gstreamer/gst/h264parse/gsth264parse.c

/* GStreamer h264 parser
 * Copyright (C) 2005 Michal Benes <michal.benes@itonis.tv>
 *           (C) 2008 Wim Taymans <wim.taymans@gmail.com>
 *
 * gsth264parse.c:
 *
 * 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.
 */


#include <stdlib.h>
#include <string.h>

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

#include "gsth264parse.h"

static GstStaticPadTemplate sinktemplate = GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/x-h264"));

static GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/x-h264"));

GST_DEBUG_CATEGORY_STATIC (h264_parse_debug);
#define GST_CAT_DEFAULT h264_parse_debug

static const GstElementDetails gst_h264_parse_details =
GST_ELEMENT_DETAILS ("H264Parse",
    "Codec/Parser",
    "Parses raw h264 stream",
    "Michal Benes <michal.benes@itonis.tv>,"
    "Wim Taymans <wim.taymans@gmail.com>");

#define DEFAULT_SPLIT_PACKETIZED     FALSE

enum
{
  PROP_0,
  PROP_SPLIT_PACKETIZED
};

typedef enum
{
  NAL_UNKNOWN = 0,
  NAL_SLICE = 1,
  NAL_SLICE_DPA = 2,
  NAL_SLICE_DPB = 3,
  NAL_SLICE_DPC = 4,
  NAL_SLICE_IDR = 5,
  NAL_SEI = 6,
  NAL_SPS = 7,
  NAL_PPS = 8,
  NAL_AU_DELIMITER = 9,
  NAL_SEQ_END = 10,
  NAL_STREAM_END = 11,
  NAL_FILTER_DATA = 12
} GstNalUnitType;

/* small linked list implementation to allocate the list entry and the data in
 * one go */
struct _GstNalList
{
  GstNalList *next;

  gint nal_type;
  gint nal_ref_idc;
  gint first_mb_in_slice;
  gint slice_type;
  gboolean slice;
  gboolean i_frame;

  GstBuffer *buffer;
};

static GstNalList *
gst_nal_list_new (GstBuffer * buffer)
{
  GstNalList *new_list;

  new_list = g_slice_new0 (GstNalList);
  new_list->buffer = buffer;

  return new_list;
}

static GstNalList *
gst_nal_list_prepend_link (GstNalList * list, GstNalList * link)
{
  link->next = list;

  return link;
}

static GstNalList *
gst_nal_list_delete_head (GstNalList * list)
{
  if (list) {
    GstNalList *old = list;

    list = list->next;

    g_slice_free (GstNalList, old);
  }
  return list;
}

/* simple bitstream parser, automatically skips over
 * emulation_prevention_three_bytes. */
typedef struct
{
  const guint8 *data;
  const guint8 *end;
  gint head;                    /* bitpos in the cache of next bit */
  guint64 cache;                /* cached bytes */
} GstNalBs;

static void
gst_nal_bs_init (GstNalBs * bs, const guint8 * data, guint size)
{
  bs->data = data;
  bs->end = data + size;
  bs->head = 0;
  /* fill with something other than 0 to detect emulation prevention bytes */
  bs->cache = 0xffffffff;
}

static guint32
gst_nal_bs_read (GstNalBs * bs, guint n)
{
  guint32 res = 0;
  gint shift;

  if (n == 0)
    return res;

  /* fill up the cache if we need to */
  while (bs->head < n) {
    guint8 byte;
    gboolean check_three_byte;

    check_three_byte = TRUE;
  next_byte:
    if (bs->data >= bs->end) {
      /* we're at the end, can't produce more than head number of bits */
      n = bs->head;
      break;
    }
    /* get the byte, this can be an emulation_prevention_three_byte that we need
     * to ignore. */
    byte = *bs->data++;
    if (check_three_byte && byte == 0x03 && ((bs->cache & 0xffff) == 0)) {
      /* next byte goes unconditionally to the cache, even if it's 0x03 */
      check_three_byte = FALSE;
      goto next_byte;
    }
    /* shift bytes in cache, moving the head bits of the cache left */
    bs->cache = (bs->cache << 8) | byte;
    bs->head += 8;
  }

  /* bring the required bits down and truncate */
  if ((shift = bs->head - n) > 0)
    res = bs->cache >> shift;
  else
    res = bs->cache;

  /* mask out required bits */
  if (n < 32)
    res &= (1 << n) - 1;

  bs->head = shift;

  return res;
}

static gboolean
gst_nal_bs_eos (GstNalBs * bs)
{
  return (bs->data >= bs->end) && (bs->head == 0);
}

/* read unsigned Exp-Golomb code */
static gint
gst_nal_bs_read_ue (GstNalBs * bs)
{
  gint i = 0;

  while (gst_nal_bs_read (bs, 1) == 0 && !gst_nal_bs_eos (bs) && i < 32)
    i++;

  return ((1 << i) - 1 + gst_nal_bs_read (bs, i));
}

/* SEI type */
typedef enum
{
  SEI_BUF_PERIOD = 0,
  SEI_PIC_TIMING = 1
      /* and more...  */
} GstSeiPayloadType;

/* SEI pic_struct type */
typedef enum
{
  SEI_PIC_STRUCT_FRAME = 0,     /* 0: %frame */
  SEI_PIC_STRUCT_TOP_FIELD = 1, /* 1: top field */
  SEI_PIC_STRUCT_BOTTOM_FIELD = 2,      /* 2: bottom field */
  SEI_PIC_STRUCT_TOP_BOTTOM = 3,        /* 3: top field, bottom field, in that order */
  SEI_PIC_STRUCT_BOTTOM_TOP = 4,        /* 4: bottom field, top field, in that order */
  SEI_PIC_STRUCT_TOP_BOTTOM_TOP = 5,    /* 5: top field, bottom field, top field repeated, in that order */
  SEI_PIC_STRUCT_BOTTOM_TOP_BOTTOM = 6, /* 6: bottom field, top field, bottom field repeated, in that order */
  SEI_PIC_STRUCT_FRAME_DOUBLING = 7,    /* 7: %frame doubling */
  SEI_PIC_STRUCT_FRAME_TRIPLING = 8     /* 8: %frame tripling */
} GstSeiPicStructType;

/* pic_struct to NumClockTS lookup table */
static const guint8 sei_num_clock_ts_table[9] = {
  1, 1, 1, 2, 2, 3, 3, 2, 3
};

#define Extended_SAR 255

/* SPS: sequential parameter sets */
struct _GstH264Sps
{
  guint8 profile_idc;
  guint8 level_idc;

  guint8 sps_id;

  guint8 pic_order_cnt_type;

  guint8 log2_max_frame_num_minus4;
  gboolean frame_mbs_only_flag;
  guint8 log2_max_pic_order_cnt_lsb_minus4;

  gboolean frame_cropping_flag;

  /* VUI parameters */
  gboolean vui_parameters_present_flag;

  gboolean timing_info_present_flag;
  guint32 num_units_in_tick;
  guint32 time_scale;
  gboolean fixed_frame_rate_flag;

  gboolean nal_hrd_parameters_present_flag;
  gboolean vcl_hrd_parameters_present_flag;
  /* hrd parameters */
  guint8 cpb_cnt_minus1;
  gint initial_cpb_removal_delay_length_minus1; /* initial_cpb_removal_delay_length_minus1 */
  gint cpb_removal_delay_length_minus1; /* cpb_removal_delay_length_minus1 */
  gint dpb_output_delay_length_minus1;  /* dpb_output_delay_length_minus1 */
  gboolean time_offset_length_minus1;

  gboolean pic_struct_present_flag;
  /* And more...  */
};
/* PPS: pic parameter sets */
struct _GstH264Pps
{
  guint8 pps_id;
  guint8 sps_id;
};

static GstH264Sps *
gst_h264_parse_get_sps (GstH264Parse * h, guint8 sps_id)
{
  GstH264Sps *sps;
  g_return_val_if_fail (h != NULL, NULL);

  if (sps_id >= MAX_SPS_COUNT) {
    GST_DEBUG_OBJECT (h, "requested sps_id=%04x out of range", sps_id);
    return NULL;
  }
  sps = h->sps_buffers[sps_id];
  if (sps == NULL) {
    GST_DEBUG_OBJECT (h, "Creating sps with sps_id=%04x", sps_id);
    sps = h->sps_buffers[sps_id] = g_slice_new0 (GstH264Sps);
    if (sps == NULL) {
      GST_DEBUG_OBJECT (h, "Allocation failed!");
    }
  }

  h->sps = h->sps_buffers[sps_id] = sps;
  return sps;
}

static GstH264Pps *
gst_h264_parse_get_pps (GstH264Parse * h, guint8 pps_id)
{
  GstH264Pps *pps;
  g_return_val_if_fail (h != NULL, NULL);
  if (pps_id >= MAX_PPS_COUNT) {
    GST_DEBUG_OBJECT (h, "requested pps_id=%04x out of range", pps_id);
    return NULL;
  }
  pps = h->pps_buffers[pps_id];
  if (pps == NULL) {
    GST_DEBUG_OBJECT (h, "Creating pps with pps_id=%04x", pps_id);
    pps = g_slice_new0 (GstH264Pps);
    if (pps == NULL) {
      GST_DEBUG_OBJECT (h, "Failed!");
    }
  }

  h->pps = h->pps_buffers[pps_id] = pps;
  return pps;
}

/* decode hrd parameters */
static gboolean
gst_vui_decode_hrd_parameters (GstH264Parse * h, GstNalBs * bs)
{
  GstH264Sps *sps = h->sps;
  gint sched_sel_idx;

  sps->cpb_cnt_minus1 = gst_nal_bs_read_ue (bs);
  if (sps->cpb_cnt_minus1 > 31U) {
    GST_ERROR_OBJECT (h, "cpb_cnt_minus1 = %d out of range",
        sps->cpb_cnt_minus1);
    return FALSE;
  }

  gst_nal_bs_read (bs, 4);      /* bit_rate_scale */
  gst_nal_bs_read (bs, 4);      /* cpb_size_scale */

  for (sched_sel_idx = 0; sched_sel_idx <= sps->cpb_cnt_minus1; sched_sel_idx++) {
    gst_nal_bs_read_ue (bs);    /* bit_rate_value_minus1 */
    gst_nal_bs_read_ue (bs);    /* cpb_size_value_minus1 */
    gst_nal_bs_read (bs, 1);    /* cbr_flag */
  }

  sps->initial_cpb_removal_delay_length_minus1 = gst_nal_bs_read (bs, 5);
  sps->cpb_removal_delay_length_minus1 = gst_nal_bs_read (bs, 5);
  sps->dpb_output_delay_length_minus1 = gst_nal_bs_read (bs, 5);
  sps->time_offset_length_minus1 = gst_nal_bs_read (bs, 5);

  return TRUE;
}

/* decode vui parameters */
static gboolean
gst_sps_decode_vui (GstH264Parse * h, GstNalBs * bs)
{
  GstH264Sps *sps = h->sps;

  if (gst_nal_bs_read (bs, 1)) {        /* aspect_ratio_info_present_flag */
    if (gst_nal_bs_read (bs, 8) == Extended_SAR) {      /* aspect_ratio_idc */
      gst_nal_bs_read (bs, 16); /* sar_width */
      gst_nal_bs_read (bs, 16); /* sar_height */
    }
  }

  if (gst_nal_bs_read (bs, 1)) {        /* overscan_info_present_flag */
    gst_nal_bs_read (bs, 1);    /* overscan_appropriate_flag */
  }

  if (gst_nal_bs_read (bs, 1)) {        /* video_signal_type_present_flag */
    gst_nal_bs_read (bs, 3);    /* video_format */
    gst_nal_bs_read (bs, 1);    /* video_full_range_flag */

    if (gst_nal_bs_read (bs, 1)) {      /* colour_description_present_flag */
      gst_nal_bs_read (bs, 8);  /* colour_primaries */
      gst_nal_bs_read (bs, 8);  /* transfer_characteristics */
      gst_nal_bs_read (bs, 8);  /* matrix_coefficients */
    }
  }

  if (gst_nal_bs_read (bs, 1)) {        /* chroma_loc_info_present_flag */
    gst_nal_bs_read_ue (bs);    /* chroma_sample_loc_type_top_field */
    gst_nal_bs_read_ue (bs);    /* chroma_sample_loc_type_bottom_field */
  }

  /*
     GST_DEBUG_OBJECT (h,
     "aspect_ratio_info_present_flag = %d, "
     "overscan_info_present_flag = %d, "
     "video_signal_type_present_flag = %d, "
     "chroma_loc_info_present_flag = %d\n",
     sps->aspect_ratio_info_present_flag, sps->overscan_info_present_flag,
     sps->video_signal_type_present_flag, sps->chroma_loc_info_present_flag);
   */

  sps->timing_info_present_flag = gst_nal_bs_read (bs, 1);
  if (sps->timing_info_present_flag) {
    guint32 num_units_in_tick = gst_nal_bs_read (bs, 32);
    guint32 time_scale = gst_nal_bs_read (bs, 32);

    /* If any of these parameters = 0, discard all timing_info */
    if (time_scale == 0) {
      GST_WARNING_OBJECT (h,
          "time_scale = 0 detected in stream (incompliant to H.264 E.2.1)."
          " Discarding related info.");
    } else if (num_units_in_tick == 0) {
      GST_WARNING_OBJECT (h,
          "num_units_in_tick  = 0 detected in stream (incompliant to H.264 E.2.1)."
          " Discarding related info.");
    } else {
      sps->num_units_in_tick = num_units_in_tick;
      sps->time_scale = time_scale;
      sps->fixed_frame_rate_flag = gst_nal_bs_read (bs, 1);
    }

    GST_DEBUG_OBJECT (h,
        "num_units_in_tick = %d, time_scale = %d, "
        "fixed_frame_rate_flag = %d\n",
        sps->num_units_in_tick, sps->time_scale, sps->fixed_frame_rate_flag);
  }

  sps->nal_hrd_parameters_present_flag = gst_nal_bs_read (bs, 1);
  if (sps->nal_hrd_parameters_present_flag) {
    gst_vui_decode_hrd_parameters (h, bs);
  }
  sps->vcl_hrd_parameters_present_flag = gst_nal_bs_read (bs, 1);
  if (sps->vcl_hrd_parameters_present_flag) {
    gst_vui_decode_hrd_parameters (h, bs);
  }
  if (sps->nal_hrd_parameters_present_flag
      || sps->vcl_hrd_parameters_present_flag) {
    gst_nal_bs_read (bs, 1);    /* low_delay_hrd_flag */
  }

  sps->pic_struct_present_flag = gst_nal_bs_read (bs, 1);

  /* Not going down anymore */
  return TRUE;

  if (gst_nal_bs_read (bs, 1)) {        /* bitstream_restriction_flag */
    gst_nal_bs_read (bs, 1);    /* motion_vectors_over_pic_boundaries_flag */
    gst_nal_bs_read_ue (bs);    /* max_bytes_per_pic_denom */
    gst_nal_bs_read_ue (bs);    /* max_bits_per_mb_denom */
    gst_nal_bs_read_ue (bs);    /* log2_max_mv_length_horizontal */
    gst_nal_bs_read_ue (bs);    /* log2_max_mv_length_vertical */
    gst_nal_bs_read_ue (bs);    /* num_reorder_frames */
    gst_nal_bs_read_ue (bs);    /* max_dec_frame_buffering */
  }
}

/* decode sequential parameter sets */
static gboolean
gst_nal_decode_sps (GstH264Parse * h, GstNalBs * bs)
{
  guint8 profile_idc, level_idc;
  guint8 sps_id;
  GstH264Sps *sps = NULL;

  profile_idc = gst_nal_bs_read (bs, 8);
  gst_nal_bs_read (bs, 1);      /* constraint_set0_flag */
  gst_nal_bs_read (bs, 1);      /* constraint_set1_flag */
  gst_nal_bs_read (bs, 1);      /* constraint_set2_flag */
  gst_nal_bs_read (bs, 1);      /* constraint_set3_flag */
  gst_nal_bs_read (bs, 4);      /* reserved */
  level_idc = gst_nal_bs_read (bs, 8);

  sps_id = gst_nal_bs_read_ue (bs);
  sps = gst_h264_parse_get_sps (h, sps_id);
  if (sps == NULL) {
    return FALSE;
  }
  sps->profile_idc = profile_idc;
  sps->level_idc = level_idc;

  if (profile_idc == 100 || profile_idc == 110 || profile_idc == 122
      || profile_idc == 244 || profile_idc == 44 ||
      profile_idc == 83 || profile_idc == 86) {
    if (gst_nal_bs_read_ue (bs) == 3) { /* chroma_format_idc */
      gst_nal_bs_read (bs, 1);  /* separate_colour_plane_flag */
    }
    gst_nal_bs_read_ue (bs);    /* bit_depth_luma_minus8 */
    gst_nal_bs_read_ue (bs);    /* bit_depth_chroma_minus8 */
    gst_nal_bs_read (bs, 1);    /* qpprime_y_zero_transform_bypass_flag */
    if (gst_nal_bs_read (bs, 1)) {      /* seq_scaling_matrix_present_flag */
      /* TODO: unfinished */
    }
  }

  sps->log2_max_frame_num_minus4 = gst_nal_bs_read_ue (bs);     /* between 0 and 12 */
  if (sps->log2_max_frame_num_minus4 > 12) {
    GST_DEBUG_OBJECT (h, "log2_max_frame_num_minus4 = %d out of range"
        " [0,12]", sps->log2_max_frame_num_minus4);
    return FALSE;
  }

  sps->pic_order_cnt_type = gst_nal_bs_read_ue (bs);
  if (sps->pic_order_cnt_type == 0) {
    sps->log2_max_pic_order_cnt_lsb_minus4 = gst_nal_bs_read_ue (bs);
  } else if (sps->pic_order_cnt_type == 1) {
    /* TODO: unfinished */
    /*
       delta_pic_order_always_zero_flag = gst_nal_bs_read (bs, 1);
       offset_for_non_ref_pic = gst_nal_bs_read_se (bs);
       offset_for_top_to_bottom_field = gst_nal_bs_read_se (bs);

       num_ref_frames_in_pic_order_cnt_cycle = gst_nal_bs_read_ue (bs);
       for( i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; i++ )
       offset_for_ref_frame[i] = gst_nal_bs_read_se (bs);
     */
  }

  gst_nal_bs_read_ue (bs);      /* max_num_ref_frames */
  gst_nal_bs_read (bs, 1);      /* gaps_in_frame_num_value_allowed_flag */
  gst_nal_bs_read_ue (bs);      /* pic_width_in_mbs_minus1 */
  gst_nal_bs_read_ue (bs);      /* pic_height_in_map_units_minus1 */

  sps->frame_mbs_only_flag = gst_nal_bs_read (bs, 1);
  if (!sps->frame_mbs_only_flag) {
    gst_nal_bs_read (bs, 1);    /* mb_adaptive_frame_field_flag */
  }

  gst_nal_bs_read (bs, 1);      /* direct_8x8_inference_flag */
  if (gst_nal_bs_read (bs, 1)) {        /* frame_cropping_flag */
    gst_nal_bs_read_ue (bs);    /* frame_crop_left_offset */
    gst_nal_bs_read_ue (bs);    /* frame_crop_right_offset */
    gst_nal_bs_read_ue (bs);    /* frame_crop_top_offset */
    gst_nal_bs_read_ue (bs);    /* frame_crop_bottom_offset */
  }

  GST_DEBUG_OBJECT (h, "Decoding SPS: profile_idc = %d, "
      "level_idc = %d, "
      "sps_id = %d, "
      "pic_order_cnt_type = %d, "
      "frame_mbs_only_flag = %d\n",
      sps->profile_idc,
      sps->level_idc,
      sps_id, sps->pic_order_cnt_type, sps->frame_mbs_only_flag);

  sps->vui_parameters_present_flag = gst_nal_bs_read (bs, 1);
  if (sps->vui_parameters_present_flag) {
    gst_sps_decode_vui (h, bs);
  }

  return TRUE;
}

/* decode pic parameter set */
static gboolean
gst_nal_decode_pps (GstH264Parse * h, GstNalBs * bs)
{
  guint8 pps_id;
  GstH264Pps *pps = NULL;

  pps_id = gst_nal_bs_read_ue (bs);
  pps = gst_h264_parse_get_pps (h, pps_id);
  if (pps == NULL) {
    return FALSE;
  }
  h->pps = pps;

  pps->sps_id = gst_nal_bs_read_ue (bs);

  /* not parsing the rest for the time being */
  return TRUE;
}

/* decode buffering periods */
static gboolean
gst_sei_decode_buffering_period (GstH264Parse * h, GstNalBs * bs)
{
  guint8 sps_id;
  gint sched_sel_idx;
  GstH264Sps *sps;

  sps_id = gst_nal_bs_read_ue (bs);
  sps = gst_h264_parse_get_sps (h, sps_id);
  if (!sps)
    return FALSE;

  if (sps->nal_hrd_parameters_present_flag) {
    for (sched_sel_idx = 0; sched_sel_idx <= sps->cpb_cnt_minus1;
        sched_sel_idx++) {
      h->initial_cpb_removal_delay[sched_sel_idx]
          = gst_nal_bs_read (bs,
          sps->initial_cpb_removal_delay_length_minus1 + 1);
      gst_nal_bs_read (bs, sps->initial_cpb_removal_delay_length_minus1 + 1);   /* initial_cpb_removal_delay_offset */
    }
  }
  if (sps->vcl_hrd_parameters_present_flag) {
    for (sched_sel_idx = 0; sched_sel_idx <= sps->cpb_cnt_minus1;
        sched_sel_idx++) {
      h->initial_cpb_removal_delay[sched_sel_idx]
          = gst_nal_bs_read (bs,
          sps->initial_cpb_removal_delay_length_minus1 + 1);
      gst_nal_bs_read (bs, sps->initial_cpb_removal_delay_length_minus1 + 1);   /* initial_cpb_removal_delay_offset */
    }
  }
#if 0
  h->ts_trn_nb = MPEGTIME_TO_GSTTIME (h->initial_cpb_removal_delay[0]); /* Assuming SchedSelIdx=0 */
#endif
  if (h->ts_trn_nb == GST_CLOCK_TIME_NONE || h->dts == GST_CLOCK_TIME_NONE)
    h->ts_trn_nb = 0;
  else
    h->ts_trn_nb = h->dts;

  GST_DEBUG_OBJECT (h, "h->ts_trn_nb updated: %" GST_TIME_FORMAT,
      GST_TIME_ARGS (h->ts_trn_nb));

  return 0;
}

/* decode SEI picture timing message */
static gboolean
gst_sei_decode_picture_timing (GstH264Parse * h, GstNalBs * bs)
{
  GstH264Sps *sps = h->sps;

  if (sps == NULL) {
    GST_WARNING_OBJECT (h, "h->sps=NULL; delayed decoding of picture timing "
        "info not implemented yet");
    return FALSE;
  }

  if (sps->nal_hrd_parameters_present_flag
      || sps->vcl_hrd_parameters_present_flag) {
    h->sei_cpb_removal_delay =
        gst_nal_bs_read (bs, sps->cpb_removal_delay_length_minus1 + 1);
    h->sei_dpb_output_delay =
        gst_nal_bs_read (bs, sps->dpb_output_delay_length_minus1 + 1);
  }
  if (sps->pic_struct_present_flag) {
    guint i, num_clock_ts;
    h->sei_pic_struct = gst_nal_bs_read (bs, 4);
    h->sei_ct_type = 0;

    if (h->sei_pic_struct > SEI_PIC_STRUCT_FRAME_TRIPLING)
      return FALSE;

    num_clock_ts = sei_num_clock_ts_table[h->sei_pic_struct];

    for (i = 0; i < num_clock_ts; i++) {
      if (gst_nal_bs_read (bs, 1)) {    /* clock_timestamp_flag */
        guint full_timestamp_flag;
        h->sei_ct_type |= 1 << gst_nal_bs_read (bs, 2);
        gst_nal_bs_read (bs, 1);        /* nuit_field_based_flag */
        gst_nal_bs_read (bs, 5);        /* counting_type */
        full_timestamp_flag = gst_nal_bs_read (bs, 1);
        gst_nal_bs_read (bs, 1);        /* discontinuity_flag */
        gst_nal_bs_read (bs, 1);        /* cnt_dropped_flag */
        gst_nal_bs_read (bs, 8);        /* n_frames */
        if (full_timestamp_flag) {
          gst_nal_bs_read (bs, 6);      /* seconds_value 0..59 */
          gst_nal_bs_read (bs, 6);      /* minutes_value 0..59 */
          gst_nal_bs_read (bs, 5);      /* hours_value 0..23 */
        } else {
          if (gst_nal_bs_read (bs, 1)) {        /* seconds_flag */
            gst_nal_bs_read (bs, 6);    /* seconds_value range 0..59 */
            if (gst_nal_bs_read (bs, 1)) {      /* minutes_flag */
              gst_nal_bs_read (bs, 6);  /* minutes_value 0..59 */
              if (gst_nal_bs_read (bs, 1))      /* hours_flag */
                gst_nal_bs_read (bs, 5);        /* hours_value 0..23 */
            }
          }
        }
        if (sps->time_offset_length_minus1 >= 0)
          gst_nal_bs_read (bs, sps->time_offset_length_minus1 + 1);     /* time_offset */
      }
    }

    GST_DEBUG_OBJECT (h, "ct_type:%X pic_struct:%d\n", h->sei_ct_type,
        h->sei_pic_struct);
  }
  return 0;
}

/* decode supplimental enhancement information */
static gboolean
gst_nal_decode_sei (GstH264Parse * h, GstNalBs * bs)
{
  guint8 tmp;
  GstSeiPayloadType payloadType = 0;
  gint8 payloadSize = 0;

  do {
    tmp = gst_nal_bs_read (bs, 8);
    payloadType += tmp;
  } while (tmp == 255);
  do {
    tmp = gst_nal_bs_read (bs, 8);
    payloadSize += tmp;
  } while (tmp == 255);
  GST_DEBUG_OBJECT (h,
      "SEI message received: payloadType = %d, payloadSize = %d bytes",
      payloadType, payloadSize);

  switch (payloadType) {
    case SEI_BUF_PERIOD:
      if (!gst_sei_decode_buffering_period (h, bs))
        return FALSE;
      break;
    case SEI_PIC_TIMING:
      /* TODO: According to H264 D2.2 Note1, it might be the case that the
       * picture timing SEI message is encountered before the corresponding SPS
       * is specified. Need to hold down the message and decode it later.  */
      if (!gst_sei_decode_picture_timing (h, bs))
        return FALSE;
      break;
    default:
      GST_DEBUG_OBJECT (h, "SEI message of payloadType = %d is recieved but not"
          " parsed", payloadType);
  }

  return TRUE;
}

/* decode slice header */
static gboolean
gst_nal_decode_slice_header (GstH264Parse * h, GstNalBs * bs)
{
  guint8 pps_id, sps_id;
  h->first_mb_in_slice = gst_nal_bs_read_ue (bs);
  h->slice_type = gst_nal_bs_read_ue (bs);

  pps_id = gst_nal_bs_read_ue (bs);
  h->pps = gst_h264_parse_get_pps (h, pps_id);
  if (!h->pps)
    return FALSE;
  /* FIXME: note that pps might be uninitialized */
  sps_id = h->pps->sps_id;
  h->sps = gst_h264_parse_get_sps (h, sps_id);
  /* FIXME: in some streams sps/pps may not be ready before the first slice
   * header. In this case it is not a good idea to _get_sps()/_pps() at this
   * point
   * TODO: scan one round beforehand for SPS/PPS before decoding slice headers?
   * */

  /* TODO: separate_color_plane_flag: from SPS, not implemented yet, assumed to
   * be false */

  h->frame_num =
      gst_nal_bs_read (bs, h->sps->log2_max_pic_order_cnt_lsb_minus4 + 4);

  if (!h->sps && !h->sps->frame_mbs_only_flag) {
    h->field_pic_flag = gst_nal_bs_read (bs, 1);
    if (h->field_pic_flag)
      h->bottom_field_flag = gst_nal_bs_read (bs, 1);
  }

  /* not parsing the rest for the time being */
  return TRUE;
}

GST_BOILERPLATE (GstH264Parse, gst_h264_parse, GstElement, GST_TYPE_ELEMENT);

static void gst_h264_parse_finalize (GObject * object);
static void gst_h264_parse_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_h264_parse_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);

static GstFlowReturn gst_h264_parse_chain (GstPad * pad, GstBuffer * buf);
static gboolean gst_h264_parse_sink_event (GstPad * pad, GstEvent * event);
static gboolean gst_h264_parse_sink_setcaps (GstPad * pad, GstCaps * caps);

static GstStateChangeReturn gst_h264_parse_change_state (GstElement * element,
    GstStateChange transition);

static void
gst_h264_parse_base_init (gpointer g_class)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class);

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&srctemplate));
  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&sinktemplate));
  gst_element_class_set_details (gstelement_class, &gst_h264_parse_details);

  GST_DEBUG_CATEGORY_INIT (h264_parse_debug, "h264parse", 0, "h264 parser");
}

static void
gst_h264_parse_class_init (GstH264ParseClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;

  gobject_class = G_OBJECT_CLASS (klass);
  gstelement_class = (GstElementClass *) klass;

  gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_h264_parse_finalize);
  gobject_class->set_property = gst_h264_parse_set_property;
  gobject_class->get_property = gst_h264_parse_get_property;

  g_object_class_install_property (gobject_class, PROP_SPLIT_PACKETIZED,
      g_param_spec_boolean ("split-packetized", "Split packetized",
          "Split NAL units of packetized streams", DEFAULT_SPLIT_PACKETIZED,
          G_PARAM_READWRITE));

  gstelement_class->change_state = gst_h264_parse_change_state;
}

static void
gst_h264_parse_init (GstH264Parse * h264parse, GstH264ParseClass * g_class)
{
  gint i;
  h264parse->sinkpad = gst_pad_new_from_static_template (&sinktemplate, "sink");
  gst_pad_set_chain_function (h264parse->sinkpad,
      GST_DEBUG_FUNCPTR (gst_h264_parse_chain));
  gst_pad_set_event_function (h264parse->sinkpad,
      GST_DEBUG_FUNCPTR (gst_h264_parse_sink_event));
  gst_pad_set_setcaps_function (h264parse->sinkpad,
      GST_DEBUG_FUNCPTR (gst_h264_parse_sink_setcaps));
  gst_element_add_pad (GST_ELEMENT (h264parse), h264parse->sinkpad);

  h264parse->srcpad = gst_pad_new_from_static_template (&srctemplate, "src");
  gst_element_add_pad (GST_ELEMENT (h264parse), h264parse->srcpad);

  h264parse->split_packetized = DEFAULT_SPLIT_PACKETIZED;
  h264parse->adapter = gst_adapter_new ();

  for (i = 0; i < MAX_SPS_COUNT; i++)
    h264parse->sps_buffers[i] = NULL;
  h264parse->sps = NULL;

  h264parse->first_mb_in_slice = -1;
  h264parse->slice_type = -1;
  h264parse->pps_id = -1;
  h264parse->frame_num = -1;
  h264parse->field_pic_flag = FALSE;
  h264parse->bottom_field_flag = FALSE;

  for (i = 0; i < 32; i++)
    h264parse->initial_cpb_removal_delay[i] = -1;
  h264parse->sei_cpb_removal_delay = 0;
  h264parse->sei_dpb_output_delay = 0;
  h264parse->sei_pic_struct = -1;
  h264parse->sei_ct_type = -1;

  h264parse->dts = GST_CLOCK_TIME_NONE;
  h264parse->ts_trn_nb = GST_CLOCK_TIME_NONE;
  h264parse->cur_duration = 0;
  h264parse->last_outbuf_dts = GST_CLOCK_TIME_NONE;
}

static void
gst_h264_parse_finalize (GObject * object)
{
  GstH264Parse *h264parse;
  gint i;

  h264parse = GST_H264PARSE (object);

  g_object_unref (h264parse->adapter);

  for (i = 0; i < MAX_SPS_COUNT; i++) {
    if (h264parse->sps_buffers[i] != NULL)
      g_slice_free (GstH264Sps, h264parse->sps_buffers[i]);
  }

  for (i = 0; i < MAX_PPS_COUNT; i++) {
    if (h264parse->pps_buffers[i] != NULL)
      g_slice_free (GstH264Pps, h264parse->pps_buffers[i]);
  }

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static void
gst_h264_parse_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstH264Parse *parse;

  parse = GST_H264PARSE (object);

  switch (prop_id) {
    case PROP_SPLIT_PACKETIZED:
      parse->split_packetized = g_value_get_boolean (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_h264_parse_get_property (GObject * object, guint prop_id, GValue * value,
    GParamSpec * pspec)
{
  GstH264Parse *parse;

  parse = GST_H264PARSE (object);

  switch (prop_id) {
    case PROP_SPLIT_PACKETIZED:
      g_value_set_boolean (value, parse->split_packetized);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static gboolean
gst_h264_parse_sink_setcaps (GstPad * pad, GstCaps * caps)
{
  gboolean res;
  GstH264Parse *h264parse;
  GstStructure *str;
  const GValue *value;
  guint8 *data;
  guint size;

  h264parse = GST_H264PARSE (GST_PAD_PARENT (pad));

  str = gst_caps_get_structure (caps, 0);

  /* packetized video has a codec_data */
  if ((value = gst_structure_get_value (str, "codec_data"))) {
    GstBuffer *buffer;
    gint profile;

    GST_DEBUG_OBJECT (h264parse, "have packetized h264");
    h264parse->packetized = TRUE;

    buffer = gst_value_get_buffer (value);
    data = GST_BUFFER_DATA (buffer);
    size = GST_BUFFER_SIZE (buffer);

    /* parse the avcC data */
    if (size < 7)
      goto avcc_too_small;
    /* parse the version, this must be 1 */
    if (data[0] != 1)
      goto wrong_version;

    /* AVCProfileIndication */
    /* profile_compat */
    /* AVCLevelIndication */
    profile = (data[1] << 16) | (data[2] << 8) | data[3];
    GST_DEBUG_OBJECT (h264parse, "profile %06x", profile);

    /* 6 bits reserved | 2 bits lengthSizeMinusOne */
    /* this is the number of bytes in front of the NAL units to mark their
     * length */
    h264parse->nal_length_size = (data[4] & 0x03) + 1;
    GST_DEBUG_OBJECT (h264parse, "nal length %u", h264parse->nal_length_size);

    /* FIXME, PPS, SPS have vital info for detecting new I-frames */
  } else {
    GST_DEBUG_OBJECT (h264parse, "have bytestream h264");
    h264parse->packetized = FALSE;
    /* we have 4 sync bytes */
    h264parse->nal_length_size = 4;
  }

  /* forward the caps */
  res = gst_pad_set_caps (h264parse->srcpad, caps);

  return res;

  /* ERRORS */
avcc_too_small:
  {
    GST_ERROR_OBJECT (h264parse, "avcC size %u < 7", size);
    return FALSE;
  }
wrong_version:
  {
    GST_ERROR_OBJECT (h264parse, "wrong avcC version");
    return FALSE;
  }
}

static void
gst_h264_parse_clear_queues (GstH264Parse * h264parse)
{
  g_list_foreach (h264parse->gather, (GFunc) gst_mini_object_unref, NULL);
  g_list_free (h264parse->gather);
  h264parse->gather = NULL;
  while (h264parse->decode) {
    gst_buffer_unref (h264parse->decode->buffer);
    h264parse->decode = gst_nal_list_delete_head (h264parse->decode);
  }
  h264parse->decode = NULL;
  h264parse->decode_len = 0;
  if (h264parse->prev) {
    gst_buffer_unref (h264parse->prev);
    h264parse->prev = NULL;
  }
  gst_adapter_clear (h264parse->adapter);
  h264parse->have_i_frame = FALSE;
}

static GstFlowReturn
gst_h264_parse_chain_forward (GstH264Parse * h264parse, gboolean discont,
    GstBuffer * buffer)
{
  GstFlowReturn res = GST_FLOW_OK;
  const guint8 *data;

  if (discont) {
    gst_adapter_clear (h264parse->adapter);
    h264parse->discont = TRUE;
  }

  gst_adapter_push (h264parse->adapter, buffer);

  while (res == GST_FLOW_OK) {
    gint i;
    gint next_nalu_pos = -1;
    gint avail;
    gboolean delta_unit = FALSE;
    gboolean got_frame = FALSE;

    avail = gst_adapter_available (h264parse->adapter);
    if (avail < h264parse->nal_length_size + 1)
      break;
    data = gst_adapter_peek (h264parse->adapter, avail);

    if (!h264parse->packetized) {
      /* Bytestream format, first 4 bytes are sync code */
      /* Find next NALU header */
      for (i = 1; i < avail - 4; ++i) {
        if (data[i + 0] == 0 && data[i + 1] == 0 && data[i + 2] == 0
            && data[i + 3] == 1) {
          next_nalu_pos = i;
          break;
        }
      }
    } else {
      guint32 nalu_size;

      nalu_size = 0;
      for (i = 0; i < h264parse->nal_length_size; i++)
        nalu_size = (nalu_size << 8) | data[i];

      GST_LOG_OBJECT (h264parse, "got NALU size %u", nalu_size);

      /* check for invalid NALU sizes, assume the size if the available bytes
       * when something is fishy */
      if (nalu_size <= 1 || nalu_size + h264parse->nal_length_size > avail) {
        nalu_size = avail - h264parse->nal_length_size;
        GST_DEBUG_OBJECT (h264parse, "fixing invalid NALU size to %u",
            nalu_size);
      }

      /* Packetized format, see if we have to split it, usually splitting is not
       * a good idea as decoders have no way of handling it. */
      if (h264parse->split_packetized) {
        if (nalu_size + h264parse->nal_length_size <= avail)
          next_nalu_pos = nalu_size + h264parse->nal_length_size;
      } else {
        next_nalu_pos = avail;
      }
    }

    /* skip nalu_size bytes or sync */
    data += h264parse->nal_length_size;
    avail -= h264parse->nal_length_size;

    /* Figure out if this is a delta unit */
    {
      GstNalUnitType nal_type;
      gint nal_ref_idc;
      GstNalBs bs;

      nal_type = (data[0] & 0x1f);
      nal_ref_idc = (data[0] & 0x60) >> 5;

      GST_DEBUG_OBJECT (h264parse, "NAL type: %d, ref_idc: %d", nal_type,
          nal_ref_idc);

      gst_nal_bs_init (&bs, data + 1, avail - 1);

      /* first parse some things needed to get to the frame type */
      switch (nal_type) {
        case NAL_SLICE:
        case NAL_SLICE_DPA:
        case NAL_SLICE_DPB:
        case NAL_SLICE_DPC:
        case NAL_SLICE_IDR:
        {
          gint first_mb_in_slice, slice_type;

          gst_nal_decode_slice_header (h264parse, &bs);
          first_mb_in_slice = h264parse->first_mb_in_slice;
          slice_type = h264parse->slice_type;

          GST_DEBUG_OBJECT (h264parse, "first MB: %d, slice type: %d",
              first_mb_in_slice, slice_type);

          switch (slice_type) {
            case 0:
            case 5:
            case 3:
            case 8:            /* SP */
              /* P frames */
              GST_DEBUG_OBJECT (h264parse, "we have a P slice");
              delta_unit = TRUE;
              break;
            case 1:
            case 6:
              /* B frames */
              GST_DEBUG_OBJECT (h264parse, "we have a B slice");
              delta_unit = TRUE;
              break;
            case 2:
            case 7:
            case 4:
            case 9:
              /* I frames */
              GST_DEBUG_OBJECT (h264parse, "we have an I slice");
              got_frame = TRUE;
              break;
          }
          break;

        }
        case NAL_SEI:
          GST_DEBUG_OBJECT (h264parse, "we have an SEI NAL");
          gst_nal_decode_sei (h264parse, &bs);
          break;
        case NAL_SPS:
          GST_DEBUG_OBJECT (h264parse, "we have an SPS NAL");
          gst_nal_decode_sps (h264parse, &bs);
          break;
        case NAL_PPS:
          GST_DEBUG_OBJECT (h264parse, "we have a PPS NAL");
          gst_nal_decode_pps (h264parse, &bs);
          break;
        case NAL_AU_DELIMITER:
          GST_DEBUG_OBJECT (h264parse, "we have an access unit delimiter.");
          break;
        default:
          GST_DEBUG_OBJECT (h264parse,
              "NAL of nal_type = %d encountered but not parsed", nal_type);
      }
    }

    /* we have a packet */
    if (next_nalu_pos > 0) {
      GstBuffer *outbuf;
      GstClockTime outbuf_dts = GST_CLOCK_TIME_NONE;

      outbuf = gst_adapter_take_buffer (h264parse->adapter, next_nalu_pos);
      outbuf_dts = gst_adapter_prev_timestamp (h264parse->adapter, NULL);       /* Better value for the second parameter? */

      /* Ignore upstream dts that stalls or goes backward. Upstream elements
       * like filesrc would keep on writing timestamp=0.  XXX: is this correct?
       * TODO: better way to detect whether upstream timstamps are useful */
      if (h264parse->last_outbuf_dts != GST_CLOCK_TIME_NONE
          && outbuf_dts != GST_CLOCK_TIME_NONE
          && outbuf_dts <= h264parse->last_outbuf_dts)
        outbuf_dts = GST_CLOCK_TIME_NONE;

      if (got_frame || delta_unit) {
        GstH264Sps *sps = h264parse->sps;
        gint duration = 1;

        if (!sps) {
          GST_DEBUG_OBJECT (h264parse, "referred SPS invalid");
          goto TIMESTAMP_FINISH;
        } else if (!sps->timing_info_present_flag) {
          GST_DEBUG_OBJECT (h264parse,
              "unable to compute timestamp: timing info not present");
          goto TIMESTAMP_FINISH;
        } else if (sps->time_scale == 0) {
          GST_DEBUG_OBJECT (h264parse,
              "unable to compute timestamp: time_scale = 0 "
              "(this is forbidden in spec; bitstream probably contains error)");
          goto TIMESTAMP_FINISH;
        }

        if (sps->pic_struct_present_flag
            && h264parse->sei_pic_struct != (guint8) - 1) {
          /* Note that when h264parse->sei_pic_struct == -1 (unspecified), there
           * are ways to infer its value. This is related to computing the
           * TopFieldOrderCnt and BottomFieldOrderCnt, which looks
           * complicated and thus not implemented for the time being. Yet
           * the value we have here is correct for many applications
           */
          switch (h264parse->sei_pic_struct) {
            case SEI_PIC_STRUCT_TOP_FIELD:
            case SEI_PIC_STRUCT_BOTTOM_FIELD:
              duration = 1;
              break;
            case SEI_PIC_STRUCT_FRAME:
            case SEI_PIC_STRUCT_TOP_BOTTOM:
            case SEI_PIC_STRUCT_BOTTOM_TOP:
              duration = 2;
              break;
            case SEI_PIC_STRUCT_TOP_BOTTOM_TOP:
            case SEI_PIC_STRUCT_BOTTOM_TOP_BOTTOM:
              duration = 3;
              break;
            case SEI_PIC_STRUCT_FRAME_DOUBLING:
              duration = 4;
              break;
            case SEI_PIC_STRUCT_FRAME_TRIPLING:
              duration = 6;
              break;
            default:
              GST_DEBUG_OBJECT (h264parse,
                  "h264parse->sei_pic_struct of unknown value %d. Not parsed",
                  h264parse->sei_pic_struct);
          }
        } else {
          duration = h264parse->field_pic_flag ? 1 : 2;
        }

        /*
         * h264parse.264 C.1.2 Timing of coded picture removal (equivalent to DTS):
         * Tr,n(0) = initial_cpb_removal_delay[ SchedSelIdx ] / 90000
         * Tr,n(n) = Tr,n(nb) + Tc * cpb_removal_delay(n)
         * where
         * Tc = num_units_in_tick / time_scale
         */

        if (h264parse->ts_trn_nb != GST_CLOCK_TIME_NONE) {
          /* buffering period is present */
          if (outbuf_dts != GST_CLOCK_TIME_NONE) {
            /* If upstream timestamp is valid, we respect it and adjust current
             * reference point */
            h264parse->ts_trn_nb = outbuf_dts -
                (GstClockTime) gst_util_uint64_scale_int
                (h264parse->sei_cpb_removal_delay * GST_SECOND,
                sps->num_units_in_tick, sps->time_scale);
          } else {
            /* If no upstream timestamp is given, we write in new timestamp */
            h264parse->dts = h264parse->ts_trn_nb +
                (GstClockTime) gst_util_uint64_scale_int
                (h264parse->sei_cpb_removal_delay * GST_SECOND,
                sps->num_units_in_tick, sps->time_scale);
          }
        } else {
          /* naive method: no removal delay specified, use best guess (add prev
           * frame duration) */
          if (outbuf_dts != GST_CLOCK_TIME_NONE)
            h264parse->dts = outbuf_dts;
          else if (h264parse->dts != GST_CLOCK_TIME_NONE)
            h264parse->dts += (GstClockTime)
                gst_util_uint64_scale_int (h264parse->cur_duration * GST_SECOND,
                sps->num_units_in_tick, sps->time_scale);
          else
            h264parse->dts = 0; /* initialization */

          /* TODO: better approach: construct a buffer queue and put all these
           * NALs into the buffer. Wait until we are able to get any valid dts
           * or such like, and dump the buffer and estimate the timestamps of
           * the NALs by their duration.
           */
        }

        h264parse->cur_duration = duration;
        h264parse->frame_cnt += 1;
        if (outbuf_dts != GST_CLOCK_TIME_NONE)
          h264parse->last_outbuf_dts = outbuf_dts;
      }

      if (outbuf_dts == GST_CLOCK_TIME_NONE)
        outbuf_dts = h264parse->dts;
      else
        h264parse->dts = outbuf_dts;

    TIMESTAMP_FINISH:
      GST_BUFFER_TIMESTAMP (outbuf) = outbuf_dts;

      GST_DEBUG_OBJECT (h264parse,
          "pushing buffer %p, size %u, ts %" GST_TIME_FORMAT, outbuf,
          next_nalu_pos, GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (outbuf)));

      if (h264parse->discont) {
        GST_BUFFER_FLAG_SET (outbuf, GST_BUFFER_FLAG_DISCONT);
        h264parse->discont = FALSE;
      }

      if (delta_unit)
        GST_BUFFER_FLAG_SET (outbuf, GST_BUFFER_FLAG_DELTA_UNIT);
      else
        GST_BUFFER_FLAG_UNSET (outbuf, GST_BUFFER_FLAG_DELTA_UNIT);

      gst_buffer_set_caps (outbuf, GST_PAD_CAPS (h264parse->srcpad));
      res = gst_pad_push (h264parse->srcpad, outbuf);
    } else {
      /* NALU can not be parsed yet, we wait for more data in the adapter. */
      break;
    }
  }
  return res;
}

static GstFlowReturn
gst_h264_parse_flush_decode (GstH264Parse * h264parse)
{
  GstFlowReturn res = GST_FLOW_OK;
  gboolean first = TRUE;

  while (h264parse->decode) {
    GstNalList *link;
    GstBuffer *buf;

    link = h264parse->decode;
    buf = link->buffer;

    GST_DEBUG_OBJECT (h264parse, "have type: %d, I frame: %d", link->nal_type,
        link->i_frame);

    if (first) {
      /* first buffer has discont */
      GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_DISCONT);
      first = FALSE;
    } else {
      /* next buffers are not discont */
      GST_BUFFER_FLAG_UNSET (buf, GST_BUFFER_FLAG_DISCONT);
    }

    if (link->i_frame)
      GST_BUFFER_FLAG_UNSET (buf, GST_BUFFER_FLAG_DELTA_UNIT);
    else
      GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_DELTA_UNIT);

    GST_DEBUG_OBJECT (h264parse, "pushing buffer %p, ts %" GST_TIME_FORMAT,
        buf, GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)));

    res = gst_pad_push (h264parse->srcpad, buf);

    h264parse->decode = gst_nal_list_delete_head (h264parse->decode);
    h264parse->decode_len--;
  }
  /* the i frame is gone now */
  h264parse->have_i_frame = FALSE;

  return res;
}

/* check that the decode queue contains a valid sync code that should be pushed
 * out before adding @buffer to the decode queue */
static GstFlowReturn
gst_h264_parse_queue_buffer (GstH264Parse * parse, GstBuffer * buffer)
{
  guint8 *data;
  guint size;
  guint32 nalu_size;
  GstNalBs bs;
  GstNalList *link;
  GstFlowReturn res = GST_FLOW_OK;
  GstClockTime timestamp;

  /* create new NALU link */
  link = gst_nal_list_new (buffer);

  /* first parse the buffer */
  data = GST_BUFFER_DATA (buffer);
  size = GST_BUFFER_SIZE (buffer);
  timestamp = GST_BUFFER_TIMESTAMP (buffer);

  link->slice = FALSE;
  link->i_frame = FALSE;

  GST_DEBUG_OBJECT (parse,
      "analyse buffer of size %u, timestamp %" GST_TIME_FORMAT, size,
      GST_TIME_ARGS (timestamp));

  /* now parse all the NAL units in this buffer, for bytestream we only have one
   * NAL unit but for packetized streams we can have multiple ones */
  while (size >= parse->nal_length_size + 1) {
    gint i;

    nalu_size = 0;
    if (parse->packetized) {
      for (i = 0; i < parse->nal_length_size; i++)
        nalu_size = (nalu_size << 8) | data[i];
    }

    /* skip nalu_size or sync bytes */
    data += parse->nal_length_size;
    size -= parse->nal_length_size;

    link->nal_ref_idc = (data[0] & 0x60) >> 5;
    link->nal_type = (data[0] & 0x1f);

    /* nalu_size is 0 for bytestream, we have a complete packet */
    GST_DEBUG_OBJECT (parse, "size: %u, NAL type: %d, ref_idc: %d",
        nalu_size, link->nal_type, link->nal_ref_idc);

    /* first parse some things needed to get to the frame type */
    if (link->nal_type >= NAL_SLICE && link->nal_type <= NAL_SLICE_IDR) {
      gst_nal_bs_init (&bs, data + 1, size - 1);

      link->first_mb_in_slice = gst_nal_bs_read_ue (&bs);
      link->slice_type = gst_nal_bs_read_ue (&bs);
      link->slice = TRUE;

      GST_DEBUG_OBJECT (parse, "first MB: %d, slice type: %d",
          link->first_mb_in_slice, link->slice_type);

      switch (link->slice_type) {
        case 0:
        case 5:
        case 3:
        case 8:                /* SP */
          /* P frames */
          GST_DEBUG_OBJECT (parse, "we have a P slice");
          break;
        case 1:
        case 6:
          /* B frames */
          GST_DEBUG_OBJECT (parse, "we have a B slice");
          break;
        case 2:
        case 7:
        case 4:
        case 9:
          /* I frames */
          GST_DEBUG_OBJECT (parse, "we have an I slice");
          link->i_frame = TRUE;
          break;
      }
    }
    /* bytestream, we can exit now */
    if (!parse->packetized)
      break;

    /* packetized format, continue parsing all packets, skip size, we already
     * skipped the nal_length_size bytes */
    data += nalu_size;
    size -= nalu_size;
  }

  /* we have an I frame in the queue, this new NAL unit is a slice but not
   * an I frame, output the decode queue */
  GST_DEBUG_OBJECT (parse, "have_I_frame: %d, I_frame: %d, slice: %d",
      parse->have_i_frame, link->i_frame, link->slice);
  if (parse->have_i_frame && !link->i_frame && link->slice) {
    GST_DEBUG_OBJECT (parse, "flushing decode queue");
    res = gst_h264_parse_flush_decode (parse);
  }
  if (link->i_frame)
    /* we're going to add a new I-frame in the queue */
    parse->have_i_frame = TRUE;

  parse->decode = gst_nal_list_prepend_link (parse->decode, link);
  parse->decode_len++;
  GST_DEBUG_OBJECT (parse,
      "copied %d bytes of NAL to decode queue. queue size %d", size,
      parse->decode_len);

  return res;
}

static guint
gst_h264_parse_find_start_reverse (GstH264Parse * parse, guint8 * data,
    guint size, guint32 * code)
{
  guint32 search = *code;

  while (size > 0) {
    /* the sync code is kept in reverse */
    search = (search << 8) | (data[size - 1]);
    if (search == 0x01000000)
      break;

    size--;
  }
  *code = search;

  return size - 1;
}

static GstFlowReturn
gst_h264_parse_chain_reverse (GstH264Parse * h264parse, gboolean discont,
    GstBuffer * buffer)
{
  GstFlowReturn res = GST_FLOW_OK;
  GstBuffer *gbuf = NULL;

  /* if we have a discont, move buffers to the decode list */
  if (G_UNLIKELY (discont)) {
    guint start, stop, last;
    guint32 code;
    GstBuffer *prev;
    GstClockTime timestamp;

    GST_DEBUG_OBJECT (h264parse,
        "received discont, copy gathered buffers for decoding");

    /* init start code accumulator */
    stop = -1;
    prev = h264parse->prev;
    h264parse->prev = NULL;

    while (h264parse->gather) {
      guint8 *data;

      /* get new buffer and init the start code search to the end position */
      if (gbuf != NULL)
        gst_buffer_unref (gbuf);
      gbuf = GST_BUFFER_CAST (h264parse->gather->data);

      /* remove from the gather list, they are in reverse order */
      h264parse->gather =
          g_list_delete_link (h264parse->gather, h264parse->gather);

      if (h264parse->packetized) {
        /* packetized the packets are already split, we can just parse and 
         * store them */
        GST_DEBUG_OBJECT (h264parse, "copied packetized buffer");
        res = gst_h264_parse_queue_buffer (h264parse, gbuf);
        gbuf = NULL;
      } else {
        /* bytestream, we have to split the NALUs on the sync markers */
        code = 0xffffffff;
        if (prev) {
          /* if we have a previous buffer or a leftover, merge them together
           * now */
          GST_DEBUG_OBJECT (h264parse, "merging previous buffer");
          gbuf = gst_buffer_join (gbuf, prev);
          prev = NULL;
        }

        last = GST_BUFFER_SIZE (gbuf);
        data = GST_BUFFER_DATA (gbuf);
        timestamp = GST_BUFFER_TIMESTAMP (gbuf);

        GST_DEBUG_OBJECT (h264parse,
            "buffer size: %u, timestamp %" GST_TIME_FORMAT, last,
            GST_TIME_ARGS (timestamp));

        while (last > 0) {
          GST_DEBUG_OBJECT (h264parse, "scan from %u", last);
          /* find a start code searching backwards in this buffer */
          start =
              gst_h264_parse_find_start_reverse (h264parse, data, last, &code);
          if (start != -1) {
            GstBuffer *decode;

            GST_DEBUG_OBJECT (h264parse, "found start code at %u", start);

            /* we found a start code, copy everything starting from it to the
             * decode queue. */
            decode = gst_buffer_create_sub (gbuf, start, last - start);

            GST_BUFFER_TIMESTAMP (decode) = timestamp;

            /* see what we have here */
            res = gst_h264_parse_queue_buffer (h264parse, decode);

            last = start;
          } else {
            /* no start code found, keep the buffer and merge with potential next
             * buffer. */
            GST_DEBUG_OBJECT (h264parse, "no start code, keeping buffer to %u",
                last);
            prev = gst_buffer_create_sub (gbuf, 0, last);
            gst_buffer_unref (gbuf);
            gbuf = NULL;
            break;
          }
        }
      }
    }
    if (prev) {
      GST_DEBUG_OBJECT (h264parse, "keeping buffer");
      h264parse->prev = prev;
    }
  }
  if (buffer) {
    /* add buffer to gather queue */
    GST_DEBUG_OBJECT (h264parse, "gathering buffer %p, size %u", buffer,
        GST_BUFFER_SIZE (buffer));
    h264parse->gather = g_list_prepend (h264parse->gather, buffer);
  }

  if (gbuf) {
    gst_buffer_unref (gbuf);
    gbuf = NULL;
  }

  return res;
}

static GstFlowReturn
gst_h264_parse_chain (GstPad * pad, GstBuffer * buffer)
{
  GstFlowReturn res;
  GstH264Parse *h264parse;
  gboolean discont;
  GstCaps *caps;

  h264parse = GST_H264PARSE (GST_PAD_PARENT (pad));

  if (!GST_PAD_CAPS (h264parse->srcpad)) {
    /* Set default caps if the sink caps were not negotiated, this is when we
     * are reading from a file or so */
    caps = gst_caps_new_simple ("video/x-h264", NULL);

    /* Set source caps */
    if (!gst_pad_set_caps (h264parse->srcpad, caps))
      goto caps_failed;

    /* we assume the bytestream format. If the data turns out to be packetized,
     * we have a problem because we don't know the length of the nalu_size
     * indicator. Packetized input MUST set the codec_data. */
    h264parse->packetized = FALSE;
    h264parse->nal_length_size = 4;

    gst_caps_unref (caps);
  }

  discont = GST_BUFFER_IS_DISCONT (buffer);

  GST_DEBUG_OBJECT (h264parse, "received buffer of size %u",
      GST_BUFFER_SIZE (buffer));

  if (h264parse->segment.rate > 0.0)
    res = gst_h264_parse_chain_forward (h264parse, discont, buffer);
  else
    res = gst_h264_parse_chain_reverse (h264parse, discont, buffer);

  return res;

  /* ERRORS */
caps_failed:
  {
    GST_ELEMENT_ERROR (GST_ELEMENT (h264parse),
        CORE, NEGOTIATION, (NULL), ("failed to set caps"));
    gst_caps_unref (caps);
    return GST_FLOW_ERROR;
  }
}

static gboolean
gst_h264_parse_sink_event (GstPad * pad, GstEvent * event)
{
  GstH264Parse *h264parse;
  gboolean res;

  h264parse = GST_H264PARSE (gst_pad_get_parent (pad));

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_FLUSH_STOP:
      GST_DEBUG_OBJECT (h264parse, "received FLUSH stop");
      gst_segment_init (&h264parse->segment, GST_FORMAT_UNDEFINED);
      gst_h264_parse_clear_queues (h264parse);
      res = gst_pad_push_event (h264parse->srcpad, event);
      break;
    case GST_EVENT_EOS:
      GST_DEBUG_OBJECT (h264parse, "received EOS");
      if (h264parse->segment.rate < 0.0) {
        gst_h264_parse_chain_reverse (h264parse, TRUE, NULL);
        gst_h264_parse_flush_decode (h264parse);
      }
      res = gst_pad_push_event (h264parse->srcpad, event);
      break;
    case GST_EVENT_NEWSEGMENT:
    {
      gdouble rate, applied_rate;
      GstFormat format;
      gint64 start, stop, pos;
      gboolean update;

      gst_event_parse_new_segment_full (event, &update, &rate, &applied_rate,
          &format, &start, &stop, &pos);

      /* now configure the values */
      gst_segment_set_newsegment_full (&h264parse->segment, update,
          rate, applied_rate, format, start, stop, pos);

      GST_DEBUG_OBJECT (h264parse,
          "Pushing newseg rate %g, applied rate %g, format %d, start %"
          G_GINT64_FORMAT ", stop %" G_GINT64_FORMAT ", pos %" G_GINT64_FORMAT,
          rate, applied_rate, format, start, stop, pos);

      res = gst_pad_push_event (h264parse->srcpad, event);
      break;
    }
    default:
      res = gst_pad_push_event (h264parse->srcpad, event);
      break;

  }
  gst_object_unref (h264parse);

  return res;
}

static GstStateChangeReturn
gst_h264_parse_change_state (GstElement * element, GstStateChange transition)
{
  GstH264Parse *h264parse;
  GstStateChangeReturn ret;

  h264parse = GST_H264PARSE (element);

  switch (transition) {
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      gst_segment_init (&h264parse->segment, GST_FORMAT_UNDEFINED);
      break;
    default:
      break;
  }

  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);

  switch (transition) {
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      gst_h264_parse_clear_queues (h264parse);
      break;
    default:
      break;
  }

  return ret;
}


static gboolean
plugin_init (GstPlugin * plugin)
{
  return gst_element_register (plugin, "h264parse",
      GST_RANK_NONE, GST_TYPE_H264PARSE);
}

GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "h264parse",
    "Element parsing raw h264 streams",
    plugin_init, VERSION, "LGPL", GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN)