++) {
	lival = *idata++;
	rival = *idata++;

	odata++ = lival pan;
	*odata++ = rival;
	}
	} else {
	pan = 1.0 + filter->panorama;
	for (i = 0; i < num_samples; i++) {
	lival = *idata++;
	rival = *idata++;

	*odata++ = lival;
	odata++ = rival pan;
	}
	}
	}

	/* this function does the actual processing
	*/
	static GstFlowReturn
	gst_audio_panorama_transform (GstBaseTransform * base, GstBuffer * inbuf,
	GstBuffer * outbuf)
	{
	GstAudioPanorama *filter = GST_AUDIO_PANORAMA (base);
	GstClockTime timestamp, stream_time;
	GstMapInfo inmap, outmap;

	timestamp = GST_BUFFER_TIMESTAMP (inbuf);
	stream_time =
	gst_segment_to_stream_time (&base->segment, GST_FORMAT_TIME, timestamp);

	GST_DEBUG_OBJECT (filter, "sync to %" GST_TIME_FORMAT,
	GST_TIME_ARGS (timestamp));

	if (GST_CLOCK_TIME_IS_VALID (stream_time))
	gst_object_sync_values (GST_OBJECT (filter), stream_time);

	gst_buffer_map (inbuf, &inmap, GST_MAP_READ);
	gst_buffer_map (outbuf, &outmap, GST_MAP_WRITE);

	if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (inbuf, GST_BUFFER_FLAG_GAP))) {
	GST_BUFFER_FLAG_SET (outbuf, GST_BUFFER_FLAG_GAP);
	memset (outmap.data, 0, outmap.size);
	} else {
	/* output always stereo, input mono or stereo,
	* and info describes input format */
	guint num_samples = outmap.size / (2 * GST_AUDIO_INFO_BPS (&filter->info));

	filter->process (filter, inmap.data, outmap.data, num_samples);
	}

	gst_buffer_unmap (inbuf, &inmap);
	gst_buffer_unmap (outbuf, &outmap);

	return GST_FLOW_OK;
	}