getvlc.c

视频的h263解码

/************************************************************************
 *
 *  getvlc.c, variable length decoding for tmndecode (H.263 decoder)
 *  Copyright (C) 1996  Telenor R&D, Norway
 *        Karl Olav Lillevold <[e-mail]>
 *
 *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *  Karl Olav Lillevold               <[e-mail]>
 *  Telenor Research and Development
 *  P.O.Box 83                        tel.:   [phone]
 *  N-2007 Kjeller, Norway            fax.:   [phone]
 *
 *  Robert Danielsen                  e-mail: [e-mail]
 *  Telenor Research and Development  www:    http://www.nta.no/brukere/DVC/
 *  P.O.Box 83                        tel.:   [phone]
 *  N-2007 Kjeller, Norway            fax.:   [phone]
 *  
 ************************************************************************/

/*
 * based on mpeg2decode, (C) 1994, MPEG Software Simulation Group
 * and mpeg2play, (C) 1994 Stefan Eckart
 *                         <[e-mail]>
 *
 */


#include <stdio.h>

#include "config.h"
#include "tmndec.h"
#include "global.h"
#include "getvlc.h"

int getTMNMV()
{
  int code;

  if (trace)
    printf("motion_code (");

  if (getbits1())
  {
    if (trace)
      printf("1): 0\n");
    return 0;
  }

  if ((code = showbits(12))>=512)
  {
    code = (code>>8) - 2;
    flushbits(TMNMVtab0[code].len);

    if (trace)
    {
      printf("0");
      printbits(code+2,4,TMNMVtab0[code].len);
      printf("): %d\n", TMNMVtab0[code].val);
    }

    return TMNMVtab0[code].val;
  }

  if (code>=128)
  {
    code = (code>>2) -32;
    flushbits(TMNMVtab1[code].len);

    if (trace)
    {
      printf("0");
      printbits(code+32,10,TMNMVtab1[code].len);
      printf("): %d\n",TMNMVtab1[code].val);
    }

    return TMNMVtab1[code].val;
  }

  if ((code-=5)<0)
  {
    if (!quiet)
      fprintf(stderr,"Invalid motion_vector code\n");
    fault=1;
    return 0;
  }

  flushbits(TMNMVtab2[code].len);

  if (trace)
  {
    printf("0");
    printbits(code+5,12,TMNMVtab2[code].len);
    printf("): %d\n",TMNMVtab2[code].val);
  }

  return TMNMVtab2[code].val;
}


int getMCBPC()
{
  int code;

  if (trace)
    printf("MCBPC (");

  code = showbits(9);

  if (code == 1) {
    /* macroblock stuffing */
    if (trace)
      printf("000000001): stuffing\n");
    flushbits(9);
    return 255;
  }

  if (code == 0) {
    if (!quiet) 
      fprintf(stderr,"Invalid MCBPC code\n");
    fault = 1;
    return 0;
  }
    
  if (code>=256)
  {
    flushbits(1);
    if (trace)
      printf("1): %d\n",0);
    return 0;
  }
    
  flushbits(MCBPCtab[code].len);

  if (trace)
  {
    printbits(code,9,MCBPCtab[code].len);
    printf("): %d\n",MCBPCtab[code].val);
  }

  return MCBPCtab[code].val;
}

int getMODB()
{
  int code;
  int MODB;

  if (trace)
    printf("MODB (");

  code = showbits(2);

  if (code < 2) {
    if (trace)
      printf("0): MODB = 0\n");
    MODB = 0;
    flushbits(1);
  }
  else if (code == 2) {
    if (trace)
      printf("10): MODB = 1\n");
    MODB = 1;
    flushbits(2);
  }
  else { /* code == 3 */
    if (trace)
      printf("11): MODB = 2\n");
    MODB = 2;
    flushbits(2);
  }
  return MODB;
}


int getMCBPCintra()
{
  int code;

  if (trace)
    printf("MCBPCintra (");

  code = showbits(9);

  if (code == 1) {
    /* macroblock stuffing */
    if (trace)
      printf("000000001): stuffing\n");
    flushbits(9);
    return 255;
  }

  if (code < 8) {
    if (!quiet) 
      fprintf(stderr,"Invalid MCBPCintra code\n");
    fault = 1;
    return 0;
  }

  code >>= 3;
    
  if (code>=32)
  {
    flushbits(1);
    if (trace)
      printf("1): %d\n",3);
    return 3;
  }

  flushbits(MCBPCtabintra[code].len);

  if (trace)
  {
    printbits(code,6,MCBPCtabintra[code].len);
    printf("): %d\n",MCBPCtabintra[code].val);
  }

  return MCBPCtabintra[code].val;
}

int getCBPY()
{
  int code;

  if (trace)
    printf("CBPY (");

  code = showbits(6);
  if (code < 2) {
    if (!quiet) 
      fprintf(stderr,"Invalid CBPY code\n");
    fault = 1;
    return -1;
  }
    
  if (code>=48)
  {
    flushbits(2);
    if (trace)
      printf("11): %d\n",0);
    return 0;
  }

  flushbits(CBPYtab[code].len);

  if (trace)
  {
    printbits(code,6,CBPYtab[code].len);
    printf("): %d\n",CBPYtab[code].val);
  }

  return CBPYtab[code].val;
}