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[/] [mpeg2fpga/] [trunk/] [tools/] [mpeg2dec/] [systems.c] - Blame information for rev 2

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1 2 kdv
/* systems.c, systems-specific routines                                 */
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/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */
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/*
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 * Disclaimer of Warranty
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 *
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 * These software programs are available to the user without any license fee or
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 * royalty on an "as is" basis.  The MPEG Software Simulation Group disclaims
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 * any and all warranties, whether express, implied, or statuary, including any
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 * implied warranties or merchantability or of fitness for a particular
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 * purpose.  In no event shall the copyright-holder be liable for any
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 * incidental, punitive, or consequential damages of any kind whatsoever
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 * arising from the use of these programs.
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 *
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 * This disclaimer of warranty extends to the user of these programs and user's
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 * customers, employees, agents, transferees, successors, and assigns.
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 *
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 * The MPEG Software Simulation Group does not represent or warrant that the
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 * programs furnished hereunder are free of infringement of any third-party
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 * patents.
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 *
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 * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,
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 * are subject to royalty fees to patent holders.  Many of these patents are
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 * general enough such that they are unavoidable regardless of implementation
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 * design.
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 *
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include "config.h"
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#include "global.h"
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/* initialize buffer, call once before first getbits or showbits */
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/* parse system layer, ignore everything we don't need */
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void Next_Packet()
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{
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  unsigned int code;
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  int l;
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  for(;;)
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  {
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    code = Get_Long();
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    /* remove system layer byte stuffing */
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    while ((code & 0xffffff00) != 0x100)
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      code = (code<<8) | Get_Byte();
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    switch(code)
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    {
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    case PACK_START_CODE: /* pack header */
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      /* skip pack header (system_clock_reference and mux_rate) */
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      ld->Rdptr += 8;
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      break;
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    case VIDEO_ELEMENTARY_STREAM:
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      code = Get_Word();             /* packet_length */
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      ld->Rdmax = ld->Rdptr + code;
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      code = Get_Byte();
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      if((code>>6)==0x02)
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      {
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        ld->Rdptr++;
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        code=Get_Byte();  /* parse PES_header_data_length */
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        ld->Rdptr+=code;    /* advance pointer by PES_header_data_length */
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        return;
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      }
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      else if(code==0xff)
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      {
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        /* parse MPEG-1 packet header */
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        while((code=Get_Byte())== 0xFF);
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      }
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      /* stuffing bytes */
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      if(code>=0x40)
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      {
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        if(code>=0x80)
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        {
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          fprintf(stderr,"Error in packet header\n");
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          exit(1);
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        }
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        /* skip STD_buffer_scale */
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        ld->Rdptr++;
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        code = Get_Byte();
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      }
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      if(code>=0x30)
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      {
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        if(code>=0x40)
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        {
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          fprintf(stderr,"Error in packet header\n");
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          exit(1);
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        }
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        /* skip presentation and decoding time stamps */
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        ld->Rdptr += 9;
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      }
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      else if(code>=0x20)
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      {
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        /* skip presentation time stamps */
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        ld->Rdptr += 4;
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      }
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      else if(code!=0x0f)
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      {
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        fprintf(stderr,"Error in packet header\n");
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        exit(1);
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      }
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      return;
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    case ISO_END_CODE: /* end */
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      /* simulate a buffer full of sequence end codes */
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      l = 0;
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      while (l<2048)
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      {
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        ld->Rdbfr[l++] = SEQUENCE_END_CODE>>24;
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        ld->Rdbfr[l++] = SEQUENCE_END_CODE>>16;
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        ld->Rdbfr[l++] = SEQUENCE_END_CODE>>8;
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        ld->Rdbfr[l++] = SEQUENCE_END_CODE&0xff;
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      }
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      ld->Rdptr = ld->Rdbfr;
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      ld->Rdmax = ld->Rdbfr + 2048;
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      return;
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    default:
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      if(code>=SYSTEM_START_CODE)
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      {
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        /* skip system headers and non-video packets*/
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        code = Get_Word();
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        ld->Rdptr += code;
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      }
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      else
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      {
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        fprintf(stderr,"Unexpected startcode %08x in system layer\n",code);
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        exit(1);
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      }
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      break;
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    }
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  }
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}
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void Flush_Buffer32()
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{
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  int Incnt;
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  ld->Bfr = 0;
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  Incnt = ld->Incnt;
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  Incnt -= 32;
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  if (System_Stream_Flag && (ld->Rdptr >= ld->Rdmax-4))
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  {
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    while (Incnt <= 24)
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    {
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      if (ld->Rdptr >= ld->Rdmax)
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        Next_Packet();
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      ld->Bfr |= Get_Byte() << (24 - Incnt);
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      Incnt += 8;
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    }
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  }
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  else
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  {
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    while (Incnt <= 24)
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    {
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      if (ld->Rdptr >= ld->Rdbfr+2048)
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        Fill_Buffer();
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      ld->Bfr |= *ld->Rdptr++ << (24 - Incnt);
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      Incnt += 8;
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    }
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  }
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  ld->Incnt = Incnt;
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#ifdef VERIFY 
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  ld->Bitcnt += 32;
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#endif /* VERIFY */
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}
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unsigned int Get_Bits32()
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{
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  unsigned int l;
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  l = Show_Bits(32);
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  Flush_Buffer32();
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  return l;
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}
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int Get_Long()
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{
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  int i;
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  i = Get_Word();
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  return (i<<16) | Get_Word();
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}
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