teletextdec: New teletext decoder plugin based in zvbi

https://bugzilla.gnome.org/show_bug.cgi?id=619739

4 files changed, 1273 insertions, 0 deletions

diff --git a/ext/teletextdec/Makefile.am b/ext/teletextdec/Makefile.am
new file mode 100644
index 000000000..c153c563b
--- /dev/null
+++ b/ext/teletextdec/Makefile.am
@@ -0,0 +1,10 @@
+plugin_LTLIBRARIES = libgstteletextdec.la
+
+libgstteletextdec_la_SOURCES = gstteletextdec.c teletext.c
+
+libgstteletextdec_la_CFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_CFLAGS) $(TELETEXTDEC_CFLAGS)
+libgstteletextdec_la_LIBADD = $(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_LIBS) $(TELETEXTDEC_LIBS)
+libgstteletextdec_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS)
+libgstteletextdec_la_LIBTOOLFLAGS = --tag=disable-static
+
+noinst_HEADERS = gstteletextdec.h
diff --git a/ext/teletextdec/gstteletextdec.c b/ext/teletextdec/gstteletextdec.c
new file mode 100644
index 000000000..74295c6a7
--- /dev/null
+++ b/ext/teletextdec/gstteletextdec.c
@@ -0,0 +1,1114 @@
+/*
+ * GStreamer
+ * Copyright (C) 2009 Sebastian <sebp@k-d-w.org>
+ * Copyright (C) 2010 Andoni Morales Alastruey <ylatuya@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301  USA
+ */
+
+/**
+ * SECTION:element-teletextdec
+ *
+ * Decode PES stream containing teletext information to RGBA stream
+ *
+ * <refsect2>
+ * <title>Example launch line</title>
+ * |[
+ * gst-launch -v -m filesrc location=recording.mpeg ! mpegtsdemux ! private/teletext ! teletextdec ! ffmpegcolorspace ! ximagesink
+ * ]|
+ * </refsect2>
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gst/gst.h>
+#include <gst/video/video.h>
+#include <string.h>
+
+#include "gstteletextdec.h"
+
+GST_DEBUG_CATEGORY_STATIC (gst_teletextdec_debug);
+#define GST_CAT_DEFAULT gst_teletextdec_debug
+
+#define SUBTITLES_PAGE 888
+#define MAX_SLICES 32
+
+/* Filter signals and args */
+enum
+{
+  LAST_SIGNAL
+};
+
+enum
+{
+  PROP_0,
+  PROP_PAGENO,
+  PROP_SUBNO,
+  PROP_SUBTITLES_MODE,
+  PROP_SUBS_TEMPLATE
+};
+
+enum
+{
+  VBI_ERROR = -1,
+  VBI_SUCCESS = 0,
+  VBI_NEW_FRAME = 1
+};
+
+typedef enum
+{
+  DATA_UNIT_EBU_TELETEXT_NON_SUBTITLE = 0x02,
+  DATA_UNIT_EBU_TELETEXT_SUBTITLE = 0x03,
+  DATA_UNIT_EBU_TELETEXT_INVERTED = 0x0C,
+
+  DATA_UNIT_ZVBI_WSS_CPR1204 = 0xB4,
+  DATA_UNIT_ZVBI_CLOSED_CAPTION_525 = 0xB5,
+  DATA_UNIT_ZVBI_MONOCHROME_SAMPLES_525 = 0xB6,
+
+  DATA_UNIT_VPS = 0xC3,
+  DATA_UNIT_WSS = 0xC4,
+  DATA_UNIT_CLOSED_CAPTION = 0xC5,
+  DATA_UNIT_MONOCHROME_SAMPLES = 0xC6,
+
+  DATA_UNIT_STUFFING = 0xFF,
+} data_unit_id;
+
+typedef struct
+{
+  int pgno;
+  int subno;
+} page_info;
+
+typedef enum
+{
+  SYSTEM_525 = 0,
+  SYSTEM_625
+} systems;
+
+static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS
+    ("video/mpeg,mpegversion=2,systemstream=TRUE ; private/teletext")
+    );
+
+static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
+    GST_PAD_SRC,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS (GST_VIDEO_CAPS_RGBA "; text/plain ; text/html")
+    );
+
+/* debug category for filtering log messages */
+#define DEBUG_INIT(bla) \
+  GST_DEBUG_CATEGORY_INIT (gst_teletextdec_debug, "teletext", 0, "Teletext decoder");
+
+GST_BOILERPLATE_FULL (GstTeletextDec, gst_teletextdec, GstElement,
+    GST_TYPE_ELEMENT, DEBUG_INIT);
+
+static void gst_teletextdec_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec);
+static void gst_teletextdec_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec);
+static void gst_teletextdec_finalize (GObject * object);
+
+static GstStateChangeReturn gst_teletextdec_change_state (GstElement * element,
+    GstStateChange transition);
+
+static GstFlowReturn gst_teletextdec_chain (GstPad * pad, GstBuffer * buf);
+static gboolean gst_teletextdec_sink_setcaps (GstPad * pad, GstCaps * caps);
+static gboolean gst_teletextdec_sink_event (GstPad * pad, GstEvent * event);
+static GstPadLinkReturn gst_teletextdec_src_set_caps (GstPad * pad,
+    GstCaps * caps);
+
+static vbi_bool gst_teletextdec_convert (vbi_dvb_demux * dx, gpointer user_data,
+    const vbi_sliced * sliced, guint n_lines, gint64 pts);
+static void gst_teletextdec_event_handler (vbi_event * ev, void *user_data);
+
+static GstFlowReturn gst_teletextdec_push_page (GstTeletextDec * teletext);
+static GstFlowReturn gst_teletextdec_export_text_page (GstTeletextDec *
+    teletext, vbi_page * page, GstBuffer ** buf);
+static GstFlowReturn gst_teletextdec_export_html_page (GstTeletextDec *
+    teletext, vbi_page * page, GstBuffer ** buf);
+static GstFlowReturn gst_teletextdec_export_rgba_page (GstTeletextDec *
+    teletext, vbi_page * page, GstBuffer ** buf);
+
+static gboolean gst_teletextdec_push_preroll_buffer (GstTeletextDec * teletext);
+static void gst_teletextdec_process_telx_buffer (GstTeletextDec * teletext,
+    GstBuffer * buf);
+static void gst_teletextdec_process_pes_buffer (GstTeletextDec * teletext,
+    GstBuffer * buf);
+static gboolean gst_teletextdec_extract_data_units (GstTeletextDec * teletext,
+    GstTeletextFrame * f, guint8 * packet, guint * offset, gint size);
+
+static void gst_teletextdec_zvbi_init (GstTeletextDec * teletext);
+static void gst_teletextdec_zvbi_clear (GstTeletextDec * teletext);
+
+/* GObject vmethod implementations */
+
+static void
+gst_teletextdec_base_init (gpointer klass)
+{
+  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
+
+  gst_element_class_set_details_simple (element_class,
+      "Teletext decoder",
+      "Decoder",
+      "Decode PES or raw VBI stream containing teletext information to RGBA, HTML and text",
+      "Sebastian Pölsterl <sebp@k-d-w.org>, "
+      "Andoni Morales Alastruey <ylatuya@gmail.com>");
+
+  gst_element_class_add_pad_template (element_class,
+      gst_static_pad_template_get (&src_template));
+  gst_element_class_add_pad_template (element_class,
+      gst_static_pad_template_get (&sink_template));
+}
+
+/* initialize the gstteletext's class */
+static void
+gst_teletextdec_class_init (GstTeletextDecClass * klass)
+{
+  GObjectClass *gobject_class;
+  GstElementClass *gstelement_class;
+
+  gobject_class = G_OBJECT_CLASS (klass);
+  gobject_class->set_property = gst_teletextdec_set_property;
+  gobject_class->get_property = gst_teletextdec_get_property;
+  gobject_class->finalize = gst_teletextdec_finalize;
+
+  gstelement_class = GST_ELEMENT_CLASS (klass);
+  gstelement_class->change_state = gst_teletextdec_change_state;
+
+  g_object_class_install_property (gobject_class, PROP_PAGENO,
+      g_param_spec_int ("page", "Page number",
+          "Number of page that should displayed",
+          100, 999, 100, G_PARAM_READWRITE));
+
+  g_object_class_install_property (gobject_class, PROP_SUBNO,
+      g_param_spec_int ("subpage", "Sub-page number",
+          "Number of sub-page that should displayed (-1 for all)",
+          -1, 0x99, -1, G_PARAM_READWRITE));
+
+  g_object_class_install_property (gobject_class, PROP_SUBTITLES_MODE,
+      g_param_spec_boolean ("subtitles-mode", "Enable subtitles mode",
+          "Enables subtitles mode for text output stripping the blank lines and "
+          "the teletext state lines", FALSE, G_PARAM_READWRITE));
+
+  g_object_class_install_property (gobject_class, PROP_SUBS_TEMPLATE,
+      g_param_spec_string ("subtitles-template", "Subtitles output template",
+          "Output template used to print each one of the subtitles lines",
+          g_strescape ("%s\n", NULL), G_PARAM_READWRITE));
+}
+
+/* initialize the new element
+ * initialize instance structure
+ */
+static void
+gst_teletextdec_init (GstTeletextDec * teletext, GstTeletextDecClass * klass)
+{
+  /* Create sink pad */
+  teletext->sinkpad = gst_pad_new_from_static_template (&sink_template, "sink");
+  gst_pad_set_setcaps_function (teletext->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_teletextdec_sink_setcaps));
+  gst_pad_set_chain_function (teletext->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_teletextdec_chain));
+  gst_pad_set_event_function (teletext->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_teletextdec_sink_event));
+  gst_element_add_pad (GST_ELEMENT (teletext), teletext->sinkpad);
+
+  /* Create src pad */
+  teletext->srcpad = gst_pad_new_from_static_template (&src_template, "src");
+  gst_pad_set_setcaps_function (teletext->srcpad,
+      GST_DEBUG_FUNCPTR (gst_teletextdec_src_set_caps));
+  gst_element_add_pad (GST_ELEMENT (teletext), teletext->srcpad);
+
+  teletext->demux = NULL;
+  teletext->decoder = NULL;
+  teletext->pageno = 0x100;
+  teletext->subno = -1;
+  teletext->subtitles_mode = FALSE;
+  teletext->subtitles_template = g_strescape ("%s\n", NULL);
+
+  teletext->in_timestamp = GST_CLOCK_TIME_NONE;
+  teletext->in_duration = GST_CLOCK_TIME_NONE;
+
+  teletext->rate_numerator = 0;
+  teletext->rate_denominator = 1;
+
+  teletext->queue = NULL;
+  teletext->queue_lock = g_mutex_new ();
+
+  teletext->frame = g_new0 (GstTeletextFrame, 1);
+  teletext->frame->sliced_begin = g_new (vbi_sliced, MAX_SLICES);
+
+  teletext->last_ts = 0;
+
+  teletext->process_buf_func = NULL;
+}
+
+static void
+gst_teletextdec_finalize (GObject * object)
+{
+  GstTeletextDec *teletext = GST_TELETEXTDEC (object);
+
+  g_mutex_free (teletext->queue_lock);
+
+  g_free (teletext->frame);
+
+  G_OBJECT_CLASS (parent_class)->finalize (object);
+}
+
+static void
+gst_teletextdec_zvbi_init (GstTeletextDec * teletext)
+{
+  g_return_if_fail (teletext != NULL);
+
+  GST_LOG_OBJECT (teletext, "Initializing structures");
+
+  teletext->decoder = vbi_decoder_new ();
+
+  vbi_event_handler_register (teletext->decoder,
+      VBI_EVENT_TTX_PAGE | VBI_EVENT_CAPTION,
+      gst_teletextdec_event_handler, teletext);
+
+  g_mutex_lock (teletext->queue_lock);
+  teletext->queue = g_queue_new ();
+  g_mutex_unlock (teletext->queue_lock);
+}
+
+static void
+gst_teletextdec_zvbi_clear (GstTeletextDec * teletext)
+{
+  g_return_if_fail (teletext != NULL);
+
+  GST_LOG_OBJECT (teletext, "Clearing structures");
+
+  if (teletext->demux != NULL) {
+    vbi_dvb_demux_delete (teletext->demux);
+    teletext->demux = NULL;
+  }
+  if (teletext->decoder != NULL) {
+    vbi_decoder_delete (teletext->decoder);
+    teletext->decoder = NULL;
+  }
+  if (teletext->frame != NULL) {
+    g_free (teletext->frame);
+    teletext->frame = NULL;
+  }
+
+  g_mutex_lock (teletext->queue_lock);
+  if (teletext->queue != NULL) {
+    g_queue_free (teletext->queue);
+    teletext->queue = NULL;
+  }
+  g_mutex_unlock (teletext->queue_lock);
+
+  teletext->in_timestamp = GST_CLOCK_TIME_NONE;
+  teletext->in_duration = GST_CLOCK_TIME_NONE;
+  teletext->pageno = 0x100;
+  teletext->subno = -1;
+  teletext->last_ts = 0;
+}
+
+static void
+gst_teletextdec_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstTeletextDec *teletext = GST_TELETEXTDEC (object);
+
+  switch (prop_id) {
+    case PROP_PAGENO:
+      teletext->pageno = (gint) vbi_bin2bcd (g_value_get_int (value));
+      break;
+    case PROP_SUBNO:
+      teletext->subno = g_value_get_int (value);
+      break;
+    case PROP_SUBTITLES_MODE:
+      teletext->subtitles_mode = g_value_get_boolean (value);
+      break;
+    case PROP_SUBS_TEMPLATE:
+      teletext->subtitles_template = g_value_dup_string (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_teletextdec_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstTeletextDec *teletext = GST_TELETEXTDEC (object);
+
+  switch (prop_id) {
+    case PROP_PAGENO:
+      g_value_set_int (value, (gint) vbi_bcd2dec (teletext->pageno));
+      break;
+    case PROP_SUBNO:
+      g_value_set_int (value, teletext->subno);
+      break;
+    case PROP_SUBTITLES_MODE:
+      g_value_set_boolean (value, teletext->subtitles_mode);
+      break;
+    case PROP_SUBS_TEMPLATE:
+      g_value_set_string (value, teletext->subtitles_template);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static gboolean
+gst_teletextdec_sink_event (GstPad * pad, GstEvent * event)
+{
+  gboolean ret;
+  GstTeletextDec *teletext = GST_TELETEXTDEC (gst_pad_get_parent (pad));
+
+  GST_DEBUG_OBJECT (teletext, "got event %s",
+      gst_event_type_get_name (GST_EVENT_TYPE (event)));
+
+  switch (GST_EVENT_TYPE (event)) {
+    case GST_EVENT_NEWSEGMENT:
+      /* maybe save and/or update the current segment (e.g. for output
+       * clipping) or convert the event into one in a different format
+       * (e.g. BYTES to TIME) or drop it and set a flag to send a newsegment
+       * event in a different format later */
+      ret = gst_pad_push_event (teletext->srcpad, event);
+      break;
+    case GST_EVENT_EOS:
+      /* end-of-stream, we should close down all stream leftovers here */
+      gst_teletextdec_zvbi_clear (teletext);
+      ret = gst_pad_push_event (teletext->srcpad, event);
+      break;
+    case GST_EVENT_FLUSH_STOP:
+      gst_teletextdec_zvbi_clear (teletext);
+      gst_teletextdec_zvbi_init (teletext);
+      ret = gst_pad_push_event (teletext->srcpad, event);
+      break;
+    default:
+      ret = gst_pad_event_default (pad, event);
+      break;
+  }
+
+  gst_object_unref (teletext);
+
+  return ret;
+}
+
+static GstStateChangeReturn
+gst_teletextdec_change_state (GstElement * element, GstStateChange transition)
+{
+  GstStateChangeReturn ret;
+  GstTeletextDec *teletext;
+
+  teletext = GST_TELETEXTDEC (element);
+
+  switch (transition) {
+    case GST_STATE_CHANGE_READY_TO_PAUSED:
+      gst_teletextdec_zvbi_init (teletext);
+      break;
+    default:
+      break;
+  }
+
+  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
+  if (ret != GST_STATE_CHANGE_SUCCESS)
+    return ret;
+
+  switch (transition) {
+    case GST_STATE_CHANGE_PAUSED_TO_READY:
+      gst_teletextdec_zvbi_clear (teletext);
+      break;
+    default:
+      break;
+  }
+
+  return ret;
+}
+
+static gboolean
+gst_teletextdec_sink_setcaps (GstPad * pad, GstCaps * caps)
+{
+  GstTeletextDec *teletext = GST_TELETEXTDEC (gst_pad_get_parent (pad));
+  GstStructure *structure = gst_caps_get_structure (caps, 0);
+  const gchar *mimetype = gst_structure_get_name (structure);
+
+  GST_DEBUG_OBJECT (teletext, "%s:%s, caps=%" GST_PTR_FORMAT,
+      GST_DEBUG_PAD_NAME (pad), caps);
+
+  if (g_strcmp0 (mimetype, "private/teletext") == 0) {
+    teletext->process_buf_func = gst_teletextdec_process_telx_buffer;
+    goto accept_caps;
+  } else if (g_strcmp0 (mimetype, "video/mpeg") == 0) {
+    gint version;
+    gboolean is_systemstream;
+
+    if (!gst_structure_get_int (structure, "mpegversion", &version) ||
+        !gst_structure_get_boolean (structure, "systemstream",
+            &is_systemstream))
+      goto refuse_caps;
+
+    if (version != 2 || !is_systemstream)
+      goto refuse_caps;
+
+    teletext->process_buf_func = gst_teletextdec_process_pes_buffer;
+    teletext->demux = vbi_dvb_pes_demux_new (gst_teletextdec_convert, teletext);
+    goto accept_caps;
+  } else
+    goto refuse_caps;
+
+accept_caps:
+  {
+    gst_object_unref (teletext);
+    return gst_teletextdec_push_preroll_buffer (teletext);
+  }
+
+refuse_caps:
+  {
+    GST_ERROR_OBJECT (teletext,
+        "pad %s refused renegotiation to %" GST_PTR_FORMAT,
+        GST_PAD_NAME (pad), caps);
+    gst_object_unref (teletext);
+    return FALSE;
+  }
+}
+
+static gboolean
+gst_teletextdec_src_set_caps (GstPad * pad, GstCaps * caps)
+{
+  GstTeletextDec *teletext;
+  GstStructure *structure = NULL;
+  const gchar *mimetype;
+
+  teletext = GST_TELETEXTDEC (gst_pad_get_parent (pad));
+  GST_DEBUG_OBJECT (teletext, "Linking teletext source pad");
+
+  if (gst_caps_is_empty (caps)) {
+    GST_ERROR_OBJECT (teletext,
+        "pad %s refused renegotiation to %" GST_PTR_FORMAT,
+        GST_PAD_NAME (pad), caps);
+    goto refuse_caps;
+  }
+
+  gst_pad_set_caps (gst_pad_get_peer (pad), caps);
+
+  structure = gst_caps_get_structure (caps, 0);
+  mimetype = gst_structure_get_name (structure);
+
+  if (g_strcmp0 (mimetype, "video/x-raw-rgb") == 0) {
+    teletext->output_format = GST_TELETEXTDEC_OUTPUT_FORMAT_RGBA;
+    GST_DEBUG_OBJECT (teletext, "Selected RGBA output format");
+  } else if (g_strcmp0 (mimetype, "text/html") == 0) {
+    teletext->output_format = GST_TELETEXTDEC_OUTPUT_FORMAT_HTML;
+    GST_DEBUG_OBJECT (teletext, "Selected HTML output format");
+  } else if (g_strcmp0 (mimetype, "text/plain") == 0) {
+    teletext->output_format = GST_TELETEXTDEC_OUTPUT_FORMAT_TEXT;
+    GST_DEBUG_OBJECT (teletext, "Selected text output format");
+  } else
+    goto refuse_caps;
+
+  gst_object_unref (teletext);
+  return TRUE;
+
+
+refuse_caps:
+  {
+    gst_object_unref (teletext);
+    return FALSE;
+  }
+}
+
+static void
+gst_teletextdec_reset_frame (GstTeletextDec * teletext)
+{
+  teletext->frame->current_slice = teletext->frame->sliced_begin;
+  teletext->frame->sliced_end = teletext->frame->sliced_begin + MAX_SLICES;
+  teletext->frame->last_field = 0;
+  teletext->frame->last_field_line = 0;
+  teletext->frame->last_frame_line = 0;
+}
+
+static void
+gst_teletextdec_process_pes_buffer (GstTeletextDec * teletext, GstBuffer * buf)
+{
+  vbi_dvb_demux_feed (teletext->demux, GST_BUFFER_DATA (buf),
+      GST_BUFFER_SIZE (buf));
+  return;
+}
+
+static void
+gst_teletextdec_process_telx_buffer (GstTeletextDec * teletext, GstBuffer * buf)
+{
+  guint8 *data = GST_BUFFER_DATA (buf);
+  const gint size = GST_BUFFER_SIZE (buf);
+  guint offset = 0;
+  gint res;
+
+  teletext->in_timestamp = GST_BUFFER_TIMESTAMP (buf);
+  teletext->in_duration = GST_BUFFER_DURATION (buf);
+
+  if (teletext->frame == NULL) {
+    gst_teletextdec_reset_frame (teletext);
+  }
+
+  while (offset < size) {
+    res =
+        gst_teletextdec_extract_data_units (teletext, teletext->frame, data,
+        &offset, size);
+
+    if (res == VBI_NEW_FRAME) {
+      /* We have a new frame, it's time to feed the decoder */
+      vbi_sliced *s;
+      gint n_lines;
+
+      n_lines = teletext->frame->current_slice - teletext->frame->sliced_begin;
+      GST_LOG_OBJECT (teletext, "Completed frame, decoding new %d lines",
+          n_lines);
+      s = g_memdup (teletext->frame->sliced_begin,
+          n_lines * sizeof (vbi_sliced));
+      vbi_decode (teletext->decoder, s, n_lines, teletext->last_ts);
+      /* From vbi_decode():
+       * timestamp shall advance by 1/30 to 1/25 seconds whenever calling this
+       * function. Failure to do so will be interpreted as frame dropping, which
+       * starts a resynchronization cycle, eventually a channel switch may be assumed
+       * which resets even more decoder state. So even if a frame did not contain
+       * any useful data this function must be called, with lines set to zero.
+       */
+      teletext->last_ts += 0.04;
+
+      g_free (s);
+      gst_teletextdec_reset_frame (teletext);
+    } else if (res == VBI_ERROR) {
+      gst_teletextdec_reset_frame (teletext);
+      return;
+    }
+  }
+  return;
+}
+
+static vbi_bool
+gst_teletextdec_convert (vbi_dvb_demux * dx,
+    gpointer user_data, const vbi_sliced * sliced, guint n_lines, gint64 pts)
+{
+  gdouble sample_time;
+  vbi_sliced *s;
+
+  GstTeletextDec *teletext = GST_TELETEXTDEC (user_data);
+
+  GST_DEBUG_OBJECT (teletext, "Converting %u lines to decode", n_lines);
+
+  sample_time = pts * (1 / 90000.0);
+
+  s = g_memdup (sliced, n_lines * sizeof (vbi_sliced));
+  vbi_decode (teletext->decoder, s, n_lines, sample_time);
+  g_free (s);
+
+  return GST_FLOW_OK;
+}
+
+static void
+gst_teletextdec_event_handler (vbi_event * ev, void *user_data)
+{
+  page_info *pi;
+  vbi_pgno pgno;
+  vbi_subno subno;
+
+  GstTeletextDec *teletext = GST_TELETEXTDEC (user_data);
+
+  switch (ev->type) {
+    case VBI_EVENT_TTX_PAGE:
+      pgno = ev->ev.ttx_page.pgno;
+      subno = ev->ev.ttx_page.subno;
+
+      if (pgno != teletext->pageno
+          || (teletext->subno != -1 && subno != teletext->subno))
+        return;
+
+      GST_DEBUG_OBJECT (teletext, "Received teletext page %03d.%02d",
+          (gint) vbi_bcd2dec (pgno), (gint) vbi_bcd2dec (subno));
+
+      pi = g_new (page_info, 1);
+      pi->pgno = pgno;
+      pi->subno = subno;
+
+      g_mutex_lock (teletext->queue_lock);
+      g_queue_push_tail (teletext->queue, pi);
+      g_mutex_unlock (teletext->queue_lock);
+      break;
+    case VBI_EVENT_CAPTION:
+      /* TODO: Handle subtitles in caption teletext pages */
+      GST_DEBUG_OBJECT (teletext, "Received caption page. Not implemented");
+      break;
+    default:
+      break;
+  }
+  return;
+}
+
+/* this function does the actual processing
+ */
+static GstFlowReturn
+gst_teletextdec_chain (GstPad * pad, GstBuffer * buf)
+{
+  GstTeletextDec *teletext = GST_TELETEXTDEC (GST_PAD_PARENT (pad));
+  GstFlowReturn ret = GST_FLOW_OK;
+
+  teletext->in_timestamp = GST_BUFFER_TIMESTAMP (buf);
+  teletext->in_duration = GST_BUFFER_DURATION (buf);
+
+  teletext->process_buf_func (teletext, buf);
+  gst_buffer_unref (buf);
+
+  g_mutex_lock (teletext->queue_lock);
+  if (!g_queue_is_empty (teletext->queue)) {
+    ret = gst_teletextdec_push_page (teletext);
+    if (ret != GST_FLOW_OK)
+      goto error;
+  }
+  g_mutex_unlock (teletext->queue_lock);
+
+  return ret;
+
+/* ERRORS */
+error:
+  {
+    if (GST_FLOW_IS_FATAL (ret)) {
+      GST_ELEMENT_ERROR (teletext, STREAM, FAILED,
+          ("Internal data stream error."),
+          ("stream stopped, reason %s", gst_flow_get_name (ret)));
+      gst_pad_push_event (teletext->srcpad, gst_event_new_eos ());
+    }
+    return ret;
+  }
+}
+
+static GstFlowReturn
+gst_teletextdec_push_page (GstTeletextDec * teletext)
+{
+  GstFlowReturn ret = GST_FLOW_OK;
+  GstBuffer *buf;
+  vbi_page page;
+  page_info *pi;
+  gint pgno, subno;
+  gboolean success;
+
+  pi = (page_info *) g_queue_pop_head (teletext->queue);
+
+  pgno = vbi_bcd2dec (pi->pgno);
+  subno = vbi_bcd2dec (pi->subno);
+
+  GST_INFO_OBJECT (teletext, "Fetching teletext page %03d.%02d", pgno, subno);
+
+  success = vbi_fetch_vt_page (teletext->decoder, &page, pi->pgno, pi->subno,
+      VBI_WST_LEVEL_3p5, 25, FALSE);
+  if (G_UNLIKELY (!success))
+    goto fetch_page_failed;
+
+  switch (teletext->output_format) {
+    case GST_TELETEXTDEC_OUTPUT_FORMAT_TEXT:
+      ret = gst_teletextdec_export_text_page (teletext, &page, &buf);
+      break;
+    case GST_TELETEXTDEC_OUTPUT_FORMAT_HTML:
+      ret = gst_teletextdec_export_html_page (teletext, &page, &buf);
+      break;
+    case GST_TELETEXTDEC_OUTPUT_FORMAT_RGBA:
+      ret = gst_teletextdec_export_rgba_page (teletext, &page, &buf);
+      break;
+    default:
+      g_assert_not_reached ();
+      break;
+  }
+  vbi_unref_page (&page);
+  g_free (pi);
+
+  if (ret != GST_FLOW_OK)
+    goto alloc_failed;
+
+  GST_BUFFER_TIMESTAMP (buf) = teletext->in_timestamp;
+  GST_BUFFER_DURATION (buf) = teletext->in_duration;
+
+  GST_INFO_OBJECT (teletext, "Pushing buffer of size %d",
+      GST_BUFFER_SIZE (buf));
+
+  ret = gst_pad_push (teletext->srcpad, buf);
+  if (ret != GST_FLOW_OK)
+    goto push_failed;
+
+  return GST_FLOW_OK;
+
+fetch_page_failed:
+  {
+    GST_ELEMENT_ERROR (teletext, RESOURCE, READ, (NULL), (NULL));
+    return GST_FLOW_ERROR;
+  }
+
+alloc_failed:
+  {
+    GST_ERROR_OBJECT (teletext, "Error allocating output buffer, reason %s",
+        gst_flow_get_name (ret));
+    return ret;
+  }
+
+push_failed:
+  {
+    GST_ERROR_OBJECT (teletext, "Pushing buffer failed, reason %s",
+        gst_flow_get_name (ret));
+    return ret;
+  }
+}
+
+static gint
+gst_teletextdec_parse_subtitles_page (GstTeletextDec * teletext,
+    vbi_page * page, gchar ** text)
+{
+  const gint line_length = page->columns;
+  gchar *line;
+  GString *subs;
+  gint length, i;
+
+  subs = g_string_new ("");
+  line = g_malloc (line_length + 1);
+  /* Print lines 2 to 23 */
+  for (i = 1; i < 23; i++) {
+    vbi_print_page_region (page, line, line_length + 1, "UTF-8", TRUE, 0,
+        0, i, page->columns, 1);
+    /* Add the null character */
+    line[line_length] = '\0';
+    /* Strip blank lines */
+    g_strstrip (line);
+    if (g_strcmp0 (line, "")) {
+      g_string_append_printf (subs, teletext->subtitles_template, line);
+    }
+  }
+  if (!g_strcmp0 (subs->str, ""))
+    g_string_append (subs, "\n");
+
+  *text = subs->str;
+  length = subs->len + 1;
+  g_string_free (subs, FALSE);
+  g_free (line);
+  return length;
+}
+
+static GstFlowReturn
+gst_teletextdec_export_text_page (GstTeletextDec * teletext, vbi_page * page,
+    GstBuffer ** buf)
+{
+  GstCaps *caps;
+  GstFlowReturn ret;
+  gchar *text;
+  guint size;
+
+  if (teletext->subtitles_mode) {
+    size = gst_teletextdec_parse_subtitles_page (teletext, page, &text);
+  } else {
+    size = page->columns * page->rows;
+    text = g_malloc (size);
+    vbi_print_page (page, text, size, "UTF-8", FALSE, TRUE);
+  }
+
+  /* Allocate new buffer */
+  caps = gst_caps_new_simple ("text/plain", NULL);
+  ret = gst_pad_alloc_buffer (teletext->srcpad, GST_BUFFER_OFFSET_NONE,
+      size, caps, &(*buf));
+  if (G_LIKELY (ret == GST_FLOW_OK))
+    GST_BUFFER_DATA (*buf) = GST_BUFFER_MALLOCDATA (*buf) = (guint8 *) text;
+  else
+    gst_buffer_unref (*buf);
+
+  gst_caps_unref (caps);
+  return ret;
+}
+
+static GstFlowReturn
+gst_teletextdec_export_html_page (GstTeletextDec * teletext, vbi_page * page,
+    GstBuffer ** buf)
+{
+  GstCaps *caps;
+  GstFlowReturn ret;
+  gchar *html;
+  guint size;
+  vbi_export *ex;
+  gchar *err;
+
+  if (!(ex = vbi_export_new ("html", &err))) {
+    GST_ELEMENT_ERROR (teletext, LIBRARY, SETTINGS,
+        ("Can't open the HTML export module: %s", err), (NULL));
+    g_free (err);
+    return GST_FLOW_ERROR;
+  }
+
+  /* export to NULL to get size of the memory needed to allocate the page */
+  size = vbi_export_mem (ex, NULL, 0, page);
+  if (size < 0)
+    return GST_FLOW_ERROR;
+  html = g_malloc (size);
+  vbi_export_mem (ex, html, size, page);
+
+  /* Allocate new buffer */
+  caps = gst_caps_new_simple ("text/html", NULL);
+  ret = gst_pad_alloc_buffer (teletext->srcpad, GST_BUFFER_OFFSET_NONE,
+      size, caps, &(*buf));
+  if (G_LIKELY (ret == GST_FLOW_OK))
+    GST_BUFFER_DATA (*buf) = GST_BUFFER_MALLOCDATA (*buf) = (guint8 *) html;
+
+  gst_caps_unref (caps);
+  return ret;
+}
+
+static GstFlowReturn
+gst_teletextdec_export_rgba_page (GstTeletextDec * teletext, vbi_page * page,
+    GstBuffer ** buf)
+{
+  guint size;
+  GstCaps *caps, *out_caps;
+  GstFlowReturn ret;
+  gint width, height;
+  GstPadTemplate *templ;
+
+  /* one character occupies 12 x 10 pixels */
+  width = page->columns * 12;
+  height = page->rows * 10;
+
+  caps = gst_caps_new_simple ("video/x-raw-rgb",
+      "width", G_TYPE_INT, width,
+      "height", G_TYPE_INT, height,
+      "framerate", GST_TYPE_FRACTION, teletext->rate_numerator,
+      teletext->rate_denominator, NULL);
+
+  templ = gst_static_pad_template_get (&src_template);
+  out_caps = gst_caps_intersect (caps, gst_pad_template_get_caps (templ));
+  gst_caps_unref (caps);
+  gst_object_unref (templ);
+
+  size = (guint) width *(guint) height *sizeof (vbi_rgba);
+
+  ret = gst_pad_alloc_buffer_and_set_caps (teletext->srcpad,
+      GST_BUFFER_OFFSET_NONE, size, out_caps, &(*buf));
+
+  if (ret == GST_FLOW_OK) {
+    GST_DEBUG_OBJECT (teletext, "Creating image with %d rows and %d cols",
+        page->rows, page->columns);
+    vbi_draw_vt_page (page, VBI_PIXFMT_RGBA32_LE,
+        (vbi_rgba *) GST_BUFFER_DATA (*buf), FALSE, TRUE);
+  }
+
+  gst_caps_unref (out_caps);
+  return ret;
+}
+
+static gboolean
+gst_teletextdec_push_preroll_buffer (GstTeletextDec * teletext)
+{
+  GstFlowReturn ret;
+  GstBuffer *buf;
+  gboolean res = TRUE;
+  GstStructure *structure;
+  const gchar *mimetype;
+  GstCaps *out_caps, *peer_caps, *pad_caps;
+
+  /* the stream is sparse, we send a dummy buffer for preroll */
+  peer_caps = gst_pad_peer_get_caps (teletext->srcpad);
+  pad_caps = gst_pad_get_caps (teletext->srcpad);
+  out_caps = gst_caps_intersect (pad_caps, peer_caps);
+
+  if (gst_caps_is_empty (out_caps)) {
+    res = FALSE;
+    goto beach;
+  }
+
+  structure = gst_caps_get_structure (out_caps, 0);
+  mimetype = gst_structure_get_name (structure);
+  if (g_strcmp0 (mimetype, "video/x-raw-rgb") == 0) {
+    /* omit preroll buffer for this format */
+    goto beach;
+  }
+
+  buf = gst_buffer_new ();
+  gst_buffer_set_caps (buf, out_caps);
+  ret = gst_pad_push (teletext->srcpad, buf);
+  if (ret != GST_FLOW_OK)
+    res = FALSE;
+
+beach:
+  {
+    gst_caps_unref (out_caps);
+    gst_caps_unref (pad_caps);
+    gst_caps_unref (peer_caps);
+    return res;
+  }
+}
+
+
+/* Converts the line_offset / field_parity byte of a VBI data unit. */
+static void
+gst_teletextdec_lofp_to_line (guint * field, guint * field_line,
+    guint * frame_line, guint lofp, systems system)
+{
+  uint line_offset;
+
+  /* field_parity */
+  *field = !(lofp & (1 << 5));
+
+  line_offset = lofp & 31;
+
+  if (line_offset > 0) {
+    static const guint field_start[2][2] = {
+      {0, 263},
+      {0, 313},
+    };
+
+    *field_line = line_offset;
+    *frame_line = field_start[system][*field] + line_offset;
+  } else {
+    *field_line = 0;
+    *frame_line = 0;
+  }
+}
+
+static int
+gst_teletextdec_line_address (GstTeletextDec * teletext,
+    GstTeletextFrame * frame, vbi_sliced ** spp, guint lofp, systems system)
+{
+  guint field;
+  guint field_line;
+  guint frame_line;
+
+  if (G_UNLIKELY (frame->current_slice >= frame->sliced_end)) {
+    GST_LOG_OBJECT (teletext, "Out of sliced VBI buffer space (%d lines).",
+        (int) (frame->sliced_end - frame->sliced_begin));
+    return VBI_ERROR;
+  }
+
+  gst_teletextdec_lofp_to_line (&field, &field_line, &frame_line, lofp, system);
+
+  GST_LOG_OBJECT (teletext, "Line %u/%u=%u.", field, field_line, frame_line);
+
+  if (frame_line != 0) {
+    GST_LOG_OBJECT (teletext, "Last frame Line %u.", frame->last_frame_line);
+    if (frame_line <= frame->last_frame_line) {
+      GST_LOG_OBJECT (teletext, "New frame");
+      return VBI_NEW_FRAME;
+    }
+
+    /* new segment flag */
+    if (lofp < 0) {
+      GST_LOG_OBJECT (teletext, "New frame");
+      return VBI_NEW_FRAME;
+    }
+
+    frame->last_field = field;
+    frame->last_field_line = field_line;
+    frame->last_frame_line = frame_line;
+
+    *spp = frame->current_slice++;
+    (*spp)->line = frame_line;
+  } else {
+    /* Undefined line. */
+    return VBI_ERROR;
+  }
+
+  return VBI_SUCCESS;
+}
+
+static gboolean
+gst_teletextdec_extract_data_units (GstTeletextDec * teletext,
+    GstTeletextFrame * f, guint8 * packet, guint * offset, gint size)
+{
+  guint8 *data_unit;
+  guint i;
+
+  while (*offset < size) {
+    vbi_sliced *s = NULL;
+    gint data_unit_id, data_unit_length;
+
+    data_unit = packet + *offset;
+    data_unit_id = data_unit[0];
+    data_unit_length = data_unit[1];
+    GST_LOG_OBJECT (teletext, "vbi header %02x %02x %02x\n", data_unit[0],
+        data_unit[1], data_unit[2]);
+
+    switch (data_unit_id) {
+      case DATA_UNIT_STUFFING:
+      {
+        *offset += 2 + data_unit_length;
+        break;
+      }
+
+      case DATA_UNIT_EBU_TELETEXT_NON_SUBTITLE:
+      case DATA_UNIT_EBU_TELETEXT_SUBTITLE:
+      {
+        gint res;
+
+        if (G_UNLIKELY (data_unit_length != 1 + 1 + 42)) {
+          /* Skip this data unit */
+          GST_WARNING_OBJECT (teletext, "The data unit length is not 44 bytes");
+          *offset += 2 + data_unit_length;
+          break;
+        }
+
+        res =
+            gst_teletextdec_line_address (teletext, f, &s, data_unit[2],
+            SYSTEM_625);
+        if (G_UNLIKELY (res == VBI_ERROR)) {
+          /* Can't retrieve line address, skip this data unit */
+          GST_WARNING_OBJECT (teletext,
+              "Could not retrieve line address for this data unit");
+          return VBI_ERROR;
+        }
+        if (G_UNLIKELY (f->last_field_line > 0
+                && (f->last_field_line - 7 >= 23 - 7))) {
+          GST_WARNING_OBJECT (teletext, "Bad line: %d", f->last_field_line - 7);
+          return VBI_ERROR;
+        }
+        if (res == VBI_NEW_FRAME) {
+          /* New frame */
+          return VBI_NEW_FRAME;
+        }
+        s->id = VBI_SLICED_TELETEXT_B;
+        for (i = 0; i < 42; i++)
+          s->data[i] = vbi_rev8 (data_unit[4 + i]);
+        *offset += 46;
+        break;
+      }
+
+      case DATA_UNIT_ZVBI_WSS_CPR1204:
+      case DATA_UNIT_ZVBI_CLOSED_CAPTION_525:
+      case DATA_UNIT_ZVBI_MONOCHROME_SAMPLES_525:
+      case DATA_UNIT_VPS:
+      case DATA_UNIT_WSS:
+      case DATA_UNIT_CLOSED_CAPTION:
+      case DATA_UNIT_MONOCHROME_SAMPLES:
+      {
+        /*Not supported yet */
+        *offset += 2 + data_unit_length;
+        break;
+      }
+
+      default:
+      {
+        /* corrupted stream, increase the offset by one until we sync */
+        GST_LOG_OBJECT (teletext, "Corrupted, increasing offset by one");
+        *offset += 1;
+        break;
+      }
+    }
+  }
+  return VBI_SUCCESS;
+}
diff --git a/ext/teletextdec/gstteletextdec.h b/ext/teletextdec/gstteletextdec.h
new file mode 100644
index 000000000..807c0034f
--- /dev/null
+++ b/ext/teletextdec/gstteletextdec.h
@@ -0,0 +1,106 @@
+/*
+ * GStreamer
+ * Copyright (C) 2009 Sebastian <sebp@k-d-w.org>
+ * Copyright (C) 2010 Andoni Morales Alastruey <ylatuya@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * mod1ify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301  USA
+ */
+
+#ifndef __GST_TELETEXTDEC_H__
+#define __GST_TELETEXTDEC_H__
+
+#include <gst/gst.h>
+#include <libzvbi.h>
+
+G_BEGIN_DECLS
+#define GST_TYPE_TELETEXTDEC \
+  (gst_teletextdec_get_type())
+#define GST_TELETEXTDEC(obj) \
+  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_TELETEXTDEC,GstTeletextDec))
+#define GST_TELETEXTDEC_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_TELETEXTDEC,GstTeletextDecClass))
+#define GST_IS_TELETEXTDEC(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_TELETEXTDEC))
+#define GST_IS_TELETEXTDEC_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_TELETEXTDEC))
+typedef struct _GstTeletextDec GstTeletextDec;
+typedef struct _GstTeletextDecClass GstTeletextDecClass;
+typedef struct _GstTeletextFrame GstTeletextFrame;
+typedef enum _GstTeletextOutputFormat GstTeletextOutputFormat;
+
+enum _GstTeletextOutputFormat
+{
+  GST_TELETEXTDEC_OUTPUT_FORMAT_RGBA,
+  GST_TELETEXTDEC_OUTPUT_FORMAT_TEXT,
+  GST_TELETEXTDEC_OUTPUT_FORMAT_HTML,
+  GST_TELETEXTDEC_OUTPUT_FORMAT_SUBTITLES
+};
+
+typedef void (*GstTeletextProcessBufferFunc) (GstTeletextDec *
+    teletext, GstBuffer * buf);
+
+struct _GstTeletextDec
+{
+  GstElement element;
+
+  GstPad *sinkpad;
+  GstPad *srcpad;
+
+  GstClockTime in_timestamp;
+  GstClockTime in_duration;
+  gint rate_numerator;
+  gint rate_denominator;
+
+  /* Props */
+  gint pageno;
+  gint subno;
+  gboolean subtitles_mode;
+  gchar *subtitles_template;
+
+  vbi_dvb_demux *demux;
+  vbi_decoder *decoder;
+  vbi_export *exporter;
+  GQueue *queue;
+  GMutex *queue_lock;
+
+  GstTeletextFrame *frame;
+  float last_ts;
+  GstTeletextOutputFormat output_format;
+
+  GstTeletextProcessBufferFunc process_buf_func;
+};
+
+struct _GstTeletextFrame
+{
+  vbi_sliced *sliced_begin;
+  vbi_sliced *sliced_end;
+  vbi_sliced *current_slice;
+
+  guint last_field;
+  guint last_field_line;
+  guint last_frame_line;
+};
+
+
+struct _GstTeletextDecClass
+{
+  GstElementClass parent_class;
+};
+
+GType gst_teletextdec_get_type (void);
+
+G_END_DECLS
+#endif /* __GST_TELETEXTDEC_H__ */
diff --git a/ext/teletextdec/teletext.c b/ext/teletextdec/teletext.c
new file mode 100644
index 000000000..f4661745c
--- /dev/null
+++ b/ext/teletextdec/teletext.c
@@ -0,0 +1,43 @@
+/*
+ * GStreamer
+ * Copyright (C) 2009 Sebastian <sebp@k-d-w.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * mod1ify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301  USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gst/gst.h>
+#include "gstteletextdec.h"
+
+/* entry point to initialize the plug-in
+ * initialize the plug-in itself
+ * register the element factories and other features
+ */
+static gboolean
+teletext_init (GstPlugin * teletext)
+{
+  return gst_element_register (teletext, "teletextdec", GST_RANK_NONE,
+      GST_TYPE_TELETEXTDEC);
+}
+
+GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
+    GST_VERSION_MINOR,
+    "teletext",
+    "Teletext plugin",
+    teletext_init, VERSION, "LGPL", "GStreamer", "http://gstreamer.net/")