audiofxbasefirfilter: Add property for not draining the history on kernel changes

Currently this only works if the kernel size doesn't change, in the future
it will be possible to change the kernel size too without draining
the complete history and without loosing anything.

Partially based on a patch by
Thiago Santos <thiago.sousa.santos@collabora.co.uk>

gst/audiofx/audiofirfilter.c

@@ -148,9 +148,6 @@ gst_audio_fir_filter_update_kernel (GstAudioFIRFilter * self, GValueArray * va)
   gdouble *kernel;
   guint i;
 
-  gst_audio_fx_base_fir_filter_push_residue (GST_AUDIO_FX_BASE_FIR_FILTER
-      (self));
-
   if (va) {
     if (self->kernel)
       g_value_array_free (self->kernel);
@@ -231,9 +228,7 @@ gst_audio_fir_filter_set_property (GObject * object, guint prop_id,
   switch (prop_id) {
     case PROP_KERNEL:
       g_mutex_lock (self->lock);
-      gst_audio_fx_base_fir_filter_push_residue (GST_AUDIO_FX_BASE_FIR_FILTER
-          (self));
-
+      /* update kernel already pushes residues */
       gst_audio_fir_filter_update_kernel (self, g_value_dup_boxed (value));
       g_mutex_unlock (self->lock);
       break;

gst/audiofx/audiofxbasefirfilter.c

@@ -59,10 +59,12 @@ GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
 enum
 {
   PROP_0 = 0,
-  PROP_LOW_LATENCY
+  PROP_LOW_LATENCY,
+  PROP_DRAIN_ON_CHANGES
 };
 
 #define DEFAULT_LOW_LATENCY FALSE
+#define DEFAULT_DRAIN_ON_CHANGES TRUE
 
 GST_BOILERPLATE_FULL (GstAudioFXBaseFIRFilter, gst_audio_fx_base_fir_filter,
     GstAudioFilter, GST_TYPE_AUDIO_FILTER, DEBUG_INIT);
@@ -290,6 +292,8 @@ process_fft_##channels##_##width (GstAudioFXBaseFIRFilter * self, const g##ctype
     self->buffer_fill = buffer_fill = kernel_length - 1; \
   } \
   \
+  g_assert (self->buffer_length == block_length); \
+  \
   while (input_samples) { \
     pass = MIN (buffer_length - buffer_fill, input_samples); \
     \
@@ -505,6 +509,12 @@ gst_audio_fx_base_fir_filter_set_property (GObject * object, guint prop_id,
       GST_BASE_TRANSFORM_UNLOCK (self);
       break;
     }
+    case PROP_DRAIN_ON_CHANGES:{
+      GST_BASE_TRANSFORM_LOCK (self);
+      self->drain_on_changes = g_value_get_boolean (value);
+      GST_BASE_TRANSFORM_UNLOCK (self);
+      break;
+    }
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -521,6 +531,9 @@ gst_audio_fx_base_fir_filter_get_property (GObject * object, guint prop_id,
     case PROP_LOW_LATENCY:
       g_value_set_boolean (value, self->low_latency);
       break;
+    case PROP_DRAIN_ON_CHANGES:
+      g_value_set_boolean (value, self->drain_on_changes);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -564,6 +577,22 @@ gst_audio_fx_base_fir_filter_class_init (GstAudioFXBaseFIRFilterClass * klass)
           "Can only be changed in states < PAUSED!", DEFAULT_LOW_LATENCY,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstAudioFXBaseFIRFilter::drain-on-changes:
+   *
+   * Whether the filter should be drained when its coeficients change
+   *
+   * Note: Currently this only works if the kernel size is not changed!
+   * Support for drainless kernel size changes will be added in the future.
+   *
+   * Since: 0.10.18
+   */
+  g_object_class_install_property (gobject_class, PROP_DRAIN_ON_CHANGES,
+      g_param_spec_boolean ("drain-on-changes", "Drain on changes",
+          "Drains the filter when its coeficients change",
+          DEFAULT_DRAIN_ON_CHANGES,
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   trans_class->transform =
       GST_DEBUG_FUNCPTR (gst_audio_fx_base_fir_filter_transform);
   trans_class->start = GST_DEBUG_FUNCPTR (gst_audio_fx_base_fir_filter_start);
@@ -588,6 +617,7 @@ gst_audio_fx_base_fir_filter_init (GstAudioFXBaseFIRFilter * self,
   self->nsamples_in = 0;
 
   self->low_latency = DEFAULT_LOW_LATENCY;
+  self->drain_on_changes = DEFAULT_DRAIN_ON_CHANGES;
 
   gst_pad_set_query_function (GST_BASE_TRANSFORM (self)->srcpad,
       gst_audio_fx_base_fir_filter_query);
@@ -1009,7 +1039,16 @@ gst_audio_fx_base_fir_filter_set_kernel (GstAudioFXBaseFIRFilter * self,
   g_return_if_fail (self != NULL);
 
   GST_BASE_TRANSFORM_LOCK (self);
-  if (self->buffer) {
+
+  latency_changed = (self->latency != latency
+      || (!self->low_latency && self->kernel_length < FFT_THRESHOLD
+          && kernel_length >= FFT_THRESHOLD)
+      || (!self->low_latency && self->kernel_length >= FFT_THRESHOLD
+          && kernel_length < FFT_THRESHOLD));
+
+  /* FIXME: If the latency changes, the buffer size changes too and we
+   * have to drain in any case until this is fixed in the future */
+  if (self->buffer && (!self->drain_on_changes || latency_changed)) {
     gst_audio_fx_base_fir_filter_push_residue (self);
     self->start_ts = GST_CLOCK_TIME_NONE;
     self->start_off = GST_BUFFER_OFFSET_NONE;
@@ -1018,17 +1057,13 @@ gst_audio_fx_base_fir_filter_set_kernel (GstAudioFXBaseFIRFilter * self,
     self->buffer_fill = 0;
   }
 
-  latency_changed = (self->latency != latency
-      || (!self->low_latency && self->kernel_length < FFT_THRESHOLD
-          && kernel_length >= FFT_THRESHOLD)
-      || (!self->low_latency && self->kernel_length >= FFT_THRESHOLD
-          && kernel_length < FFT_THRESHOLD));
-
   g_free (self->kernel);
-  g_free (self->buffer);
-  self->buffer = NULL;
-  self->buffer_fill = 0;
-  self->buffer_length = 0;
+  if (!self->drain_on_changes || latency_changed) {
+    g_free (self->buffer);
+    self->buffer = NULL;
+    self->buffer_fill = 0;
+    self->buffer_length = 0;
+  }
 
   self->kernel = kernel;
   self->kernel_length = kernel_length;

gst/audiofx/audiofxbasefirfilter.h

@@ -62,6 +62,9 @@ struct _GstAudioFXBaseFIRFilter {
   guint64 latency;              /* pre-latency of the filter kernel */
   gboolean low_latency;         /* work in slower low latency mode */
 
+  gboolean drain_on_changes;    /* If the filter should be drained when
+                                 * coeficients change */
+
   /* < private > */
   GstAudioFXBaseFIRFilterProcessFunc process;