scopes: first version of a scopes plugin using a new baseclass

Add a new baseclass for writing visualisation plugins. Provide a simple wave
oscilloscope as a first subclass.

https://bugzilla.gnome.org/show_bug.cgi?id=651536

configure.ac

@@ -346,6 +346,7 @@ AG_GST_CHECK_PLUGIN(real)
 AG_GST_CHECK_PLUGIN(rtpmux)
 AG_GST_CHECK_PLUGIN(rtpvp8)
 AG_GST_CHECK_PLUGIN(scaletempo)
+AG_GST_CHECK_PLUGIN(scopes)
 AG_GST_CHECK_PLUGIN(sdi)
 AG_GST_CHECK_PLUGIN(sdp)
 AG_GST_CHECK_PLUGIN(segmentclip)
@@ -1897,6 +1898,7 @@ gst/real/Makefile
 gst/rtpmux/Makefile
 gst/rtpvp8/Makefile
 gst/scaletempo/Makefile
+gst/scopes/Makefile
 gst/sdi/Makefile
 gst/sdp/Makefile
 gst/segmentclip/Makefile

gst/scopes/Makefile.am

@@ -0,0 +1,30 @@
+plugin_LTLIBRARIES = libgstscopes.la
+
+libgstscopes_la_SOURCES = \
+    gstbasescope.c plugin.c \
+    gstwavescope.c gstwavescope.h
+
+libgstscopes_la_CFLAGS = $(GST_PLUGINS_BAD_CFLAGS)\
+	$(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_CFLAGS) $(GST_CFLAGS)
+libgstscopes_la_LIBADD = \
+	$(GST_PLUGINS_BASE_LIBS) -lgstaudio-$(GST_MAJORMINOR) \
+	-lgstvideo-$(GST_MAJORMINOR) $(GST_BASE_LIBS) $(GST_LIBS)
+libgstscopes_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS)
+libgstscopes_la_LIBTOOLFLAGS = --tag=disable-static
+
+noinst_HEADERS = gstbasescope.h gstwavescope.h
+
+Android.mk: Makefile.am $(BUILT_SOURCES)
+	androgenizer \
+	-:PROJECT scopes -:SHARED scopes \
+	 -:TAGS eng debug \
+         -:REL_TOP $(top_srcdir) -:ABS_TOP $(abs_top_srcdir) \
+	 -:SOURCES $(libgstscopes_la_SOURCES) \
+	 -:CFLAGS $(DEFS) $(DEFAULT_INCLUDES) $(libgstscopes_la_CFLAGS) \
+	 -:LDFLAGS $(libgstscopes_la_LDFLAGS) \
+	           $(libgstscopes_la_LIBADD) \
+	           -ldl \
+	 -:PASSTHROUGH LOCAL_ARM_MODE:=arm \
+		       LOCAL_MODULE_PATH:='$$(TARGET_OUT)/lib/gstreamer-0.10' \
+	> $@
+

gst/scopes/gstbasescope.c

@@ -0,0 +1,422 @@
+/* GStreamer
+ * Copyright (C) <2011> Stefan Kost <ensonic@users.sf.net>
+ *
+ * gstbasescope.h: base class for audio visualisation elements
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+/**
+ * SECTION:gstbasescope
+ *
+ * A basclass for scopes. Takes care of re-fitting the audio-rate to video-rate.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include <string.h>
+
+#include "gstbasescope.h"
+
+GST_DEBUG_CATEGORY_STATIC (base_scope_debug);
+#define GST_CAT_DEFAULT (base_scope_debug)
+
+static GstBaseTransformClass *parent_class = NULL;
+
+static void gst_base_scope_class_init (GstBaseScopeClass * klass);
+static void gst_base_scope_init (GstBaseScope * scope,
+    GstBaseScopeClass * g_class);
+static void gst_base_scope_dispose (GObject * object);
+
+static gboolean gst_base_scope_src_negotiate (GstBaseScope * scope);
+static gboolean gst_base_scope_src_setcaps (GstPad * pad, GstCaps * caps);
+static gboolean gst_base_scope_sink_setcaps (GstPad * pad, GstCaps * caps);
+
+static GstFlowReturn gst_base_scope_chain (GstPad * pad, GstBuffer * buffer);
+static GstStateChangeReturn gst_base_scope_change_state (GstElement * element,
+    GstStateChange transition);
+
+GType
+gst_base_scope_get_type (void)
+{
+  static volatile gsize base_scope_type = 0;
+
+  if (g_once_init_enter (&base_scope_type)) {
+    static const GTypeInfo base_scope_info = {
+      sizeof (GstBaseScopeClass),
+      NULL,
+      NULL,
+      (GClassInitFunc) gst_base_scope_class_init,
+      NULL,
+      NULL,
+      sizeof (GstBaseScope),
+      0,
+      (GInstanceInitFunc) gst_base_scope_init,
+    };
+    GType _type;
+
+    _type = g_type_register_static (GST_TYPE_ELEMENT,
+        "GstBaseScope", &base_scope_info, G_TYPE_FLAG_ABSTRACT);
+    g_once_init_leave (&base_scope_type, _type);
+  }
+  return (GType) base_scope_type;
+}
+
+static void
+gst_base_scope_class_init (GstBaseScopeClass * klass)
+{
+  GObjectClass *gobject_class = (GObjectClass *) klass;
+  GstElementClass *element_class = (GstElementClass *) klass;
+
+  parent_class = g_type_class_peek_parent (klass);
+
+  GST_DEBUG_CATEGORY_INIT (base_scope_debug, "basescope", 0,
+      "scope audio visualisation base class");
+
+  gobject_class->dispose = gst_base_scope_dispose;
+  element_class->change_state = GST_DEBUG_FUNCPTR (gst_base_scope_change_state);
+}
+
+static void
+gst_base_scope_init (GstBaseScope * scope, GstBaseScopeClass * g_class)
+{
+  GstPadTemplate *pad_template;
+
+  /* create the sink and src pads */
+  pad_template =
+      gst_element_class_get_pad_template (GST_ELEMENT_CLASS (g_class), "sink");
+  g_return_if_fail (pad_template != NULL);
+  scope->sinkpad = gst_pad_new_from_template (pad_template, "sink");
+  gst_pad_set_chain_function (scope->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_base_scope_chain));
+  gst_pad_set_setcaps_function (scope->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_base_scope_sink_setcaps));
+  gst_element_add_pad (GST_ELEMENT (scope), scope->sinkpad);
+
+  pad_template =
+      gst_element_class_get_pad_template (GST_ELEMENT_CLASS (g_class), "src");
+  g_return_if_fail (pad_template != NULL);
+  scope->srcpad = gst_pad_new_from_template (pad_template, "src");
+  gst_pad_set_setcaps_function (scope->srcpad,
+      GST_DEBUG_FUNCPTR (gst_base_scope_src_setcaps));
+  gst_element_add_pad (GST_ELEMENT (scope), scope->srcpad);
+
+  scope->adapter = gst_adapter_new ();
+  scope->inbuf = gst_buffer_new ();
+
+  /* reset the initial video state */
+  scope->width = 320;
+  scope->height = 200;
+  scope->fps_n = 25;            /* desired frame rate */
+  scope->fps_d = 1;
+  scope->frame_duration = GST_CLOCK_TIME_NONE;
+
+  /* reset the initial audio state */
+  scope->rate = GST_AUDIO_DEF_RATE;
+  scope->channels = 2;
+
+  scope->next_ts = GST_CLOCK_TIME_NONE;
+
+}
+
+static void
+gst_base_scope_dispose (GObject * object)
+{
+  GstBaseScope *scope = GST_BASE_SCOPE (object);
+
+  if (scope->adapter) {
+    g_object_unref (scope->adapter);
+    scope->adapter = NULL;
+  }
+  if (scope->inbuf) {
+    gst_buffer_unref (scope->inbuf);
+    scope->inbuf = NULL;
+  }
+
+  G_OBJECT_CLASS (parent_class)->dispose (object);
+}
+
+static gboolean
+gst_base_scope_sink_setcaps (GstPad * pad, GstCaps * caps)
+{
+  GstBaseScope *scope;
+  GstStructure *structure;
+  gint channels;
+  gint rate;
+  gboolean res = TRUE;
+
+  scope = GST_BASE_SCOPE (gst_pad_get_parent (pad));
+  structure = gst_caps_get_structure (caps, 0);
+
+  if (!gst_structure_get_int (structure, "channels", &channels) ||
+      !gst_structure_get_int (structure, "rate", &rate))
+    goto missing_caps_details;
+
+  if (channels != 2)
+    goto wrong_channels;
+
+  if (rate <= 0)
+    goto wrong_rate;
+
+  scope->channels = channels;
+  scope->rate = rate;
+
+  GST_DEBUG_OBJECT (scope, "audio: channels %d, rate %d",
+      scope->channels, scope->rate);
+
+done:
+  gst_object_unref (scope);
+  return res;
+
+  /* Errors */
+missing_caps_details:
+  {
+    GST_WARNING_OBJECT (scope, "missing channels or rate in the caps");
+    res = FALSE;
+    goto done;
+  }
+wrong_channels:
+  {
+    GST_WARNING_OBJECT (scope, "number of channels must be 2, but is %d",
+        channels);
+    res = FALSE;
+    goto done;
+  }
+wrong_rate:
+  {
+    GST_WARNING_OBJECT (scope, "sample rate must be >0, but is %d", rate);
+    res = FALSE;
+    goto done;
+  }
+}
+
+static gboolean
+gst_base_scope_src_negotiate (GstBaseScope * scope)
+{
+  GstCaps *othercaps, *target, *intersect;
+  GstStructure *structure;
+  const GstCaps *templ;
+
+  templ = gst_pad_get_pad_template_caps (scope->srcpad);
+
+  GST_DEBUG_OBJECT (scope, "performing negotiation");
+
+  /* see what the peer can do */
+  othercaps = gst_pad_peer_get_caps (scope->srcpad);
+  if (othercaps) {
+    intersect = gst_caps_intersect (othercaps, templ);
+    gst_caps_unref (othercaps);
+
+    if (gst_caps_is_empty (intersect))
+      goto no_format;
+
+    target = gst_caps_copy_nth (intersect, 0);
+    gst_caps_unref (intersect);
+  } else {
+    target = gst_caps_ref ((GstCaps *) templ);
+  }
+
+  structure = gst_caps_get_structure (target, 0);
+  gst_structure_fixate_field_nearest_int (structure, "width", scope->width);
+  gst_structure_fixate_field_nearest_int (structure, "height", scope->height);
+  gst_structure_fixate_field_nearest_fraction (structure, "framerate",
+      scope->fps_n, scope->fps_d);
+
+  GST_DEBUG_OBJECT (scope, "final caps are %" GST_PTR_FORMAT, target);
+
+  gst_pad_set_caps (scope->srcpad, target);
+  gst_caps_unref (target);
+
+  return TRUE;
+
+no_format:
+  {
+    gst_caps_unref (intersect);
+    return FALSE;
+  }
+}
+
+static gboolean
+gst_base_scope_src_setcaps (GstPad * pad, GstCaps * caps)
+{
+  GstBaseScope *scope;
+  GstBaseScopeClass *klass;
+  gint w, h;
+  gint num, denom;
+  GstVideoFormat format;
+  gboolean res = TRUE;
+
+  scope = GST_BASE_SCOPE (gst_pad_get_parent (pad));
+  klass = GST_BASE_SCOPE_CLASS (G_OBJECT_GET_CLASS (scope));
+
+  if (!gst_video_format_parse_caps (caps, &format, &w, &h)) {
+    goto missing_caps_details;
+  }
+  if (!gst_video_parse_caps_framerate (caps, &num, &denom)) {
+    goto missing_caps_details;
+  }
+
+  scope->width = w;
+  scope->height = h;
+  scope->fps_n = num;
+  scope->fps_d = denom;
+  scope->video_format = format;
+
+  scope->frame_duration = gst_util_uint64_scale_int (GST_SECOND,
+      scope->fps_d, scope->fps_n);
+  scope->spf = gst_util_uint64_scale_int (scope->rate,
+      scope->fps_d, scope->fps_n);
+
+  /*
+     synaesthesia_resize (scope->si, scope->width, scope->height);
+   */
+  if (klass->setup)
+    res = klass->setup (scope);
+
+  GST_DEBUG_OBJECT (scope, "video: dimension %dx%d, framerate %d/%d, spf %d",
+      scope->width, scope->height, scope->fps_n, scope->fps_d, scope->spf);
+
+done:
+  gst_object_unref (scope);
+  return res;
+
+  /* Errors */
+missing_caps_details:
+  {
+    GST_WARNING_OBJECT (scope,
+        "missing width, height or framerate in the caps");
+    res = FALSE;
+    goto done;
+  }
+}
+
+static GstFlowReturn
+gst_base_scope_chain (GstPad * pad, GstBuffer * buffer)
+{
+  GstFlowReturn ret = GST_FLOW_OK;
+  GstBaseScope *scope;
+  GstBaseScopeClass *klass;
+  GstBuffer *inbuf;
+  guint32 avail, bytesperread;
+  guint bpp;
+  gboolean (*render) (GstBaseScope * scope, GstBuffer * audio,
+      GstBuffer * video);
+
+  scope = GST_BASE_SCOPE (gst_pad_get_parent (pad));
+  klass = GST_BASE_SCOPE_CLASS (G_OBJECT_GET_CLASS (scope));
+
+  render = klass->render;
+
+  GST_LOG_OBJECT (scope, "chainfunc called");
+
+  /* resync on DISCONT */
+  if (GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DISCONT)) {
+    scope->next_ts = GST_CLOCK_TIME_NONE;
+    gst_adapter_clear (scope->adapter);
+  }
+
+  if (GST_PAD_CAPS (scope->srcpad) == NULL) {
+    if (!gst_base_scope_src_negotiate (scope))
+      return GST_FLOW_NOT_NEGOTIATED;
+  }
+
+  /* Match timestamps from the incoming audio */
+  if (GST_BUFFER_TIMESTAMP (buffer) != GST_CLOCK_TIME_NONE)
+    scope->next_ts = GST_BUFFER_TIMESTAMP (buffer);
+
+  gst_adapter_push (scope->adapter, buffer);
+
+  /* this is what we want */
+  bytesperread = scope->spf * scope->channels * sizeof (gint16);
+
+  bpp = gst_video_format_get_pixel_stride (scope->video_format, 0);
+
+  inbuf = scope->inbuf;
+  /* FIXME: the timestamp in the adapter would be different */
+  gst_buffer_copy_metadata (inbuf, buffer, GST_BUFFER_COPY_ALL);
+
+  /* this is what we have */
+  avail = gst_adapter_available (scope->adapter);
+  while (avail > bytesperread) {
+    GstBuffer *outbuf;
+
+    ret = gst_pad_alloc_buffer_and_set_caps (scope->srcpad,
+        GST_BUFFER_OFFSET_NONE,
+        scope->width * scope->height * bpp,
+        GST_PAD_CAPS (scope->srcpad), &outbuf);
+
+    /* no buffer allocated, we don't care why. */
+    if (ret != GST_FLOW_OK)
+      break;
+
+    GST_BUFFER_TIMESTAMP (outbuf) = scope->next_ts;
+    GST_BUFFER_DURATION (outbuf) = scope->frame_duration;
+    memset (GST_BUFFER_DATA (outbuf), 0, GST_BUFFER_SIZE (outbuf));
+
+    GST_BUFFER_DATA (inbuf) =
+        (guint8 *) gst_adapter_peek (scope->adapter, bytesperread);
+    GST_BUFFER_SIZE (inbuf) = bytesperread;
+
+    /*
+       guchar * out_frame = (guchar *)
+       scope_update (scope->si, scope->datain);
+       memcpy (GST_BUFFER_DATA (outbuf), out_frame, GST_BUFFER_SIZE (outbuf));
+     */
+    /* call class->render() vmethod */
+    if (render)
+      if (!render (scope, inbuf, outbuf)) {
+        ret = GST_FLOW_ERROR;
+      }
+
+    ret = gst_pad_push (scope->srcpad, outbuf);
+    outbuf = NULL;
+
+    /* FIXME: we want to ev. take less
+     * we need to align the audio-rate, video-rate and blocksize for render
+     */
+    gst_adapter_flush (scope->adapter, bytesperread);
+
+    if (ret != GST_FLOW_OK)
+      break;
+
+    if (scope->next_ts != GST_CLOCK_TIME_NONE)
+      scope->next_ts += scope->frame_duration;
+
+    avail = gst_adapter_available (scope->adapter);
+  }
+
+  gst_object_unref (scope);
+
+  return ret;
+}
+
+static GstStateChangeReturn
+gst_base_scope_change_state (GstElement * element, GstStateChange transition)
+{
+  GstBaseScope *scope;
+
+  scope = GST_BASE_SCOPE (element);
+
+  switch (transition) {
+    case GST_STATE_CHANGE_READY_TO_PAUSED:
+      scope->next_ts = GST_CLOCK_TIME_NONE;
+      gst_adapter_clear (scope->adapter);
+      break;
+    default:
+      break;
+  }
+
+  return GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
+}

gst/scopes/gstbasescope.h

@@ -0,0 +1,81 @@
+/* GStreamer
+ * Copyright (C) <2011> Stefan Kost <ensonic@users.sf.net>
+ *
+ * gstbasescope.c: base class for audio visualisation elements
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __GST_BASE_SCOPE_H__
+#define __GST_BASE_SCOPE_H__
+
+#include <gst/gst.h>
+#include <gst/base/gstbasetransform.h>
+
+#include <gst/video/video.h>
+#include <gst/audio/audio.h>
+#include <gst/base/gstadapter.h>
+
+G_BEGIN_DECLS
+#define GST_TYPE_BASE_SCOPE            (gst_base_scope_get_type())
+#define GST_BASE_SCOPE(obj)            (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_BASE_SCOPE,GstBaseScope))
+#define GST_BASE_SCOPE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_BASE_SCOPE,GstBaseScopeClass))
+#define GST_IS_SYNAESTHESIA(obj)         (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_BASE_SCOPE))
+#define GST_IS_SYNAESTHESIA_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_BASE_SCOPE))
+typedef struct _GstBaseScope GstBaseScope;
+typedef struct _GstBaseScopeClass GstBaseScopeClass;
+
+struct _GstBaseScope
+{
+  GstElement parent;
+
+  /* pads */
+  GstPad *srcpad, *sinkpad;
+
+  GstAdapter *adapter;
+  GstBuffer *inbuf;
+
+  guint64 next_ts;              /* the timestamp of the next frame */
+  guint64 frame_duration;
+  guint bps;                    /* bytes per sample        */
+  guint spf;                    /* samples per video frame */
+
+  /* video state */
+  GstVideoFormat video_format;
+  gint fps_n, fps_d;
+  gint width;
+  gint height;
+  gint channels;
+
+  /* audio state */
+  gint sample_rate;
+  gint rate;
+};
+
+struct _GstBaseScopeClass
+{
+  GstElementClass parent_class;
+
+  /* virtual function, called whenever the format changes */
+  gboolean (*setup) (GstBaseScope * scope);
+
+  /* virtual function for rendering a frame */
+  gboolean (*render) (GstBaseScope * scope, GstBuffer * audio, GstBuffer * video);
+};
+
+GType gst_base_scope_get_type (void);
+
+G_END_DECLS
+#endif /* __GST_BASE_SCOPE_H__ */

gst/scopes/gstwavescope.c

@@ -0,0 +1,141 @@
+/* GStreamer
+ * Copyright (C) <2011> Stefan Kost <ensonic@users.sf.net>
+ *
+ * gstwavescope.c: simple oscilloscope
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+/**
+ * SECTION:element-wavescope
+ * @see_also: goom
+ *
+ * Wavescope is a simple audio visualisation element. It renders the waveforms
+ * like on an oscilloscope.
+ *
+ * <refsect2>
+ * <title>Example launch line</title>
+ * |[
+ * gst-launch audiotestsrc ! audioconvert ! wavescope ! ximagesink
+ * ]|
+ * </refsect2>
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstwavescope.h"
+
+static GstStaticPadTemplate gst_wave_scope_src_template =
+GST_STATIC_PAD_TEMPLATE ("src",
+    GST_PAD_SRC,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS (GST_VIDEO_CAPS_xRGB_HOST_ENDIAN)
+    );
+
+static GstStaticPadTemplate gst_wave_scope_sink_template =
+GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS (GST_AUDIO_INT_STANDARD_PAD_TEMPLATE_CAPS)
+    );
+
+
+GST_DEBUG_CATEGORY_STATIC (wave_scope_debug);
+#define GST_CAT_DEFAULT wave_scope_debug
+
+static gboolean gst_wave_scope_setup (GstBaseScope * scope);
+static gboolean gst_wave_scope_render (GstBaseScope * scope, GstBuffer * audio,
+    GstBuffer * video);
+
+
+GST_BOILERPLATE (GstWaveScope, gst_wave_scope, GstBaseScope,
+    GST_TYPE_BASE_SCOPE);
+
+static void
+gst_wave_scope_base_init (gpointer g_class)
+{
+  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
+
+  gst_element_class_set_details_simple (element_class, "Waveform oscilloscope",
+      "Visualization",
+      "Simple waveform oscilloscope", "Stefan Kost <ensonic@users.sf.net>");
+
+  gst_element_class_add_pad_template (element_class,
+      gst_static_pad_template_get (&gst_wave_scope_src_template));
+  gst_element_class_add_pad_template (element_class,
+      gst_static_pad_template_get (&gst_wave_scope_sink_template));
+}
+
+static void
+gst_wave_scope_class_init (GstWaveScopeClass * g_class)
+{
+  /*GObjectClass *gobject_class = (GObjectClass *) g_class; */
+  GstBaseScopeClass *scope_class = (GstBaseScopeClass *) g_class;
+
+  scope_class->setup = GST_DEBUG_FUNCPTR (gst_wave_scope_setup);
+  scope_class->render = GST_DEBUG_FUNCPTR (gst_wave_scope_render);
+}
+
+static void
+gst_wave_scope_init (GstWaveScope * scope, GstWaveScopeClass * g_class)
+{
+  /* do nothing */
+}
+
+static gboolean
+gst_wave_scope_setup (GstBaseScope * scope)
+{
+  return TRUE;
+}
+
+static gboolean
+gst_wave_scope_render (GstBaseScope * scope, GstBuffer * audio,
+    GstBuffer * video)
+{
+  guint8 *vdata = GST_BUFFER_DATA (video);
+  gint16 *adata = (gint16 *) GST_BUFFER_DATA (audio);
+  guint i, c, s, x, y, off, oy;
+  guint num_samples;
+  gfloat dx, dy;
+  guint bpp = gst_video_format_get_pixel_stride (scope->video_format, 0);
+  guint bpl = bpp * scope->width;
+
+  /* draw dots */
+  num_samples = GST_BUFFER_SIZE (audio) / (scope->channels * sizeof (gint16));
+  dx = (gfloat) scope->width / (gfloat) num_samples;
+  dy = scope->height / 65536.0;
+  oy = scope->height / 2;
+  s = 0;
+  for (i = 0; i < num_samples; i++) {
+    x = (guint) ((gfloat) i * dx);
+    for (c = 0; c < scope->channels; c++) {
+      y = (guint) (oy + (gfloat) adata[s++] * dy);
+      off = (y * bpl) + (x * bpp);
+      vdata[off + 0] = 0xFF;
+      vdata[off + 1] = 0xFF;
+      vdata[off + 2] = 0xFF;
+    }
+  }
+  return TRUE;
+}
+
+gboolean
+gst_wave_scope_plugin_init (GstPlugin * plugin)
+{
+  GST_DEBUG_CATEGORY_INIT (wave_scope_debug, "wavescope", 0, "wavescope");
+
+  return gst_element_register (plugin, "wavescope", GST_RANK_NONE,
+      GST_TYPE_WAVE_SCOPE);
+}

gst/scopes/gstwavescope.h

@@ -0,0 +1,50 @@
+/* GStreamer
+ * Copyright (C) <2011> Stefan Kost <ensonic@users.sf.net>
+ *
+ * gstwavescope.h: simple oscilloscope
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+
+#ifndef __GST_WAVE_SCOPE_H__
+#define __GST_WAVE_SCOPE_H__
+
+#include "gstbasescope.h"
+
+G_BEGIN_DECLS
+#define GST_TYPE_WAVE_SCOPE            (gst_wave_scope_get_type())
+#define GST_WAVE_SCOPE(obj)            (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_WAVE_SCOPE,GstWaveScope))
+#define GST_WAVE_SCOPE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_WAVE_SCOPE,GstWaveScopeClass))
+#define GST_IS_WAVE_SCOPE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_WAVE_SCOPE))
+#define GST_IS_WAVE_SCOPE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_WAVE_SCOPE))
+typedef struct _GstWaveScope GstWaveScope;
+typedef struct _GstWaveScopeClass GstWaveScopeClass;
+
+struct _GstWaveScope
+{
+  GstBaseScope parent;
+};
+
+struct _GstWaveScopeClass
+{
+  GstBaseScopeClass parent_class;
+};
+
+GType gst_wave_scope_get_type (void);
+gboolean gst_wave_scope_plugin_init (GstPlugin * plugin);
+
+G_END_DECLS
+#endif /* __GST_WAVE_SCOPE_H__ */

gst/scopes/plugin.c

@@ -0,0 +1,37 @@
+/* GStreamer
+ * Copyright (C) <2011> Stefan Kost <ensonic@users.sf.net>
+ *
+ * plugin.c: scopes plugin
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include <gst/gst.h>
+#include "gstwavescope.h"
+
+static gboolean
+plugin_init (GstPlugin * plugin)
+{
+  return gst_wave_scope_plugin_init (plugin);
+}
+
+GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
+    GST_VERSION_MINOR,
+    "scopes",
+    "Creates video visualizations of audio input",
+    plugin_init, VERSION, "GPL", GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN)