audiofx/echo: added surround-delay and surround-mask

Add a new boolean surround-delay property that makes
audioecho just apply a delay to certain channels to create
a surround effect, rather than an echo on all
channels. This is useful when upmixing from stereo - for example.

Add a surround-mask property to control which channels
are considered surround sound channels when adding a
delay with surround-delay = true

Original patch from Jochen Henneberg <jh@henneberg-systemdesign.com>

gst/audiofx/audioecho.c

@@ -32,11 +32,18 @@
  * will be used. This can only be set before going to the PAUSED or PLAYING
  * state and will be set to the current delay by default.
  *
+ * audioecho can also be used to apply a configurable delay to audio channels
+ * by setting surround-delay=true. In that mode, it just delays "surround
+ * channels" by the delay amount instead of performing an echo. The
+ * channels that are configured surround channels for the delay are
+ * selected using the surround-channels mask property.
+ *
  * <refsect2>
- * <title>Example launch line</title>
+ * <title>Example launch lines</title>
  * |[
  * gst-launch-1.0 autoaudiosrc ! audioconvert ! audioecho delay=500000000 intensity=0.6 feedback=0.4 ! audioconvert ! autoaudiosink
  * gst-launch-1.0 filesrc location="melo1.ogg" ! decodebin ! audioconvert ! audioecho delay=50000000 intensity=0.6 feedback=0.4 ! audioconvert ! autoaudiosink
+ * gst-launch-1.0 audiotestsrc ! audioconvert ! audio/x-raw,channels=4 ! audioecho surround-delay=true delay=500000000 ! audioconvert ! autoaudiosink
  * ]|
  * </refsect2>
  */
@@ -55,13 +62,18 @@
 #define GST_CAT_DEFAULT gst_audio_echo_debug
 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
 
+/* Everything except the first 2 channels are considered surround */
+#define DEFAULT_SURROUND_MASK ~((guint64)(0x3))
+
 enum
 {
   PROP_0,
   PROP_DELAY,
   PROP_MAX_DELAY,
   PROP_INTENSITY,
-  PROP_FEEDBACK
+  PROP_FEEDBACK,
+  PROP_SUR_DELAY,
+  PROP_SUR_MASK
 };
 
 #define ALLOWED_CAPS \
@@ -135,6 +147,19 @@ gst_audio_echo_class_init (GstAudioEchoClass * klass)
           0.0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS
           | GST_PARAM_CONTROLLABLE));
 
+  g_object_class_install_property (gobject_class, PROP_SUR_DELAY,
+      g_param_spec_boolean ("surround-delay", "Enable Surround Delay",
+          "Delay Surround Channels when TRUE instead of applying an echo effect",
+          FALSE,
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_CONTROLLABLE));
+
+  g_object_class_install_property (gobject_class, PROP_SUR_MASK,
+      g_param_spec_uint64 ("surround-mask", "Surround Mask",
+          "A bitmask of channels that are considered surround and delayed when surround-delay = TRUE",
+          1, G_MAXUINT64, DEFAULT_SURROUND_MASK,
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS |
+          GST_PARAM_MUTABLE_READY));
+
   gst_element_class_set_static_metadata (gstelement_class, "Audio echo",
       "Filter/Effect/Audio",
       "Adds an echo or reverb effect to an audio stream",
@@ -158,6 +183,8 @@ gst_audio_echo_init (GstAudioEcho * self)
   self->max_delay = 1;
   self->intensity = 0.0;
   self->feedback = 0.0;
+  self->surdelay = FALSE;
+  self->surround_mask = DEFAULT_SURROUND_MASK;
 
   g_mutex_init (&self->lock);
 
@@ -242,6 +269,18 @@ gst_audio_echo_set_property (GObject * object, guint prop_id,
       g_mutex_unlock (&self->lock);
       break;
     }
+    case PROP_SUR_DELAY:{
+      g_mutex_lock (&self->lock);
+      self->surdelay = g_value_get_boolean (value);
+      g_mutex_unlock (&self->lock);
+      break;
+    }
+    case PROP_SUR_MASK:{
+      g_mutex_lock (&self->lock);
+      self->surround_mask = g_value_get_uint64 (value);
+      g_mutex_unlock (&self->lock);
+      break;
+    }
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -275,6 +314,17 @@ gst_audio_echo_get_property (GObject * object, guint prop_id,
       g_value_set_float (value, self->feedback);
       g_mutex_unlock (&self->lock);
       break;
+    case PROP_SUR_DELAY:
+      g_mutex_lock (&self->lock);
+      g_value_set_boolean (value, self->surdelay);
+      g_mutex_unlock (&self->lock);
+      break;
+    case PROP_SUR_MASK:{
+      g_mutex_lock (&self->lock);
+      g_value_set_uint64 (value, self->surround_mask);
+      g_mutex_unlock (&self->lock);
+      break;
+    }
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -347,16 +397,30 @@ gst_audio_echo_transform_##name (GstAudioEcho * self, \
     guint echo0_index = ((echo_index + self->buffer_pos) % self->buffer_size_frames) * channels; \
     guint echo1_index = ((echo_index + self->buffer_pos +1) % self->buffer_size_frames) * channels; \
     guint rbout_index = (self->buffer_pos % self->buffer_size_frames) * channels; \
+    guint64 channel_mask = 1; \
     for (j = 0; j < channels; j++) { \
+      if (self->surdelay == FALSE) { \
         gdouble in = data[i*channels + j]; \
         gdouble echo0 = buffer[echo0_index + j]; \
         gdouble echo1 = buffer[echo1_index + j]; \
         gdouble echo = echo0 + (echo1-echo0)*echo_off; \
         type out = in + self->intensity * echo; \
         \
+        GST_DEBUG ( "not adding delay on Surround Channel %d", j); \
         data[i*channels + j] = out; \
         \
         buffer[rbout_index + j] = in + self->feedback * echo; \
+      } else if (channel_mask & self->surround_mask) { \
+        gdouble in = data[i*channels + j]; \
+        gdouble echo0 = buffer[echo0_index + j]; \
+        type out = echo0; \
+        GST_DEBUG ( "Adding delay on Surround Channel %d", j); \
+        \
+        data[i*channels + j] = out; \
+        \
+        buffer[rbout_index + j] = in; \
+      } \
+      channel_mask <<= 1; \
     } \
     self->buffer_pos = (self->buffer_pos + 1) % self->buffer_size_frames; \
   } \

gst/audiofx/audioecho.h

@@ -47,6 +47,8 @@ struct _GstAudioEcho
   guint64 max_delay;
   gfloat intensity;
   gfloat feedback;
+  gboolean surdelay;
+  guint64 surround_mask;
 
   /* < private > */
   GstAudioEchoProcessFunc process;