layer3.c

PPC流行的播放软件gsplayer源码2.24版

  for (i = 0; i < 6; ++i) {
    z[i +  0] = 0;
    z[i +  6] = mad_f_mul(yptr[ 0 + 0], wptr[0]);

    MAD_F_ML0(hi, lo, yptr[ 0 + 6], wptr[6]);
    MAD_F_MLA(hi, lo, yptr[12 + 0], wptr[0]);

    z[i + 12] = MAD_F_MLZ(hi, lo);

    MAD_F_ML0(hi, lo, yptr[12 + 6], wptr[6]);
    MAD_F_MLA(hi, lo, yptr[24 + 0], wptr[0]);

    z[i + 18] = MAD_F_MLZ(hi, lo);

    z[i + 24] = mad_f_mul(yptr[24 + 6], wptr[6]);
    z[i + 30] = 0;

    ++yptr;
    ++wptr;
  }
}

/*
 * NAME:	III_overlap()
 * DESCRIPTION:	perform overlap-add of windowed IMDCT outputs
 */
static
void III_overlap(mad_fixed_t const output[36], mad_fixed_t overlap[18],
		 mad_fixed_t sample[18][32], unsigned int sb)
{
  unsigned int i;

# if defined(ASO_INTERLEAVE2)
  {
    register mad_fixed_t tmp1, tmp2;

    tmp1 = overlap[0];
    tmp2 = overlap[1];

    for (i = 0; i < 16; i += 2) {
      sample[i + 0][sb] = output[i + 0 +  0] + tmp1;
      overlap[i + 0]    = output[i + 0 + 18];
      tmp1 = overlap[i + 2];

      sample[i + 1][sb] = output[i + 1 +  0] + tmp2;
      overlap[i + 1]    = output[i + 1 + 18];
      tmp2 = overlap[i + 3];
    }

    sample[16][sb] = output[16 +  0] + tmp1;
    overlap[16]    = output[16 + 18];
    sample[17][sb] = output[17 +  0] + tmp2;
    overlap[17]    = output[17 + 18];
  }
# elif 0
  for (i = 0; i < 18; i += 2) {
    sample[i + 0][sb] = output[i + 0 +  0] + overlap[i + 0];
    overlap[i + 0]    = output[i + 0 + 18];

    sample[i + 1][sb] = output[i + 1 +  0] + overlap[i + 1];
    overlap[i + 1]    = output[i + 1 + 18];
  }
# else
  for (i = 0; i < 18; ++i) {
    sample[i][sb] = output[i +  0] + overlap[i];
    overlap[i]    = output[i + 18];
  }
# endif
}

/*
 * NAME:	III_overlap_z()
 * DESCRIPTION:	perform "overlap-add" of zero IMDCT outputs
 */
static __inline
void III_overlap_z(mad_fixed_t overlap[18],
		   mad_fixed_t sample[18][32], unsigned int sb)
{
  unsigned int i;

# if defined(ASO_INTERLEAVE2)
  {
    register mad_fixed_t tmp1, tmp2;

    tmp1 = overlap[0];
    tmp2 = overlap[1];

    for (i = 0; i < 16; i += 2) {
      sample[i + 0][sb] = tmp1;
      overlap[i + 0]    = 0;
      tmp1 = overlap[i + 2];

      sample[i + 1][sb] = tmp2;
      overlap[i + 1]    = 0;
      tmp2 = overlap[i + 3];
    }

    sample[16][sb] = tmp1;
    overlap[16]    = 0;
    sample[17][sb] = tmp2;
    overlap[17]    = 0;
  }
# else
  for (i = 0; i < 18; ++i) {
    sample[i][sb] = overlap[i];
    overlap[i]    = 0;
  }
# endif
}

/*
 * NAME:	III_freqinver()
 * DESCRIPTION:	perform subband frequency inversion for odd sample lines
 */
static
void III_freqinver(mad_fixed_t sample[18][32], unsigned int sb)
{
  unsigned int i;

# if 1 || defined(ASO_INTERLEAVE1) || defined(ASO_INTERLEAVE2)
  {
    register mad_fixed_t tmp1, tmp2;

    tmp1 = sample[1][sb];
    tmp2 = sample[3][sb];

    for (i = 1; i < 13; i += 4) {
      sample[i + 0][sb] = -tmp1;
      tmp1 = sample[i + 4][sb];
      sample[i + 2][sb] = -tmp2;
      tmp2 = sample[i + 6][sb];
    }

    sample[13][sb] = -tmp1;
    tmp1 = sample[17][sb];
    sample[15][sb] = -tmp2;
    sample[17][sb] = -tmp1;
  }
# else
  for (i = 1; i < 18; i += 2)
    sample[i][sb] = -sample[i][sb];
# endif
}

/*
 * NAME:	III_decode()
 * DESCRIPTION:	decode frame main_data
 */
static
enum mad_error III_decode(struct mad_bitptr *ptr, struct mad_frame *frame,
			  struct sideinfo *si, unsigned int nch)
{
  struct mad_header *header = &frame->header;
  unsigned int sfreqi, ngr, gr;

  {
    unsigned int sfreq;

    sfreq = header->samplerate;
    if (header->flags & MAD_FLAG_MPEG_2_5_EXT)
      sfreq *= 2;

    /* 48000 => 0, 44100 => 1, 32000 => 2,
       24000 => 3, 22050 => 4, 16000 => 5 */
    sfreqi = ((sfreq >>  7) & 0x000f) +
             ((sfreq >> 15) & 0x0001) - 8;

    if (header->flags & MAD_FLAG_MPEG_2_5_EXT)
      sfreqi += 3;
  }

  /* scalefactors, Huffman decoding, requantization */

  ngr = (header->flags & MAD_FLAG_LSF_EXT) ? 1 : 2;

  for (gr = 0; gr < ngr; ++gr) {
    struct granule *granule = &si->gr[gr];
    unsigned char const *sfbwidth[2];
    mad_fixed_t xr[2][576];
    unsigned int ch;
    enum mad_error error;

    for (ch = 0; ch < nch; ++ch) {
      struct channel *channel = &granule->ch[ch];
      unsigned int part2_length;

      sfbwidth[ch] = sfbwidth_table[sfreqi].l;
      if (channel->block_type == 2) {
	sfbwidth[ch] = (channel->flags & mixed_block_flag) ?
	  sfbwidth_table[sfreqi].m : sfbwidth_table[sfreqi].s;
      }

      if (header->flags & MAD_FLAG_LSF_EXT) {
	part2_length = III_scalefactors_lsf(ptr, channel,
					    ch == 0 ? 0 : &si->gr[1].ch[1],
					    header->mode_extension);
      }
      else {
	part2_length = III_scalefactors(ptr, channel, &si->gr[0].ch[ch],
					gr == 0 ? 0 : si->scfsi[ch]);
      }

      error = III_huffdecode(ptr, xr[ch], channel, sfbwidth[ch], part2_length);
      if (error)
	return error;
    }

    /* joint stereo processing */

    if (header->mode == MAD_MODE_JOINT_STEREO && header->mode_extension) {
      error = III_stereo(xr, granule, header, sfbwidth[0]);
      if (error)
	return error;
    }

    /* reordering, alias reduction, IMDCT, overlap-add, frequency inversion */

    for (ch = 0; ch < nch; ++ch) {
      struct channel const *channel = &granule->ch[ch];
      mad_fixed_t (*sample)[32] = &frame->sbsample[ch][18 * gr];
      unsigned int sb, l, i, sblimit;
      mad_fixed_t output[36];

      if (channel->block_type == 2) {
	III_reorder(xr[ch], channel, sfbwidth[ch]);

# if !defined(OPT_STRICT)
	/*
	 * According to ISO/IEC 11172-3, "Alias reduction is not applied for
	 * granules with block_type == 2 (short block)." However, other
	 * sources suggest alias reduction should indeed be performed on the
	 * lower two subbands of mixed blocks. Most other implementations do
	 * this, so by default we will too.
	 */
	if (channel->flags & mixed_block_flag)
	  III_aliasreduce(xr[ch], 36);
# endif
      }
      else
	III_aliasreduce(xr[ch], 576);

      l = 0;

      /* subbands 0-1 */

      if (channel->block_type != 2 || (channel->flags & mixed_block_flag)) {
	unsigned int block_type;

	block_type = channel->block_type;
	if (channel->flags & mixed_block_flag)
	  block_type = 0;

	/* long blocks */
	for (sb = 0; sb < 2; ++sb, l += 18) {
	  III_imdct_l(&xr[ch][l], output, block_type);
	  III_overlap(output, (*frame->overlap)[ch][sb], sample, sb);
	}
      }
      else {
	/* short blocks */
	for (sb = 0; sb < 2; ++sb, l += 18) {
	  III_imdct_s(&xr[ch][l], output);
	  III_overlap(output, (*frame->overlap)[ch][sb], sample, sb);
	}
      }

      III_freqinver(sample, 1);

      /* (nonzero) subbands 2-31 */

      i = 576;
      while (i > 36 && xr[ch][i - 1] == 0)
	--i;

      sblimit = 32 - (576 - i) / 18;

      if (channel->block_type != 2) {
	/* long blocks */
	for (sb = 2; sb < sblimit; ++sb, l += 18) {
	  III_imdct_l(&xr[ch][l], output, channel->block_type);
	  III_overlap(output, (*frame->overlap)[ch][sb], sample, sb);

	  if (sb & 1)
	    III_freqinver(sample, sb);
	}
      }
      else {
	/* short blocks */
	for (sb = 2; sb < sblimit; ++sb, l += 18) {
	  III_imdct_s(&xr[ch][l], output);
	  III_overlap(output, (*frame->overlap)[ch][sb], sample, sb);

	  if (sb & 1)
	    III_freqinver(sample, sb);
	}
      }

      /* remaining (zero) subbands */

      for (sb = sblimit; sb < 32; ++sb) {
	III_overlap_z((*frame->overlap)[ch][sb], sample, sb);

	if (sb & 1)
	  III_freqinver(sample, sb);
      }
    }
  }

  return MAD_ERROR_NONE;
}

/*
 * NAME:	layer->III()
 * DESCRIPTION:	decode a single Layer III frame
 */
int mad_layer_III(struct mad_stream *stream, struct mad_frame *frame)
{
  struct mad_header *header = &frame->header;
  unsigned int nch, priv_bitlen, next_md_begin = 0;
  unsigned int si_len, data_bitlen, md_len;
  unsigned int frame_space, frame_used, frame_free;
  struct mad_bitptr ptr;
  struct sideinfo si;
  enum mad_error error;
  int result = 0;

  /* allocate Layer III dynamic structures */

  if (stream->main_data == 0) {
    stream->main_data = malloc(MAD_BUFFER_MDLEN);
    if (stream->main_data == 0) {
      stream->error = MAD_ERROR_NOMEM;
      return -1;
    }
  }

  if (frame->overlap == 0) {
    //frame->overlap = calloc(2 * 32 * 18, sizeof(mad_fixed_t));
	frame->overlap = malloc(2 * 32 * 18 * sizeof(mad_fixed_t));
	memset(frame->overlap, 0, 2 * 32 * 18 * sizeof(mad_fixed_t));
    if (frame->overlap == 0) {
      stream->error = MAD_ERROR_NOMEM;
      return -1;
    }
  }

  nch = MAD_NCHANNELS(header);
  si_len = (header->flags & MAD_FLAG_LSF_EXT) ?
    (nch == 1 ? 9 : 17) : (nch == 1 ? 17 : 32);

  /* check frame sanity */

  if (stream->next_frame - mad_bit_nextbyte(&stream->ptr) <
      (signed int) si_len) {
    stream->error = MAD_ERROR_BADFRAMELEN;
    stream->md_len = 0;
    return -1;
  }

  /* check CRC word */

  if (header->flags & MAD_FLAG_PROTECTION) {
    header->crc_check =
      mad_bit_crc(stream->ptr, si_len * CHAR_BIT, header->crc_check);

    if (header->crc_check != header->crc_target &&
	!(frame->options & MAD_OPTION_IGNORECRC)) {
      stream->error = MAD_ERROR_BADCRC;
      result = -1;
    }
  }

  /* decode frame side information */

  error = III_sideinfo(&stream->ptr, nch, header->flags & MAD_FLAG_LSF_EXT,
		       &si, &data_bitlen, &priv_bitlen);
  if (error && result == 0) {
    stream->error = error;
    result = -1;
  }

  header->flags        |= priv_bitlen;
  header->private_bits |= si.private_bits;

  /* find main_data of next frame */

  {
    struct mad_bitptr peek;
    unsigned long header;

    mad_bit_init(&peek, stream->next_frame);

    header = mad_bit_read(&peek, 32);
    if ((header & 0xffe60000L) /* syncword | layer */ == 0xffe20000L) {
      if (!(header & 0x00010000L))  /* protection_bit */
	mad_bit_skip(&peek, 16);  /* crc_check */

      next_md_begin =
	mad_bit_read(&peek, (header & 0x00080000L) /* ID */ ? 9 : 8);
    }

    mad_bit_finish(&peek);
  }

  /* find main_data of this frame */

  frame_space = stream->next_frame - mad_bit_nextbyte(&stream->ptr);

  if (next_md_begin > si.main_data_begin + frame_space)
    next_md_begin = 0;

  md_len = si.main_data_begin + frame_space - next_md_begin;

  frame_used = 0;

  if (si.main_data_begin == 0) {
    ptr = stream->ptr;
    stream->md_len = 0;

    frame_used = md_len;
  }
  else {
    if (si.main_data_begin > stream->md_len) {
      if (result == 0) {
	stream->error = MAD_ERROR_BADDATAPTR;
	result = -1;
      }
    }
    else {
      mad_bit_init(&ptr,
		   *stream->main_data + stream->md_len - si.main_data_begin);

      if (md_len > si.main_data_begin) {
	assert(stream->md_len + md_len -
	       si.main_data_begin <= MAD_BUFFER_MDLEN);

	memcpy(*stream->main_data + stream->md_len,
	       mad_bit_nextbyte(&stream->ptr),
	       frame_used = md_len - si.main_data_begin);
	stream->md_len += frame_used;
      }
    }
  }

  frame_free = frame_space - frame_used;

  /* decode main_data */

  if (result == 0) {
    error = III_decode(&ptr, frame, &si, nch);
    if (error) {
      stream->error = error;
      result = -1;
    }

    /* designate ancillary bits */

    stream->anc_ptr    = ptr;
    stream->anc_bitlen = md_len * CHAR_BIT - data_bitlen;
  }

# if 0 && defined(DEBUG)
  fprintf(stderr,
	  "main_data_begin:%u, md_len:%u, frame_free:%u, "
	  "data_bitlen:%u, anc_bitlen: %u\n",
	  si.main_data_begin, md_len, frame_free,
	  data_bitlen, stream->anc_bitlen);
# endif

  /* preload main_data buffer with up to 511 bytes for next frame(s) */

  if (frame_free >= next_md_begin) {
    memcpy(*stream->main_data,
	   stream->next_frame - next_md_begin, next_md_begin);
    stream->md_len = next_md_begin;
  }
  else {
    if (md_len < si.main_data_begin) {
      unsigned int extra;

      extra = si.main_data_begin - md_len;
      if (extra + frame_free > next_md_begin)
	extra = next_md_begin - frame_free;

      if (extra < stream->md_len) {
	memmove(*stream->main_data,
		*stream->main_data + stream->md_len - extra, extra);
	stream->md_len = extra;
      }
    }
    else
      stream->md_len = 0;

    memcpy(*stream->main_data + stream->md_len,
	   stream->next_frame - frame_free, frame_free);
    stream->md_len += frame_free;
  }

  return result;
}