getvlc.c

基于H.263的图像压缩编解码的C源码

/************************************************************************
 *
 *  getvlc.c, variable length decoding for tmndecode (H.263 decoder)
 *
 ************************************************************************/

#include <stdio.h>

#include "config.h"
#include "main.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;
}