mp3internalshuffman.cpp

流媒体传输协议的实现代码,非常有用.可以支持rtsp mms等流媒体传输协议

static unsigned rsf_get_scale_factors_2(MP3SideInfo::gr_info_s_t *gr_info) {
  unsigned char const* pnt;
  int i;
  unsigned int slen;
  int n = 0;
  int numbits = 0;

#ifdef undef
  if(i_stereo) /* i_stereo AND second channel -> do_layer3() checks this */
    slen = i_slen2[gr_info->scalefac_compress>>1];
  else
#endif
    slen = n_slen2[gr_info->scalefac_compress];

  gr_info->preflag = (slen>>15) & 0x1;

  n = 0;  
  if( gr_info->block_type == 2 ) {
    n++;
    if(gr_info->mixed_block_flag)
      n++;
  }

  pnt = stab[n][(slen>>12)&0x7];

  for(i=0;i<4;i++) {
    int num = slen & 0x7;
    slen >>= 3;
    numbits += pnt[i] * num;
  }

  return numbits;
}

static unsigned getScaleFactorsLength(MP3SideInfo::gr_info_s_t* gr,
				      Boolean isMPEG2) {
  return isMPEG2 ? rsf_get_scale_factors_2(gr)
                 : rsf_get_scale_factors_1(gr);
}

static int rsf_huffman_decoder(BitVector& bv,
			       struct huffcodetab const* h,
			       int* x, int* y, int* v, int* w); // forward

void MP3HuffmanDecode(MP3SideInfo::gr_info_s_t* gr, int isMPEG2,
		      unsigned char const* fromBasePtr,
		      unsigned fromBitOffset, unsigned fromLength,
		      unsigned& scaleFactorsLength,
		      MP3HuffmanEncodingInfo& hei) {
   unsigned i;
   int x, y, v, w;
   struct huffcodetab *h;
   BitVector bv((unsigned char*)fromBasePtr, fromBitOffset, fromLength);

   /* Compute the size of the scale factors (& also advance bv): */
   scaleFactorsLength = getScaleFactorsLength(gr, isMPEG2);
   bv.skipBits(scaleFactorsLength);

   initialize_huffman();

   hei.reg1Start = hei.reg2Start = hei.numSamples = 0;

   /* Read bigvalues area. */
   if (gr->big_values < gr->region1start + gr->region2start) {
     gr->big_values = gr->region1start + gr->region2start; /* sanity check */
   }
   for (i = 0; i < gr->big_values; ++i) {
     if (i < gr->region1start) {
       /* in region 0 */
       h = &rsf_ht[gr->table_select[0]];
     } else if (i < gr->region2start) {
       /* in region 1 */
       h = &rsf_ht[gr->table_select[1]];
       if (hei.reg1Start == 0) {
	 hei.reg1Start = bv.curBitIndex();
       }
     } else {
       /* in region 2 */
       h = &rsf_ht[gr->table_select[2]];
       if (hei.reg2Start == 0) {
	 hei.reg2Start = bv.curBitIndex();
       }
     }
     
     hei.allBitOffsets[i] = bv.curBitIndex();
     rsf_huffman_decoder(bv, h, &x, &y, &v, &w);
     if (hei.decodedValues != NULL) {
       // Record the decoded values:
       unsigned* ptr = &hei.decodedValues[4*i];
       ptr[0] = x; ptr[1] = y; ptr[2] = v; ptr[3] = w;
     }
   }
   hei.bigvalStart = bv.curBitIndex();
   
   /* Read count1 area. */
   h = &rsf_ht[gr->count1table_select+32];
   while (bv.curBitIndex() < bv.totNumBits() &&  i < SSLIMIT*SBLIMIT) {
     hei.allBitOffsets[i] = bv.curBitIndex();
     rsf_huffman_decoder(bv, h, &x, &y, &v, &w);
     if (hei.decodedValues != NULL) {
       // Record the decoded values:
       unsigned* ptr = &hei.decodedValues[4*i];
       ptr[0] = x; ptr[1] = y; ptr[2] = v; ptr[3] = w;
     }
     ++i;
   }

   hei.allBitOffsets[i] = bv.curBitIndex();
   hei.numSamples = i;
}

HUFFBITS dmask = 1 << (SIZEOF_HUFFBITS*8-1);
unsigned int hs = SIZEOF_HUFFBITS*8;

/* do the huffman-decoding 						*/
static int rsf_huffman_decoder(BitVector& bv,
		struct huffcodetab const* h, // ptr to huffman code record
			/* unsigned */ int *x, // returns decoded x value
			/* unsigned */ int *y,  // returns decoded y value
			       int* v, int* w) {
  HUFFBITS level;
  unsigned point = 0;
  int error = 1;
  level     = dmask;
  *x = *y = *v = *w = 0;
  if (h->val == NULL) return 2;

  /* table 0 needs no bits */
  if (h->treelen == 0) return 0;

  /* Lookup in Huffman table. */

  do {
    if (h->val[point][0]==0) {   /*end of tree*/
      *x = h->val[point][1] >> 4;
      *y = h->val[point][1] & 0xf;

      error = 0;
      break;
    } 
    if (bv.get1Bit()) {
      while (h->val[point][1] >= MXOFF) point += h->val[point][1]; 
      point += h->val[point][1];
    }
    else {
      while (h->val[point][0] >= MXOFF) point += h->val[point][0]; 
      point += h->val[point][0];
    }
    level >>= 1;
  } while (level  || (point < h->treelen) );
/////  } while (level  || (point < rsf_ht->treelen) );
  
  /* Check for error. */
  
  if (error) { /* set x and y to a medium value as a simple concealment */
    printf("Illegal Huffman code in data.\n");
    *x = ((h->xlen-1) << 1);
    *y = ((h->ylen-1) << 1);
  }

  /* Process sign encodings for quadruples tables. */

  if (h->tablename[0] == '3'
      && (h->tablename[1] == '2' || h->tablename[1] == '3')) {
     *v = (*y>>3) & 1;
     *w = (*y>>2) & 1;
     *x = (*y>>1) & 1;
     *y = *y & 1;

     if (*v)
        if (bv.get1Bit() == 1) *v = -*v;
     if (*w)
        if (bv.get1Bit() == 1) *w = -*w;
     if (*x)
        if (bv.get1Bit() == 1) *x = -*x;
     if (*y)
        if (bv.get1Bit() == 1) *y = -*y;
     }
     
  /* Process sign and escape encodings for dual tables. */
  
  else {
     if (h->linbits)
       if ((h->xlen-1) == (unsigned)*x) 
         *x += bv.getBits(h->linbits);
     if (*x)
        if (bv.get1Bit() == 1) *x = -*x;
     if (h->linbits)	  
       if ((h->ylen-1) == (unsigned)*y)
         *y += bv.getBits(h->linbits);
     if (*y)
        if (bv.get1Bit() == 1) *y = -*y;
  }
	  
  return error;  
}

#ifdef DO_HUFFMAN_ENCODING
inline int getNextSample(unsigned char const*& fromPtr) {
  int sample
#ifdef FOUR_BYTE_SAMPLES
    = (fromPtr[0]<<24) | (fromPtr[1]<<16) | (fromPtr[2]<<8) | fromPtr[3];
#else
#ifdef TWO_BYTE_SAMPLES
    = (fromPtr[0]<<8) | fromPtr[1];
#else
    // ONE_BYTE_SAMPLES
    = fromPtr[0];
#endif
#endif
  fromPtr += BYTES_PER_SAMPLE_VALUE;
  return sample;
}

static void rsf_huffman_encoder(BitVector& bv,
				struct huffcodetab* h,
				int x, int y, int v, int w); // forward

unsigned MP3HuffmanEncode(MP3SideInfo::gr_info_s_t const* gr,
			  unsigned char const* fromPtr,
			  unsigned char* toPtr, unsigned toBitOffset,
			  unsigned numHuffBits) {
   unsigned i;
   struct huffcodetab *h;
   int x, y, v, w;
   BitVector bv(toPtr, toBitOffset, numHuffBits);

   initialize_huffman();

   // Encode big_values area:
   unsigned big_values = gr->big_values;
   if (big_values < gr->region1start + gr->region2start) {
     big_values = gr->region1start + gr->region2start; /* sanity check */
   }
   for (i = 0; i < big_values; ++i) {
     if (i < gr->region1start) {
       /* in region 0 */
       h = &rsf_ht[gr->table_select[0]];
     } else if (i < gr->region2start) {
       /* in region 1 */
       h = &rsf_ht[gr->table_select[1]];
     } else {
       /* in region 2 */
       h = &rsf_ht[gr->table_select[2]];
     }
     
     x = getNextSample(fromPtr);
     y = getNextSample(fromPtr);
     v = getNextSample(fromPtr);
     w = getNextSample(fromPtr);
     rsf_huffman_encoder(bv, h, x, y, v, w);
   }
   
   // Encode count1 area:
   h = &rsf_ht[gr->count1table_select+32];
   while (bv.curBitIndex() < bv.totNumBits() &&  i < SSLIMIT*SBLIMIT) {
     x = getNextSample(fromPtr);
     y = getNextSample(fromPtr);
     v = getNextSample(fromPtr);
     w = getNextSample(fromPtr);
     rsf_huffman_encoder(bv, h, x, y, v, w);
     ++i;
   }

   return i;
}

static Boolean lookupHuffmanTableEntry(struct huffcodetab const* h,
				       HUFFBITS bits, unsigned bitsLength,
				       unsigned char& xy) {
  unsigned point = 0;
  unsigned mask = 1;
  unsigned numBitsTestedSoFar = 0;
  do {
    if (h->val[point][0]==0) { // end of tree
      xy = h->val[point][1];
      if (h->hlen[xy] == 0) { // this entry hasn't already been used
	h->table[xy] = bits;
	h->hlen[xy] = bitsLength;
	return True;
      } else { // this entry has already been seen
	return False;
      }
    }
    
    if (numBitsTestedSoFar++ == bitsLength) {
      // We don't yet have enough bits for this prefix
      return False;
    }
    if (bits&mask) {
      while (h->val[point][1] >= MXOFF) point += h->val[point][1]; 
      point += h->val[point][1];
    } else {
      while (h->val[point][0] >= MXOFF) point += h->val[point][0]; 
      point += h->val[point][0];
    }
    mask <<= 1;
  } while (mask || (point < h->treelen));

  return False;
}

static void buildHuffmanEncodingTable(struct huffcodetab* h) {
  h->table = new unsigned long[256];
  h->hlen = new unsigned char[256];
  if (h->table == NULL || h->hlen == NULL) { h->table = NULL; return; }
  for (unsigned i = 0; i < 256; ++i) {
    h->table[i] = 0; h->hlen[i] = 0;
  }

  // Look up entries for each possible bit sequence length:
  unsigned maxNumEntries = h->xlen * h->ylen;
  unsigned numEntries = 0;
  unsigned powerOf2 = 1;
  for (unsigned bitsLength = 1;
       bitsLength <= 8*SIZEOF_HUFFBITS; ++bitsLength) {
    powerOf2 *= 2;
    for (HUFFBITS bits = 0; bits < powerOf2; ++bits) {
      // Find the table value - if any - for 'bits' (length 'bitsLength'):
      unsigned char xy;
      if (lookupHuffmanTableEntry(h, bits, bitsLength, xy)) {
	++numEntries;
	if (numEntries == maxNumEntries) return; // we're done
      }
    }
  }
#ifdef DEBUG
  fprintf(stderr, "Didn't find enough entries!\n"); // shouldn't happen
#endif
}

static void lookupXYandPutBits(BitVector& bv, struct huffcodetab const* h,
			       unsigned char xy) {
  HUFFBITS bits = h->table[xy];
  unsigned bitsLength = h->hlen[xy];

  // Note that "bits" is in reverse order, so read them from right-to-left:
  while (bitsLength-- > 0) {
    bv.put1Bit(bits&0x00000001);
    bits >>= 1;
  }
}

static void putLinbits(BitVector& bv, struct huffcodetab const* h,
		       HUFFBITS bits) {
  bv.putBits(bits, h->linbits);
}

static void rsf_huffman_encoder(BitVector& bv,
				struct huffcodetab* h,
				int x, int y, int v, int w) {
  if (h->val == NULL) return;

  /* table 0 produces no bits */
  if (h->treelen == 0) return;

  if (h->table == NULL) {
    // We haven't yet built the encoding array for this table; do it now:
    buildHuffmanEncodingTable(h);
    if (h->table == NULL) return;
  }

  Boolean xIsNeg = False, yIsNeg = False, vIsNeg = False, wIsNeg = False;
  unsigned char xy;

#ifdef FOUR_BYTE_SAMPLES
#else
#ifdef TWO_BYTE_SAMPLES
  // Convert 2-byte negative numbers to their 4-byte equivalents:
  if (x&0x8000) x |= 0xFFFF0000;
  if (y&0x8000) y |= 0xFFFF0000;
  if (v&0x8000) v |= 0xFFFF0000;
  if (w&0x8000) w |= 0xFFFF0000;
#else
  // ONE_BYTE_SAMPLES
  // Convert 1-byte negative numbers to their 4-byte equivalents:
  if (x&0x80) x |= 0xFFFFFF00;
  if (y&0x80) y |= 0xFFFFFF00;
  if (v&0x80) v |= 0xFFFFFF00;
  if (w&0x80) w |= 0xFFFFFF00;
#endif
#endif

  if (h->tablename[0] == '3'
      && (h->tablename[1] == '2' || h->tablename[1] == '3')) {// quad tables
    if (x < 0) { xIsNeg = True; x = -x; }
    if (y < 0) { yIsNeg = True; y = -y; }
    if (v < 0) { vIsNeg = True; v = -v; }
    if (w < 0) { wIsNeg = True; w = -w; }

    // Sanity check: x,y,v,w must all be 0 or 1:
    if (x>1 || y>1 || v>1 || w>1) {
#ifdef DEBUG
      fprintf(stderr, "rsf_huffman_encoder quad sanity check fails: %x,%x,%x,%x\n", x, y, v, w);
#endif
    }

    xy = (v<<3)|(w<<2)|(x<<1)|y;
    lookupXYandPutBits(bv, h, xy);

    if (v) bv.put1Bit(vIsNeg);
    if (w) bv.put1Bit(wIsNeg);
    if (x) bv.put1Bit(xIsNeg);
    if (y) bv.put1Bit(yIsNeg);
  } else { // dual tables
    // Sanity check: v and w must be 0:
    if (v != 0 || w != 0) {
#ifdef DEBUG
      fprintf(stderr, "rsf_huffman_encoder dual sanity check 1 fails: %x,%x,%x,%x\n", x, y, v, w);
#endif
    }

    if (x < 0) { xIsNeg = True; x = -x; }
    if (y < 0) { yIsNeg = True; y = -y; }

    // Sanity check: x and y must be <= 255:
    if (x > 255 || y > 255) {
#ifdef DEBUG
      fprintf(stderr, "rsf_huffman_encoder dual sanity check 2 fails: %x,%x,%x,%x\n", x, y, v, w);
#endif
    }

    int xl1 = h->xlen-1;
    int yl1 = h->ylen-1;
    unsigned linbitsX = 0; unsigned linbitsY = 0;

    if (((x < xl1) || (xl1 == 0)) && (y < yl1)) {
      // normal case
      xy = (x<<4)|y;
      lookupXYandPutBits(bv, h, xy);
      if (x) bv.put1Bit(xIsNeg);
      if (y) bv.put1Bit(yIsNeg);
    } else if (x >= xl1) {
      linbitsX = (unsigned)(x - xl1);
      if (linbitsX > h->linmax) {
#ifdef DEBUG
	fprintf(stderr,"warning: Huffman X table overflow\n");
#endif
	linbitsX = h->linmax;
      };

      if (y >= yl1) {
	xy = (xl1<<4)|yl1;
	lookupXYandPutBits(bv, h, xy);
	linbitsY = (unsigned)(y - yl1);
	if (linbitsY > h->linmax) {
#ifdef DEBUG
	  fprintf(stderr,"warning: Huffman Y table overflow\n");
#endif
	  linbitsY = h->linmax;
	};

	if (h->linbits) putLinbits(bv, h, linbitsX);
	if (x) bv.put1Bit(xIsNeg);
	if (h->linbits) putLinbits(bv, h, linbitsY);
	if (y) bv.put1Bit(yIsNeg);
      } else { /* x >= h->xlen, y < h->ylen */
	xy = (xl1<<4)|y;
	lookupXYandPutBits(bv, h, xy);
	if (h->linbits) putLinbits(bv, h, linbitsX);
	if (x) bv.put1Bit(xIsNeg);
	if (y) bv.put1Bit(yIsNeg);
      }
    } else { /* ((x < h->xlen) && (y >= h->ylen)) */
      xy = (x<<4)|yl1;
      lookupXYandPutBits(bv, h, xy);
      linbitsY = y-yl1;
      if (linbitsY > h->linmax) {
#ifdef DEBUG
	fprintf(stderr,"warning: Huffman Y table overflow\n");
#endif
	linbitsY = h->linmax;
      };
      if (x) bv.put1Bit(xIsNeg);
      if (h->linbits) putLinbits(bv, h, linbitsY);
      if (y) bv.put1Bit(yIsNeg);
    }
  }
}
#endif

#ifdef undef
/* The system uses a variety of data files.  By opening them via this
   function, we can accommodate various locations. */

FILE *OpenTableFile(name)
char *name;
{
char fulname[80];
FILE *f;

     fulname[0] = '\0';

    strcat(fulname, name);
    if( (f=fopen(fulname,"r"))==NULL ) {
        fprintf(stderr,"OpenTable: could not find %s\n", fulname);
    }

/* The following was used to generate an internal version of the file #####*/
    {
FILE *testfd = fopen("rsf_hufftab.c", "w");
unsigned char buf[100];
unsigned i;
for (i = 0; i < 100; ++i) buf[i] = '\0';
while (fgets(buf, 100, f) != NULL) {
  unsigned j;
  for (j = 0; buf[j] != '\0'; ++j) {
    fprintf(testfd, "0x%02x, ", buf[j]);
  }
  for (i = 0; i < 100; ++i) buf[i] = '\0';
}
fclose(testfd);
exit(0);
    }
/*#####*/
    return f;
}
#endif