/*****************************************************************************
 *
 *  XVID MPEG-4 VIDEO CODEC
 *  - Bitstream reader/writer -
 *
 *  Copyright (C) 2001-2003 Peter Ross <pross@xvid.org>
 *                     2003 Cristoph Lampert <gruel@web.de>
 *
 *  This program is free software ; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation ; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program ; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * $Id: bitstream.cpp,v 1.1 2005/01/04 13:44:37 jeanlf Exp $
 *
 ****************************************************************************/

#include "bitstream.h"
#include "quant_matrix.h"

#ifdef WIN32
#include <stdio.h>
#endif

//----------------------------

inline dword ByteSwap(dword a){
   return (a<<24) | ((a&0xff00) << 8) | ((a&0xff0000) >> 8) | (a>>24);
}

//----------------------------

void Bitstream::Init(const void *bitstream, dword _length){

   dword adjbitstream = (dword)bitstream;

   /*
    * Start the stream on a dword boundary, by rounding down to the
    * previous dword and skipping the intervening bytes.
    */
   long bitpos = ((sizeof(dword)-1) & (long)bitstream);
   adjbitstream = adjbitstream - bitpos;
   start = tail = (dword *) adjbitstream;

   if(_length){
      dword tmp = *start;
#ifndef ARCH_IS_BIG_ENDIAN
      tmp = ByteSwap(tmp);
#endif
      bufa = tmp;
      if(_length>4){
         tmp = *(start + 1);
#ifndef ARCH_IS_BIG_ENDIAN
         tmp = ByteSwap(tmp);
#endif
         bufb = tmp;
      }else
         bufb = 0;
   }else
      bufa = bufb = 0;

   buf = 0;
   pos = initpos = bitpos*8;
   length = _length;
}

//---------------------------

/* reads n bits from bitstream without changing the stream pos */

dword Bitstream::ShowBits(dword bits){

   int nbit = (bits + pos) - 32;
   if(nbit > 0)
      return ((bufa & (0xffffffff >> pos)) << nbit) | (bufb >> (32 - nbit));
   return (bufa & (0xffffffff >> pos)) >> (32 - pos - bits);
}

//---------------------------
// skip n bits forward in bitstream
void Bitstream::Skip(dword bits){

   pos += bits;
   if(pos >= 32){
      dword tmp;

      bufa = bufb;
      tmp = *((dword *) tail + 2);
#ifndef ARCH_IS_BIG_ENDIAN
      tmp = ByteSwap(tmp);
#endif
      bufb = tmp;
      tail++;
      pos -= 32;
   }
}

//---------------------------
/* show nbits from next byte alignment */
dword Bitstream::ShowBitsFromByteAlign(int bits){

   int bspos = pos + NumBitsToByteAlign();
   int nbit = (bits + bspos) - 32;

   if (bspos >= 32) {
      return bufb >> (32 - nbit);
   } else   if (nbit > 0) {
      return ((bufa & (0xffffffff >> bspos)) << nbit) | (bufb >> (32 - nbit));
   } else {
      return (bufa & (0xffffffff >> bspos)) >> (32 - bspos - bits);
   }

}

//---------------------------
/* read n bits from bitstream */
dword Bitstream::GetBits(dword n){
   dword ret = ShowBits(n);
   Skip(n);
   return ret;
}

//---------------------------

static const dword intra_dc_threshold_table[] = {
   32,                     /* never use */
   13,
   15,
   17,
   19,
   21,
   23,
   1,
};

//----------------------------

void Bitstream::get_matrix(byte * matrix){

   int i = 0;
   int last, value = 0;

   do {
      last = value;
      value = GetBits(8);
      matrix[scan_tables[0][i++]] = value;
   }
   while (value != 0 && i < 64);
        i--;    /* fix little bug at coeff not full */

   while (i < 64) {
      matrix[scan_tables[0][i++]] = last;
   }
}

//----------------------------
/*
 * for PVOP addbits == fcode - 1
 * for BVOP addbits == max(fcode,bcode) - 1
 * returns mbpos
 */
int S_decoder::read_video_packet_header(Bitstream *bs, const int addbits, int *quant, int *fcode_forward, int *fcode_backward, int *intra_dc_threshold){

   int startcode_bits = NUMBITS_VP_RESYNC_MARKER + addbits;
   int mbnum_bits = log2bin(mb_width *  mb_height - 1);
   int mbnum;
   int hec = 0;

   bs->Skip(bs->NumBitsToByteAlign());
   bs->Skip(startcode_bits);

   DPRINTF(XVID_DEBUG_STARTCODE, "<video_packet_header>\n");

   if (shape != VIDOBJLAY_SHAPE_RECTANGULAR)
   {
      hec = bs->GetBit();     /* header_extension_code */
      if (hec && !(sprite_enable == SPRITE_STATIC /* && current_coding_type = I_VOP */))
      {
         bs->Skip(13);        /* vop_width */
         READ_MARKER();
         bs->Skip(13);        /* vop_height */
         READ_MARKER();
         bs->Skip(13);        /* vop_horizontal_mc_spatial_ref */
         READ_MARKER();
         bs->Skip(13);        /* vop_vertical_mc_spatial_ref */
         READ_MARKER();
      }
   }

   mbnum = bs->GetBits(mbnum_bits);    /* macroblock_number */
   DPRINTF(XVID_DEBUG_HEADER, "mbnum %i\n", mbnum);

   if (shape != VIDOBJLAY_SHAPE_BINARY_ONLY)
   {
      *quant = bs->GetBits(quant_bits);   /* quant_scale */
      DPRINTF(XVID_DEBUG_HEADER, "quant %i\n", *quant);
   }

   if (shape == VIDOBJLAY_SHAPE_RECTANGULAR)
      hec = bs->GetBit();     /* header_extension_code */


   DPRINTF(XVID_DEBUG_HEADER, "header_extension_code %i\n", hec);
   if (hec)
   {
      int time_base;
      int time_increment = 0;
      int coding_type;

      for (time_base=0; bs->GetBit()!=0; time_base++);      /* modulo_time_base */
      READ_MARKER();
      if (time_inc_bits)
         time_increment = (bs->GetBits(time_inc_bits));  /* vop_time_increment */
      READ_MARKER();
      //DPRINTF(XVID_DEBUG_HEADER,"time %i:%i\n", time_base, time_increment);

      coding_type = bs->GetBits(2);
      DPRINTF(XVID_DEBUG_HEADER,"coding_type %i\n", coding_type);

      if (shape != VIDOBJLAY_SHAPE_RECTANGULAR)
      {
         bs->Skip(1);   /* change_conv_ratio_disable */
         if (coding_type != I_VOP)
            bs->Skip(1);   /* vop_shape_coding_type */
      }

      if (shape != VIDOBJLAY_SHAPE_BINARY_ONLY)
      {
         *intra_dc_threshold = intra_dc_threshold_table[bs->GetBits(3)];

         if (sprite_enable == SPRITE_GMC && coding_type == S_VOP &&
            sprite_warping_points > 0)
         {
            /* TODO: sprite trajectory */
         }
         if(reduced_resolution_enable && shape == VIDOBJLAY_SHAPE_RECTANGULAR && (coding_type == P_VOP || coding_type == I_VOP)){
            bs->Skip(1); /* XXX: vop_reduced_resolution */
         }

         if (coding_type != I_VOP && fcode_forward)
         {
            *fcode_forward = bs->GetBits(3);
            DPRINTF(XVID_DEBUG_HEADER,"fcode_forward %i\n", *fcode_forward);
         }

         if (coding_type == B_VOP && fcode_backward)
         {
            *fcode_backward = bs->GetBits(3);
            DPRINTF(XVID_DEBUG_HEADER,"fcode_backward %i\n", *fcode_backward);
         }
      }

   }

   if (newpred_enable) {
      int vop_id;
      int vop_id_for_prediction;

      vop_id = bs->GetBits(MIN(time_inc_bits + 3, 15));
      DPRINTF(XVID_DEBUG_HEADER, "vop_id %i\n", vop_id);
      if (bs->GetBit()) /* vop_id_for_prediction_indication */
      {
         vop_id_for_prediction = bs->GetBits(MIN(time_inc_bits + 3, 15));
         DPRINTF(XVID_DEBUG_HEADER, "vop_id_for_prediction %i\n", vop_id_for_prediction);
      }
      READ_MARKER();
   }

   return mbnum;
}

//----------------------------
/* vol estimation header */
void S_decoder::read_vol_complexity_estimation_header(Bitstream * bs){

   ESTIMATION * e = &estimation;

   e->method = bs->GetBits(2);   /* estimation_method */
   DPRINTF(XVID_DEBUG_HEADER,"+ complexity_estimation_header; method=%i\n", e->method);

   if (e->method == 0 || e->method == 1){
      if(!bs->GetBit()){
                              //shape_complexity_estimation_disable
         e->opaque = bs->GetBit();     /* opaque */
         e->transparent = bs->GetBit();      /* transparent */
         e->intra_cae = bs->GetBit();     /* intra_cae */
         e->inter_cae = bs->GetBit();     /* inter_cae */
         e->no_update = bs->GetBit();     /* no_update */
         e->upsampling = bs->GetBit();    /* upsampling */
      }

      if (!bs->GetBit())   /* texture_complexity_estimation_set_1_disable */
      {
         e->intra_blocks = bs->GetBit();     /* intra_blocks */
         e->inter_blocks = bs->GetBit();     /* inter_blocks */
         e->inter4v_blocks = bs->GetBit();      /* inter4v_blocks */
         e->not_coded_blocks = bs->GetBit();    /* not_coded_blocks */
      }
   }

   READ_MARKER();

   if (!bs->GetBit()){
                              //texture_complexity_estimation_set_2_disable
      e->dct_coefs = bs->GetBit();     /* dct_coefs */
      e->dct_lines = bs->GetBit();     /* dct_lines */
      e->vlc_symbols = bs->GetBit();      /* vlc_symbols */
      e->vlc_bits = bs->GetBit();      /* vlc_bits */
   }

   if (!bs->GetBit()){
                              //motion_compensation_complexity_disable
      e->apm = bs->GetBit();     /* apm */
      e->npm = bs->GetBit();     /* npm */
      e->interpolate_mc_q = bs->GetBit();    /* interpolate_mc_q */
      e->forw_back_mc_q = bs->GetBit();      /* forw_back_mc_q */
      e->halfpel2 = bs->GetBit();      /* halfpel2 */
      e->halfpel4 = bs->GetBit();      /* halfpel4 */
   }

   READ_MARKER();

   if (e->method == 1){
      if (!bs->GetBit()){
                              //version2_complexity_estimation_disable
         e->sadct = bs->GetBit();      /* sadct */
         e->quarterpel = bs->GetBit();    /* quarterpel */
      }
   }
}

//----------------------------
/* vop estimation header */
void S_decoder::read_vop_complexity_estimation_header(Bitstream * bs, int coding_type){

   ESTIMATION * e = &estimation;

   if (e->method == 0 || e->method == 1)
   {
      if (coding_type == I_VOP) {
         if (e->opaque)    bs->Skip(8);   /* dcecs_opaque */
         if (e->transparent) bs->Skip(8); /* */
         if (e->intra_cae) bs->Skip(8);   /* */
         if (e->inter_cae) bs->Skip(8);   /* */
         if (e->no_update) bs->Skip(8);   /* */
         if (e->upsampling)   bs->Skip(8);   /* */
         if (e->intra_blocks) bs->Skip(8);   /* */
         if (e->not_coded_blocks) bs->Skip(8);  /* */
         if (e->dct_coefs) bs->Skip(8);   /* */
         if (e->dct_lines) bs->Skip(8);   /* */
         if (e->vlc_symbols) bs->Skip(8); /* */
         if (e->vlc_bits)  bs->Skip(8);   /* */
         if (e->sadct)     bs->Skip(8);   /* */
      }

      if (coding_type == P_VOP) {
         if (e->opaque) bs->Skip(8);      /* */
         if (e->transparent) bs->Skip(8); /* */
         if (e->intra_cae) bs->Skip(8);   /* */
         if (e->inter_cae) bs->Skip(8);   /* */
         if (e->no_update) bs->Skip(8);   /* */
         if (e->upsampling) bs->Skip(8);  /* */
         if (e->intra_blocks) bs->Skip(8);   /* */
         if (e->not_coded_blocks)   bs->Skip(8);   /* */
         if (e->dct_coefs) bs->Skip(8);   /* */
         if (e->dct_lines) bs->Skip(8);   /* */
         if (e->vlc_symbols) bs->Skip(8); /* */
         if (e->vlc_bits)  bs->Skip(8);   /* */
         if (e->inter_blocks) bs->Skip(8);   /* */
         if (e->inter4v_blocks) bs->Skip(8); /* */
         if (e->apm)       bs->Skip(8);   /* */
         if (e->npm)       bs->Skip(8);   /* */
         if (e->forw_back_mc_q) bs->Skip(8); /* */
         if (e->halfpel2)  bs->Skip(8);   /* */
         if (e->halfpel4)  bs->Skip(8);   /* */
         if (e->sadct)     bs->Skip(8);   /* */
         if (e->quarterpel)   bs->Skip(8);   /* */
      }
      if (coding_type == B_VOP) {
         if (e->opaque)    bs->Skip(8);   /* */
         if (e->transparent)  bs->Skip(8);   /* */
         if (e->intra_cae) bs->Skip(8);   /* */
         if (e->inter_cae) bs->Skip(8);   /* */
         if (e->no_update) bs->Skip(8);   /* */
         if (e->upsampling)   bs->Skip(8);   /* */
         if (e->intra_blocks) bs->Skip(8);   /* */
         if (e->not_coded_blocks) bs->Skip(8);  /* */
         if (e->dct_coefs) bs->Skip(8);   /* */
         if (e->dct_lines) bs->Skip(8);   /* */
         if (e->vlc_symbols)  bs->Skip(8);   /* */
         if (e->vlc_bits)  bs->Skip(8);   /* */
         if (e->inter_blocks) bs->Skip(8);   /* */
         if (e->inter4v_blocks) bs->Skip(8); /* */
         if (e->apm)       bs->Skip(8);   /* */
         if (e->npm)       bs->Skip(8);   /* */
         if (e->forw_back_mc_q) bs->Skip(8); /* */
         if (e->halfpel2)  bs->Skip(8);   /* */
         if (e->halfpel4)  bs->Skip(8);   /* */
         if (e->interpolate_mc_q) bs->Skip(8);  /* */
         if (e->sadct)     bs->Skip(8);   /* */
         if (e->quarterpel)   bs->Skip(8);   /* */
      }

      if (coding_type == S_VOP && sprite_enable == SPRITE_STATIC) {
         if (e->intra_blocks) bs->Skip(8);   /* */
         if (e->not_coded_blocks) bs->Skip(8);  /* */
         if (e->dct_coefs) bs->Skip(8);   /* */
         if (e->dct_lines) bs->Skip(8);   /* */
         if (e->vlc_symbols)  bs->Skip(8);   /* */
         if (e->vlc_bits)  bs->Skip(8);   /* */
         if (e->inter_blocks) bs->Skip(8);   /* */
         if (e->inter4v_blocks)  bs->Skip(8);   /* */
         if (e->apm)       bs->Skip(8);   /* */
         if (e->npm)       bs->Skip(8);   /* */
         if (e->forw_back_mc_q)  bs->Skip(8);   /* */
         if (e->halfpel2)  bs->Skip(8);   /* */
         if (e->halfpel4)  bs->Skip(8);   /* */
         if (e->interpolate_mc_q) bs->Skip(8);  /* */
      }
   }
}

//----------------------------
// decode headers
// returns coding_type, or -1 if error

#define VIDOBJ_START_CODE_MASK      0x0000001f
#define VIDOBJLAY_START_CODE_MASK   0x0000000f

int S_decoder::BitstreamReadHeaders(Bitstream * bs, bool &rounding, bool *reduced_resolution, dword *quant, dword *fcode_forward,
   dword *fcode_backward, dword *intra_dc_threshold, WARPPOINTS *gmc_warp){

   dword vol_ver_id;
   dword coding_type;
   dword start_code;
   dword time_incr = 0;
   int time_increment = 0;
   int resize = 0;

   while((bs->Pos() >> 3) < bs->length){
      bs->ByteAlign();
      start_code = bs->ShowBits(32);

      switch(start_code){
      case VISOBJSEQ_START_CODE:
         {
            DPRINTF(XVID_DEBUG_STARTCODE, "<visual_object_sequence>\n");

            bs->Skip(32);     //visual_object_sequence_start_code
            int profile = bs->GetBits(8);  //profile_and_level_indication

            DPRINTF(XVID_DEBUG_HEADER, "profile_and_level_indication %i\n", profile);
         }
         break;
      case VISOBJSEQ_STOP_CODE:
         {
                              //visual_object_sequence_stop_code
            bs->Skip(32);
            DPRINTF(XVID_DEBUG_STARTCODE, "</visual_object_sequence>\n");
            
         }
         break;
      case VISOBJ_START_CODE:
         {
            DPRINTF(XVID_DEBUG_STARTCODE, "<visual_object>\n");
            
            bs->Skip(32);  //visual_object_start_code

            int visobj_ver_id;
                              //is_visual_object_identified
            if(bs->GetBit()){
               visobj_ver_id = bs->GetBits(4);  /* visual_object_ver_id */
               DPRINTF(XVID_DEBUG_HEADER,"visobj_ver_id %i\n", visobj_ver_id);
               bs->Skip(3);   //visual_object_priority
            }else{
               visobj_ver_id = 1;
            }
            
            if(bs->ShowBits(4) != VISOBJ_TYPE_VIDEO){
                              //visual_object_type
               DPRINTF(XVID_DEBUG_ERROR, "visual_object_type != video\n");
               return -1;
            }
            bs->Skip(4);
                              //video_signal_type
            
            if(bs->GetBit()){
               DPRINTF(XVID_DEBUG_HEADER,"+ video_signal_type\n");
               bs->Skip(3);   /* video_format */
               bs->Skip(1);   /* video_range */
               if (bs->GetBit()) /* color_description */
               {
                  DPRINTF(XVID_DEBUG_HEADER,"+ color_description");
                  bs->Skip(8);   /* color_primaries */
                  bs->Skip(8);   /* transfer_characteristics */
                  bs->Skip(8);   /* matrix_coefficients */
               }
            }
         }
         break;
      case GRPOFVOP_START_CODE:
         {
            DPRINTF(XVID_DEBUG_STARTCODE, "<group_of_vop>\n");

            bs->Skip(32);
            {
               int hours, minutes, seconds;

               hours = bs->GetBits(5);
               minutes = bs->GetBits(6);
               READ_MARKER();
               seconds = bs->GetBits(6);
               //DPRINTF(XVID_DEBUG_HEADER, "time %ih%im%is\n", hours,minutes,seconds);
            }
            bs->Skip(1);   /* closed_gov */
            bs->Skip(1);   /* broken_link */
         }
         break;
      case VOP_START_CODE:
         {
            
            DPRINTF(XVID_DEBUG_STARTCODE, "<vop>\n");
            
            bs->Skip(32);  /* vop_start_code */
            
            coding_type = bs->GetBits(2); /* vop_coding_type */
            DPRINTF(XVID_DEBUG_HEADER, "coding_type %i\n", coding_type);
            
            /*********************** for decode B-frame time ***********************/
            while (bs->GetBit() != 0)  /* time_base */
               time_incr++;
            
            READ_MARKER();
            
            if (time_inc_bits) {
               time_increment = (bs->GetBits(time_inc_bits));  /* vop_time_increment */
            }
            
            DPRINTF(XVID_DEBUG_HEADER, "time_base %i\n", time_incr);
            DPRINTF(XVID_DEBUG_HEADER, "time_increment %i\n", time_increment);
            
            //DPRINTF(XVID_DEBUG_TIMECODE, "%c %i:%i\n", coding_type == I_VOP ? 'I' : coding_type == P_VOP ? 'P' : coding_type == B_VOP ? 'B' : 'S', time_incr, time_increment);
            if (coding_type != B_VOP) {
               last_time_base = time_base;
               time_base += time_incr;
               time = time_increment;
               
#if 0
               time_base * time_inc_resolution +
                  time_increment;
#endif
               time_pp = (dword)
                  (time_inc_resolution + time - last_non_b_time)%time_inc_resolution;
               last_non_b_time = time;
            } else {
               time = time_increment;
#if 0
               (last_time_base +
                  time_incr) * time_inc_resolution + time_increment;
#endif
               time_bp = (dword)
                  (time_inc_resolution + last_non_b_time - time)%time_inc_resolution;
            }
            DPRINTF(XVID_DEBUG_HEADER,"time_pp=%i\n", time_pp);
            DPRINTF(XVID_DEBUG_HEADER,"time_bp=%i\n", time_bp);
            
            READ_MARKER();
            
            if (!bs->GetBit())   /* vop_coded */
            {
               DPRINTF(XVID_DEBUG_HEADER, "vop_coded==false\n");
               return N_VOP;
            }
            
            if (newpred_enable) {
               int vop_id;
               int vop_id_for_prediction;
               
               vop_id = bs->GetBits(MIN(time_inc_bits + 3, 15));
               DPRINTF(XVID_DEBUG_HEADER, "vop_id %i\n", vop_id);
               if (bs->GetBit()) /* vop_id_for_prediction_indication */
               {
                  vop_id_for_prediction = bs->GetBits(MIN(time_inc_bits + 3, 15));
                  DPRINTF(XVID_DEBUG_HEADER, "vop_id_for_prediction %i\n", vop_id_for_prediction);
               }
               READ_MARKER();
            }
            
                              //fix a little bug by MinChen <chenm002@163.com>
            if((shape != VIDOBJLAY_SHAPE_BINARY_ONLY) &&
               ((coding_type == P_VOP) || (coding_type == S_VOP && sprite_enable == SPRITE_GMC))){
               rounding = !!bs->GetBit();  //rounding_type
               DPRINTF(XVID_DEBUG_HEADER, "rounding %i\n", rounding);
            }
            
            if(reduced_resolution_enable && shape == VIDOBJLAY_SHAPE_RECTANGULAR && (coding_type == P_VOP || coding_type == I_VOP)) {
               
               *reduced_resolution = !!bs->GetBit();
               DPRINTF(XVID_DEBUG_HEADER, "reduced_resolution %i\n", *reduced_resolution);
            }else{
               *reduced_resolution = false;
            }
            
            if (shape != VIDOBJLAY_SHAPE_RECTANGULAR) {
               if(!(sprite_enable == SPRITE_STATIC && coding_type == I_VOP)) {
                  
                  dword width, height;
                  dword horiz_mc_ref, vert_mc_ref;
                  
                  width = bs->GetBits(13);
                  READ_MARKER();
                  height = bs->GetBits(13);
                  READ_MARKER();
                  horiz_mc_ref = bs->GetBits(13);
                  READ_MARKER();
                  vert_mc_ref = bs->GetBits(13);
                  READ_MARKER();
                  
                  DPRINTF(XVID_DEBUG_HEADER, "width %i\n", width);
                  DPRINTF(XVID_DEBUG_HEADER, "height %i\n", height);
                  DPRINTF(XVID_DEBUG_HEADER, "horiz_mc_ref %i\n", horiz_mc_ref);
                  DPRINTF(XVID_DEBUG_HEADER, "vert_mc_ref %i\n", vert_mc_ref);
               }
               
               bs->Skip(1);   /* change_conv_ratio_disable */
               if (bs->GetBit()) /* vop_constant_alpha */
               {
                  bs->Skip(8);   /* vop_constant_alpha_value */
               }
            }
            
            if (shape != VIDOBJLAY_SHAPE_BINARY_ONLY) {
               
               if (!complexity_estimation_disable)
               {
                  read_vop_complexity_estimation_header(bs, coding_type);
               }
               
               /* intra_dc_vlc_threshold */
               *intra_dc_threshold =
                  intra_dc_threshold_table[bs->GetBits(3)];
               
               top_field_first = 0;
               alternate_vertical_scan = 0;
               
               if(interlacing){
                  top_field_first = bs->GetBit();
                  DPRINTF(XVID_DEBUG_HEADER, "interlace top_field_first %i\n", top_field_first);
                  alternate_vertical_scan = bs->GetBit();
                  DPRINTF(XVID_DEBUG_HEADER, "interlace alternate_vertical_scan %i\n", alternate_vertical_scan);
                  
               }
            }
            
            if ((sprite_enable == SPRITE_STATIC || sprite_enable== SPRITE_GMC) && coding_type == S_VOP) {
               
               int i;
               
               for (i = 0 ; i < sprite_warping_points; i++)
               {
                  int length;
                  int x = 0, y = 0;
                  
                  /* sprite code borowed from ffmpeg; thx Michael Niedermayer <michaelni@gmx.at> */
                  length = bs->bs_get_spritetrajectory();
                  if(length){
                     x= bs->GetBits(length);
                     if ((x >> (length - 1)) == 0) /* if MSB not set it is negative*/
                        x = - (x ^ ((1 << length) - 1));
                  }
                  READ_MARKER();
                  
                  length = bs->bs_get_spritetrajectory();
                  if(length){
                     y = bs->GetBits(length);
                     if ((y >> (length - 1)) == 0) /* if MSB not set it is negative*/
                        y = - (y ^ ((1 << length) - 1));
                  }
                  READ_MARKER();
                  
                  gmc_warp->duv[i].x = x;
                  gmc_warp->duv[i].y = y;
                  
                  //DPRINTF(XVID_DEBUG_HEADER,"sprite_warping_point[%i] xy=(%i,%i)\n", i, x, y);
               }
               
               if (sprite_brightness_change)
               {
                  /* XXX: brightness_change_factor() */
               }
               if (sprite_enable == SPRITE_STATIC)
               {
                  /* XXX: todo */
               }
               
            }
            
            if ((*quant = bs->GetBits(quant_bits)) < 1)  /* vop_quant */
               *quant = 1;
            DPRINTF(XVID_DEBUG_HEADER, "quant %i\n", *quant);
            
            if (coding_type != I_VOP) {
               *fcode_forward = bs->GetBits(3); /* fcode_forward */
               DPRINTF(XVID_DEBUG_HEADER, "fcode_forward %i\n", *fcode_forward);
            }
            
            if (coding_type == B_VOP) {
               *fcode_backward = bs->GetBits(3);   /* fcode_backward */
               DPRINTF(XVID_DEBUG_HEADER, "fcode_backward %i\n", *fcode_backward);
            }
            if(!scalability){
               if ((shape != VIDOBJLAY_SHAPE_RECTANGULAR) &&
                  (coding_type != I_VOP)) {
                  bs->Skip(1);   /* vop_shape_coding_type */
               }
            }
            return coding_type;
            
         }
         break;
      case USERDATA_START_CODE:
         {
            char tmp[256];
            int i;

            bs->Skip(32);  /* user_data_start_code */

            tmp[0] = bs->ShowBits(8);

            for(i = 1; i < 256; i++){
               tmp[i] = (bs->ShowBits(16) & 0xFF);

               if(tmp[i] == 0)
                  break;

               bs->Skip(8);
            }

            //DPRINTF(XVID_DEBUG_STARTCODE, "<user_data>: %s\n", tmp);

            /* read xvid bitstream version */
#ifdef WIN32
            {
               char packed;
               int version, build;
               if(MemCmp(tmp, "XviD", 4) == 0) {
                  sscanf(tmp, "XviD%d", &bs_version);
                  DPRINTF(XVID_DEBUG_HEADER, "xvid bitstream version=%i", bs_version);
               }

             /* divx detection */
               i = sscanf(tmp, "DivX%dBuild%d%c", &version, &build, &packed);
               if (i < 2)
                  i = sscanf(tmp, "DivX%db%d%c", &version, &build, &packed);
               if (i >= 2){
                  packed_mode = (i == 3 && packed == 'p');
                  //DPRINTF(XVID_DEBUG_HEADER, "divx version=%i, build=%i packed=%i\n", version, build, packed_mode);
               }
            }
#endif
         }
         break;
      default:
         switch(start_code & ~VIDOBJ_START_CODE_MASK){
         case VIDOBJ_START_CODE:
            {

               DPRINTF(XVID_DEBUG_STARTCODE, "<video_object>\n");
               DPRINTF(XVID_DEBUG_HEADER, "vo id %i\n", start_code & VIDOBJ_START_CODE_MASK);
                              //video_object_start_code
               bs->Skip(32);
            }
            break;
         case VIDOBJLAY_START_CODE:
            {

               DPRINTF(XVID_DEBUG_STARTCODE, "<video_object_layer>\n");
               DPRINTF(XVID_DEBUG_HEADER, "vol id %i\n", start_code & VIDOBJLAY_START_CODE_MASK);
               
               bs->Skip(32);  //video_object_layer_start_code
               bs->Skip(1);   //random_accessible_vol
               
               bs->Skip(8);   //video_object_type_indication
               
               if(bs->GetBit()){
                              //is_object_layer_identifier
                  DPRINTF(XVID_DEBUG_HEADER, "+ is_object_layer_identifier\n");
                  vol_ver_id = bs->GetBits(4);  /* video_object_layer_verid */
                  DPRINTF(XVID_DEBUG_HEADER,"ver_id %i\n", vol_ver_id);
                  bs->Skip(3);   /* video_object_layer_priority */
               }else{
                  vol_ver_id = 1;
               }
               
               aspect_ratio = bs->GetBits(4);
               
               if(aspect_ratio == VIDOBJLAY_AR_EXTPAR){
                              //aspect_ratio_info
                  DPRINTF(XVID_DEBUG_HEADER, "+ aspect_ratio_info\n");
                  par_width = bs->GetBits(8);   /* par_width */
                  par_height = bs->GetBits(8);  /* par_height */
               }
               
               if(bs->GetBit()){
                              //vol_control_parameters
                  DPRINTF(XVID_DEBUG_HEADER, "+ vol_control_parameters\n");
                  bs->Skip(2);   /* chroma_format */
                  low_delay = (bs->GetBit()!=0);
                  DPRINTF(XVID_DEBUG_HEADER, "low_delay %i\n", (int)low_delay);
                  if (bs->GetBit()) /* vbv_parameters */
                  {
                     unsigned int bitrate;
                     unsigned int buffer_size;
                     unsigned int occupancy;
                     
                     DPRINTF(XVID_DEBUG_HEADER,"+ vbv_parameters\n");
                     
                     bitrate = bs->GetBits(15) << 15; /* first_half_bit_rate */
                     READ_MARKER();
                     bitrate |= bs->GetBits(15);      /* latter_half_bit_rate */
                     READ_MARKER();
                     
                     buffer_size = bs->GetBits(15) << 3; /* first_half_vbv_buffer_size */
                     READ_MARKER();
                     buffer_size |= bs->GetBits(3);      /* latter_half_vbv_buffer_size */
                     
                     occupancy = bs->GetBits(11) << 15;  /* first_half_vbv_occupancy */
                     READ_MARKER();
                     occupancy |= bs->GetBits(15); /* latter_half_vbv_occupancy */
                     READ_MARKER();
                     
                     DPRINTF(XVID_DEBUG_HEADER,"bitrate %d (unit=400 bps)\n", bitrate);
                     DPRINTF(XVID_DEBUG_HEADER,"buffer_size %d (unit=16384 bits)\n", buffer_size);
                     DPRINTF(XVID_DEBUG_HEADER,"occupancy %d (unit=64 bits)\n", occupancy);
                  }
               }else{
                  low_delay = low_delay_default;
               }
               
                              //video_object_layer_shape
               shape = bs->GetBits(2);
               
               DPRINTF(XVID_DEBUG_HEADER, "shape %i\n", shape);
               if(shape != VIDOBJLAY_SHAPE_RECTANGULAR){
                  DPRINTF(XVID_DEBUG_ERROR,"non-rectangular shapes are not supported\n");
               }
               
               if(shape == VIDOBJLAY_SHAPE_GRAYSCALE && vol_ver_id != 1){
                              //video_object_layer_shape_extension
                  bs->Skip(4);
               }
               
               READ_MARKER();
               
               /********************** for decode B-frame time ***********************/
               time_inc_resolution = bs->GetBits(16); /* vop_time_increment_resolution */
               DPRINTF(XVID_DEBUG_HEADER,"vop_time_increment_resolution %i\n", time_inc_resolution);
               
#if 0
               time_inc_resolution--;
#endif
               
               if(time_inc_resolution > 0){
                  time_inc_bits = log2bin(time_inc_resolution-1);
               }else{
#if 0
                  time_inc_bits = 0;
#endif
                  /* for "old" xvid compatibility, set time_inc_bits = 1 */
                  time_inc_bits = 1;
               }
               
               READ_MARKER();
               
               if(bs->GetBit()){
                              //fixed_vop_rate
                  DPRINTF(XVID_DEBUG_HEADER, "+ fixed_vop_rate\n");
                  bs->Skip(time_inc_bits);   //fixed_vop_time_increment
               }
               
               if(shape != VIDOBJLAY_SHAPE_BINARY_ONLY){
                  
                  if(shape == VIDOBJLAY_SHAPE_RECTANGULAR){
                     dword _width, _height;
                     
                     READ_MARKER();
                     _width = bs->GetBits(13);  //video_object_layer_width
                     READ_MARKER();
                     _height = bs->GetBits(13); //video_object_layer_height
                     READ_MARKER();
                     
                     DPRINTF(XVID_DEBUG_HEADER, "width %i\n", _width);
                     DPRINTF(XVID_DEBUG_HEADER, "height %i\n", _height);
                     
                     if(width != _width || height != _height){
                        if(fixed_dimensions){
                           DPRINTF(XVID_DEBUG_ERROR, "decoder width/height does not match bitstream\n");
                           return -1;
                        }
                        resize = 1;
                        width = _width;
                        height = _height;
                     }
                  }
                  
                  interlacing = !!bs->GetBit();
                  DPRINTF(XVID_DEBUG_HEADER, "interlacing %i\n", interlacing);
                  
                  if(!bs->GetBit()){
                              //obmc_disable
                     DPRINTF(XVID_DEBUG_ERROR, "obmc_disabled==false not supported\n");
                     /* TODO */
                     /* fucking divx4.02 has this enabled */
                  }
                  
                  sprite_enable = bs->GetBits((vol_ver_id == 1 ? 1 : 2));
                  
                  if(sprite_enable == SPRITE_STATIC || sprite_enable == SPRITE_GMC){
                     int low_latency_sprite_enable;
                     
                     if(sprite_enable != SPRITE_GMC){
                        int sprite_width;
                        int sprite_height;
                        int sprite_left_coord;
                        int sprite_top_coord;
                        sprite_width = bs->GetBits(13);     /* sprite_width */
                        READ_MARKER();
                        sprite_height = bs->GetBits(13); /* sprite_height */
                        READ_MARKER();
                        sprite_left_coord = bs->GetBits(13);   /* sprite_left_coordinate */
                        READ_MARKER();
                        sprite_top_coord = bs->GetBits(13); /* sprite_top_coordinate */
                        READ_MARKER();
                     }
                     sprite_warping_points = bs->GetBits(6);      /* no_of_sprite_warping_points */
                     sprite_warping_accuracy = bs->GetBits(2);    /* sprite_warping_accuracy */
                     sprite_brightness_change = bs->GetBits(1);      /* brightness_change */
                     if (sprite_enable != SPRITE_GMC)
                     {
                        low_latency_sprite_enable = bs->GetBits(1);     /* low_latency_sprite_enable */
                     }
                  }
                  
                  if(vol_ver_id != 1 && shape != VIDOBJLAY_SHAPE_RECTANGULAR){
                              //sadct_disable
                     bs->Skip(1);
                  }
                  
                  if(bs->GetBit()){
                              //not_8_bit
                     DPRINTF(XVID_DEBUG_HEADER, "not_8_bit==true (ignored)\n");
                     quant_bits = bs->GetBits(4);  /* quant_precision */
                     bs->Skip(4);   /* bits_per_pixel */
                  }else{
                     quant_bits = 5;
                  }
                  
                  if(shape == VIDOBJLAY_SHAPE_GRAYSCALE){
                     bs->Skip(1);   /* no_gray_quant_update */
                     bs->Skip(1);   /* composition_method */
                     bs->Skip(1);   /* linear_composition */
                  }
                  
                  quant_type = bs->GetBit();
                  DPRINTF(XVID_DEBUG_HEADER, "quant_type %i\n", quant_type);
                  
                  if(quant_type){
                     if (bs->GetBit()) //load_intra_quant_mat
                     {
                        byte matrix[64];
                        
                        DPRINTF(XVID_DEBUG_HEADER, "load_intra_quant_mat\n");
                        
                        bs->get_matrix(matrix);
                        set_intra_matrix(mpeg_quant_matrices, matrix);
                     }else
                        set_intra_matrix(mpeg_quant_matrices, get_default_intra_matrix());
                     
                     if (bs->GetBit()) /* load_inter_quant_mat */
                     {
                        byte matrix[64];
                        
                        DPRINTF(XVID_DEBUG_HEADER, "load_inter_quant_mat\n");
                        
                        bs->get_matrix(matrix);
                        set_inter_matrix(mpeg_quant_matrices, matrix);
                     }else
                        set_inter_matrix(mpeg_quant_matrices, get_default_inter_matrix());
                     
                     if (shape == VIDOBJLAY_SHAPE_GRAYSCALE) {
                        DPRINTF(XVID_DEBUG_ERROR, "greyscale matrix not supported\n");
                        return -1;
                     }
                     
                  }
                  
                  if(vol_ver_id != 1){
                     quarterpel = bs->GetBit();
                     DPRINTF(XVID_DEBUG_HEADER,"quarterpel %i\n", quarterpel);
                  }else
                     quarterpel = 0;
                  
                  
                  complexity_estimation_disable = bs->GetBit();
                  if(!complexity_estimation_disable){
                     read_vol_complexity_estimation_header(bs);
                  }
                  
                  bs->Skip(1);   //resync_marker_disable
                  
                  if(bs->GetBit()){
                              //data_partitioned
                     DPRINTF(XVID_DEBUG_ERROR, "data_partitioned not supported\n");
                     bs->Skip(1);   /* reversible_vlc */
                  }
                  
                  if(vol_ver_id != 1){
                     newpred_enable = !!bs->GetBit();
                     if (newpred_enable)  /* newpred_enable */
                     {
                        DPRINTF(XVID_DEBUG_HEADER, "+ newpred_enable\n");
                        bs->Skip(2);   /* requested_upstream_message_type */
                        bs->Skip(1);   /* newpred_segment_type */
                     }
                     reduced_resolution_enable = !!bs->GetBit(); //reduced_resolution_vop_enable
                     DPRINTF(XVID_DEBUG_HEADER, "reduced_resolution_enable %i\n", reduced_resolution_enable);
                  }else{
                     newpred_enable = false;
                     reduced_resolution_enable = false;
                  }
                  
                  scalability = (bs->GetBit()!=0);
                  if(scalability){
                     DPRINTF(XVID_DEBUG_ERROR, "scalability not supported\n");
                     bs->Skip(1);   /* hierarchy_type */
                     bs->Skip(4);   /* ref_layer_id */
                     bs->Skip(1);   /* ref_layer_sampling_direc */
                     bs->Skip(5);   /* hor_sampling_factor_n */
                     bs->Skip(5);   /* hor_sampling_factor_m */
                     bs->Skip(5);   /* vert_sampling_factor_n */
                     bs->Skip(5);   /* vert_sampling_factor_m */
                     bs->Skip(1);   /* enhancement_type */
                     if(shape == VIDOBJLAY_SHAPE_BINARY /* && hierarchy_type==0 */) {
                        bs->Skip(1);   /* use_ref_shape */
                        bs->Skip(1);   /* use_ref_texture */
                        bs->Skip(5);   /* shape_hor_sampling_factor_n */
                        bs->Skip(5);   /* shape_hor_sampling_factor_m */
                        bs->Skip(5);   /* shape_vert_sampling_factor_n */
                        bs->Skip(5);   /* shape_vert_sampling_factor_m */
                     }
                     return -1;
                  }
               }else{
                              //shape == BINARY_ONLY
                  if(vol_ver_id != 1){
                     scalability = (bs->GetBit()!=0);
                     if(scalability){
                        DPRINTF(XVID_DEBUG_ERROR, "scalability not supported\n");
                        bs->Skip(4);   /* ref_layer_id */
                        bs->Skip(5);   /* hor_sampling_factor_n */
                        bs->Skip(5);   /* hor_sampling_factor_m */
                        bs->Skip(5);   /* vert_sampling_factor_n */
                        bs->Skip(5);   /* vert_sampling_factor_m */
                        return -1;
                     }
                  }
                  bs->Skip(1);   /* resync_marker_disable */
                  
               }
               
               return (resize ? -3 : -2);   //VOL
               
            }
            break;
         default:
            {
                              //start_code == ?
               //if(bs->ShowBits(24) == 0x000001)
               if((start_code&0x00ffffff) == 0x000001){
                  DPRINTF(XVID_DEBUG_STARTCODE, "<unknown: %x>\n", bs->ShowBits(32));
               }
               bs->Skip(8);
            }
         }
      }
   }

#if 0
   DPRINTF("*** WARNING: no vop_start_code found");
#endif
   return -1;                 //ignore it
}

//----------------------------

