gstreamer/gst-libs/gst/vaapi/gstvaapidecoder_mpeg4.c

/*
 *  gstvaapidecoder_mpeg4.c - MPEG-4 decoder
 *
 *  Copyright (C) 2011-2013 Intel Corporation
 *    Author: Halley Zhao <halley.zhao@intel.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:gstvaapidecoder_mpeg4
 * @short_description: MPEG-4 decoder, include h263/divx/xvid support
 */

#include "sysdeps.h"
#include <gst/base/gstbitreader.h>
#include <gst/codecparsers/gstmpeg4parser.h>
#include "gstvaapidecoder_mpeg4.h"
#include "gstvaapidecoder_objects.h"
#include "gstvaapidecoder_priv.h"
#include "gstvaapidisplay_priv.h"
#include "gstvaapiobject_priv.h"

#define DEBUG 1
#include "gstvaapidebug.h"

#define GST_VAAPI_DECODER_MPEG4_CAST(decoder) \
    ((GstVaapiDecoderMpeg4 *)(decoder))

typedef struct _GstVaapiDecoderMpeg4Private GstVaapiDecoderMpeg4Private;
typedef struct _GstVaapiDecoderMpeg4Class GstVaapiDecoderMpeg4Class;

struct _GstVaapiDecoderMpeg4Private
{
  GstVaapiProfile profile;
  guint level;
  guint width;
  guint height;
  guint fps_n;
  guint fps_d;
  guint coding_type;
  GstMpeg4VisualObjectSequence vos_hdr;
  GstMpeg4VisualObject vo_hdr;
  GstMpeg4VideoSignalType signal_type;
  GstMpeg4VideoObjectLayer vol_hdr;
  GstMpeg4VideoObjectPlane vop_hdr;
  GstMpeg4VideoPlaneShortHdr svh_hdr;
  GstMpeg4VideoPacketHdr packet_hdr;
  GstMpeg4SpriteTrajectory sprite_trajectory;
  VAIQMatrixBufferMPEG4 iq_matrix;
  GstVaapiPicture *curr_picture;
  // forward reference pic
  GstVaapiPicture *next_picture;
  // backward reference pic
  GstVaapiPicture *prev_picture;
  GstClockTime seq_pts;
  GstClockTime gop_pts;
  GstClockTime pts_diff;
  GstClockTime max_pts;
  // anchor sync time base for any picture type,
  // it is time base of backward reference frame
  GstClockTime last_sync_time;
  // time base for recent I/P/S frame,
  // it is time base of forward reference frame for B frame
  GstClockTime sync_time;

  /* last non-b-frame time by resolution */
  GstClockTime last_non_b_scale_time;
  GstClockTime non_b_scale_time;
  GstClockTime trb;
  GstClockTime trd;
  // temporal_reference of previous frame of svh
  guint8 prev_t_ref;
  guint is_opened:1;
  guint is_first_field:1;
  guint size_changed:1;
  guint profile_changed:1;
  guint progressive_sequence:1;
  guint closed_gop:1;
  guint broken_link:1;
  guint calculate_pts_diff:1;
  guint is_svh:1;
};

/**
 * GstVaapiDecoderMpeg4:
 *
 * A decoder based on Mpeg4.
 */
struct _GstVaapiDecoderMpeg4
{
  /*< private > */
  GstVaapiDecoder parent_instance;
  GstVaapiDecoderMpeg4Private priv;
};

/**
 * GstVaapiDecoderMpeg4Class:
 *
 * A decoder class based on Mpeg4.
 */
struct _GstVaapiDecoderMpeg4Class
{
  /*< private > */
  GstVaapiDecoderClass parent_class;
};

G_DEFINE_TYPE (GstVaapiDecoderMpeg4, gst_vaapi_decoder_mpeg4,
    GST_TYPE_VAAPI_DECODER);

static void
gst_vaapi_decoder_mpeg4_close (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;

  gst_vaapi_picture_replace (&priv->curr_picture, NULL);
  gst_vaapi_picture_replace (&priv->next_picture, NULL);
  gst_vaapi_picture_replace (&priv->prev_picture, NULL);
}

static gboolean
gst_vaapi_decoder_mpeg4_open (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoder *const base_decoder = GST_VAAPI_DECODER (decoder);
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstCaps *caps = NULL;
  GstStructure *structure = NULL;

  gst_vaapi_decoder_mpeg4_close (decoder);

  priv->is_svh = 0;
  caps = gst_vaapi_decoder_get_caps (base_decoder);
  if (caps) {
    structure = gst_caps_get_structure (caps, 0);
    if (structure) {
      if (gst_structure_has_name (structure, "video/x-h263")) {
        priv->is_svh = 1;
        priv->profile = GST_VAAPI_PROFILE_MPEG4_SIMPLE;
        priv->prev_t_ref = -1;
      }
    }
  }
  return TRUE;
}

static void
gst_vaapi_decoder_mpeg4_destroy (GstVaapiDecoder * base_decoder)
{
  GstVaapiDecoderMpeg4 *const decoder =
      GST_VAAPI_DECODER_MPEG4_CAST (base_decoder);

  gst_vaapi_decoder_mpeg4_close (decoder);
}

static gboolean
gst_vaapi_decoder_mpeg4_create (GstVaapiDecoder * base_decoder)
{
  GstVaapiDecoderMpeg4 *const decoder =
      GST_VAAPI_DECODER_MPEG4_CAST (base_decoder);
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;

  priv->profile = GST_VAAPI_PROFILE_MPEG4_SIMPLE;
  priv->seq_pts = GST_CLOCK_TIME_NONE;
  priv->gop_pts = GST_CLOCK_TIME_NONE;
  priv->max_pts = GST_CLOCK_TIME_NONE;
  priv->calculate_pts_diff = TRUE;
  priv->size_changed = TRUE;
  priv->profile_changed = TRUE;
  return TRUE;
}

static GstVaapiDecoderStatus
gst_vaapi_decoder_mpeg4_reset (GstVaapiDecoder * base_decoder)
{
  gst_vaapi_decoder_mpeg4_destroy (base_decoder);
  gst_vaapi_decoder_mpeg4_create (base_decoder);
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static inline void
copy_quant_matrix (guint8 dst[64], const guint8 src[64])
{
  memcpy (dst, src, 64);
}

static GstVaapiDecoderStatus
ensure_context (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiProfile profiles[2];
  GstVaapiEntrypoint entrypoint = GST_VAAPI_ENTRYPOINT_VLD;
  guint i, n_profiles = 0;
  gboolean reset_context = FALSE;

  if (priv->profile_changed) {
    GST_DEBUG ("profile changed");
    priv->profile_changed = FALSE;
    reset_context = TRUE;

    profiles[n_profiles++] = priv->profile;
    if (priv->profile == GST_VAAPI_PROFILE_MPEG4_SIMPLE)
      profiles[n_profiles++] = GST_VAAPI_PROFILE_MPEG4_ADVANCED_SIMPLE;

    for (i = 0; i < n_profiles; i++) {
      if (gst_vaapi_display_has_decoder (GST_VAAPI_DECODER_DISPLAY (decoder),
              profiles[i], entrypoint))
        break;
    }
    if (i == n_profiles)
      return GST_VAAPI_DECODER_STATUS_ERROR_UNSUPPORTED_PROFILE;
    priv->profile = profiles[i];
  }

  if (priv->size_changed) {
    GST_DEBUG ("size changed");
    priv->size_changed = FALSE;
    reset_context = TRUE;
  }

  if (reset_context) {
    GstVaapiContextInfo info;

    info.profile = priv->profile;
    info.entrypoint = entrypoint;
    info.chroma_type = GST_VAAPI_CHROMA_TYPE_YUV420;
    info.width = priv->width;
    info.height = priv->height;
    info.ref_frames = 2;
    reset_context =
        gst_vaapi_decoder_ensure_context (GST_VAAPI_DECODER (decoder), &info);
    if (!reset_context)
      return GST_VAAPI_DECODER_STATUS_ERROR_UNKNOWN;
  }
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
ensure_quant_matrix (GstVaapiDecoderMpeg4 * decoder, GstVaapiPicture * picture)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  VAIQMatrixBufferMPEG4 *iq_matrix;

  if (!priv->vol_hdr.load_intra_quant_mat
      && !priv->vol_hdr.load_non_intra_quant_mat) {
    return GST_VAAPI_DECODER_STATUS_SUCCESS;
  }

  picture->iq_matrix = GST_VAAPI_IQ_MATRIX_NEW (MPEG4, decoder);
  if (!picture->iq_matrix) {
    GST_DEBUG ("failed to allocate IQ matrix");
    return GST_VAAPI_DECODER_STATUS_ERROR_ALLOCATION_FAILED;
  }
  iq_matrix = picture->iq_matrix->param;

  if (priv->vol_hdr.load_intra_quant_mat) {
    iq_matrix->load_intra_quant_mat = 1;
    copy_quant_matrix (iq_matrix->intra_quant_mat,
        priv->vol_hdr.intra_quant_mat);
  } else
    iq_matrix->load_intra_quant_mat = 0;

  if (priv->vol_hdr.load_non_intra_quant_mat) {
    iq_matrix->load_non_intra_quant_mat = 1;
    copy_quant_matrix (iq_matrix->non_intra_quant_mat,
        priv->vol_hdr.non_intra_quant_mat);
  } else
    iq_matrix->load_non_intra_quant_mat = 0;


  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static inline GstVaapiDecoderStatus
render_picture (GstVaapiDecoderMpeg4 * decoder, GstVaapiPicture * picture)
{
  if (!gst_vaapi_picture_output (picture))
    return GST_VAAPI_DECODER_STATUS_ERROR_ALLOCATION_FAILED;
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

/* decode_picture() start to decode a frame/picture
 * decode_current_picture() finishe decoding a frame/picture
 * (commit buffer to driver for decoding)
 */
static GstVaapiDecoderStatus
decode_current_picture (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiPicture *const picture = priv->curr_picture;
  GstVaapiDecoderStatus status = GST_VAAPI_DECODER_STATUS_SUCCESS;

  if (picture) {
    if (!gst_vaapi_picture_decode (picture))
      status = GST_VAAPI_DECODER_STATUS_ERROR_UNKNOWN;
    if (!GST_VAAPI_PICTURE_IS_REFERENCE (picture)) {
      if ((priv->prev_picture && priv->next_picture) ||
          (priv->closed_gop && priv->next_picture))
        status = render_picture (decoder, picture);
    }
    gst_vaapi_picture_replace (&priv->curr_picture, NULL);
  }
  return status;
}

static GstVaapiDecoderStatus
decode_sequence (GstVaapiDecoderMpeg4 * decoder, const guint8 * buf,
    guint buf_size)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstMpeg4VisualObjectSequence *const vos_hdr = &priv->vos_hdr;
  GstVaapiProfile profile;

  if (gst_mpeg4_parse_visual_object_sequence (vos_hdr, buf,
          buf_size) != GST_MPEG4_PARSER_OK) {
    GST_DEBUG ("failed to parse sequence header");
    return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
  }

  priv->level = vos_hdr->level;
  switch (vos_hdr->profile) {
    case GST_MPEG4_PROFILE_SIMPLE:
      profile = GST_VAAPI_PROFILE_MPEG4_SIMPLE;
      break;
    case GST_MPEG4_PROFILE_ADVANCED_SIMPLE:
    case GST_MPEG4_PROFILE_SIMPLE_SCALABLE:    /* shared profile with ADVANCED_SIMPLE */
      profile = GST_VAAPI_PROFILE_MPEG4_ADVANCED_SIMPLE;
      break;
    default:
      GST_DEBUG ("unsupported profile %d", vos_hdr->profile);
      return GST_VAAPI_DECODER_STATUS_ERROR_UNSUPPORTED_PROFILE;
  }
  if (priv->profile != profile) {
    priv->profile = profile;
    priv->profile_changed = TRUE;
  }
  priv->seq_pts = GST_VAAPI_DECODER_CODEC_FRAME (decoder)->pts;
  priv->size_changed = TRUE;

  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
decode_sequence_end (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiDecoderStatus status;

  if (priv->curr_picture) {
    status = decode_current_picture (decoder);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
    status = render_picture (decoder, priv->curr_picture);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
  }

  if (priv->next_picture) {
    status = render_picture (decoder, priv->next_picture);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
  }
  return GST_VAAPI_DECODER_STATUS_END_OF_STREAM;
}

static GstVaapiDecoderStatus
decode_visual_object (GstVaapiDecoderMpeg4 * decoder, const guint8 * buf,
    guint buf_size)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstMpeg4VisualObject *vo_hdr = &priv->vo_hdr;
  GstMpeg4VideoSignalType *signal_type = &priv->signal_type;

  if (gst_mpeg4_parse_visual_object (vo_hdr, signal_type, buf,
          buf_size) != GST_MPEG4_PARSER_OK) {
    GST_DEBUG ("failed to parse visual object");
    return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
  }

  /* XXX: video_signal_type isn't used for decoding */
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
decode_video_object_layer (GstVaapiDecoderMpeg4 * decoder, const guint8 * buf,
    guint buf_size)
{
  GstVaapiDecoder *const base_decoder = GST_VAAPI_DECODER (decoder);
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstMpeg4VisualObject *vo_hdr = &priv->vo_hdr;
  GstMpeg4VideoObjectLayer *vol_hdr = &priv->vol_hdr;

  if (gst_mpeg4_parse_video_object_layer (vol_hdr, vo_hdr, buf,
          buf_size) != GST_MPEG4_PARSER_OK) {
    GST_DEBUG ("failed to parse video object layer");
    return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
  }

  priv->width = vol_hdr->width;
  priv->height = vol_hdr->height;

  priv->progressive_sequence = !vol_hdr->interlaced;

  if (vol_hdr->fixed_vop_rate) {
    priv->fps_n = vol_hdr->vop_time_increment_resolution;
    priv->fps_d = vol_hdr->fixed_vop_time_increment;
    gst_vaapi_decoder_set_framerate (base_decoder, priv->fps_n, priv->fps_d);
  }

  gst_vaapi_decoder_set_pixel_aspect_ratio (base_decoder,
      priv->vol_hdr.par_width, priv->vol_hdr.par_height);
  gst_vaapi_decoder_set_picture_size (base_decoder, priv->width, priv->height);

  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
decode_gop (GstVaapiDecoderMpeg4 * decoder, const guint8 * buf, guint buf_size)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstMpeg4GroupOfVOP gop;
  GstClockTime gop_time;

  if (buf_size > 4) {
    if (gst_mpeg4_parse_group_of_vop (&gop, buf,
            buf_size) != GST_MPEG4_PARSER_OK) {
      GST_DEBUG ("failed to parse GOP");
      return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
    }
  } else {
    gop.closed = 1;
    gop.broken_link = 0;
    gop.hours = 0;
    gop.minutes = 0;
    gop.seconds = 0;
  }

  priv->closed_gop = gop.closed;
  priv->broken_link = gop.broken_link;

  GST_DEBUG ("GOP %02u:%02u:%02u (closed_gop %d, broken_link %d)",
      gop.hours, gop.minutes, gop.seconds, priv->closed_gop, priv->broken_link);

  gop_time = gop.hours * 3600 + gop.minutes * 60 + gop.seconds;
  priv->last_sync_time = gop_time;
  priv->sync_time = gop_time;

  if (priv->gop_pts != GST_CLOCK_TIME_NONE)
    priv->pts_diff += gop_time * GST_SECOND - priv->gop_pts;
  priv->gop_pts = gop_time * GST_SECOND;
  priv->calculate_pts_diff = TRUE;
  priv->is_first_field = TRUE;

  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static void
calculate_pts_diff (GstVaapiDecoderMpeg4 * decoder,
    GstMpeg4VideoObjectLayer * vol_hdr, GstMpeg4VideoObjectPlane * vop_hdr)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstClockTime frame_timestamp;

  frame_timestamp = GST_VAAPI_DECODER_CODEC_FRAME (decoder)->pts;
  if (frame_timestamp && frame_timestamp != GST_CLOCK_TIME_NONE) {
    /* Buffer with timestamp */
    if (priv->max_pts != GST_CLOCK_TIME_NONE && frame_timestamp < priv->max_pts) {
      frame_timestamp = priv->max_pts +
          gst_util_uint64_scale ((vol_hdr->fixed_vop_rate ?
              vol_hdr->fixed_vop_time_increment : 1),
          GST_SECOND, vol_hdr->vop_time_increment_resolution);
    }
  } else {
    /* Buffer without timestamp set */
    if (priv->max_pts == GST_CLOCK_TIME_NONE)   /* first buffer */
      frame_timestamp = 0;
    else {
      GstClockTime tmp_pts;
      tmp_pts = priv->pts_diff + priv->gop_pts +
          vop_hdr->modulo_time_base * GST_SECOND +
          gst_util_uint64_scale (vop_hdr->time_increment,
          GST_SECOND, vol_hdr->vop_time_increment_resolution);
      if (tmp_pts > priv->max_pts)
        frame_timestamp = tmp_pts;
      else
        frame_timestamp = priv->max_pts +
            gst_util_uint64_scale ((vol_hdr->fixed_vop_rate ?
                vol_hdr->fixed_vop_time_increment : 1),
            GST_SECOND, vol_hdr->vop_time_increment_resolution);
    }
  }

  priv->pts_diff = frame_timestamp -
      (priv->gop_pts + vop_hdr->modulo_time_base * GST_SECOND +
      gst_util_uint64_scale (vop_hdr->time_increment, GST_SECOND,
          vol_hdr->vop_time_increment_resolution));
}

static GstVaapiDecoderStatus
decode_picture (GstVaapiDecoderMpeg4 * decoder, const guint8 * buf,
    guint buf_size)
{
  GstMpeg4ParseResult parser_result = GST_MPEG4_PARSER_OK;
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstMpeg4VideoObjectPlane *const vop_hdr = &priv->vop_hdr;
  GstMpeg4VideoObjectLayer *const vol_hdr = &priv->vol_hdr;
  GstMpeg4SpriteTrajectory *const sprite_trajectory = &priv->sprite_trajectory;
  GstVaapiPicture *picture;
  GstVaapiDecoderStatus status;
  GstClockTime pts;

  // context depends on priv->width and priv->height, so we move parse_vop a little earlier
  if (priv->is_svh) {
    parser_result =
        gst_mpeg4_parse_video_plane_short_header (&priv->svh_hdr, buf,
        buf_size);

  } else {
    parser_result =
        gst_mpeg4_parse_video_object_plane (vop_hdr, sprite_trajectory, vol_hdr,
        buf, buf_size);
    /* Need to skip this frame if VOP was not coded */
    if (GST_MPEG4_PARSER_OK == parser_result && !vop_hdr->coded)
      return (GstVaapiDecoderStatus) GST_VAAPI_DECODER_STATUS_DROP_FRAME;
  }

  if (parser_result != GST_MPEG4_PARSER_OK) {
    GST_DEBUG ("failed to parse picture header");
    return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
  }

  if (priv->is_svh) {
    priv->width = priv->svh_hdr.vop_width;
    priv->height = priv->svh_hdr.vop_height;
  } else {
    if (!vop_hdr->width && !vop_hdr->height) {
      vop_hdr->width = vol_hdr->width;
      vop_hdr->height = vol_hdr->height;
    }
    priv->width = vop_hdr->width;
    priv->height = vop_hdr->height;
  }

  status = ensure_context (decoder);
  if (status != GST_VAAPI_DECODER_STATUS_SUCCESS) {
    GST_DEBUG ("failed to reset context");
    return status;
  }

  if (priv->curr_picture) {
    status = decode_current_picture (decoder);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
  }

  priv->curr_picture = GST_VAAPI_PICTURE_NEW (MPEG4, decoder);
  if (!priv->curr_picture) {
    GST_DEBUG ("failed to allocate picture");
    return GST_VAAPI_DECODER_STATUS_ERROR_ALLOCATION_FAILED;
  }
  picture = priv->curr_picture;

  status = ensure_quant_matrix (decoder, picture);
  if (status != GST_VAAPI_DECODER_STATUS_SUCCESS) {
    GST_DEBUG ("failed to reset quantizer matrix");
    return status;
  }

  /* 7.6.7 Temporal prediction structure
   * forward reference frame     B B B B B B      backward reference frame
   *            |                                              |
   *  nearest I/P/S in the past with vop_coded ==1             |
   *                         nearest I/P/S in the future with any vop_coded
   * FIXME: it said that B frame shouldn't use backward reference frame
   *        when backward reference frame coded is 0
   */
  if (priv->is_svh) {
    priv->coding_type = priv->svh_hdr.picture_coding_type;
  } else {
    priv->coding_type = priv->vop_hdr.coding_type;
  }
  switch (priv->coding_type) {
    case GST_MPEG4_I_VOP:
      picture->type = GST_VAAPI_PICTURE_TYPE_I;
      if (priv->is_svh || vop_hdr->coded)
        GST_VAAPI_PICTURE_FLAG_SET (picture, GST_VAAPI_PICTURE_FLAG_REFERENCE);
      break;
    case GST_MPEG4_P_VOP:
      picture->type = GST_VAAPI_PICTURE_TYPE_P;
      if (priv->is_svh || vop_hdr->coded)
        GST_VAAPI_PICTURE_FLAG_SET (picture, GST_VAAPI_PICTURE_FLAG_REFERENCE);
      break;
    case GST_MPEG4_B_VOP:
      picture->type = GST_VAAPI_PICTURE_TYPE_B;
      break;
    case GST_MPEG4_S_VOP:
      picture->type = GST_VAAPI_PICTURE_TYPE_S;
      // see 3.175 reference VOP
      if (vop_hdr->coded)
        GST_VAAPI_PICTURE_FLAG_SET (picture, GST_VAAPI_PICTURE_FLAG_REFERENCE);
      break;
    default:
      GST_DEBUG ("unsupported picture type %d", priv->coding_type);
      return GST_VAAPI_DECODER_STATUS_ERROR_UNKNOWN;
  }

  if (!priv->is_svh && !vop_hdr->coded) {
    status = render_picture (decoder, priv->prev_picture);
    return status;
  }

  if (priv->is_svh) {
    guint temp_ref = priv->svh_hdr.temporal_reference;
    guint delta_ref;

    if (temp_ref < priv->prev_t_ref) {
      temp_ref += 256;
    }
    delta_ref = temp_ref - priv->prev_t_ref;

    pts = priv->sync_time;
    // see temporal_reference definition in spec, 30000/1001Hz
    pts += gst_util_uint64_scale (delta_ref, GST_SECOND * 1001, 30000);
    priv->sync_time = pts;
    priv->prev_t_ref = priv->svh_hdr.temporal_reference;
  } else {
    /* Update priv->pts_diff */
    if (priv->calculate_pts_diff) {
      calculate_pts_diff (decoder, vol_hdr, vop_hdr);
      priv->calculate_pts_diff = FALSE;
    }

    /* Update presentation time, 6.3.5 */
    if (vop_hdr->coding_type != GST_MPEG4_B_VOP) {
      // increment basing on decoding order
      priv->last_sync_time = priv->sync_time;
      priv->sync_time = priv->last_sync_time + vop_hdr->modulo_time_base;
      pts = priv->sync_time * GST_SECOND;
      pts +=
          gst_util_uint64_scale (vop_hdr->time_increment, GST_SECOND,
          vol_hdr->vop_time_increment_resolution);
      priv->last_non_b_scale_time = priv->non_b_scale_time;
      priv->non_b_scale_time =
          priv->sync_time * vol_hdr->vop_time_increment_resolution +
          vop_hdr->time_increment;
      priv->trd = priv->non_b_scale_time - priv->last_non_b_scale_time;
    } else {
      // increment basing on display oder
      pts = (priv->last_sync_time + vop_hdr->modulo_time_base) * GST_SECOND;
      pts +=
          gst_util_uint64_scale (vop_hdr->time_increment, GST_SECOND,
          vol_hdr->vop_time_increment_resolution);
      priv->trb =
          (priv->last_sync_time +
          vop_hdr->modulo_time_base) * vol_hdr->vop_time_increment_resolution +
          vop_hdr->time_increment - priv->last_non_b_scale_time;
    }
  }
  picture->pts = pts + priv->pts_diff;
  if (priv->max_pts == GST_CLOCK_TIME_NONE || priv->max_pts < picture->pts)
    priv->max_pts = picture->pts;

  /* Update reference pictures */
  /* XXX: consider priv->vol_hdr.low_delay, consider packed video frames for DivX/XviD */
  if (GST_VAAPI_PICTURE_IS_REFERENCE (picture)) {
    if (priv->next_picture)
      status = render_picture (decoder, priv->next_picture);
    gst_vaapi_picture_replace (&priv->prev_picture, priv->next_picture);
    gst_vaapi_picture_replace (&priv->next_picture, picture);
  }
  return status;
}

static inline guint
get_vop_coding_type (GstVaapiPicture * picture)
{
  return picture->type - GST_VAAPI_PICTURE_TYPE_I;
}

static gboolean
fill_picture (GstVaapiDecoderMpeg4 * decoder, GstVaapiPicture * picture)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  VAPictureParameterBufferMPEG4 *const pic_param = picture->param;
  GstMpeg4VideoObjectPlane *const vop_hdr = &priv->vop_hdr;

  /* Fill in VAPictureParameterBufferMPEG4 */
  pic_param->forward_reference_picture = VA_INVALID_ID;
  pic_param->backward_reference_picture = VA_INVALID_ID;

  pic_param->vol_fields.value = 0;
  pic_param->vop_fields.value = 0;
  if (priv->is_svh) {
    // vol_hdr Parameters
    pic_param->vol_fields.bits.short_video_header = 1;
    // does the following vol_hdr parameters matter for short video header?
    pic_param->vol_fields.bits.chroma_format = 1;       // I420, see table 6-15.
    pic_param->vol_fields.bits.interlaced = 0;
    pic_param->vol_fields.bits.obmc_disable = 1;
    pic_param->vol_fields.bits.sprite_enable = 0;
    pic_param->vol_fields.bits.sprite_warping_accuracy = 0;
    pic_param->vol_fields.bits.quant_type = 0;  //method 1; $7.4.4
    pic_param->vol_fields.bits.quarter_sample = 0;
    pic_param->vol_fields.bits.data_partitioned = 0;
    pic_param->vol_fields.bits.reversible_vlc = 0;
    pic_param->vol_fields.bits.resync_marker_disable = 1;
    pic_param->no_of_sprite_warping_points = 0;
    pic_param->quant_precision = 5;
    // VOP parameters
    pic_param->vop_width = priv->svh_hdr.vop_width;
    pic_param->vop_height = priv->svh_hdr.vop_height;
    pic_param->vop_fields.bits.vop_coding_type =
        priv->svh_hdr.picture_coding_type;
    pic_param->vop_time_increment_resolution =
        priv->vol_hdr.vop_time_increment_resolution;

    pic_param->num_gobs_in_vop = priv->svh_hdr.num_gobs_in_vop;
    pic_param->num_macroblocks_in_gob = priv->svh_hdr.num_macroblocks_in_gob;
  } else {
    int i;

    // VOL parameters
    pic_param->vol_fields.bits.short_video_header = 0;
    pic_param->vol_fields.bits.chroma_format = priv->vol_hdr.chroma_format;
    pic_param->vol_fields.bits.interlaced = priv->vol_hdr.interlaced;
    pic_param->vol_fields.bits.obmc_disable = priv->vol_hdr.obmc_disable;
    pic_param->vol_fields.bits.sprite_enable = priv->vol_hdr.sprite_enable;
    pic_param->vol_fields.bits.sprite_warping_accuracy =
        priv->vol_hdr.sprite_warping_accuracy;
    pic_param->vol_fields.bits.quant_type = priv->vol_hdr.quant_type;
    pic_param->vol_fields.bits.quarter_sample = priv->vol_hdr.quarter_sample;
    pic_param->vol_fields.bits.data_partitioned =
        priv->vol_hdr.data_partitioned;
    pic_param->vol_fields.bits.reversible_vlc = priv->vol_hdr.reversible_vlc;
    pic_param->vol_fields.bits.resync_marker_disable =
        priv->vol_hdr.resync_marker_disable;
    pic_param->no_of_sprite_warping_points =
        priv->vol_hdr.no_of_sprite_warping_points;

    for (i = 0; i < 3 && i < priv->vol_hdr.no_of_sprite_warping_points; i++) {
      pic_param->sprite_trajectory_du[i] =
          priv->sprite_trajectory.vop_ref_points[i];
      pic_param->sprite_trajectory_dv[i] =
          priv->sprite_trajectory.sprite_ref_points[i];
    }
    pic_param->quant_precision = priv->vol_hdr.quant_precision;

    // VOP parameters
    pic_param->vop_width = vop_hdr->width;
    pic_param->vop_height = vop_hdr->height;
    pic_param->vop_fields.bits.vop_coding_type = vop_hdr->coding_type;
    pic_param->vop_fields.bits.vop_rounding_type = vop_hdr->rounding_type;
    pic_param->vop_fields.bits.intra_dc_vlc_thr = vop_hdr->intra_dc_vlc_thr;
    pic_param->vop_fields.bits.top_field_first = vop_hdr->top_field_first;
    pic_param->vop_fields.bits.alternate_vertical_scan_flag =
        vop_hdr->alternate_vertical_scan_flag;

    pic_param->vop_fcode_forward = vop_hdr->fcode_forward;
    pic_param->vop_fcode_backward = vop_hdr->fcode_backward;
    pic_param->vop_time_increment_resolution =
        priv->vol_hdr.vop_time_increment_resolution;
  }

  pic_param->TRB = 0;
  pic_param->TRD = 0;
  switch (priv->coding_type) {
    case GST_MPEG4_B_VOP:
      pic_param->TRB = priv->trb;
      pic_param->backward_reference_picture = priv->next_picture->surface_id;
      pic_param->vop_fields.bits.backward_reference_vop_coding_type =
          get_vop_coding_type (priv->next_picture);
      // fall-through
    case GST_MPEG4_P_VOP:
      pic_param->TRD = priv->trd;
      if (priv->prev_picture)
        pic_param->forward_reference_picture = priv->prev_picture->surface_id;
      break;
  }

  if (priv->vol_hdr.interlaced) {
    priv->is_first_field ^= 1;
  }
  return TRUE;
}

static GstVaapiDecoderStatus
decode_slice (GstVaapiDecoderMpeg4 * decoder,
    const guint8 * buf, guint buf_size, gboolean has_packet_header)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiPicture *const picture = priv->curr_picture;
  GstVaapiSlice *slice;
  VASliceParameterBufferMPEG4 *slice_param;

  GST_DEBUG ("decoder silce: %p, %u bytes)", buf, buf_size);

  // has_packet_header is ture for the 2+ slice
  if (!has_packet_header && !fill_picture (decoder, picture))
    return GST_VAAPI_DECODER_STATUS_ERROR_UNKNOWN;

  slice = GST_VAAPI_SLICE_NEW (MPEG4, decoder, buf, buf_size);
  if (!slice) {
    GST_DEBUG ("failed to allocate slice");
    return GST_VAAPI_DECODER_STATUS_ERROR_ALLOCATION_FAILED;
  }
  gst_vaapi_picture_add_slice (picture, slice);

  /* Fill in VASliceParameterBufferMPEG4 */
  slice_param = slice->param;
  if (priv->is_svh) {
    slice_param->macroblock_offset = (priv->svh_hdr.size) % 8;
    slice_param->macroblock_number = 0;
    // the header of first gob_layer is empty (gob_header_empty=1), use vop_quant
    slice_param->quant_scale = priv->svh_hdr.vop_quant;
  } else {
    if (has_packet_header) {
      slice_param->macroblock_offset = priv->packet_hdr.size % 8;
      slice_param->macroblock_number = priv->packet_hdr.macroblock_number;
      slice_param->quant_scale = priv->packet_hdr.quant_scale;
    } else {
      slice_param->macroblock_offset = priv->vop_hdr.size % 8;
      slice_param->macroblock_number = 0;
      slice_param->quant_scale = priv->vop_hdr.quant;
    }
  }
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
decode_packet (GstVaapiDecoderMpeg4 * decoder, GstMpeg4Packet packet)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstMpeg4Packet *tos = &packet;
  GstVaapiDecoderStatus status;

  // packet.size is the size from current marker to the next.
  if (tos->type == GST_MPEG4_VISUAL_OBJ_SEQ_START) {
    status =
        decode_sequence (decoder, packet.data + packet.offset, packet.size);
  } else if (tos->type == GST_MPEG4_VISUAL_OBJ_SEQ_END) {
    status = decode_sequence_end (decoder);
  } else if (tos->type == GST_MPEG4_VISUAL_OBJ) {
    status =
        decode_visual_object (decoder, packet.data + packet.offset,
        packet.size);
  } else if (tos->type >= GST_MPEG4_VIDEO_OBJ_FIRST
      && tos->type <= GST_MPEG4_VIDEO_OBJ_LAST) {
    GST_WARNING
        ("unexpected marker: (GST_MPEG4_VIDEO_OBJ_FIRST, GST_MPEG4_VIDEO_OBJ_LAST)");
    status = GST_VAAPI_DECODER_STATUS_SUCCESS;
  } else if (tos->type >= GST_MPEG4_VIDEO_LAYER_FIRST
      && tos->type <= GST_MPEG4_VIDEO_LAYER_LAST) {
    status =
        decode_video_object_layer (decoder, packet.data + packet.offset,
        packet.size);
  } else if (tos->type == GST_MPEG4_GROUP_OF_VOP) {
    status = decode_gop (decoder, packet.data + packet.offset, packet.size);
  } else if (tos->type == GST_MPEG4_VIDEO_OBJ_PLANE) {
    GstMpeg4Packet video_packet;
    const guint8 *_data;
    gint _data_size;

    status = decode_picture (decoder, packet.data + packet.offset, packet.size);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;

    /* decode slice
     * A resync marker shall only be located immediately before a macroblock
     * (or video packet header if exists) and aligned with a byte
     * either start_code or resync_marker are scaned/measured by byte,
     * while the header itself are parsed/measured in bit
     * it means: resync_marker(video_packet_header) start from byte boundary,
     * while MB doesn't start from byte boundary -- it is what 'macroblock_offset'
     * in slice refer to
     */
    _data = packet.data + packet.offset + priv->vop_hdr.size / 8;
    _data_size = packet.size - (priv->vop_hdr.size / 8);

    if (priv->vol_hdr.resync_marker_disable) {
      status = decode_slice (decoder, _data, _data_size, FALSE);
      if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
        return status;
    } else {
      GstMpeg4ParseResult ret = GST_MPEG4_PARSER_OK;
      gboolean first_slice = TRUE;

      // next start_code is required to determine the end of last slice
      _data_size += 4;

      while (_data_size > 0) {
        // we can skip user data here
        ret =
            gst_mpeg4_parse (&video_packet, TRUE, &priv->vop_hdr, _data, 0,
            _data_size);
        if (ret != GST_MPEG4_PARSER_OK) {
          break;
        }

        if (first_slice) {
          status = decode_slice (decoder, _data, video_packet.size, FALSE);
          if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
            return status;
          first_slice = FALSE;
        } else {
          _data += video_packet.offset;
          _data_size -= video_packet.offset;

          ret =
              gst_mpeg4_parse_video_packet_header (&priv->packet_hdr,
              &priv->vol_hdr, &priv->vop_hdr, &priv->sprite_trajectory, _data,
              _data_size);
          if (ret != GST_MPEG4_PARSER_OK)
            return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
          status =
              decode_slice (decoder, _data + priv->packet_hdr.size / 8,
              video_packet.size - priv->packet_hdr.size / 8, TRUE);
          if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
            return status;
        }

        _data += video_packet.size;
        _data_size -= video_packet.size;
      }
    }
    status = decode_current_picture (decoder);
  } else if (tos->type == GST_MPEG4_USER_DATA
      || tos->type == GST_MPEG4_VIDEO_SESSION_ERR
      || tos->type == GST_MPEG4_FBA
      || tos->type == GST_MPEG4_FBA_PLAN
      || tos->type == GST_MPEG4_MESH
      || tos->type == GST_MPEG4_MESH_PLAN
      || tos->type == GST_MPEG4_STILL_TEXTURE_OBJ
      || tos->type == GST_MPEG4_TEXTURE_SPATIAL
      || tos->type == GST_MPEG4_TEXTURE_SNR_LAYER
      || tos->type == GST_MPEG4_TEXTURE_TILE
      || tos->type == GST_MPEG4_SHAPE_LAYER
      || tos->type == GST_MPEG4_STUFFING
      || tos->type == GST_MPEG4_SYSTEM_FIRST
      || tos->type == GST_MPEG4_SYSTEM_LAST) {
    GST_WARNING ("Ignore marker: %x\n", tos->type);
    status = GST_VAAPI_DECODER_STATUS_SUCCESS;
  } else {
    GST_ERROR ("unsupported start code %x\n", tos->type);
    status = GST_VAAPI_DECODER_STATUS_SUCCESS;
  }

  return status;
}

static GstVaapiDecoderStatus
decode_buffer (GstVaapiDecoderMpeg4 * decoder, const guchar * buf,
    guint buf_size)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiDecoderStatus status;
  GstMpeg4Packet packet;
  guint ofs;

  if (priv->is_svh) {
    status = decode_picture (decoder, buf, buf_size);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;

    ofs = priv->svh_hdr.size / 8;
    status = decode_slice (decoder, buf + ofs, buf_size - ofs, FALSE);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
  } else {
    packet.data = buf;
    packet.offset = 0;
    packet.size = buf_size;
    packet.type = (GstMpeg4StartCode) packet.data[0];

    status = decode_packet (decoder, packet);
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
  }
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
gst_vaapi_decoder_mpeg4_decode_codec_data (GstVaapiDecoder * base_decoder,
    const guchar * _buf, guint _buf_size)
{
  GstVaapiDecoderMpeg4 *const decoder =
      GST_VAAPI_DECODER_MPEG4_CAST (base_decoder);
  GstVaapiDecoderStatus status = GST_VAAPI_DECODER_STATUS_SUCCESS;
  GstMpeg4ParseResult result = GST_MPEG4_PARSER_OK;
  GstMpeg4Packet packet;
  guchar *buf;
  guint pos, buf_size;

  // add additional 0x000001b2 to enclose the last header
  buf_size = _buf_size + 4;
  buf = malloc (buf_size);
  memcpy (buf, _buf, buf_size);
  buf[buf_size - 4] = 0;
  buf[buf_size - 3] = 0;
  buf[buf_size - 2] = 1;
  buf[buf_size - 1] = 0xb2;

  pos = 0;

  while (result == GST_MPEG4_PARSER_OK && pos < buf_size) {
    result = gst_mpeg4_parse (&packet, FALSE, NULL, buf, pos, buf_size);
    if (result != GST_MPEG4_PARSER_OK) {
      break;
    }
    status = decode_packet (decoder, packet);
    if (GST_VAAPI_DECODER_STATUS_SUCCESS == status) {
      pos = packet.offset + packet.size;
    } else {
      GST_WARNING ("decode mp4 packet failed when decoding codec data\n");
      break;
    }
  }
  free (buf);
  return status;
}

static GstVaapiDecoderStatus
ensure_decoder (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiDecoderStatus status;

  if (!priv->is_opened) {
    priv->is_opened = gst_vaapi_decoder_mpeg4_open (decoder);
    if (!priv->is_opened)
      return GST_VAAPI_DECODER_STATUS_ERROR_UNSUPPORTED_CODEC;

    status =
        gst_vaapi_decoder_decode_codec_data (GST_VAAPI_DECODER_CAST (decoder));
    if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
      return status;
  }
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
gst_vaapi_decoder_mpeg4_parse (GstVaapiDecoder * base_decoder,
    GstAdapter * adapter, gboolean at_eos, GstVaapiDecoderUnit * unit)
{
  GstVaapiDecoderMpeg4 *const decoder =
      GST_VAAPI_DECODER_MPEG4_CAST (base_decoder);
  GstVaapiDecoderMpeg4Private *const priv = &decoder->priv;
  GstVaapiDecoderStatus status;
  GstMpeg4Packet packet;
  GstMpeg4ParseResult result;
  const guchar *buf;
  guint size, buf_size, flags = 0;

  status = ensure_decoder (decoder);
  if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
    return status;

  size = gst_adapter_available (adapter);
  buf = gst_adapter_map (adapter, size);
  if (!buf)
    return GST_VAAPI_DECODER_STATUS_ERROR_NO_DATA;

  packet.type = GST_MPEG4_USER_DATA;
  if (priv->is_svh)
    result = gst_h263_parse (&packet, buf, 0, size);
  else
    result = gst_mpeg4_parse (&packet, FALSE, NULL, buf, 0, size);
  if (result == GST_MPEG4_PARSER_NO_PACKET_END && at_eos)
    packet.size = size - packet.offset;
  else if (result == GST_MPEG4_PARSER_ERROR)
    return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
  else if (result != GST_MPEG4_PARSER_OK)
    return GST_VAAPI_DECODER_STATUS_ERROR_NO_DATA;

  buf_size = packet.size;
  gst_adapter_flush (adapter, packet.offset);
  unit->size = buf_size;

  /* Check for start of new picture */
  switch (packet.type) {
    case GST_MPEG4_VIDEO_SESSION_ERR:
    case GST_MPEG4_FBA:
    case GST_MPEG4_FBA_PLAN:
    case GST_MPEG4_MESH:
    case GST_MPEG4_MESH_PLAN:
    case GST_MPEG4_STILL_TEXTURE_OBJ:
    case GST_MPEG4_TEXTURE_SPATIAL:
    case GST_MPEG4_TEXTURE_SNR_LAYER:
    case GST_MPEG4_TEXTURE_TILE:
    case GST_MPEG4_SHAPE_LAYER:
    case GST_MPEG4_STUFFING:
      gst_adapter_flush (adapter, packet.size);
      return GST_VAAPI_DECODER_STATUS_ERROR_NO_DATA;
    case GST_MPEG4_USER_DATA:
      flags |= GST_VAAPI_DECODER_UNIT_FLAG_SKIP;
      break;
    case GST_MPEG4_VISUAL_OBJ_SEQ_END:
      flags |= GST_VAAPI_DECODER_UNIT_FLAG_FRAME_END;
      flags |= GST_VAAPI_DECODER_UNIT_FLAG_STREAM_END;
      break;
    case GST_MPEG4_VIDEO_OBJ_PLANE:
      flags |= GST_VAAPI_DECODER_UNIT_FLAG_SLICE;
      flags |= GST_VAAPI_DECODER_UNIT_FLAG_FRAME_END;
      /* fall-through */
    case GST_MPEG4_VISUAL_OBJ_SEQ_START:
    case GST_MPEG4_VISUAL_OBJ:
    case GST_MPEG4_GROUP_OF_VOP:
      flags |= GST_VAAPI_DECODER_UNIT_FLAG_FRAME_START;
      break;
    default:
      if (packet.type >= GST_MPEG4_VIDEO_OBJ_FIRST &&
          packet.type <= GST_MPEG4_VIDEO_OBJ_LAST) {
        gst_adapter_flush (adapter, packet.size);
        return GST_VAAPI_DECODER_STATUS_ERROR_NO_DATA;
      }
      if (packet.type >= GST_MPEG4_VIDEO_LAYER_FIRST &&
          packet.type <= GST_MPEG4_VIDEO_LAYER_LAST) {
        break;
      }
      if (packet.type >= GST_MPEG4_SYSTEM_FIRST &&
          packet.type <= GST_MPEG4_SYSTEM_LAST) {
        flags |= GST_VAAPI_DECODER_UNIT_FLAG_SKIP;
        break;
      }
      GST_WARNING ("unsupported start code (0x%02x)", packet.type);
      return GST_VAAPI_DECODER_STATUS_ERROR_BITSTREAM_PARSER;
  }
  GST_VAAPI_DECODER_UNIT_FLAG_SET (unit, flags);
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static GstVaapiDecoderStatus
gst_vaapi_decoder_mpeg4_decode (GstVaapiDecoder * base_decoder,
    GstVaapiDecoderUnit * unit)
{
  GstVaapiDecoderMpeg4 *const decoder =
      GST_VAAPI_DECODER_MPEG4_CAST (base_decoder);
  GstVaapiDecoderStatus status;
  GstBuffer *const buffer =
      GST_VAAPI_DECODER_CODEC_FRAME (decoder)->input_buffer;
  GstMapInfo map_info;

  status = ensure_decoder (decoder);
  if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
    return status;

  if (!gst_buffer_map (buffer, &map_info, GST_MAP_READ)) {
    GST_ERROR ("failed to map buffer");
    return GST_VAAPI_DECODER_STATUS_ERROR_UNKNOWN;
  }

  status = decode_buffer (decoder, map_info.data + unit->offset, unit->size);
  gst_buffer_unmap (buffer, &map_info);
  if (status != GST_VAAPI_DECODER_STATUS_SUCCESS)
    return status;
  return GST_VAAPI_DECODER_STATUS_SUCCESS;
}

static void
gst_vaapi_decoder_mpeg4_finalize (GObject * object)
{
  GstVaapiDecoder *const base_decoder = GST_VAAPI_DECODER (object);

  gst_vaapi_decoder_mpeg4_destroy (base_decoder);
  G_OBJECT_CLASS (gst_vaapi_decoder_mpeg4_parent_class)->finalize (object);
}

static void
gst_vaapi_decoder_mpeg4_class_init (GstVaapiDecoderMpeg4Class * klass)
{
  GObjectClass *const object_class = G_OBJECT_CLASS (klass);
  GstVaapiDecoderClass *const decoder_class = GST_VAAPI_DECODER_CLASS (klass);

  object_class->finalize = gst_vaapi_decoder_mpeg4_finalize;

  decoder_class->reset = gst_vaapi_decoder_mpeg4_reset;
  decoder_class->parse = gst_vaapi_decoder_mpeg4_parse;
  decoder_class->decode = gst_vaapi_decoder_mpeg4_decode;
  decoder_class->decode_codec_data = gst_vaapi_decoder_mpeg4_decode_codec_data;
}

static void
gst_vaapi_decoder_mpeg4_init (GstVaapiDecoderMpeg4 * decoder)
{
  GstVaapiDecoder *const base_decoder = GST_VAAPI_DECODER (decoder);

  gst_vaapi_decoder_mpeg4_create (base_decoder);
}

/**
 * gst_vaapi_decoder_mpeg4_new:
 * @display: a #GstVaapiDisplay
 * @caps: a #GstCaps holding codec information
 *
 * Creates a new #GstVaapiDecoder for MPEG-2 decoding.  The @caps can
 * hold extra information like codec-data and pictured coded size.
 *
 * Return value: the newly allocated #GstVaapiDecoder object
 */
GstVaapiDecoder *
gst_vaapi_decoder_mpeg4_new (GstVaapiDisplay * display, GstCaps * caps)
{
  return g_object_new (GST_TYPE_VAAPI_DECODER_MPEG4, "display", display,
      "caps", caps, NULL);
}