gstreamer/gst/videoparsers/gstmpeg4videoparse.c

/* GStreamer
 * Copyright (C) <2008> Mindfruit B.V.
 *   @author Sjoerd Simons <sjoerd@luon.net>
 * Copyright (C) <2007> Julien Moutte <julien@fluendo.com>
 * Copyright (C) <2011> Mark Nauwelaerts <mark.nauwelaerts@collabora.co.uk>
 * Copyright (C) <2011> Nokia Corporation
 * Copyright (C) <2011> Intel
 * Copyright (C) <2011> Collabora Ltd.
 * Copyright (C) <2011> Thibault Saunier <thibault.saunier@collabora.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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>
#include <gst/base/gstbytereader.h>
#include <gst/pbutils/codec-utils.h>
#include <gst/video/video.h>

#include "gstmpeg4videoparse.h"

GST_DEBUG_CATEGORY (mpeg4v_parse_debug);
#define GST_CAT_DEFAULT mpeg4v_parse_debug

static GstStaticPadTemplate src_template =
GST_STATIC_PAD_TEMPLATE ("src", GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/mpeg, "
        "mpegversion = (int) 4, "
        "parsed = (boolean) true, " "systemstream = (boolean) false")
    );

static GstStaticPadTemplate sink_template =
GST_STATIC_PAD_TEMPLATE ("sink", GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/mpeg, "
        "mpegversion = (int) 4, " "systemstream = (boolean) false")
    );

/* Properties */
#define DEFAULT_PROP_DROP TRUE
#define DEFAULT_CONFIG_INTERVAL (0)

enum
{
  PROP_0,
  PROP_DROP,
  PROP_CONFIG_INTERVAL,
  PROP_LAST
};

#define gst_mpeg4vparse_parent_class parent_class
G_DEFINE_TYPE (GstMpeg4VParse, gst_mpeg4vparse, GST_TYPE_BASE_PARSE);

static gboolean gst_mpeg4vparse_start (GstBaseParse * parse);
static gboolean gst_mpeg4vparse_stop (GstBaseParse * parse);
static GstFlowReturn gst_mpeg4vparse_handle_frame (GstBaseParse * parse,
    GstBaseParseFrame * frame, gint * skipsize);
static GstFlowReturn gst_mpeg4vparse_parse_frame (GstBaseParse * parse,
    GstBaseParseFrame * frame);
static GstFlowReturn gst_mpeg4vparse_pre_push_frame (GstBaseParse * parse,
    GstBaseParseFrame * frame);
static gboolean gst_mpeg4vparse_set_caps (GstBaseParse * parse, GstCaps * caps);
static GstCaps *gst_mpeg4vparse_get_caps (GstBaseParse * parse,
    GstCaps * filter);

static void gst_mpeg4vparse_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_mpeg4vparse_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);
static gboolean gst_mpeg4vparse_event (GstBaseParse * parse, GstEvent * event);
static gboolean gst_mpeg4vparse_src_event (GstBaseParse * parse,
    GstEvent * event);

static void
gst_mpeg4vparse_set_property (GObject * object, guint property_id,
    const GValue * value, GParamSpec * pspec)
{
  GstMpeg4VParse *parse = GST_MPEG4VIDEO_PARSE (object);

  switch (property_id) {
    case PROP_DROP:
      parse->drop = g_value_get_boolean (value);
      break;
    case PROP_CONFIG_INTERVAL:
      parse->interval = g_value_get_uint (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
  }
}

static void
gst_mpeg4vparse_get_property (GObject * object, guint property_id,
    GValue * value, GParamSpec * pspec)
{
  GstMpeg4VParse *parse = GST_MPEG4VIDEO_PARSE (object);

  switch (property_id) {
    case PROP_DROP:
      g_value_set_boolean (value, parse->drop);
      break;
    case PROP_CONFIG_INTERVAL:
      g_value_set_uint (value, parse->interval);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
  }
}

static void
gst_mpeg4vparse_class_init (GstMpeg4VParseClass * klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GstBaseParseClass *parse_class = GST_BASE_PARSE_CLASS (klass);
  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  gobject_class->set_property = gst_mpeg4vparse_set_property;
  gobject_class->get_property = gst_mpeg4vparse_get_property;

  g_object_class_install_property (gobject_class, PROP_DROP,
      g_param_spec_boolean ("drop", "drop",
          "Drop data untill valid configuration data is received either "
          "in the stream or through caps", DEFAULT_PROP_DROP,
          G_PARAM_CONSTRUCT | G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_CONFIG_INTERVAL,
      g_param_spec_uint ("config-interval",
          "Configuration Send Interval",
          "Send Configuration Insertion Interval in seconds (configuration headers "
          "will be multiplexed in the data stream when detected.) (0 = disabled)",
          0, 3600, DEFAULT_CONFIG_INTERVAL,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  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));

  gst_element_class_set_details_simple (element_class,
      "MPEG 4 video elementary stream parser", "Codec/Parser/Video",
      "Parses MPEG-4 Part 2 elementary video streams",
      "Julien Moutte <julien@fluendo.com>");

  GST_DEBUG_CATEGORY_INIT (mpeg4v_parse_debug, "mpeg4videoparse", 0,
      "MPEG-4 video parser");

  /* Override BaseParse vfuncs */
  parse_class->start = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_start);
  parse_class->stop = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_stop);
  parse_class->handle_frame = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_handle_frame);
  parse_class->pre_push_frame =
      GST_DEBUG_FUNCPTR (gst_mpeg4vparse_pre_push_frame);
  parse_class->set_sink_caps = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_set_caps);
  parse_class->get_sink_caps = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_get_caps);
  parse_class->sink_event = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_event);
  parse_class->src_event = GST_DEBUG_FUNCPTR (gst_mpeg4vparse_src_event);
}

static void
gst_mpeg4vparse_init (GstMpeg4VParse * parse)
{
  parse->interval = DEFAULT_CONFIG_INTERVAL;
  parse->last_report = GST_CLOCK_TIME_NONE;

  gst_base_parse_set_pts_interpolation (GST_BASE_PARSE (parse), FALSE);
}

static void
gst_mpeg4vparse_reset_frame (GstMpeg4VParse * mp4vparse)
{
  /* done parsing; reset state */
  mp4vparse->last_sc = -1;
  mp4vparse->vop_offset = -1;
  mp4vparse->vo_found = FALSE;
  mp4vparse->vol_offset = -1;
}

static void
gst_mpeg4vparse_reset (GstMpeg4VParse * mp4vparse)
{
  gst_mpeg4vparse_reset_frame (mp4vparse);
  mp4vparse->update_caps = TRUE;
  mp4vparse->profile = NULL;
  mp4vparse->level = NULL;
  mp4vparse->pending_key_unit_ts = GST_CLOCK_TIME_NONE;
  mp4vparse->force_key_unit_event = NULL;

  gst_buffer_replace (&mp4vparse->config, NULL);
  memset (&mp4vparse->vol, 0, sizeof (mp4vparse->vol));
}

static gboolean
gst_mpeg4vparse_start (GstBaseParse * parse)
{
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);

  GST_DEBUG_OBJECT (parse, "start");

  gst_mpeg4vparse_reset (mp4vparse);
  /* at least this much for a valid frame */
  gst_base_parse_set_min_frame_size (parse, 6);

  return TRUE;
}

static gboolean
gst_mpeg4vparse_stop (GstBaseParse * parse)
{
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);

  GST_DEBUG_OBJECT (parse, "stop");

  gst_mpeg4vparse_reset (mp4vparse);

  return TRUE;
}

static gboolean
gst_mpeg4vparse_process_config (GstMpeg4VParse * mp4vparse,
    const guint8 * data, guint offset, gsize size)
{
  /* only do stuff if something new */
  if (mp4vparse->config
      && !gst_buffer_memcmp (mp4vparse->config, offset, data, size))
    return TRUE;

  if (mp4vparse->vol_offset < 0) {
    GST_WARNING ("No video object Layer parsed in this frame, cannot accept "
        "config");
    return FALSE;
  }

  /* If the parsing fail, we accept the config only if we don't have
   * any config yet. */
  if (gst_mpeg4_parse_video_object_layer (&mp4vparse->vol,
          NULL, data + mp4vparse->vol_offset,
          size - mp4vparse->vol_offset) != GST_MPEG4_PARSER_OK &&
      mp4vparse->config)
    return FALSE;

  GST_LOG_OBJECT (mp4vparse, "Width/Height: %u/%u, "
      "time increment resolution: %u fixed time increment: %u",
      mp4vparse->vol.width, mp4vparse->vol.height,
      mp4vparse->vol.vop_time_increment_resolution,
      mp4vparse->vol.fixed_vop_time_increment);


  GST_LOG_OBJECT (mp4vparse, "accepting parsed config size %" G_GSSIZE_FORMAT,
      size);

  if (mp4vparse->config != NULL)
    gst_buffer_unref (mp4vparse->config);

  mp4vparse->config = gst_buffer_new_wrapped (g_memdup (data, size), size);

  /* trigger src caps update */
  mp4vparse->update_caps = TRUE;

  return TRUE;
}

static gboolean
gst_mpeg4vparse_get_vop_coded (GstMpeg4VParse * mp4vparse, const guint8 * data,
    gint vop_offset, gsize size, gsize frame_size)
{
  if (frame_size > 9) {         /* assuming bigger frame will always have vop_coded (saves some parsing) */
    return TRUE;
  } else if (size > vop_offset + 3) {
    GstBitReader reader;
    guint8 value;

    gst_bit_reader_init (&reader, data + vop_offset + 1, size - vop_offset);
    gst_bit_reader_skip (&reader, 2);   /* VOP_coding_type */

    /* modulo_time_base (ends with 0) */
    while (gst_bit_reader_get_bits_uint8 (&reader, &value, 1) && value);

    /* marker_bit */
    g_return_val_if_fail (gst_bit_reader_get_bits_uint8 (&reader, &value, 1)
        && value, TRUE);

    /* VOP_time_increment */
    gst_bit_reader_skip (&reader, mp4vparse->vol.vop_time_increment_bits);

    /* marker_bit */
    g_return_val_if_fail (gst_bit_reader_get_bits_uint8 (&reader, &value, 1)
        && value, TRUE);

    /* VOP_coded */
    if (!gst_bit_reader_get_bits_uint8 (&reader, &value, 1)) {
      return FALSE;
    }

    return value;
  }

  return FALSE;
}

/* caller guarantees at least start code in @buf at @off */
static gboolean
gst_mpeg4vparse_process_sc (GstMpeg4VParse * mp4vparse, GstMpeg4Packet * packet,
    gsize size)
{

  GST_LOG_OBJECT (mp4vparse, "process startcode %x", packet->type);

  /* if we found a VOP, next start code ends it,
   * except for final VOS end sequence code included in last VOP-frame */
  if (mp4vparse->vop_offset >= 0 &&
      packet->type != GST_MPEG4_VISUAL_OBJ_SEQ_END) {
    if (G_LIKELY (size > mp4vparse->vop_offset + 1)) {
      mp4vparse->intra_frame =
          ((packet->data[mp4vparse->vop_offset + 1] >> 6 & 0x3) == 0);
    } else {
      GST_WARNING_OBJECT (mp4vparse, "no data following VOP startcode");
      mp4vparse->intra_frame = FALSE;
    }
    mp4vparse->vop_coded =
        gst_mpeg4vparse_get_vop_coded (mp4vparse, packet->data,
        mp4vparse->vop_offset, size, packet->offset - 3);
    GST_LOG_OBJECT (mp4vparse,
        "ending frame of size %d, is intra %d, vop_coded %d",
        packet->offset - 3, mp4vparse->intra_frame, mp4vparse->vop_coded);
    return TRUE;
  }

  switch (packet->type) {
    case GST_MPEG4_VIDEO_OBJ_PLANE:
    case GST_MPEG4_GROUP_OF_VOP:
    {

      if (packet->type == GST_MPEG4_VIDEO_OBJ_PLANE) {
        GST_LOG_OBJECT (mp4vparse, "startcode is VOP");
        mp4vparse->vop_offset = packet->offset;
      } else {
        GST_LOG_OBJECT (mp4vparse, "startcode is GOP");
      }
      /* parse config data ending here if proper startcodes found earlier;
       * preferably start at VOS (visual object sequence),
       * otherwise at VO (video object) */
      if (mp4vparse->vo_found) {

        /*Do not take care startcode into account */
        gst_mpeg4vparse_process_config (mp4vparse,
            packet->data, packet->offset, packet->offset - 3);

        /* avoid accepting again for a VOP sc following a GOP sc */
        mp4vparse->vo_found = FALSE;
      }
      break;
    }
    case GST_MPEG4_VISUAL_OBJ_SEQ_START:
      GST_LOG_OBJECT (mp4vparse, "Visual Sequence Start");
      mp4vparse->vo_found = TRUE;
      mp4vparse->profile = gst_codec_utils_mpeg4video_get_profile (packet->data
          + packet->offset + 1, packet->offset);
      mp4vparse->level = gst_codec_utils_mpeg4video_get_level (packet->data
          + packet->offset + 1, packet->offset);
      break;
    case GST_MPEG4_VISUAL_OBJ:
      GST_LOG_OBJECT (mp4vparse, "Visual Object");
    default:
      if (packet->type >= GST_MPEG4_VIDEO_LAYER_FIRST &&
          packet->type <= GST_MPEG4_VIDEO_LAYER_LAST) {

        GST_LOG_OBJECT (mp4vparse, "Video Object Layer");

        /*  wee keep track of the offset to parse later on */
        if (mp4vparse->vol_offset < 0)
          mp4vparse->vol_offset = packet->offset;

        /* VO (video object) cases */
      } else if (packet->type <= GST_MPEG4_VIDEO_OBJ_LAST) {
        GST_LOG_OBJECT (mp4vparse, "Video object");
        mp4vparse->vo_found = TRUE;
      }
      break;
  }

  /* at least need to have a VOP in a frame */
  return FALSE;
}

static GstFlowReturn
gst_mpeg4vparse_handle_frame (GstBaseParse * parse,
    GstBaseParseFrame * frame, gint * skipsize)
{
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);
  GstMpeg4Packet packet;
  GstMapInfo map;
  guint8 *data = NULL;
  gsize size;
  gint off = 0;
  gboolean ret = FALSE;
  guint framesize;

  gst_buffer_map (frame->buffer, &map, GST_MAP_READ);
  data = map.data;
  size = map.size;

retry:
  /* at least start code and subsequent byte */
  if (G_UNLIKELY (size - off < 5)) {
    *skipsize = 1;
    goto out;
  }

  /* avoid stale cached parsing state */
  if (frame->flags & GST_BASE_PARSE_FRAME_FLAG_NEW_FRAME) {
    GST_LOG_OBJECT (mp4vparse, "parsing new frame");
    gst_mpeg4vparse_reset_frame (mp4vparse);
  } else {
    GST_LOG_OBJECT (mp4vparse, "resuming frame parsing");
  }

  /* if already found a previous start code, e.g. start of frame, go for next */
  if (mp4vparse->last_sc >= 0) {
    off = mp4vparse->last_sc;
    goto next;
  }

  /* didn't find anything that looks like a sync word, skip */
  switch (gst_mpeg4_parse (&packet, TRUE, NULL, data, off, size)) {
    case (GST_MPEG4_PARSER_NO_PACKET):
    case (GST_MPEG4_PARSER_ERROR):
      *skipsize = size - 3;
      goto out;
    default:
      break;
  }
  off = packet.offset;

  /* possible frame header, but not at offset 0? skip bytes before sync */
  if (G_UNLIKELY (off > 3)) {
    *skipsize = off - 3;
    goto out;
  }

  switch (packet.type) {
    case GST_MPEG4_GROUP_OF_VOP:
    case GST_MPEG4_VISUAL_OBJ_SEQ_START:
    case GST_MPEG4_VIDEO_OBJ_PLANE:
      break;
    default:
      if (packet.type <= GST_MPEG4_VIDEO_OBJ_LAST)
        break;
      /* undesirable sc */
      GST_LOG_OBJECT (mp4vparse, "start code is no VOS, VO, VOP or GOP");
      goto retry;
  }

  /* found sc */
  mp4vparse->last_sc = 0;

  /* examine start code, which should not end frame at present */
  gst_mpeg4vparse_process_sc (mp4vparse, &packet, size);

next:
  GST_LOG_OBJECT (mp4vparse, "Looking for frame end");

  /* start is fine as of now */
  *skipsize = 0;
  /* position a bit further than last sc */
  off++;

  /* so now we have start code at start of data; locate next packet */
  switch (gst_mpeg4_parse (&packet, TRUE, NULL, data, off, size)) {
    case (GST_MPEG4_PARSER_NO_PACKET_END):
      ret = gst_mpeg4vparse_process_sc (mp4vparse, &packet, size);
      if (ret)
        break;
    case (GST_MPEG4_PARSER_NO_PACKET):
    case (GST_MPEG4_PARSER_ERROR):
      /* if draining, take all */
      if (GST_BASE_PARSE_DRAINING (parse)) {
        framesize = size;
        ret = TRUE;
      } else {
        /* resume scan where we left it */
        mp4vparse->last_sc = size - 3;
      }
      goto out;
      break;
    default:
      /* decide whether this startcode ends a frame */
      ret = gst_mpeg4vparse_process_sc (mp4vparse, &packet, size);
      break;
  }

  off = packet.offset;

  if (ret) {
    framesize = off - 3;
  } else {
    goto next;
  }

out:
  gst_buffer_unmap (frame->buffer, &map);

  if (ret) {
    GstFlowReturn res;

    g_assert (framesize <= map.size);
    res = gst_mpeg4vparse_parse_frame (parse, frame);
    if (res == GST_BASE_PARSE_FLOW_DROPPED)
      frame->flags |= GST_BASE_PARSE_FRAME_FLAG_DROP;
    return gst_base_parse_finish_frame (parse, frame, framesize);
  }

  return GST_FLOW_OK;
}

static void
gst_mpeg4vparse_update_src_caps (GstMpeg4VParse * mp4vparse)
{
  GstCaps *caps = NULL;
  GstStructure *s = NULL;

  GST_LOG_OBJECT (mp4vparse, "Updating caps");

  /* only update if no src caps yet or explicitly triggered */
  if (G_LIKELY (gst_pad_has_current_caps (GST_BASE_PARSE_SRC_PAD (mp4vparse)) &&
          !mp4vparse->update_caps))
    return;

  /* carry over input caps as much as possible; override with our own stuff */
  caps = gst_pad_get_current_caps (GST_BASE_PARSE_SINK_PAD (mp4vparse));
  if (caps) {
    GstCaps *tmp = gst_caps_copy (caps);
    gst_caps_unref (caps);
    caps = tmp;
    s = gst_caps_get_structure (caps, 0);
  } else {
    caps = gst_caps_new_simple ("video/mpeg",
        "mpegversion", G_TYPE_INT, 4, NULL);
  }

  gst_caps_set_simple (caps, "systemstream", G_TYPE_BOOLEAN, FALSE,
      "parsed", G_TYPE_BOOLEAN, TRUE, NULL);

  if (mp4vparse->profile && mp4vparse->level) {
    gst_caps_set_simple (caps, "profile", G_TYPE_STRING, mp4vparse->profile,
        "level", G_TYPE_STRING, mp4vparse->level, NULL);
  }

  if (mp4vparse->config != NULL) {
    gst_caps_set_simple (caps, "codec_data",
        GST_TYPE_BUFFER, mp4vparse->config, NULL);
  }

  if (mp4vparse->vol.width > 0 && mp4vparse->vol.height > 0) {
    gst_caps_set_simple (caps, "width", G_TYPE_INT, mp4vparse->vol.width,
        "height", G_TYPE_INT, mp4vparse->vol.height, NULL);
  }

  /* perhaps we have a framerate */
  if (mp4vparse->vol.fixed_vop_time_increment != 0 &&
      (!s || !gst_structure_has_field (s, "framerate"))) {
    gint fps_num = mp4vparse->vol.vop_time_increment_resolution;
    gint fps_den = mp4vparse->vol.fixed_vop_time_increment;
    GstClockTime latency = gst_util_uint64_scale (GST_SECOND, fps_den, fps_num);

    gst_caps_set_simple (caps, "framerate",
        GST_TYPE_FRACTION, fps_num, fps_den, NULL);
    gst_base_parse_set_frame_rate (GST_BASE_PARSE (mp4vparse),
        fps_num, fps_den, 0, 0);
    gst_base_parse_set_latency (GST_BASE_PARSE (mp4vparse), latency, latency);
  }

  /* or pixel-aspect-ratio */
  if (mp4vparse->vol.par_width > 0 && mp4vparse->vol.par_height > 0 &&
      (!s || !gst_structure_has_field (s, "pixel-aspect-ratio"))) {
    gst_caps_set_simple (caps, "pixel-aspect-ratio",
        GST_TYPE_FRACTION, mp4vparse->vol.par_width,
        mp4vparse->vol.par_height, NULL);
  }

  gst_pad_set_caps (GST_BASE_PARSE_SRC_PAD (mp4vparse), caps);
  gst_caps_unref (caps);

  mp4vparse->update_caps = FALSE;
}

static GstFlowReturn
gst_mpeg4vparse_parse_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
{
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);
  GstBuffer *buffer = frame->buffer;

  gst_mpeg4vparse_update_src_caps (mp4vparse);

  if (mp4vparse->intra_frame)
    GST_BUFFER_FLAG_UNSET (buffer, GST_BUFFER_FLAG_DELTA_UNIT);
  else
    GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT);

  if (!mp4vparse->vop_coded)    /* buffer without VOP_coded has no data */
    GST_BUFFER_DURATION (buffer) = 0;

  if (G_UNLIKELY (mp4vparse->drop && !mp4vparse->config)) {
    GST_LOG_OBJECT (mp4vparse, "dropping frame as no config yet");
    return GST_BASE_PARSE_FLOW_DROPPED;
  } else
    return GST_FLOW_OK;
}

static GstEvent *
check_pending_key_unit_event (GstEvent * pending_event, GstSegment * segment,
    GstClockTime timestamp, guint flags, GstClockTime pending_key_unit_ts)
{
  GstClockTime running_time, stream_time;
  gboolean all_headers;
  guint count;
  GstEvent *event = NULL;

  g_return_val_if_fail (segment != NULL, NULL);

  if (pending_event == NULL)
    goto out;

  if (GST_CLOCK_TIME_IS_VALID (pending_key_unit_ts) &&
      timestamp == GST_CLOCK_TIME_NONE)
    goto out;

  running_time = gst_segment_to_running_time (segment,
      GST_FORMAT_TIME, timestamp);

  GST_INFO ("now %" GST_TIME_FORMAT " wanted %" GST_TIME_FORMAT,
      GST_TIME_ARGS (running_time), GST_TIME_ARGS (pending_key_unit_ts));
  if (GST_CLOCK_TIME_IS_VALID (pending_key_unit_ts) &&
      running_time < pending_key_unit_ts)
    goto out;

  if (flags & GST_BUFFER_FLAG_DELTA_UNIT) {
    GST_DEBUG ("pending force key unit, waiting for keyframe");
    goto out;
  }

  stream_time = gst_segment_to_stream_time (segment,
      GST_FORMAT_TIME, timestamp);

  gst_video_event_parse_upstream_force_key_unit (pending_event,
      NULL, &all_headers, &count);

  event =
      gst_video_event_new_downstream_force_key_unit (timestamp, stream_time,
      running_time, all_headers, count);
  gst_event_set_seqnum (event, gst_event_get_seqnum (pending_event));

out:
  return event;
}

static void
gst_mpeg4vparse_prepare_key_unit (GstMpeg4VParse * parse, GstEvent * event)
{
  GstClockTime running_time;
  guint count;

  parse->pending_key_unit_ts = GST_CLOCK_TIME_NONE;
  gst_event_replace (&parse->force_key_unit_event, NULL);

  gst_video_event_parse_downstream_force_key_unit (event,
      NULL, NULL, &running_time, NULL, &count);

  GST_INFO_OBJECT (parse, "pushing downstream force-key-unit event %d "
      "%" GST_TIME_FORMAT " count %d", gst_event_get_seqnum (event),
      GST_TIME_ARGS (running_time), count);
  gst_pad_push_event (GST_BASE_PARSE_SRC_PAD (parse), event);
}


static GstFlowReturn
gst_mpeg4vparse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
{
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);
  GstBuffer *buffer = frame->buffer;
  gboolean push_codec = FALSE;
  GstEvent *event = NULL;

  if ((event = check_pending_key_unit_event (mp4vparse->force_key_unit_event,
              &parse->segment, GST_BUFFER_TIMESTAMP (buffer),
              GST_BUFFER_FLAGS (buffer), mp4vparse->pending_key_unit_ts))) {
    gst_mpeg4vparse_prepare_key_unit (mp4vparse, event);
    push_codec = TRUE;
  }

  /* periodic config sending */
  if (mp4vparse->interval > 0 || push_codec) {
    GstClockTime timestamp = GST_BUFFER_TIMESTAMP (buffer);
    guint64 diff;

    /* init */
    if (!GST_CLOCK_TIME_IS_VALID (mp4vparse->last_report)) {
      mp4vparse->last_report = timestamp;
    }

    if (!GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT)) {
      if (timestamp > mp4vparse->last_report)
        diff = timestamp - mp4vparse->last_report;
      else
        diff = 0;

      GST_LOG_OBJECT (mp4vparse,
          "now %" GST_TIME_FORMAT ", last config %" GST_TIME_FORMAT,
          GST_TIME_ARGS (timestamp), GST_TIME_ARGS (mp4vparse->last_report));

      GST_LOG_OBJECT (mp4vparse,
          "interval since last config %" GST_TIME_FORMAT, GST_TIME_ARGS (diff));

      if (GST_TIME_AS_SECONDS (diff) >= mp4vparse->interval || push_codec) {
        GstMapInfo cmap;
        gsize csize;
        gboolean diffconf;

        /* we need to send config now first */
        GST_INFO_OBJECT (parse, "inserting config in stream");
        gst_buffer_map (mp4vparse->config, &cmap, GST_MAP_READ);
        diffconf = (gst_buffer_get_size (buffer) < cmap.size)
            || gst_buffer_memcmp (buffer, 0, cmap.data, cmap.size);
        csize = cmap.size;
        gst_buffer_unmap (mp4vparse->config, &cmap);

        /* avoid inserting duplicate config */
        if (diffconf) {
          GstBuffer *superbuf;

          /* insert header */
          superbuf =
              gst_buffer_append (gst_buffer_ref (mp4vparse->config),
              gst_buffer_ref (buffer));
          gst_buffer_copy_into (superbuf, buffer, GST_BUFFER_COPY_METADATA, 0,
              csize);
          gst_buffer_replace (&frame->out_buffer, superbuf);
          gst_buffer_unref (superbuf);
        } else {
          GST_INFO_OBJECT (parse, "... but avoiding duplication");
        }

        if (G_UNLIKELY (timestamp != -1)) {
          mp4vparse->last_report = timestamp;
        }
      }
    }
  }

  return GST_FLOW_OK;
}

static gboolean
gst_mpeg4vparse_set_caps (GstBaseParse * parse, GstCaps * caps)
{
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);
  GstStructure *s;
  const GValue *value;
  GstBuffer *buf;
  GstMapInfo map;
  guint8 *data;
  gsize size;

  GstMpeg4Packet packet;
  GstMpeg4ParseResult res;

  GST_DEBUG_OBJECT (parse, "setcaps called with %" GST_PTR_FORMAT, caps);

  s = gst_caps_get_structure (caps, 0);

  if ((value = gst_structure_get_value (s, "codec_data")) != NULL
      && (buf = gst_value_get_buffer (value))) {
    /* best possible parse attempt,
     * src caps are based on sink caps so it will end up in there
     * whether sucessful or not */
    gst_buffer_map (buf, &map, GST_MAP_READ);
    data = map.data;
    size = map.size;
    res = gst_mpeg4_parse (&packet, TRUE, NULL, data, 0, size);

    while (res == GST_MPEG4_PARSER_OK || res == GST_MPEG4_PARSER_NO_PACKET_END) {

      if (packet.type >= GST_MPEG4_VIDEO_LAYER_FIRST &&
          packet.type <= GST_MPEG4_VIDEO_LAYER_LAST)
        mp4vparse->vol_offset = packet.offset;

      res = gst_mpeg4_parse (&packet, TRUE, NULL, data, packet.offset, size);
    }

    /* And take it as config */
    gst_mpeg4vparse_process_config (mp4vparse, data, 3, size);
    gst_buffer_unmap (buf, &map);
  }

  /* let's not interfere and accept regardless of config parsing success */
  return TRUE;
}


static GstCaps *
gst_mpeg4vparse_get_caps (GstBaseParse * parse, GstCaps * filter)
{
  GstCaps *peercaps, *templ;
  GstCaps *res;

  templ = gst_pad_get_pad_template_caps (GST_BASE_PARSE_SINK_PAD (parse));
  peercaps = gst_pad_get_allowed_caps (GST_BASE_PARSE_SRC_PAD (parse));

  if (peercaps) {
    guint i, n;

    /* Remove the parsed field */
    peercaps = gst_caps_make_writable (peercaps);
    n = gst_caps_get_size (peercaps);
    for (i = 0; i < n; i++) {
      GstStructure *s = gst_caps_get_structure (peercaps, i);

      gst_structure_remove_field (s, "parsed");
    }

    res = gst_caps_intersect_full (peercaps, templ, GST_CAPS_INTERSECT_FIRST);
    gst_caps_unref (peercaps);

    /* Append the template caps because we still want to accept
     * caps without any fields in the case upstream does not
     * know anything.
     */
    gst_caps_append (res, templ);
  } else {
    res = templ;
  }

  if (filter) {
    GstCaps *tmp = gst_caps_intersect_full (res, filter,
        GST_CAPS_INTERSECT_FIRST);
    gst_caps_unref (res);
    res = tmp;
  }


  return res;
}

static gboolean
gst_mpeg4vparse_event (GstBaseParse * parse, GstEvent * event)
{
  gboolean res;
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_CUSTOM_DOWNSTREAM:
    {
      GstClockTime timestamp, stream_time, running_time;
      gboolean all_headers;
      guint count;

      if (gst_video_event_is_force_key_unit (event)) {
        gst_video_event_parse_downstream_force_key_unit (event,
            &timestamp, &stream_time, &running_time, &all_headers, &count);

        GST_INFO_OBJECT (mp4vparse, "received downstream force key unit event, "
            "seqnum %d running_time %" GST_TIME_FORMAT
            " all_headers %d count %d", gst_event_get_seqnum (event),
            GST_TIME_ARGS (running_time), all_headers, count);

        if (mp4vparse->force_key_unit_event) {
          GST_INFO_OBJECT (mp4vparse, "ignoring force key unit event "
              "as one is already queued");
        } else {
          mp4vparse->pending_key_unit_ts = running_time;
          gst_event_replace (&mp4vparse->force_key_unit_event, event);
        }
        gst_event_unref (event);
        res = TRUE;
      } else {
        res = GST_BASE_PARSE_CLASS (parent_class)->sink_event (parse, event);
      }
      break;
    }
    default:
      res = GST_BASE_PARSE_CLASS (parent_class)->sink_event (parse, event);
      break;
  }
  return res;
}

static gboolean
gst_mpeg4vparse_src_event (GstBaseParse * parse, GstEvent * event)
{
  gboolean res;
  GstMpeg4VParse *mp4vparse = GST_MPEG4VIDEO_PARSE (parse);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_CUSTOM_UPSTREAM:
    {
      GstClockTime running_time;
      gboolean all_headers;
      guint count;

      if (gst_video_event_is_force_key_unit (event)) {
        gst_video_event_parse_upstream_force_key_unit (event,
            &running_time, &all_headers, &count);

        GST_INFO_OBJECT (mp4vparse, "received upstream force-key-unit event, "
            "seqnum %d running_time %" GST_TIME_FORMAT
            " all_headers %d count %d", gst_event_get_seqnum (event),
            GST_TIME_ARGS (running_time), all_headers, count);

        if (all_headers) {
          mp4vparse->pending_key_unit_ts = running_time;
          gst_event_replace (&mp4vparse->force_key_unit_event, event);
        }
      }
      res = GST_BASE_PARSE_CLASS (parent_class)->src_event (parse, event);
      break;
    }
    default:
      res = GST_BASE_PARSE_CLASS (parent_class)->src_event (parse, event);
      break;
  }

  return res;
}