bitstream.c

MP3编码程序和资料

	    assert(-1 <= v && v <= 1);
	}

	ix += 4;
	putbits2(gfp,huffbits + h->table[p], h->hlen[p]);
	bits += h->hlen[p];
    }
#ifdef DEBUG
    DEBUGF("%ld %d %d %d\n",gfc->bs.totbit -gegebo, gi->count1bits, gi->big_values, gi->count1);
#endif
    return bits;
}

/*
  Implements the pseudocode of page 98 of the IS
  */

static INLINE int
HuffmanCode(lame_global_flags *gfp, unsigned int table_select, int x, int y)
{
  /*    lame_internal_flags *gfc=gfp->internal_flags;*/
    unsigned int code, ext, xlen;
    int cbits, xbits;
    unsigned int signx, signy, linbits;
    const struct huffcodetab *h;

    cbits = 0;
    xbits = 0;
    code  = 0;
    signx = signy = 0;

    if (x < 0) {
	signx++;
	x = -x;
    }

    if (y < 0) {
	signy++;
	y = -y;
    }

    assert(table_select>0);
    h = &(ht[table_select]);
    linbits = h->xlen;
    ext = signx;
    xlen = h->xlen;

    if (table_select > 15) {
	/* use ESC-words */
	if (x > 14) {
	    int linbitsx = x - 15;
	    assert(linbitsx <= h->linmax);
	    ext |= linbitsx << 1;
	    xbits = linbits;
	    x = 15;
	}

	if (y > 14) {
	    int linbitsy = y - 15;
	    assert(linbitsy <= h->linmax);
	    ext <<= linbits;
	    ext |= linbitsy;
	    xbits += linbits;
	    y = 15;
	}
	xlen = 16;
    }

    if (x != 0) {
	cbits--;
    }

    if (y != 0) {
	ext <<= 1;
	ext |= signy;
	cbits--;
    }

    xbits -= cbits;

    assert(x <= 15);
    assert(y <= 15);

    x = x * xlen + y;

    code = h->table[x];
    cbits += h->hlen[x];

    assert(cbits <= 32);
    assert(xbits <= 32);

    putbits2(gfp,code, cbits);
    putbits2(gfp, ext, xbits);
    return cbits+xbits;
}

static int
Huffmancodebits(lame_global_flags *gfp,unsigned int tableindex, int start, int end, int *ix)
{
    int i,bits;

    assert(tableindex < 32);
    if (!tableindex) return 0;

    bits=0;
    for (i = start; i < end; i += 2) {
      bits +=HuffmanCode(gfp,tableindex, ix[i], ix[i + 1]);
    }
    return bits;
}



/*
  Note the discussion of huffmancodebits() on pages 28
  and 29 of the IS, as well as the definitions of the side
  information on pages 26 and 27.
  */
static int
ShortHuffmancodebits(lame_global_flags *gfp,int *ix, gr_info *gi)
{
    lame_internal_flags *gfc=gfp->internal_flags;
    int bits=0;
    int region1Start, region2Start;
    
    region1Start=3*gfc->scalefac_band.s[3];
    if (region1Start > gi->big_values) 	region1Start = gi->big_values;

    /* short blocks do not have a region2 */
    region2Start=gi->big_values;
    bits +=Huffmancodebits(gfp,gi->table_select[0], 0, region1Start, ix);
    bits +=Huffmancodebits(gfp,gi->table_select[1], region1Start, region2Start, ix);
    return bits;
}

static int
LongHuffmancodebits(lame_global_flags *gfp,int *ix, gr_info *gi)
{
    lame_internal_flags *gfc=gfp->internal_flags;
    int i, bigvalues,bits=0;
    int region1Start, region2Start;

    bigvalues = gi->big_values;
    assert(0 <= bigvalues && bigvalues <= 576);

    i = gi->region0_count + 1;
    assert(i < 23);
    region1Start = gfc->scalefac_band.l[i];
    i += gi->region1_count + 1;
    assert(i < 23);
    region2Start = gfc->scalefac_band.l[i];

    if (region1Start > bigvalues)
	region1Start = bigvalues;

    if (region2Start > bigvalues)
	region2Start = bigvalues;

    bits +=Huffmancodebits(gfp,gi->table_select[0], 0, region1Start, ix);
    bits +=Huffmancodebits(gfp,gi->table_select[1], region1Start, region2Start, ix);
    bits +=Huffmancodebits(gfp,gi->table_select[2], region2Start, bigvalues, ix);
    return bits;
}

static INLINE int
writeMainData(lame_global_flags *gfp,
      int              l3_enc[2][2][576],
  	III_scalefac_t   scalefac[2][2] )
{
    int gr, ch, sfb,data_bits,scale_bits,tot_bits=0;
    lame_internal_flags *gfc=gfp->internal_flags;
    III_side_info_t *l3_side;

    l3_side = &gfc->l3_side;
    if (gfp->version == 1) {
	/* MPEG 1 */
	for (gr = 0; gr < 2; gr++) {
	    for (ch = 0; ch < gfc->stereo; ch++) {
		gr_info *gi = &l3_side->gr[gr].ch[ch].tt;
		int slen1 = slen1_tab[gi->scalefac_compress];
		int slen2 = slen2_tab[gi->scalefac_compress];
		data_bits=0;
		scale_bits=0;

#ifdef DEBUG
		hogege = gfc->bs.totbit;
#endif
		if (gi->block_type == SHORT_TYPE) {
		    for (sfb = 0; sfb < SBPSY_s; sfb++) {
			int slen = sfb < 6 ? slen1 : slen2;

			assert(scalefac[gr][ch].s[sfb][0]>=0);
			assert(scalefac[gr][ch].s[sfb][1]>=0);
			assert(scalefac[gr][ch].s[sfb][2]>=0);

			putbits2(gfp,scalefac[gr][ch].s[sfb][0], slen);
			putbits2(gfp,scalefac[gr][ch].s[sfb][1], slen);
			putbits2(gfp,scalefac[gr][ch].s[sfb][2], slen);
			scale_bits += 3*slen;
		    }
		    data_bits += ShortHuffmancodebits(gfp,l3_enc[gr][ch], gi);
		} else {
		    int i;
		    for (i = 0; i < sizeof(scfsi_band) / sizeof(int) - 1;
			 i++) {
			if (gr != 0 && l3_side->scfsi[ch][i])
			    continue;

			for (sfb = scfsi_band[i]; sfb < scfsi_band[i + 1];
			     sfb++) {

			    assert(scalefac[gr][ch].l[sfb]>=0);
			    putbits2(gfp,scalefac[gr][ch].l[sfb],
				    sfb < 11 ? slen1 : slen2);
			    scale_bits += sfb < 11 ? slen1 : slen2;
			}
		    }
		    data_bits +=LongHuffmancodebits(gfp,l3_enc[gr][ch], gi);
		}
		data_bits +=huffman_coder_count1(gfp,l3_enc[gr][ch], gi);
#ifdef DEBUG
		DEBUGF("<%ld> ", gfc->bs.totbit-hogege);
#endif
		/* does bitcount in quantize.c agree with actual bit count?*/
		assert(data_bits==gi->part2_3_length-gi->part2_length);
		assert(scale_bits==gi->part2_length);
		tot_bits += scale_bits + data_bits;

	    } /* for ch */
	} /* for gr */
    } else {
	/* MPEG 2 */
	gr = 0;
	for (ch = 0; ch < gfc->stereo; ch++) {
	    gr_info *gi = &l3_side->gr[gr].ch[ch].tt;
	    int i, sfb_partition;
	    assert(gi->sfb_partition_table);
	    data_bits = 0;
	    scale_bits=0;

	    sfb = 0;
	    sfb_partition = 0;
	    if (gi->block_type == SHORT_TYPE) {
		for (; sfb_partition < 4; sfb_partition++) {
		    int sfbs = gi->sfb_partition_table[sfb_partition] / 3;
		    int slen = gi->slen[sfb_partition];
		    for (i = 0; i < sfbs; i++, sfb++) {
			putbits2(gfp,Max(scalefac[gr][ch].s[sfb][0], 0U), slen);
			putbits2(gfp,Max(scalefac[gr][ch].s[sfb][1], 0U), slen);
			putbits2(gfp,Max(scalefac[gr][ch].s[sfb][2], 0U), slen);
			scale_bits += 3*slen;
		    }
		}
		data_bits += ShortHuffmancodebits(gfp,l3_enc[gr][ch], gi);
	    } else {
		for (; sfb_partition < 4; sfb_partition++) {
		    int sfbs = gi->sfb_partition_table[sfb_partition];
		    int slen = gi->slen[sfb_partition];
		    for (i = 0; i < sfbs; i++, sfb++) {
			putbits2(gfp,Max(scalefac[gr][ch].l[sfb], 0U), slen);
			scale_bits += slen;
		    }
		}
		data_bits +=LongHuffmancodebits(gfp,l3_enc[gr][ch], gi);
	    }
	    data_bits +=huffman_coder_count1(gfp,l3_enc[gr][ch], gi);

	    /* does bitcount in quantize.c agree with actual bit count?*/
	    assert(data_bits==gi->part2_3_length-gi->part2_length);
	    assert(scale_bits==gi->part2_length);
	    tot_bits += scale_bits + data_bits;
	} /* for ch */
    } /* for gf */
    return tot_bits;
} /* main_data */




void
flush_bitstream(lame_global_flags *gfp)
{
  lame_internal_flags *gfc=gfp->internal_flags;
  int flushbits,remaining_headers;
  int bitsPerFrame, mean_bits;
  int last_ptr,first_ptr;
  first_ptr=gfc->w_ptr;           /* first header to add to bitstream */
  last_ptr = gfc->h_ptr - 1;   /* last header to add to bitstream */
  if (last_ptr==-1) last_ptr=MAX_HEADER_BUF-1;   

  /* add this many bits to bitstream so we can flush all headers */
  flushbits = gfc->header[last_ptr].write_timing - gfc->bs.totbit;

  if (flushbits >= 0) {
    /* if flushbits >= 0, some headers have not yet been written */
    /* reduce flushbits by the size of the headers */
    remaining_headers= 1+last_ptr - first_ptr;
    if (last_ptr < first_ptr) 
      remaining_headers= 1+last_ptr - first_ptr + MAX_HEADER_BUF;
    flushbits -= remaining_headers*8*gfc->sideinfo_len;
  }


  /* finally, add some bits so that the last frame is complete
   * these bits are not necessary to decode the last frame, but
   * some decoders will ignore last frame if these bits are missing 
   */
  getframebits(gfp,&bitsPerFrame,&mean_bits);
  flushbits += bitsPerFrame;
  if (flushbits<0) {
#if 0
    /* if flushbits < 0, this would mean that the buffer looks like:
     * (data...)  last_header  (data...)  (extra data that should not be here...)
     */
    DEBUGF("last header write_timing = %i \n",gfc->header[last_ptr].write_timing);
    DEBUGF("first header write_timing = %i \n",gfc->header[first_ptr].write_timing);
    DEBUGF("bs.totbit:                 %i \n",gfc->bs.totbit);
    DEBUGF("first_ptr, last_ptr        %i %i \n",first_ptr,last_ptr);
    DEBUGF("remaining_headers =        %i \n",remaining_headers);
    DEBUGF("bitsperframe:              %i \n",bitsPerFrame);
    DEBUGF("sidelen:                   %i \n",gfc->sideinfo_len);
#endif
    ERRORF("strange error flushing buffer ... \n");
  } else {
    drain_into_ancillary(gfp,flushbits);
  }

  assert (gfc->header[last_ptr].write_timing + bitsPerFrame  == gfc->bs.totbit);
}




void add_dummy_vbrframe(lame_global_flags *gfp,int bitsPerFrame)
{
  lame_internal_flags *gfc = gfp->internal_flags;
  int bits;

  gfc->header[gfc->h_ptr].ptr = 0;
  memset(gfc->header[gfc->h_ptr].buf, 0, gfc->sideinfo_len);
  bits = bitsPerFrame-8*gfc->sideinfo_len;

  /* add one byte, cause header to be written */
  putbits2(gfp,0,8);   
  /* setup for next header */
  gfc->h_ptr = (gfc->h_ptr + 1) & (MAX_HEADER_BUF - 1);
  gfc->header[gfc->h_ptr].write_timing = bitsPerFrame;

  drain_into_ancillary(gfp,bits-8);

}



/*
  format_bitstream()

  This is called after a frame of audio has been quantized and coded.
  It will write the encoded audio to the bitstream. Note that
  from a layer3 encoder's perspective the bit stream is primarily
  a series of main_data() blocks, with header and side information
  inserted at the proper locations to maintain framing. (See Figure A.7
  in the IS).
  */
int
format_bitstream(lame_global_flags *gfp, int bitsPerFrame,
      int              l3_enc[2][2][576],
  	III_scalefac_t   scalefac[2][2] )
{
    lame_internal_flags *gfc=gfp->internal_flags;
    int bits;
    III_side_info_t *l3_side;
    l3_side = &gfc->l3_side;

    drain_into_ancillary(gfp,l3_side->resvDrain_pre);

    encodeSideInfo2(gfp,bitsPerFrame);
    bits = 8*gfc->sideinfo_len;
    bits+=writeMainData(gfp,l3_enc,scalefac);
    drain_into_ancillary(gfp,l3_side->resvDrain_post);
    bits += l3_side->resvDrain_post;

    l3_side->main_data_begin += (bitsPerFrame-bits)/8;
    if ((l3_side->main_data_begin * 8) != gfc->ResvSize ) {
      ERRORF("bit reservoir error: \n"
             "l3_side->main_data_begin: %i \n"
             "Resvoir size:             %i \n"
             "resv drain (post)         %i \n"
             "resv drain (pre)          %i \n"
             "header and sideinfo:      %i \n"
             "data bits:                %i \n"
             "total bits:               %i (remainder: %i) \n"
             "bitsperframe:             %i \n",

             8*l3_side->main_data_begin,
             gfc->ResvSize,
             l3_side->resvDrain_post,
             l3_side->resvDrain_pre,
             8*gfc->sideinfo_len,
             bits-l3_side->resvDrain_post-8*gfc->sideinfo_len,
             bits, bits % 8,
             bitsPerFrame
      );

      gfc->ResvSize = l3_side->main_data_begin*8;
    };
    assert(gfc->bs.totbit % 8 == 0);

    if (gfc->bs.totbit > 1000000000UL ) {
      /* to avoid totbit overflow, (at 8h encoding at 128kbs) lets reset bit counter*/
      int i;
      for (i=0 ; i< MAX_HEADER_BUF ; ++i) 
	gfc->header[i].write_timing -= gfc->bs.totbit;      
      gfc->bs.totbit=0;
    }
    return 0;
}