midiparse: add basic midi parser

Parses midi files and outputs buffers with midi events.

1 files changed, 906 insertions, 0 deletions

diff --git a/gst/midi/midiparse.c b/gst/midi/midiparse.c
new file mode 100644
index 000000000..171c136ff
--- /dev/null
+++ b/gst/midi/midiparse.c
@@ -0,0 +1,906 @@
+/*
+ * midiparse - midi parser plugin for gstreamer
+ *
+ * Copyright 2013 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * 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., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/**
+ * SECTION:element-midiparse
+ * @see_also: timidity, wildmidi
+ *
+ * This element renders midi-files as audio streams using
+ * <ulink url="http://midiparse.sourceforge.net//">MidiParse</ulink>.
+ * It offers better sound quality compared to the timidity or wildmidi element.
+ *
+ * <refsect2>
+ * <title>Example pipeline</title>
+ * |[
+ * gst-launch-1.0 filesrc location=song.mid ! midiparse ! pulsesink
+ * ]| This example pipeline will parse the midi and render to raw audio which is
+ * played via pulseaudio.
+ * </refsect2>
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <gst/gst.h>
+#include <string.h>
+#include <glib.h>
+
+#include "midiparse.h"
+
+GST_DEBUG_CATEGORY_STATIC (gst_midi_parse_debug);
+#define GST_CAT_DEFAULT gst_midi_parse_debug
+
+enum
+{
+  /* FILL ME */
+  LAST_SIGNAL
+};
+
+enum
+{
+  PROP_0,
+  /* FILL ME */
+};
+
+typedef struct
+{
+  guint8 *data;
+  guint size;
+  guint offset;
+
+  guint8 running_status;
+  GstClockTime position;
+
+} GstMidiTrack;
+
+static void gst_midi_parse_finalize (GObject * object);
+
+static gboolean gst_midi_parse_sink_event (GstPad * pad, GstObject * parent,
+    GstEvent * event);
+static gboolean gst_midi_parse_src_event (GstPad * pad, GstObject * parent,
+    GstEvent * event);
+
+static GstStateChangeReturn gst_midi_parse_change_state (GstElement * element,
+    GstStateChange transition);
+static gboolean gst_midi_parse_activate (GstPad * pad, GstObject * parent);
+static gboolean gst_midi_parse_activatemode (GstPad * pad, GstObject * parent,
+    GstPadMode mode, gboolean active);
+
+static void gst_midi_parse_loop (GstPad * sinkpad);
+static GstFlowReturn gst_midi_parse_chain (GstPad * sinkpad, GstObject * parent,
+    GstBuffer * buffer);
+
+static gboolean gst_midi_parse_src_query (GstPad * pad, GstObject * parent,
+    GstQuery * query);
+
+static void gst_midi_parse_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec);
+static void gst_midi_parse_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec);
+
+static GstStaticPadTemplate sink_factory = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("audio/midi; audio/riff-midi")
+    );
+
+static GstStaticPadTemplate src_factory = GST_STATIC_PAD_TEMPLATE ("src",
+    GST_PAD_SRC,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("audio/x-midi-event"));
+
+#define parent_class gst_midi_parse_parent_class
+G_DEFINE_TYPE (GstMidiParse, gst_midi_parse, GST_TYPE_ELEMENT);
+
+/* initialize the plugin's class */
+static void
+gst_midi_parse_class_init (GstMidiParseClass * klass)
+{
+  GObjectClass *gobject_class;
+  GstElementClass *gstelement_class;
+
+  gobject_class = (GObjectClass *) klass;
+  gstelement_class = (GstElementClass *) klass;
+
+  gobject_class->finalize = gst_midi_parse_finalize;
+  gobject_class->set_property = gst_midi_parse_set_property;
+  gobject_class->get_property = gst_midi_parse_get_property;
+
+  gst_element_class_add_pad_template (gstelement_class,
+      gst_static_pad_template_get (&src_factory));
+  gst_element_class_add_pad_template (gstelement_class,
+      gst_static_pad_template_get (&sink_factory));
+  gst_element_class_set_static_metadata (gstelement_class, "MidiParse",
+      "Codec/Decoder/Audio",
+      "Midi Parser Element", "Wim Taymans <wim.taymans@gmail.com>");
+
+  GST_DEBUG_CATEGORY_INIT (gst_midi_parse_debug, "midiparse",
+      0, "MIDI parser plugin");
+
+  gstelement_class->change_state = gst_midi_parse_change_state;
+}
+
+/* initialize the new element
+ * instantiate pads and add them to element
+ * set functions
+ * initialize structure
+ */
+static void
+gst_midi_parse_init (GstMidiParse * filter)
+{
+  filter->sinkpad = gst_pad_new_from_static_template (&sink_factory, "sink");
+
+  gst_pad_set_activatemode_function (filter->sinkpad,
+      gst_midi_parse_activatemode);
+  gst_pad_set_activate_function (filter->sinkpad, gst_midi_parse_activate);
+  gst_pad_set_event_function (filter->sinkpad, gst_midi_parse_sink_event);
+  gst_pad_set_chain_function (filter->sinkpad, gst_midi_parse_chain);
+  gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
+
+  filter->srcpad = gst_pad_new_from_static_template (&src_factory, "src");
+
+  gst_pad_set_query_function (filter->srcpad, gst_midi_parse_src_query);
+  gst_pad_set_event_function (filter->srcpad, gst_midi_parse_src_event);
+  gst_pad_use_fixed_caps (filter->srcpad);
+
+  gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
+
+  gst_segment_init (&filter->segment, GST_FORMAT_TIME);
+
+  filter->adapter = gst_adapter_new ();
+}
+
+static void
+gst_midi_parse_finalize (GObject * object)
+{
+  GstMidiParse *midiparse;
+
+  midiparse = GST_MIDI_PARSE (object);
+
+  g_object_unref (midiparse->adapter);
+
+  G_OBJECT_CLASS (parent_class)->finalize (object);
+}
+
+static gboolean
+gst_midi_parse_src_query (GstPad * pad, GstObject * parent, GstQuery * query)
+{
+  gboolean res = TRUE;
+  GstMidiParse *midiparse = GST_MIDI_PARSE (parent);
+
+  switch (GST_QUERY_TYPE (query)) {
+    case GST_QUERY_DURATION:
+      gst_query_set_duration (query, GST_FORMAT_TIME,
+          midiparse->segment.duration);
+      break;
+    case GST_QUERY_POSITION:
+      gst_query_set_position (query, GST_FORMAT_TIME,
+          midiparse->segment.position);
+      break;
+    case GST_QUERY_FORMATS:
+      gst_query_set_formats (query, 1, GST_FORMAT_TIME);
+      break;
+    case GST_QUERY_SEGMENT:
+      gst_query_set_segment (query, midiparse->segment.rate,
+          midiparse->segment.format, midiparse->segment.start,
+          midiparse->segment.stop);
+      break;
+    case GST_QUERY_SEEKING:
+      gst_query_set_seeking (query, midiparse->segment.format,
+          TRUE, 0, midiparse->segment.duration);
+      break;
+    default:
+      res = gst_pad_query_default (pad, parent, query);
+      break;
+  }
+
+  return res;
+}
+
+static GstEvent *
+gst_midi_parse_get_new_segment_event (GstMidiParse * midiparse,
+    GstFormat format)
+{
+  GstSegment *segment, newseg;
+  GstEvent *event;
+
+  segment = &midiparse->segment;
+  newseg = *segment;
+
+  newseg.format = format;
+  newseg.start = segment->start;
+  newseg.stop = segment->stop;
+  newseg.time = segment->time;
+
+  event = gst_event_new_segment (&newseg);
+
+  return event;
+}
+
+static gboolean
+gst_midi_parse_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
+{
+  gboolean res = FALSE;
+
+  GST_DEBUG_OBJECT (pad, "%s event received", GST_EVENT_TYPE_NAME (event));
+
+  switch (GST_EVENT_TYPE (event)) {
+    default:
+      break;
+  }
+  gst_event_unref (event);
+
+  return res;
+}
+
+
+static gboolean
+gst_midi_parse_activate (GstPad * sinkpad, GstObject * parent)
+{
+  GstQuery *query;
+  gboolean pull_mode;
+
+  query = gst_query_new_scheduling ();
+
+  if (!gst_pad_peer_query (sinkpad, query)) {
+    gst_query_unref (query);
+    goto activate_push;
+  }
+
+  pull_mode = gst_query_has_scheduling_mode_with_flags (query,
+      GST_PAD_MODE_PULL, GST_SCHEDULING_FLAG_SEEKABLE);
+  gst_query_unref (query);
+
+  if (!pull_mode)
+    goto activate_push;
+
+  GST_DEBUG_OBJECT (sinkpad, "activating pull");
+  return gst_pad_activate_mode (sinkpad, GST_PAD_MODE_PULL, TRUE);
+
+activate_push:
+  {
+    GST_DEBUG_OBJECT (sinkpad, "activating push");
+    return gst_pad_activate_mode (sinkpad, GST_PAD_MODE_PUSH, TRUE);
+  }
+}
+
+static gboolean
+gst_midi_parse_activatemode (GstPad * pad, GstObject * parent,
+    GstPadMode mode, gboolean active)
+{
+  gboolean res;
+
+  switch (mode) {
+    case GST_PAD_MODE_PUSH:
+      res = TRUE;
+      break;
+    case GST_PAD_MODE_PULL:
+      if (active) {
+        res = gst_pad_start_task (pad, (GstTaskFunction) gst_midi_parse_loop,
+            pad, NULL);
+      } else {
+        res = gst_pad_stop_task (pad);
+      }
+      break;
+    default:
+      res = FALSE;
+      break;
+  }
+  return res;
+}
+
+static gboolean
+parse_MThd (GstMidiParse * midiparse, guint8 * data, guint size)
+{
+  guint16 format, ntracks, division;
+  gboolean multitrack;
+
+  format = GST_READ_UINT16_BE (data);
+  switch (format) {
+    case 0:
+      multitrack = FALSE;
+      break;
+    case 1:
+      multitrack = TRUE;
+      break;
+    default:
+    case 2:
+      goto invalid_format;
+  }
+  ntracks = GST_READ_UINT16_BE (data + 2);
+  if (ntracks > 1 && !multitrack)
+    goto invalid_tracks;
+
+  division = GST_READ_UINT16_BE (data + 4);
+  if (division & 0x8000)
+    goto invalid_division;
+
+  GST_DEBUG_OBJECT (midiparse, "format %u, tracks %u, division %u",
+      format, ntracks, division);
+
+  midiparse->ntracks = ntracks;
+  midiparse->division = division;
+
+  return TRUE;
+
+invalid_format:
+  {
+    GST_ERROR_OBJECT (midiparse, "unsupported midi format %u", format);
+    return FALSE;
+  }
+invalid_tracks:
+  {
+    GST_ERROR_OBJECT (midiparse, "invalid number of tracks %u for format %u",
+        ntracks, format);
+    return FALSE;
+  }
+invalid_division:
+  {
+    GST_ERROR_OBJECT (midiparse, "unsupported division");
+    return FALSE;
+  }
+}
+
+static guint
+parse_varlen (GstMidiParse * midiparse, guint8 * data, guint size,
+    gint32 * result)
+{
+  gint32 res;
+  gint i;
+
+  res = 0;
+  for (i = 0; i < 4; i++) {
+    if (size == 0)
+      return 0;
+
+    res = (res << 7) | ((data[i]) & 0x7f);
+    if ((data[i] & 0x80) == 0) {
+      *result = res;
+      return i + 1;
+    }
+  }
+  return 0;
+}
+
+static gboolean
+update_track_position (GstMidiParse * midiparse, GstMidiTrack * track)
+{
+  gint32 delta_time;
+  guint8 *data;
+  guint size, consumed;
+
+  if (track->offset >= track->size)
+    goto eot;
+
+  data = track->data + track->offset;
+  size = track->size - track->offset;
+
+  consumed = parse_varlen (midiparse, data, size, &delta_time);
+  if (consumed == 0)
+    goto eot;
+
+  track->position += delta_time;
+  track->offset += consumed;
+
+  GST_LOG_OBJECT (midiparse, "updated track to %" GST_TIME_FORMAT,
+      GST_TIME_ARGS (track->position));
+
+  return TRUE;
+
+  /* ERRORS */
+eot:
+  {
+    GST_DEBUG_OBJECT (midiparse, "track ended");
+    track->position = GST_CLOCK_TIME_NONE;
+    return FALSE;
+  }
+}
+
+static gboolean
+parse_MTrk (GstMidiParse * midiparse, guint8 * data, guint size)
+{
+  GstMidiTrack *track;
+
+  track = g_slice_new (GstMidiTrack);
+  track->data = data;
+  track->size = size;
+  track->offset = 0;
+  track->position = 0;
+  track->running_status = 0xff;
+  update_track_position (midiparse, track);
+
+  midiparse->tracks = g_list_append (midiparse->tracks, track);
+
+  return TRUE;
+}
+
+static guint
+gst_midi_parse_chunk (GstMidiParse * midiparse, guint8 * data, guint size)
+{
+  guint32 type, length = 0;
+
+  if (size < 8)
+    goto short_chunk;
+
+  length = GST_READ_UINT32_BE (data + 4);
+
+  GST_DEBUG_OBJECT (midiparse, "have type %c%c%c%c, length %u",
+      data[0], data[1], data[2], data[3], length);
+
+  if (size < length + 8)
+    goto short_chunk;
+
+  type = *((guint32 *) data);
+
+  switch (type) {
+    case GST_MAKE_FOURCC ('M', 'T', 'h', 'd'):
+      if (!parse_MThd (midiparse, data + 8, length))
+        goto invalid_format;
+      break;
+    case GST_MAKE_FOURCC ('M', 'T', 'r', 'k'):
+      if (!parse_MTrk (midiparse, data + 8, length))
+        goto invalid_format;
+      break;
+    default:
+      GST_LOG_OBJECT (midiparse, "ignore chunk");
+      break;
+  }
+  return length + 8;
+
+  /* ERRORS */
+short_chunk:
+  {
+    GST_LOG_OBJECT (midiparse, "not enough data %u < %u", length + 8, size);
+    return 0;
+  }
+invalid_format:
+  {
+    GST_ERROR_OBJECT (midiparse, "invalid format");
+    return 0;
+  }
+}
+
+static GstFlowReturn
+gst_midi_parse_parse_song (GstMidiParse * midiparse)
+{
+  GstCaps *outcaps;
+  guint8 *data;
+  guint size;
+
+  GST_DEBUG_OBJECT (midiparse, "Parsing song");
+
+  size = gst_adapter_available (midiparse->adapter);
+  data = gst_adapter_take (midiparse->adapter, size);
+
+  midiparse->tempo = 60;
+
+  while (size) {
+    guint consumed;
+
+    consumed = gst_midi_parse_chunk (midiparse, data, size);
+    if (consumed == 0)
+      goto short_file;
+
+    data += consumed;
+    size -= consumed;
+  }
+
+  outcaps = gst_caps_copy (gst_pad_get_pad_template_caps (midiparse->srcpad));
+  gst_pad_set_caps (midiparse->srcpad, outcaps);
+  gst_caps_unref (outcaps);
+
+  gst_segment_init (&midiparse->segment, GST_FORMAT_TIME);
+
+  gst_pad_push_event (midiparse->srcpad,
+      gst_midi_parse_get_new_segment_event (midiparse, GST_FORMAT_TIME));
+
+  GST_DEBUG_OBJECT (midiparse, "Parsing song done");
+
+  return GST_FLOW_OK;
+
+  /* ERRORS */
+short_file:
+  {
+    GST_ERROR_OBJECT (midiparse, "not enough data");
+    g_free (data);
+    return GST_FLOW_ERROR;
+  }
+}
+
+static GstFlowReturn
+handle_meta_event (GstMidiParse * midiparse, GstMidiTrack * track)
+{
+  guint8 type;
+  guint8 *data;
+  guint size, consumed;
+  gint32 length;
+
+  track->offset += 1;
+
+  data = track->data + track->offset;
+  size = track->size - track->offset;
+
+  if (size < 1)
+    goto short_file;
+
+  type = data[0];
+
+  consumed = parse_varlen (midiparse, data + 1, size - 1, &length);
+  if (consumed == 0)
+    goto short_file;
+
+  data += consumed + 1;
+  size -= consumed + 1;
+
+  GST_DEBUG_OBJECT (midiparse, "handle meta event type 0x%02x, length %u",
+      type, length);
+
+  switch (type) {
+    case 0x51:
+    {
+      guint32 uspqn = (data[0] << 16) | (data[1] << 8) | data[2];
+      midiparse->tempo = (uspqn ? uspqn : 1);
+      GST_DEBUG_OBJECT (midiparse, "tempo %u", midiparse->tempo);
+      break;
+    }
+    default:
+      break;
+  }
+
+  track->offset += consumed + length + 1;
+
+  return GST_FLOW_OK;
+
+  /* ERRORS */
+short_file:
+  {
+    GST_DEBUG_OBJECT (midiparse, "not enough data");
+    return GST_FLOW_ERROR;
+  }
+}
+
+static GstFlowReturn
+handle_sysex_event (GstMidiParse * midiparse, guint8 event,
+    GstMidiTrack * track)
+{
+  guint8 *data;
+  guint size, consumed;
+  gint32 length;
+
+  track->offset += 1;
+
+  data = track->data + track->offset;
+  size = track->size - track->offset;
+
+  consumed = parse_varlen (midiparse, data, size, &length);
+  if (consumed == 0)
+    goto short_file;
+
+  data += consumed;
+  size -= consumed;
+
+  GST_DEBUG_OBJECT (midiparse, "handle sysex event 0x%02x, length %u",
+      event, length);
+
+  track->offset += consumed + length;
+
+  return GST_FLOW_OK;
+
+  /* ERRORS */
+short_file:
+  {
+    GST_DEBUG_OBJECT (midiparse, "not enough data");
+    return GST_FLOW_ERROR;
+  }
+}
+
+static GstFlowReturn
+handle_next_event (GstMidiParse * midiparse, GstMidiTrack * track)
+{
+  GstFlowReturn ret = GST_FLOW_OK;
+  guint8 status, event;
+  guint length;
+  guint8 *data;
+
+  data = &track->data[track->offset];
+
+  status = data[0];
+
+  GST_LOG_OBJECT (midiparse, "track %p, status 0x%02x", track, status);
+
+  if ((status & 0x80) == 0) {
+    if ((track->running_status & 0x80) == 0) {
+      GST_ERROR_OBJECT (midiparse,
+          "Undefined status and invalid running status");
+      return GST_FLOW_ERROR;
+    }
+    event = track->running_status;
+  } else {
+    event = status;
+  }
+
+  switch (event & 0xf0) {
+    case 0xf0:
+      switch (event) {
+        case 0xff:
+          ret = handle_meta_event (midiparse, track);
+          break;
+        case 0xf0:
+        case 0xf7:
+          ret = handle_sysex_event (midiparse, event, track);
+          break;
+        default:
+          GST_ERROR_OBJECT (midiparse, "unhandled event 0x%08x", event);
+          return GST_FLOW_ERROR;
+      }
+      length = 0;
+      break;
+    case 0xc0:
+    case 0xd0:
+      length = 1;
+      break;
+    default:
+      length = 2;
+      break;
+  }
+
+  if (length > 0) {
+    GstBuffer *outbuf;
+    GstMapInfo info;
+
+    outbuf = gst_buffer_new_allocate (NULL, length + 1, NULL);
+
+    gst_buffer_map (outbuf, &info, GST_MAP_WRITE);
+
+    info.data[0] = event;
+
+    if (status & 0x80) {
+      memcpy (&info.data[1], &data[1], length);
+      track->offset += length + 1;
+    } else {
+      info.data[1] = status;
+      memcpy (&info.data[2], &data[1], length - 1);
+      track->offset += length;
+    }
+    gst_buffer_unmap (outbuf, &info);
+
+    GST_BUFFER_PTS (outbuf) = gst_util_uint64_scale (track->position,
+        1000 * midiparse->tempo, midiparse->division);
+
+    GST_DEBUG_OBJECT (midiparse, "pushing %" GST_TIME_FORMAT,
+        GST_TIME_ARGS (GST_BUFFER_PTS (outbuf)));
+
+    ret = gst_pad_push (midiparse->srcpad, outbuf);
+  }
+
+  if (event < 0xF8)
+    track->running_status = event;
+
+  return ret;
+}
+
+static GstFlowReturn
+gst_midi_parse_do_play (GstMidiParse * midiparse)
+{
+  GstFlowReturn res = GST_FLOW_OK;
+  GList *walk;
+  guint64 position, next_position = GST_CLOCK_TIME_NONE;
+
+  position = midiparse->segment.position;
+
+  for (walk = midiparse->tracks; walk; walk = g_list_next (walk)) {
+    GstMidiTrack *track = walk->data;
+
+    while (track->position == position) {
+      res = handle_next_event (midiparse, track);
+      if (res != GST_FLOW_OK)
+        goto done;
+
+      update_track_position (midiparse, track);
+    }
+
+    if (track->position < next_position)
+      next_position = track->position;
+  }
+
+  if (next_position == GST_CLOCK_TIME_NONE)
+    goto eos;
+
+  midiparse->segment.position = next_position;
+
+done:
+
+  return res;
+
+eos:
+  {
+    GST_DEBUG_OBJECT (midiparse, "we are EOS");
+    return GST_FLOW_EOS;
+  }
+}
+
+static gboolean
+gst_midi_parse_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
+{
+  gboolean res;
+  GstMidiParse *midiparse = GST_MIDI_PARSE (parent);
+
+  GST_DEBUG_OBJECT (pad, "%s event received", GST_EVENT_TYPE_NAME (event));
+
+  switch (GST_EVENT_TYPE (event)) {
+    case GST_EVENT_EOS:
+      midiparse->state = GST_MIDI_PARSE_STATE_PARSE;
+      /* now start the parsing task */
+      res = gst_pad_start_task (midiparse->sinkpad,
+          (GstTaskFunction) gst_midi_parse_loop, midiparse->sinkpad, NULL);
+      /* don't forward the event */
+      gst_event_unref (event);
+      break;
+    default:
+      res = gst_pad_event_default (pad, parent, event);
+      break;
+  }
+  return res;
+}
+
+static GstFlowReturn
+gst_midi_parse_chain (GstPad * sinkpad, GstObject * parent, GstBuffer * buffer)
+{
+  GstMidiParse *midiparse;
+
+  midiparse = GST_MIDI_PARSE (parent);
+
+  /* push stuff in the adapter, we will start doing something in the sink event
+   * handler when we get EOS */
+  gst_adapter_push (midiparse->adapter, buffer);
+
+  return GST_FLOW_OK;
+}
+
+static void
+gst_midi_parse_loop (GstPad * sinkpad)
+{
+  GstMidiParse *midiparse = GST_MIDI_PARSE (GST_PAD_PARENT (sinkpad));
+  GstFlowReturn ret;
+
+  switch (midiparse->state) {
+    case GST_MIDI_PARSE_STATE_LOAD:
+    {
+      GstBuffer *buffer = NULL;
+
+      GST_DEBUG_OBJECT (midiparse, "loading song");
+
+      ret =
+          gst_pad_pull_range (midiparse->sinkpad, midiparse->offset, -1,
+          &buffer);
+
+      if (ret == GST_FLOW_EOS) {
+        GST_DEBUG_OBJECT (midiparse, "Song loaded");
+        midiparse->state = GST_MIDI_PARSE_STATE_PARSE;
+      } else if (ret != GST_FLOW_OK) {
+        GST_ELEMENT_ERROR (midiparse, STREAM, DECODE, (NULL),
+            ("Unable to read song"));
+        goto pause;
+      } else {
+        GST_DEBUG_OBJECT (midiparse, "pushing buffer");
+        gst_adapter_push (midiparse->adapter, buffer);
+        midiparse->offset += gst_buffer_get_size (buffer);
+      }
+      break;
+    }
+    case GST_MIDI_PARSE_STATE_PARSE:
+      ret = gst_midi_parse_parse_song (midiparse);
+      if (ret != GST_FLOW_OK)
+        goto pause;
+      midiparse->state = GST_MIDI_PARSE_STATE_PLAY;
+      break;
+    case GST_MIDI_PARSE_STATE_PLAY:
+      ret = gst_midi_parse_do_play (midiparse);
+      if (ret != GST_FLOW_OK)
+        goto pause;
+      break;
+    default:
+      break;
+  }
+  return;
+
+pause:
+  {
+    const gchar *reason = gst_flow_get_name (ret);
+    GstEvent *event;
+
+    GST_DEBUG_OBJECT (midiparse, "pausing task, reason %s", reason);
+    gst_pad_pause_task (sinkpad);
+    if (ret == GST_FLOW_EOS) {
+      /* perform EOS logic */
+      event = gst_event_new_eos ();
+      gst_pad_push_event (midiparse->srcpad, event);
+    } else if (ret == GST_FLOW_NOT_LINKED || ret < GST_FLOW_EOS) {
+      event = gst_event_new_eos ();
+      /* for fatal errors we post an error message, post the error
+       * first so the app knows about the error first. */
+      GST_ELEMENT_ERROR (midiparse, STREAM, FAILED,
+          ("Internal data flow error."),
+          ("streaming task paused, reason %s (%d)", reason, ret));
+      gst_pad_push_event (midiparse->srcpad, event);
+    }
+  }
+}
+
+static GstStateChangeReturn
+gst_midi_parse_change_state (GstElement * element, GstStateChange transition)
+{
+  GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
+  GstMidiParse *midiparse = GST_MIDI_PARSE (element);
+
+  switch (transition) {
+    case GST_STATE_CHANGE_NULL_TO_READY:
+      break;
+    case GST_STATE_CHANGE_READY_TO_PAUSED:
+      midiparse->offset = 0;
+      midiparse->state = GST_MIDI_PARSE_STATE_LOAD;
+      midiparse->discont = FALSE;
+      break;
+    case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
+      break;
+    default:
+      break;
+  }
+
+  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
+
+  switch (transition) {
+    case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
+      break;
+    case GST_STATE_CHANGE_PAUSED_TO_READY:
+      gst_adapter_clear (midiparse->adapter);
+      break;
+    case GST_STATE_CHANGE_READY_TO_NULL:
+      break;
+    default:
+      break;
+  }
+
+  return ret;
+}
+
+static void
+gst_midi_parse_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  switch (prop_id) {
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_midi_parse_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  switch (prop_id) {
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}