import from SF CVS

git-svn-id: https://svn.musicpd.org/mpd/trunk@1 09075e82-0dd4-0310-85a5-a0d7c8717e4f

1 files changed, 2502 insertions, 0 deletions

diff --git a/src/libmad/layer3.c b/src/libmad/layer3.c
new file mode 100644
index 000000000..e1b073c71
--- /dev/null
+++ b/src/libmad/layer3.c
@@ -0,0 +1,2502 @@
+/*
+ * libmad - MPEG audio decoder library
+ * Copyright (C) 2000-2003 Underbit Technologies, Inc.
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * $Id: layer3.c,v 1.1 2003/08/14 03:57:13 shank Exp $
+ */
+
+# ifdef HAVE_CONFIG_H
+#  include "config.h"
+# endif
+
+# include "global.h"
+
+# include <stdlib.h>
+# include <string.h>
+
+# ifdef HAVE_ASSERT_H
+#  include <assert.h>
+# endif
+
+# ifdef HAVE_LIMITS_H
+#  include <limits.h>
+# else
+#  define CHAR_BIT  8
+# endif
+
+# include "fixed.h"
+# include "bit.h"
+# include "stream.h"
+# include "frame.h"
+# include "huffman.h"
+# include "layer3.h"
+
+/* --- Layer III ----------------------------------------------------------- */
+
+enum {
+  count1table_select = 0x01,
+  scalefac_scale     = 0x02,
+  preflag	     = 0x04,
+  mixed_block_flag   = 0x08
+};
+
+enum {
+  I_STEREO  = 0x1,
+  MS_STEREO = 0x2
+};
+
+struct sideinfo {
+  unsigned int main_data_begin;
+  unsigned int private_bits;
+
+  unsigned char scfsi[2];
+
+  struct granule {
+    struct channel {
+      /* from side info */
+      unsigned short part2_3_length;
+      unsigned short big_values;
+      unsigned short global_gain;
+      unsigned short scalefac_compress;
+
+      unsigned char flags;
+      unsigned char block_type;
+      unsigned char table_select[3];
+      unsigned char subblock_gain[3];
+      unsigned char region0_count;
+      unsigned char region1_count;
+
+      /* from main_data */
+      unsigned char scalefac[39];	/* scalefac_l and/or scalefac_s */
+    } ch[2];
+  } gr[2];
+};
+
+/*
+ * scalefactor bit lengths
+ * derived from section 2.4.2.7 of ISO/IEC 11172-3
+ */
+static
+struct {
+  unsigned char slen1;
+  unsigned char slen2;
+} const sflen_table[16] = {
+  { 0, 0 }, { 0, 1 }, { 0, 2 }, { 0, 3 },
+  { 3, 0 }, { 1, 1 }, { 1, 2 }, { 1, 3 },
+  { 2, 1 }, { 2, 2 }, { 2, 3 }, { 3, 1 },
+  { 3, 2 }, { 3, 3 }, { 4, 2 }, { 4, 3 }
+};
+
+/*
+ * number of LSF scalefactor band values
+ * derived from section 2.4.3.2 of ISO/IEC 13818-3
+ */
+static
+unsigned char const nsfb_table[6][3][4] = {
+  { {  6,  5,  5, 5 },
+    {  9,  9,  9, 9 },
+    {  6,  9,  9, 9 } },
+
+  { {  6,  5,  7, 3 },
+    {  9,  9, 12, 6 },
+    {  6,  9, 12, 6 } },
+
+  { { 11, 10,  0, 0 },
+    { 18, 18,  0, 0 },
+    { 15, 18,  0, 0 } },
+
+  { {  7,  7,  7, 0 },
+    { 12, 12, 12, 0 },
+    {  6, 15, 12, 0 } },
+
+  { {  6,  6,  6, 3 },
+    { 12,  9,  9, 6 },
+    {  6, 12,  9, 6 } },
+
+  { {  8,  8,  5, 0 },
+    { 15, 12,  9, 0 },
+    {  6, 18,  9, 0 } }
+};
+
+/*
+ * MPEG-1 scalefactor band widths
+ * derived from Table B.8 of ISO/IEC 11172-3
+ */
+static
+unsigned char const sfb_48000_long[] = {
+   4,  4,  4,  4,  4,  4,  6,  6,  6,   8,  10,
+  12, 16, 18, 22, 28, 34, 40, 46, 54,  54, 192
+};
+
+static
+unsigned char const sfb_44100_long[] = {
+   4,  4,  4,  4,  4,  4,  6,  6,  8,   8,  10,
+  12, 16, 20, 24, 28, 34, 42, 50, 54,  76, 158
+};
+
+static
+unsigned char const sfb_32000_long[] = {
+   4,  4,  4,  4,  4,  4,  6,  6,  8,  10,  12,
+  16, 20, 24, 30, 38, 46, 56, 68, 84, 102,  26
+};
+
+static
+unsigned char const sfb_48000_short[] = {
+   4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  6,
+   6,  6,  6,  6,  6, 10, 10, 10, 12, 12, 12, 14, 14,
+  14, 16, 16, 16, 20, 20, 20, 26, 26, 26, 66, 66, 66
+};
+
+static
+unsigned char const sfb_44100_short[] = {
+   4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  6,
+   6,  6,  8,  8,  8, 10, 10, 10, 12, 12, 12, 14, 14,
+  14, 18, 18, 18, 22, 22, 22, 30, 30, 30, 56, 56, 56
+};
+
+static
+unsigned char const sfb_32000_short[] = {
+   4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  4,  6,
+   6,  6,  8,  8,  8, 12, 12, 12, 16, 16, 16, 20, 20,
+  20, 26, 26, 26, 34, 34, 34, 42, 42, 42, 12, 12, 12
+};
+
+static
+unsigned char const sfb_48000_mixed[] = {
+  /* long */   4,  4,  4,  4,  4,  4,  6,  6,
+  /* short */  4,  4,  4,  6,  6,  6,  6,  6,  6, 10,
+              10, 10, 12, 12, 12, 14, 14, 14, 16, 16,
+              16, 20, 20, 20, 26, 26, 26, 66, 66, 66
+};
+
+static
+unsigned char const sfb_44100_mixed[] = {
+  /* long */   4,  4,  4,  4,  4,  4,  6,  6,
+  /* short */  4,  4,  4,  6,  6,  6,  8,  8,  8, 10,
+              10, 10, 12, 12, 12, 14, 14, 14, 18, 18,
+              18, 22, 22, 22, 30, 30, 30, 56, 56, 56
+};
+
+static
+unsigned char const sfb_32000_mixed[] = {
+  /* long */   4,  4,  4,  4,  4,  4,  6,  6,
+  /* short */  4,  4,  4,  6,  6,  6,  8,  8,  8, 12,
+              12, 12, 16, 16, 16, 20, 20, 20, 26, 26,
+              26, 34, 34, 34, 42, 42, 42, 12, 12, 12
+};
+
+/*
+ * MPEG-2 scalefactor band widths
+ * derived from Table B.2 of ISO/IEC 13818-3
+ */
+static
+unsigned char const sfb_24000_long[] = {
+   6,  6,  6,  6,  6,  6,  8, 10, 12,  14,  16,
+  18, 22, 26, 32, 38, 46, 54, 62, 70,  76,  36
+};
+
+static
+unsigned char const sfb_22050_long[] = {
+   6,  6,  6,  6,  6,  6,  8, 10, 12,  14,  16,
+  20, 24, 28, 32, 38, 46, 52, 60, 68,  58,  54
+};
+
+# define sfb_16000_long  sfb_22050_long
+
+static
+unsigned char const sfb_24000_short[] = {
+   4,  4,  4,  4,  4,  4,  4,  4,  4,  6,  6,  6,  8,
+   8,  8, 10, 10, 10, 12, 12, 12, 14, 14, 14, 18, 18,
+  18, 24, 24, 24, 32, 32, 32, 44, 44, 44, 12, 12, 12
+};
+
+static
+unsigned char const sfb_22050_short[] = {
+   4,  4,  4,  4,  4,  4,  4,  4,  4,  6,  6,  6,  6,
+   6,  6,  8,  8,  8, 10, 10, 10, 14, 14, 14, 18, 18,
+  18, 26, 26, 26, 32, 32, 32, 42, 42, 42, 18, 18, 18
+};
+
+static
+unsigned char const sfb_16000_short[] = {
+   4,  4,  4,  4,  4,  4,  4,  4,  4,  6,  6,  6,  8,
+   8,  8, 10, 10, 10, 12, 12, 12, 14, 14, 14, 18, 18,
+  18, 24, 24, 24, 30, 30, 30, 40, 40, 40, 18, 18, 18
+};
+
+static
+unsigned char const sfb_24000_mixed[] = {
+  /* long */   6,  6,  6,  6,  6,  6,
+  /* short */  6,  6,  6,  8,  8,  8, 10, 10, 10, 12,
+              12, 12, 14, 14, 14, 18, 18, 18, 24, 24,
+              24, 32, 32, 32, 44, 44, 44, 12, 12, 12
+};
+
+static
+unsigned char const sfb_22050_mixed[] = {
+  /* long */   6,  6,  6,  6,  6,  6,
+  /* short */  6,  6,  6,  6,  6,  6,  8,  8,  8, 10,
+              10, 10, 14, 14, 14, 18, 18, 18, 26, 26,
+              26, 32, 32, 32, 42, 42, 42, 18, 18, 18
+};
+
+static
+unsigned char const sfb_16000_mixed[] = {
+  /* long */   6,  6,  6,  6,  6,  6,
+  /* short */  6,  6,  6,  8,  8,  8, 10, 10, 10, 12,
+              12, 12, 14, 14, 14, 18, 18, 18, 24, 24,
+              24, 30, 30, 30, 40, 40, 40, 18, 18, 18
+};
+
+/*
+ * MPEG 2.5 scalefactor band widths
+ * derived from public sources
+ */
+# define sfb_12000_long  sfb_16000_long
+# define sfb_11025_long  sfb_12000_long
+
+static
+unsigned char const sfb_8000_long[] = {
+  12, 12, 12, 12, 12, 12, 16, 20, 24,  28,  32,
+  40, 48, 56, 64, 76, 90,  2,  2,  2,   2,   2
+};
+
+# define sfb_12000_short  sfb_16000_short
+# define sfb_11025_short  sfb_12000_short
+
+static
+unsigned char const sfb_8000_short[] = {
+   8,  8,  8,  8,  8,  8,  8,  8,  8, 12, 12, 12, 16,
+  16, 16, 20, 20, 20, 24, 24, 24, 28, 28, 28, 36, 36,
+  36,  2,  2,  2,  2,  2,  2,  2,  2,  2, 26, 26, 26
+};
+
+# define sfb_12000_mixed  sfb_16000_mixed
+# define sfb_11025_mixed  sfb_12000_mixed
+
+/* the 8000 Hz short block scalefactor bands do not break after
+   the first 36 frequency lines, so this is probably wrong */
+static
+unsigned char const sfb_8000_mixed[] = {
+  /* long */  12, 12, 12,
+  /* short */  4,  4,  4,  8,  8,  8, 12, 12, 12, 16, 16, 16,
+              20, 20, 20, 24, 24, 24, 28, 28, 28, 36, 36, 36,
+               2,  2,  2,  2,  2,  2,  2,  2,  2, 26, 26, 26
+};
+
+static
+struct {
+  unsigned char const *l;
+  unsigned char const *s;
+  unsigned char const *m;
+} const sfbwidth_table[9] = {
+  { sfb_48000_long, sfb_48000_short, sfb_48000_mixed },
+  { sfb_44100_long, sfb_44100_short, sfb_44100_mixed },
+  { sfb_32000_long, sfb_32000_short, sfb_32000_mixed },
+  { sfb_24000_long, sfb_24000_short, sfb_24000_mixed },
+  { sfb_22050_long, sfb_22050_short, sfb_22050_mixed },
+  { sfb_16000_long, sfb_16000_short, sfb_16000_mixed },
+  { sfb_12000_long, sfb_12000_short, sfb_12000_mixed },
+  { sfb_11025_long, sfb_11025_short, sfb_11025_mixed },
+  {  sfb_8000_long,  sfb_8000_short,  sfb_8000_mixed }
+};
+
+/*
+ * scalefactor band preemphasis (used only when preflag is set)
+ * derived from Table B.6 of ISO/IEC 11172-3
+ */
+static
+unsigned char const pretab[22] = {
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 3, 3, 2, 0
+};
+
+/*
+ * table for requantization
+ *
+ * rq_table[x].mantissa * 2^(rq_table[x].exponent) = x^(4/3)
+ */
+static
+struct fixedfloat {
+  unsigned long mantissa  : 27;
+  unsigned short exponent :  5;
+} const rq_table[8207] = {
+# include "rq_table.dat"
+};
+
+/*
+ * fractional powers of two
+ * used for requantization and joint stereo decoding
+ *
+ * root_table[3 + x] = 2^(x/4)
+ */
+static
+mad_fixed_t const root_table[7] = {
+  MAD_F(0x09837f05) /* 2^(-3/4) == 0.59460355750136 */,
+  MAD_F(0x0b504f33) /* 2^(-2/4) == 0.70710678118655 */,
+  MAD_F(0x0d744fcd) /* 2^(-1/4) == 0.84089641525371 */,
+  MAD_F(0x10000000) /* 2^( 0/4) == 1.00000000000000 */,
+  MAD_F(0x1306fe0a) /* 2^(+1/4) == 1.18920711500272 */,
+  MAD_F(0x16a09e66) /* 2^(+2/4) == 1.41421356237310 */,
+  MAD_F(0x1ae89f99) /* 2^(+3/4) == 1.68179283050743 */
+};
+
+/*
+ * coefficients for aliasing reduction
+ * derived from Table B.9 of ISO/IEC 11172-3
+ *
+ *  c[]  = { -0.6, -0.535, -0.33, -0.185, -0.095, -0.041, -0.0142, -0.0037 }
+ * cs[i] =    1 / sqrt(1 + c[i]^2)
+ * ca[i] = c[i] / sqrt(1 + c[i]^2)
+ */
+static
+mad_fixed_t const cs[8] = {
+  +MAD_F(0x0db84a81) /* +0.857492926 */, +MAD_F(0x0e1b9d7f) /* +0.881741997 */,
+  +MAD_F(0x0f31adcf) /* +0.949628649 */, +MAD_F(0x0fbba815) /* +0.983314592 */,
+  +MAD_F(0x0feda417) /* +0.995517816 */, +MAD_F(0x0ffc8fc8) /* +0.999160558 */,
+  +MAD_F(0x0fff964c) /* +0.999899195 */, +MAD_F(0x0ffff8d3) /* +0.999993155 */
+};
+
+static
+mad_fixed_t const ca[8] = {
+  -MAD_F(0x083b5fe7) /* -0.514495755 */, -MAD_F(0x078c36d2) /* -0.471731969 */,
+  -MAD_F(0x05039814) /* -0.313377454 */, -MAD_F(0x02e91dd1) /* -0.181913200 */,
+  -MAD_F(0x0183603a) /* -0.094574193 */, -MAD_F(0x00a7cb87) /* -0.040965583 */,
+  -MAD_F(0x003a2847) /* -0.014198569 */, -MAD_F(0x000f27b4) /* -0.003699975 */
+};
+
+/*
+ * IMDCT coefficients for short blocks
+ * derived from section 2.4.3.4.10.2 of ISO/IEC 11172-3
+ *
+ * imdct_s[i/even][k] = cos((PI / 24) * (2 *       (i / 2) + 7) * (2 * k + 1))
+ * imdct_s[i /odd][k] = cos((PI / 24) * (2 * (6 + (i-1)/2) + 7) * (2 * k + 1))
+ */
+static
+mad_fixed_t const imdct_s[6][6] = {
+# include "imdct_s.dat"
+};
+
+# if !defined(ASO_IMDCT)
+/*
+ * windowing coefficients for long blocks
+ * derived from section 2.4.3.4.10.3 of ISO/IEC 11172-3
+ *
+ * window_l[i] = sin((PI / 36) * (i + 1/2))
+ */
+static
+mad_fixed_t const window_l[36] = {
+  MAD_F(0x00b2aa3e) /* 0.043619387 */, MAD_F(0x0216a2a2) /* 0.130526192 */,
+  MAD_F(0x03768962) /* 0.216439614 */, MAD_F(0x04cfb0e2) /* 0.300705800 */,
+  MAD_F(0x061f78aa) /* 0.382683432 */, MAD_F(0x07635284) /* 0.461748613 */,
+  MAD_F(0x0898c779) /* 0.537299608 */, MAD_F(0x09bd7ca0) /* 0.608761429 */,
+  MAD_F(0x0acf37ad) /* 0.675590208 */, MAD_F(0x0bcbe352) /* 0.737277337 */,
+  MAD_F(0x0cb19346) /* 0.793353340 */, MAD_F(0x0d7e8807) /* 0.843391446 */,
+
+  MAD_F(0x0e313245) /* 0.887010833 */, MAD_F(0x0ec835e8) /* 0.923879533 */,
+  MAD_F(0x0f426cb5) /* 0.953716951 */, MAD_F(0x0f9ee890) /* 0.976296007 */,
+  MAD_F(0x0fdcf549) /* 0.991444861 */, MAD_F(0x0ffc19fd) /* 0.999048222 */,
+  MAD_F(0x0ffc19fd) /* 0.999048222 */, MAD_F(0x0fdcf549) /* 0.991444861 */,
+  MAD_F(0x0f9ee890) /* 0.976296007 */, MAD_F(0x0f426cb5) /* 0.953716951 */,
+  MAD_F(0x0ec835e8) /* 0.923879533 */, MAD_F(0x0e313245) /* 0.887010833 */,
+
+  MAD_F(0x0d7e8807) /* 0.843391446 */, MAD_F(0x0cb19346) /* 0.793353340 */,
+  MAD_F(0x0bcbe352) /* 0.737277337 */, MAD_F(0x0acf37ad) /* 0.675590208 */,
+  MAD_F(0x09bd7ca0) /* 0.608761429 */, MAD_F(0x0898c779) /* 0.537299608 */,
+  MAD_F(0x07635284) /* 0.461748613 */, MAD_F(0x061f78aa) /* 0.382683432 */,
+  MAD_F(0x04cfb0e2) /* 0.300705800 */, MAD_F(0x03768962) /* 0.216439614 */,
+  MAD_F(0x0216a2a2) /* 0.130526192 */, MAD_F(0x00b2aa3e) /* 0.043619387 */,
+};
+# endif  /* ASO_IMDCT */
+
+/*
+ * windowing coefficients for short blocks
+ * derived from section 2.4.3.4.10.3 of ISO/IEC 11172-3
+ *
+ * window_s[i] = sin((PI / 12) * (i + 1/2))
+ */
+static
+mad_fixed_t const window_s[12] = {
+  MAD_F(0x0216a2a2) /* 0.130526192 */, MAD_F(0x061f78aa) /* 0.382683432 */,
+  MAD_F(0x09bd7ca0) /* 0.608761429 */, MAD_F(0x0cb19346) /* 0.793353340 */,
+  MAD_F(0x0ec835e8) /* 0.923879533 */, MAD_F(0x0fdcf549) /* 0.991444861 */,
+  MAD_F(0x0fdcf549) /* 0.991444861 */, MAD_F(0x0ec835e8) /* 0.923879533 */,
+  MAD_F(0x0cb19346) /* 0.793353340 */, MAD_F(0x09bd7ca0) /* 0.608761429 */,
+  MAD_F(0x061f78aa) /* 0.382683432 */, MAD_F(0x0216a2a2) /* 0.130526192 */,
+};
+
+/*
+ * coefficients for intensity stereo processing
+ * derived from section 2.4.3.4.9.3 of ISO/IEC 11172-3
+ *
+ * is_ratio[i] = tan(i * (PI / 12))
+ * is_table[i] = is_ratio[i] / (1 + is_ratio[i])
+ */
+static
+mad_fixed_t const is_table[7] = {
+  MAD_F(0x00000000) /* 0.000000000 */,
+  MAD_F(0x0361962f) /* 0.211324865 */,
+  MAD_F(0x05db3d74) /* 0.366025404 */,
+  MAD_F(0x08000000) /* 0.500000000 */,
+  MAD_F(0x0a24c28c) /* 0.633974596 */,
+  MAD_F(0x0c9e69d1) /* 0.788675135 */,
+  MAD_F(0x10000000) /* 1.000000000 */
+};
+
+/*
+ * coefficients for LSF intensity stereo processing
+ * derived from section 2.4.3.2 of ISO/IEC 13818-3
+ *
+ * is_lsf_table[0][i] = (1 / sqrt(sqrt(2)))^(i + 1)
+ * is_lsf_table[1][i] = (1 /      sqrt(2)) ^(i + 1)
+ */
+static
+mad_fixed_t const is_lsf_table[2][15] = {
+  {
+    MAD_F(0x0d744fcd) /* 0.840896415 */,
+    MAD_F(0x0b504f33) /* 0.707106781 */,
+    MAD_F(0x09837f05) /* 0.594603558 */,
+    MAD_F(0x08000000) /* 0.500000000 */,
+    MAD_F(0x06ba27e6) /* 0.420448208 */,
+    MAD_F(0x05a8279a) /* 0.353553391 */,
+    MAD_F(0x04c1bf83) /* 0.297301779 */,
+    MAD_F(0x04000000) /* 0.250000000 */,
+    MAD_F(0x035d13f3) /* 0.210224104 */,
+    MAD_F(0x02d413cd) /* 0.176776695 */,
+    MAD_F(0x0260dfc1) /* 0.148650889 */,
+    MAD_F(0x02000000) /* 0.125000000 */,
+    MAD_F(0x01ae89fa) /* 0.105112052 */,
+    MAD_F(0x016a09e6) /* 0.088388348 */,
+    MAD_F(0x01306fe1) /* 0.074325445 */
+  }, {
+    MAD_F(0x0b504f33) /* 0.707106781 */,
+    MAD_F(0x08000000) /* 0.500000000 */,
+    MAD_F(0x05a8279a) /* 0.353553391 */,
+    MAD_F(0x04000000) /* 0.250000000 */,
+    MAD_F(0x02d413cd) /* 0.176776695 */,
+    MAD_F(0x02000000) /* 0.125000000 */,
+    MAD_F(0x016a09e6) /* 0.088388348 */,
+    MAD_F(0x01000000) /* 0.062500000 */,
+    MAD_F(0x00b504f3) /* 0.044194174 */,
+    MAD_F(0x00800000) /* 0.031250000 */,
+    MAD_F(0x005a827a) /* 0.022097087 */,
+    MAD_F(0x00400000) /* 0.015625000 */,
+    MAD_F(0x002d413d) /* 0.011048543 */,
+    MAD_F(0x00200000) /* 0.007812500 */,
+    MAD_F(0x0016a09e) /* 0.005524272 */
+  }
+};
+
+/*
+ * NAME:	III_sideinfo()
+ * DESCRIPTION:	decode frame side information from a bitstream
+ */
+static
+enum mad_error III_sideinfo(struct mad_bitptr *ptr, unsigned int nch,
+			    int lsf, struct sideinfo *si,
+			    unsigned int *data_bitlen,
+			    unsigned int *priv_bitlen)
+{
+  unsigned int ngr, gr, ch, i;
+  enum mad_error result = MAD_ERROR_NONE;
+
+  *data_bitlen = 0;
+  *priv_bitlen = lsf ? ((nch == 1) ? 1 : 2) : ((nch == 1) ? 5 : 3);
+
+  si->main_data_begin = mad_bit_read(ptr, lsf ? 8 : 9);
+  si->private_bits    = mad_bit_read(ptr, *priv_bitlen);
+
+  ngr = 1;
+  if (!lsf) {
+    ngr = 2;
+
+    for (ch = 0; ch < nch; ++ch)
+      si->scfsi[ch] = mad_bit_read(ptr, 4);
+  }
+
+  for (gr = 0; gr < ngr; ++gr) {
+    struct granule *granule = &si->gr[gr];
+
+    for (ch = 0; ch < nch; ++ch) {
+      struct channel *channel = &granule->ch[ch];
+
+      channel->part2_3_length    = mad_bit_read(ptr, 12);
+      channel->big_values        = mad_bit_read(ptr, 9);
+      channel->global_gain       = mad_bit_read(ptr, 8);
+      channel->scalefac_compress = mad_bit_read(ptr, lsf ? 9 : 4);
+
+      *data_bitlen += channel->part2_3_length;
+
+      if (channel->big_values > 288 && result == 0)
+	result = MAD_ERROR_BADBIGVALUES;
+
+      channel->flags = 0;
+
+      /* window_switching_flag */
+      if (mad_bit_read(ptr, 1)) {
+	channel->block_type = mad_bit_read(ptr, 2);
+
+	if (channel->block_type == 0 && result == 0)
+	  result = MAD_ERROR_BADBLOCKTYPE;
+
+	if (!lsf && channel->block_type == 2 && si->scfsi[ch] && result == 0)
+	  result = MAD_ERROR_BADSCFSI;
+
+	channel->region0_count = 7;
+	channel->region1_count = 36;
+
+	if (mad_bit_read(ptr, 1))
+	  channel->flags |= mixed_block_flag;
+	else if (channel->block_type == 2)
+	  channel->region0_count = 8;
+
+	for (i = 0; i < 2; ++i)
+	  channel->table_select[i] = mad_bit_read(ptr, 5);
+
+# if defined(DEBUG)
+	channel->table_select[2] = 4;  /* not used */
+# endif
+
+	for (i = 0; i < 3; ++i)
+	  channel->subblock_gain[i] = mad_bit_read(ptr, 3);
+      }
+      else {
+	channel->block_type = 0;
+
+	for (i = 0; i < 3; ++i)
+	  channel->table_select[i] = mad_bit_read(ptr, 5);
+
+	channel->region0_count = mad_bit_read(ptr, 4);
+	channel->region1_count = mad_bit_read(ptr, 3);
+      }
+
+      /* [preflag,] scalefac_scale, count1table_select */
+      channel->flags |= mad_bit_read(ptr, lsf ? 2 : 3);
+    }
+  }
+
+  return result;
+}
+
+/*
+ * NAME:	III_scalefactors_lsf()
+ * DESCRIPTION:	decode channel scalefactors for LSF from a bitstream
+ */
+static
+unsigned int III_scalefactors_lsf(struct mad_bitptr *ptr,
+				  struct channel *channel,
+				  struct channel *gr1ch, int mode_extension)
+{
+  struct mad_bitptr start;
+  unsigned int scalefac_compress, index, slen[4], part, n, i;
+  unsigned char const *nsfb;
+
+  start = *ptr;
+
+  scalefac_compress = channel->scalefac_compress;
+  index = (channel->block_type == 2) ?
+    ((channel->flags & mixed_block_flag) ? 2 : 1) : 0;
+
+  if (!((mode_extension & I_STEREO) && gr1ch)) {
+    if (scalefac_compress < 400) {
+      slen[0] = (scalefac_compress >> 4) / 5;
+      slen[1] = (scalefac_compress >> 4) % 5;
+      slen[2] = (scalefac_compress % 16) >> 2;
+      slen[3] =  scalefac_compress %  4;
+
+      nsfb = nsfb_table[0][index];
+    }
+    else if (scalefac_compress < 500) {
+      scalefac_compress -= 400;
+
+      slen[0] = (scalefac_compress >> 2) / 5;
+      slen[1] = (scalefac_compress >> 2) % 5;
+      slen[2] =  scalefac_compress %  4;
+      slen[3] = 0;
+
+      nsfb = nsfb_table[1][index];
+    }
+    else {
+      scalefac_compress -= 500;
+
+      slen[0] = scalefac_compress / 3;
+      slen[1] = scalefac_compress % 3;
+      slen[2] = 0;
+      slen[3] = 0;
+
+      channel->flags |= preflag;
+
+      nsfb = nsfb_table[2][index];
+    }
+
+    n = 0;
+    for (part = 0; part < 4; ++part) {
+      for (i = 0; i < nsfb[part]; ++i)
+	channel->scalefac[n++] = mad_bit_read(ptr, slen[part]);
+    }
+
+    while (n < 39)
+      channel->scalefac[n++] = 0;
+  }
+  else {  /* (mode_extension & I_STEREO) && gr1ch (i.e. ch == 1) */
+    scalefac_compress >>= 1;
+
+    if (scalefac_compress < 180) {
+      slen[0] =  scalefac_compress / 36;
+      slen[1] = (scalefac_compress % 36) / 6;
+      slen[2] = (scalefac_compress % 36) % 6;
+      slen[3] = 0;
+
+      nsfb = nsfb_table[3][index];
+    }
+    else if (scalefac_compress < 244) {
+      scalefac_compress -= 180;
+
+      slen[0] = (scalefac_compress % 64) >> 4;
+      slen[1] = (scalefac_compress % 16) >> 2;
+      slen[2] =  scalefac_compress %  4;
+      slen[3] = 0;
+
+      nsfb = nsfb_table[4][index];
+    }
+    else {
+      scalefac_compress -= 244;
+
+      slen[0] = scalefac_compress / 3;
+      slen[1] = scalefac_compress % 3;
+      slen[2] = 0;
+      slen[3] = 0;
+
+      nsfb = nsfb_table[5][index];
+    }
+
+    n = 0;
+    for (part = 0; part < 4; ++part) {
+      unsigned int max, is_pos;
+
+      max = (1 << slen[part]) - 1;
+
+      for (i = 0; i < nsfb[part]; ++i) {
+	is_pos = mad_bit_read(ptr, slen[part]);
+
+	channel->scalefac[n] = is_pos;
+	gr1ch->scalefac[n++] = (is_pos == max);
+      }
+    }
+
+    while (n < 39) {
+      channel->scalefac[n] = 0;
+      gr1ch->scalefac[n++] = 0;  /* apparently not illegal */
+    }
+  }
+
+  return mad_bit_length(&start, ptr);
+}
+
+/*
+ * NAME:	III_scalefactors()
+ * DESCRIPTION:	decode channel scalefactors of one granule from a bitstream
+ */
+static
+unsigned int III_scalefactors(struct mad_bitptr *ptr, struct channel *channel,
+			      struct channel const *gr0ch, unsigned int scfsi)
+{
+  struct mad_bitptr start;
+  unsigned int slen1, slen2, sfbi;
+
+  start = *ptr;
+
+  slen1 = sflen_table[channel->scalefac_compress].slen1;
+  slen2 = sflen_table[channel->scalefac_compress].slen2;
+
+  if (channel->block_type == 2) {
+    unsigned int nsfb;
+
+    sfbi = 0;
+
+    nsfb = (channel->flags & mixed_block_flag) ? 8 + 3 * 3 : 6 * 3;
+    while (nsfb--)
+      channel->scalefac[sfbi++] = mad_bit_read(ptr, slen1);
+
+    nsfb = 6 * 3;
+    while (nsfb--)
+      channel->scalefac[sfbi++] = mad_bit_read(ptr, slen2);
+
+    nsfb = 1 * 3;
+    while (nsfb--)
+      channel->scalefac[sfbi++] = 0;
+  }
+  else {  /* channel->block_type != 2 */
+    if (scfsi & 0x8) {
+      for (sfbi = 0; sfbi < 6; ++sfbi)
+	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
+    }
+    else {
+      for (sfbi = 0; sfbi < 6; ++sfbi)
+	channel->scalefac[sfbi] = mad_bit_read(ptr, slen1);
+    }
+
+    if (scfsi & 0x4) {
+      for (sfbi = 6; sfbi < 11; ++sfbi)
+	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
+    }
+    else {
+      for (sfbi = 6; sfbi < 11; ++sfbi)
+	channel->scalefac[sfbi] = mad_bit_read(ptr, slen1);
+    }
+
+    if (scfsi & 0x2) {
+      for (sfbi = 11; sfbi < 16; ++sfbi)
+	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
+    }
+    else {
+      for (sfbi = 11; sfbi < 16; ++sfbi)
+	channel->scalefac[sfbi] = mad_bit_read(ptr, slen2);
+    }
+
+    if (scfsi & 0x1) {
+      for (sfbi = 16; sfbi < 21; ++sfbi)
+	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
+    }
+    else {
+      for (sfbi = 16; sfbi < 21; ++sfbi)
+	channel->scalefac[sfbi] = mad_bit_read(ptr, slen2);
+    }
+
+    channel->scalefac[21] = 0;
+  }
+
+  return mad_bit_length(&start, ptr);
+}
+
+/*
+ * The Layer III formula for requantization and scaling is defined by
+ * section 2.4.3.4.7.1 of ISO/IEC 11172-3, as follows:
+ *
+ *   long blocks:
+ *   xr[i] = sign(is[i]) * abs(is[i])^(4/3) *
+ *           2^((1/4) * (global_gain - 210)) *
+ *           2^-(scalefac_multiplier *
+ *               (scalefac_l[sfb] + preflag * pretab[sfb]))
+ *
+ *   short blocks:
+ *   xr[i] = sign(is[i]) * abs(is[i])^(4/3) *
+ *           2^((1/4) * (global_gain - 210 - 8 * subblock_gain[w])) *
+ *           2^-(scalefac_multiplier * scalefac_s[sfb][w])
+ *
+ *   where:
+ *   scalefac_multiplier = (scalefac_scale + 1) / 2
+ *
+ * The routines III_exponents() and III_requantize() facilitate this
+ * calculation.
+ */
+
+/*
+ * NAME:	III_exponents()
+ * DESCRIPTION:	calculate scalefactor exponents
+ */
+static
+void III_exponents(struct channel const *channel,
+		   unsigned char const *sfbwidth, signed int exponents[39])
+{
+  signed int gain;
+  unsigned int scalefac_multiplier, sfbi;
+
+  gain = (signed int) channel->global_gain - 210;
+  scalefac_multiplier = (channel->flags & scalefac_scale) ? 2 : 1;
+
+  if (channel->block_type == 2) {
+    unsigned int l;
+    signed int gain0, gain1, gain2;
+
+    sfbi = l = 0;
+
+    if (channel->flags & mixed_block_flag) {
+      unsigned int premask;
+
+      premask = (channel->flags & preflag) ? ~0 : 0;
+
+      /* long block subbands 0-1 */
+
+      while (l < 36) {
+	exponents[sfbi] = gain -
+	  (signed int) ((channel->scalefac[sfbi] + (pretab[sfbi] & premask)) <<
+			scalefac_multiplier);
+
+	l += sfbwidth[sfbi++];
+      }
+    }
+
+    /* this is probably wrong for 8000 Hz short/mixed blocks */
+
+    gain0 = gain - 8 * (signed int) channel->subblock_gain[0];
+    gain1 = gain - 8 * (signed int) channel->subblock_gain[1];
+    gain2 = gain - 8 * (signed int) channel->subblock_gain[2];
+
+    while (l < 576) {
+      exponents[sfbi + 0] = gain0 -
+	(signed int) (channel->scalefac[sfbi + 0] << scalefac_multiplier);
+      exponents[sfbi + 1] = gain1 -
+	(signed int) (channel->scalefac[sfbi + 1] << scalefac_multiplier);
+      exponents[sfbi + 2] = gain2 -
+	(signed int) (channel->scalefac[sfbi + 2] << scalefac_multiplier);
+
+      l    += 3 * sfbwidth[sfbi];
+      sfbi += 3;
+    }
+  }
+  else {  /* channel->block_type != 2 */
+    if (channel->flags & preflag) {
+      for (sfbi = 0; sfbi < 22; ++sfbi) {
+	exponents[sfbi] = gain -
+	  (signed int) ((channel->scalefac[sfbi] + pretab[sfbi]) <<
+			scalefac_multiplier);
+      }
+    }
+    else {
+      for (sfbi = 0; sfbi < 22; ++sfbi) {
+	exponents[sfbi] = gain -
+	  (signed int) (channel->scalefac[sfbi] << scalefac_multiplier);
+      }
+    }
+  }
+}
+
+/*
+ * NAME:	III_requantize()
+ * DESCRIPTION:	requantize one (positive) value
+ */
+static
+mad_fixed_t III_requantize(unsigned int value, signed int exp)
+{
+  mad_fixed_t requantized;
+  signed int frac;
+  struct fixedfloat const *power;
+
+  frac = exp % 4;  /* assumes sign(frac) == sign(exp) */
+  exp /= 4;
+
+  power = &rq_table[value];
+  requantized = power->mantissa;
+  exp += power->exponent;
+
+  if (exp < 0) {
+    if (-exp >= sizeof(mad_fixed_t) * CHAR_BIT) {
+      /* underflow */
+      requantized = 0;
+    }
+    else {
+      requantized += 1L << (-exp - 1);
+      requantized >>= -exp;
+    }
+  }
+  else {
+    if (exp >= 5) {
+      /* overflow */
+# if defined(DEBUG)
+      fprintf(stderr, "requantize overflow (%f * 2^%d)\n",
+	      mad_f_todouble(requantized), exp);
+# endif
+      requantized = MAD_F_MAX;
+    }
+    else
+      requantized <<= exp;
+  }
+
+  return frac ? mad_f_mul(requantized, root_table[3 + frac]) : requantized;
+}
+
+/* we must take care that sz >= bits and sz < sizeof(long) lest bits == 0 */
+# define MASK(cache, sz, bits)	\
+    (((cache) >> ((sz) - (bits))) & ((1 << (bits)) - 1))
+# define MASK1BIT(cache, sz)  \
+    ((cache) & (1 << ((sz) - 1)))
+
+/*
+ * NAME:	III_huffdecode()
+ * DESCRIPTION:	decode Huffman code words of one channel of one granule
+ */
+static
+enum mad_error III_huffdecode(struct mad_bitptr *ptr, mad_fixed_t xr[576],
+			      struct channel *channel,
+			      unsigned char const *sfbwidth,
+			      unsigned int part2_length)
+{
+  signed int exponents[39], exp;
+  signed int const *expptr;
+  struct mad_bitptr peek;
+  signed int bits_left, cachesz;
+  register mad_fixed_t *xrptr;
+  mad_fixed_t const *sfbound;
+  register unsigned long bitcache;
+
+  bits_left = (signed) channel->part2_3_length - (signed) part2_length;
+  if (bits_left < 0)
+    return MAD_ERROR_BADPART3LEN;
+
+  III_exponents(channel, sfbwidth, exponents);
+
+  peek = *ptr;
+  mad_bit_skip(ptr, bits_left);
+
+  /* align bit reads to byte boundaries */
+  cachesz  = mad_bit_bitsleft(&peek);
+  cachesz += ((32 - 1 - 24) + (24 - cachesz)) & ~7;
+
+  bitcache   = mad_bit_read(&peek, cachesz);
+  bits_left -= cachesz;
+
+  xrptr = &xr[0];
+
+  /* big_values */
+  {
+    unsigned int region, rcount;
+    struct hufftable const *entry;
+    union huffpair const *table;
+    unsigned int linbits, startbits, big_values, reqhits;
+    mad_fixed_t reqcache[16];
+
+    sfbound = xrptr + *sfbwidth++;
+    rcount  = channel->region0_count + 1;
+
+    entry     = &mad_huff_pair_table[channel->table_select[region = 0]];
+    table     = entry->table;
+    linbits   = entry->linbits;
+    startbits = entry->startbits;
+
+    if (table == 0)
+      return MAD_ERROR_BADHUFFTABLE;
+
+    expptr  = &exponents[0];
+    exp     = *expptr++;
+    reqhits = 0;
+
+    big_values = channel->big_values;
+
+    while (big_values-- && cachesz + bits_left > 0) {
+      union huffpair const *pair;
+      unsigned int clumpsz, value;
+      register mad_fixed_t requantized;
+
+      if (xrptr == sfbound) {
+	sfbound += *sfbwidth++;
+
+	/* change table if region boundary */
+
+	if (--rcount == 0) {
+	  if (region == 0)
+	    rcount = channel->region1_count + 1;
+	  else
+	    rcount = 0;  /* all remaining */
+
+	  entry     = &mad_huff_pair_table[channel->table_select[++region]];
+	  table     = entry->table;
+	  linbits   = entry->linbits;
+	  startbits = entry->startbits;
+
+	  if (table == 0)
+	    return MAD_ERROR_BADHUFFTABLE;
+	}
+
+	if (exp != *expptr) {
+	  exp = *expptr;
+	  reqhits = 0;
+	}
+
+	++expptr;
+      }
+
+      if (cachesz < 21) {
+	unsigned int bits;
+
+	bits       = ((32 - 1 - 21) + (21 - cachesz)) & ~7;
+	bitcache   = (bitcache << bits) | mad_bit_read(&peek, bits);
+	cachesz   += bits;
+	bits_left -= bits;
+      }
+
+      /* hcod (0..19) */
+
+      clumpsz = startbits;
+      pair    = &table[MASK(bitcache, cachesz, clumpsz)];
+
+      while (!pair->final) {
+	cachesz -= clumpsz;
+
+	clumpsz = pair->ptr.bits;
+	pair    = &table[pair->ptr.offset + MASK(bitcache, cachesz, clumpsz)];
+      }
+
+      cachesz -= pair->value.hlen;
+
+      if (linbits) {
+	/* x (0..14) */
+
+	value = pair->value.x;
+
+	switch (value) {
+	case 0:
+	  xrptr[0] = 0;
+	  break;
+
+	case 15:
+	  if (cachesz < linbits + 2) {
+	    bitcache   = (bitcache << 16) | mad_bit_read(&peek, 16);
+	    cachesz   += 16;
+	    bits_left -= 16;
+	  }
+
+	  value += MASK(bitcache, cachesz, linbits);
+	  cachesz -= linbits;
+
+	  requantized = III_requantize(value, exp);
+	  goto x_final;
+
+	default:
+	  if (reqhits & (1 << value))
+	    requantized = reqcache[value];
+	  else {
+	    reqhits |= (1 << value);
+	    requantized = reqcache[value] = III_requantize(value, exp);
+	  }
+
+	x_final:
+	  xrptr[0] = MASK1BIT(bitcache, cachesz--) ?
+	    -requantized : requantized;
+	}
+
+	/* y (0..14) */
+
+	value = pair->value.y;
+
+	switch (value) {
+	case 0:
+	  xrptr[1] = 0;
+	  break;
+
+	case 15:
+	  if (cachesz < linbits + 1) {
+	    bitcache   = (bitcache << 16) | mad_bit_read(&peek, 16);
+	    cachesz   += 16;
+	    bits_left -= 16;
+	  }
+
+	  value += MASK(bitcache, cachesz, linbits);
+	  cachesz -= linbits;
+
+	  requantized = III_requantize(value, exp);
+	  goto y_final;
+
+	default:
+	  if (reqhits & (1 << value))
+	    requantized = reqcache[value];
+	  else {
+	    reqhits |= (1 << value);
+	    requantized = reqcache[value] = III_requantize(value, exp);
+	  }
+
+	y_final:
+	  xrptr[1] = MASK1BIT(bitcache, cachesz--) ?
+	    -requantized : requantized;
+	}
+      }
+      else {
+	/* x (0..1) */
+
+	value = pair->value.x;
+
+	if (value == 0)
+	  xrptr[0] = 0;
+	else {
+	  if (reqhits & (1 << value))
+	    requantized = reqcache[value];
+	  else {
+	    reqhits |= (1 << value);
+	    requantized = reqcache[value] = III_requantize(value, exp);
+	  }
+
+	  xrptr[0] = MASK1BIT(bitcache, cachesz--) ?
+	    -requantized : requantized;
+	}
+
+	/* y (0..1) */
+
+	value = pair->value.y;
+
+	if (value == 0)
+	  xrptr[1] = 0;
+	else {
+	  if (reqhits & (1 << value))
+	    requantized = reqcache[value];
+	  else {
+	    reqhits |= (1 << value);
+	    requantized = reqcache[value] = III_requantize(value, exp);
+	  }
+
+	  xrptr[1] = MASK1BIT(bitcache, cachesz--) ?
+	    -requantized : requantized;
+	}
+      }
+
+      xrptr += 2;
+    }
+  }
+
+  if (cachesz + bits_left < 0)
+    return MAD_ERROR_BADHUFFDATA;  /* big_values overrun */
+
+  /* count1 */
+  {
+    union huffquad const *table;
+    register mad_fixed_t requantized;
+
+    table = mad_huff_quad_table[channel->flags & count1table_select];
+
+    requantized = III_requantize(1, exp);
+
+    while (cachesz + bits_left > 0 && xrptr <= &xr[572]) {
+      union huffquad const *quad;
+
+      /* hcod (1..6) */
+
+      if (cachesz < 10) {
+	bitcache   = (bitcache << 16) | mad_bit_read(&peek, 16);
+	cachesz   += 16;
+	bits_left -= 16;
+      }
+
+      quad = &table[MASK(bitcache, cachesz, 4)];
+
+      /* quad tables guaranteed to have at most one extra lookup */
+      if (!quad->final) {
+	cachesz -= 4;
+
+	quad = &table[quad->ptr.offset +
+		      MASK(bitcache, cachesz, quad->ptr.bits)];
+      }
+
+      cachesz -= quad->value.hlen;
+
+      if (xrptr == sfbound) {
+	sfbound += *sfbwidth++;
+
+	if (exp != *expptr) {
+	  exp = *expptr;
+	  requantized = III_requantize(1, exp);
+	}
+
+	++expptr;
+      }
+
+      /* v (0..1) */
+
+      xrptr[0] = quad->value.v ?
+	(MASK1BIT(bitcache, cachesz--) ? -requantized : requantized) : 0;
+
+      /* w (0..1) */
+
+      xrptr[1] = quad->value.w ?
+	(MASK1BIT(bitcache, cachesz--) ? -requantized : requantized) : 0;
+
+      xrptr += 2;
+
+      if (xrptr == sfbound) {
+	sfbound += *sfbwidth++;
+
+	if (exp != *expptr) {
+	  exp = *expptr;
+	  requantized = III_requantize(1, exp);
+	}
+
+	++expptr;
+      }
+
+      /* x (0..1) */
+
+      xrptr[0] = quad->value.x ?
+	(MASK1BIT(bitcache, cachesz--) ? -requantized : requantized) : 0;
+
+      /* y (0..1) */
+
+      xrptr[1] = quad->value.y ?
+	(MASK1BIT(bitcache, cachesz--) ? -requantized : requantized) : 0;
+
+      xrptr += 2;
+    }
+
+    if (cachesz + bits_left < 0) {
+# if 0 && defined(DEBUG)
+      fprintf(stderr, "huffman count1 overrun (%d bits)\n",
+	      -(cachesz + bits_left));
+# endif
+
+      /* technically the bitstream is misformatted, but apparently
+	 some encoders are just a bit sloppy with stuffing bits */
+
+      xrptr -= 4;
+    }
+  }
+
+  assert(-bits_left <= MAD_BUFFER_GUARD * CHAR_BIT);
+
+# if 0 && defined(DEBUG)
+  if (bits_left < 0)
+    fprintf(stderr, "read %d bits too many\n", -bits_left);
+  else if (cachesz + bits_left > 0)
+    fprintf(stderr, "%d stuffing bits\n", cachesz + bits_left);
+# endif
+
+  /* rzero */
+  while (xrptr < &xr[576]) {
+    xrptr[0] = 0;
+    xrptr[1] = 0;
+
+    xrptr += 2;
+  }
+
+  return MAD_ERROR_NONE;
+}
+
+# undef MASK
+# undef MASK1BIT
+
+/*
+ * NAME:	III_reorder()
+ * DESCRIPTION:	reorder frequency lines of a short block into subband order
+ */
+static
+void III_reorder(mad_fixed_t xr[576], struct channel const *channel,
+		 unsigned char const sfbwidth[39])
+{
+  mad_fixed_t tmp[32][3][6];
+  unsigned int sb, l, f, w, sbw[3], sw[3];
+
+  /* this is probably wrong for 8000 Hz mixed blocks */
+
+  sb = 0;
+  if (channel->flags & mixed_block_flag) {
+    sb = 2;
+
+    l = 0;
+    while (l < 36)
+      l += *sfbwidth++;
+  }
+
+  for (w = 0; w < 3; ++w) {
+    sbw[w] = sb;
+    sw[w]  = 0;
+  }
+
+  f = *sfbwidth++;
+  w = 0;
+
+  for (l = 18 * sb; l < 576; ++l) {
+    if (f-- == 0) {
+      f = *sfbwidth++ - 1;
+      w = (w + 1) % 3;
+    }
+
+    tmp[sbw[w]][w][sw[w]++] = xr[l];
+
+    if (sw[w] == 6) {
+      sw[w] = 0;
+      ++sbw[w];
+    }
+  }
+
+  memcpy(&xr[18 * sb], &tmp[sb], (576 - 18 * sb) * sizeof(mad_fixed_t));
+}
+
+/*
+ * NAME:	III_stereo()
+ * DESCRIPTION:	perform joint stereo processing on a granule
+ */
+static
+enum mad_error III_stereo(mad_fixed_t xr[2][576],
+			  struct granule const *granule,
+			  struct mad_header *header,
+			  unsigned char const *sfbwidth)
+{
+  short modes[39];
+  unsigned int sfbi, l, n, i;
+
+  if (granule->ch[0].block_type !=
+      granule->ch[1].block_type ||
+      (granule->ch[0].flags & mixed_block_flag) !=
+      (granule->ch[1].flags & mixed_block_flag))
+    return MAD_ERROR_BADSTEREO;
+
+  for (i = 0; i < 39; ++i)
+    modes[i] = header->mode_extension;
+
+  /* intensity stereo */
+
+  if (header->mode_extension & I_STEREO) {
+    struct channel const *right_ch = &granule->ch[1];
+    mad_fixed_t const *right_xr = xr[1];
+    unsigned int is_pos;
+
+    header->flags |= MAD_FLAG_I_STEREO;
+
+    /* first determine which scalefactor bands are to be processed */
+
+    if (right_ch->block_type == 2) {
+      unsigned int lower, start, max, bound[3], w;
+
+      lower = start = max = bound[0] = bound[1] = bound[2] = 0;
+
+      sfbi = l = 0;
+
+      if (right_ch->flags & mixed_block_flag) {
+	while (l < 36) {
+	  n = sfbwidth[sfbi++];
+
+	  for (i = 0; i < n; ++i) {
+	    if (right_xr[i]) {
+	      lower = sfbi;
+	      break;
+	    }
+	  }
+
+	  right_xr += n;
+	  l += n;
+	}
+
+	start = sfbi;
+      }
+
+      w = 0;
+      while (l < 576) {
+	n = sfbwidth[sfbi++];
+
+	for (i = 0; i < n; ++i) {
+	  if (right_xr[i]) {
+	    max = bound[w] = sfbi;
+	    break;
+	  }
+	}
+
+	right_xr += n;
+	l += n;
+	w = (w + 1) % 3;
+      }
+
+      if (max)
+	lower = start;
+
+      /* long blocks */
+
+      for (i = 0; i < lower; ++i)
+	modes[i] = header->mode_extension & ~I_STEREO;
+
+      /* short blocks */
+
+      w = 0;
+      for (i = start; i < max; ++i) {
+	if (i < bound[w])
+	  modes[i] = header->mode_extension & ~I_STEREO;
+
+	w = (w + 1) % 3;
+      }
+    }
+    else {  /* right_ch->block_type != 2 */
+      unsigned int bound;
+
+      bound = 0;
+      for (sfbi = l = 0; l < 576; l += n) {
+	n = sfbwidth[sfbi++];
+
+	for (i = 0; i < n; ++i) {
+	  if (right_xr[i]) {
+	    bound = sfbi;
+	    break;
+	  }
+	}
+
+	right_xr += n;
+      }
+
+      for (i = 0; i < bound; ++i)
+	modes[i] = header->mode_extension & ~I_STEREO;
+    }
+
+    /* now do the actual processing */
+
+    if (header->flags & MAD_FLAG_LSF_EXT) {
+      unsigned char const *illegal_pos = granule[1].ch[1].scalefac;
+      mad_fixed_t const *lsf_scale;
+
+      /* intensity_scale */
+      lsf_scale = is_lsf_table[right_ch->scalefac_compress & 0x1];
+
+      for (sfbi = l = 0; l < 576; ++sfbi, l += n) {
+	n = sfbwidth[sfbi];
+
+	if (!(modes[sfbi] & I_STEREO))
+	  continue;
+
+	if (illegal_pos[sfbi]) {
+	  modes[sfbi] &= ~I_STEREO;
+	  continue;
+	}
+
+	is_pos = right_ch->scalefac[sfbi];
+
+	for (i = 0; i < n; ++i) {
+	  register mad_fixed_t left;
+
+	  left = xr[0][l + i];
+
+	  if (is_pos == 0)
+	    xr[1][l + i] = left;
+	  else {
+	    register mad_fixed_t opposite;
+
+	    opposite = mad_f_mul(left, lsf_scale[(is_pos - 1) / 2]);
+
+	    if (is_pos & 1) {
+	      xr[0][l + i] = opposite;
+	      xr[1][l + i] = left;
+	    }
+	    else
+	      xr[1][l + i] = opposite;
+	  }
+	}
+      }
+    }
+    else {  /* !(header->flags & MAD_FLAG_LSF_EXT) */
+      for (sfbi = l = 0; l < 576; ++sfbi, l += n) {
+	n = sfbwidth[sfbi];
+
+	if (!(modes[sfbi] & I_STEREO))
+	  continue;
+
+	is_pos = right_ch->scalefac[sfbi];
+
+	if (is_pos >= 7) {  /* illegal intensity position */
+	  modes[sfbi] &= ~I_STEREO;
+	  continue;
+	}
+
+	for (i = 0; i < n; ++i) {
+	  register mad_fixed_t left;
+
+	  left = xr[0][l + i];
+
+	  xr[0][l + i] = mad_f_mul(left, is_table[    is_pos]);
+	  xr[1][l + i] = mad_f_mul(left, is_table[6 - is_pos]);
+	}
+      }
+    }
+  }
+
+  /* middle/side stereo */
+
+  if (header->mode_extension & MS_STEREO) {
+    register mad_fixed_t invsqrt2;
+
+    header->flags |= MAD_FLAG_MS_STEREO;
+
+    invsqrt2 = root_table[3 + -2];
+
+    for (sfbi = l = 0; l < 576; ++sfbi, l += n) {
+      n = sfbwidth[sfbi];
+
+      if (modes[sfbi] != MS_STEREO)
+	continue;
+
+      for (i = 0; i < n; ++i) {
+	register mad_fixed_t m, s;
+
+	m = xr[0][l + i];
+	s = xr[1][l + i];
+
+	xr[0][l + i] = mad_f_mul(m + s, invsqrt2);  /* l = (m + s) / sqrt(2) */
+	xr[1][l + i] = mad_f_mul(m - s, invsqrt2);  /* r = (m - s) / sqrt(2) */
+      }
+    }
+  }
+
+  return MAD_ERROR_NONE;
+}
+
+/*
+ * NAME:	III_aliasreduce()
+ * DESCRIPTION:	perform frequency line alias reduction
+ */
+static
+void III_aliasreduce(mad_fixed_t xr[576], int lines)
+{
+  mad_fixed_t const *bound;
+  int i;
+
+  bound = &xr[lines];
+  for (xr += 18; xr < bound; xr += 18) {
+    for (i = 0; i < 8; ++i) {
+      register mad_fixed_t a, b;
+      register mad_fixed64hi_t hi;
+      register mad_fixed64lo_t lo;
+
+      a = xr[-1 - i];
+      b = xr[     i];
+
+# if defined(ASO_ZEROCHECK)
+      if (a | b) {
+# endif
+	MAD_F_ML0(hi, lo,  a, cs[i]);
+	MAD_F_MLA(hi, lo, -b, ca[i]);
+
+	xr[-1 - i] = MAD_F_MLZ(hi, lo);
+
+	MAD_F_ML0(hi, lo,  b, cs[i]);
+	MAD_F_MLA(hi, lo,  a, ca[i]);
+
+	xr[     i] = MAD_F_MLZ(hi, lo);
+# if defined(ASO_ZEROCHECK)
+      }
+# endif
+    }
+  }
+}
+
+# if defined(ASO_IMDCT)
+void III_imdct_l(mad_fixed_t const [18], mad_fixed_t [36], unsigned int);
+# else
+/*
+ * NAME:	imdct36
+ * DESCRIPTION:	perform X[18]->x[36] IMDCT
+ */
+static inline
+void imdct36(mad_fixed_t const X[18], mad_fixed_t x[36])
+{
+  mad_fixed_t t0, t1, t2,  t3,  t4,  t5,  t6,  t7;
+  mad_fixed_t t8, t9, t10, t11, t12, t13, t14, t15;
+  register mad_fixed64hi_t hi;
+  register mad_fixed64lo_t lo;
+
+  MAD_F_ML0(hi, lo, X[4],  MAD_F(0x0ec835e8));
+  MAD_F_MLA(hi, lo, X[13], MAD_F(0x061f78aa));
+
+  t6 = MAD_F_MLZ(hi, lo);
+
+  MAD_F_MLA(hi, lo, (t14 = X[1] - X[10]), -MAD_F(0x061f78aa));
+  MAD_F_MLA(hi, lo, (t15 = X[7] + X[16]), -MAD_F(0x0ec835e8));
+
+  t0 = MAD_F_MLZ(hi, lo);
+
+  MAD_F_MLA(hi, lo, (t8  = X[0] - X[11] - X[12]),  MAD_F(0x0216a2a2));
+  MAD_F_MLA(hi, lo, (t9  = X[2] - X[9]  - X[14]),  MAD_F(0x09bd7ca0));
+  MAD_F_MLA(hi, lo, (t10 = X[3] - X[8]  - X[15]), -MAD_F(0x0cb19346));
+  MAD_F_MLA(hi, lo, (t11 = X[5] - X[6]  - X[17]), -MAD_F(0x0fdcf549));
+
+  x[7]  = MAD_F_MLZ(hi, lo);
+  x[10] = -x[7];
+
+  MAD_F_ML0(hi, lo, t8,  -MAD_F(0x0cb19346));
+  MAD_F_MLA(hi, lo, t9,   MAD_F(0x0fdcf549));
+  MAD_F_MLA(hi, lo, t10,  MAD_F(0x0216a2a2));
+  MAD_F_MLA(hi, lo, t11, -MAD_F(0x09bd7ca0));
+
+  x[19] = x[34] = MAD_F_MLZ(hi, lo) - t0;
+
+  t12 = X[0] - X[3] + X[8] - X[11] - X[12] + X[15];
+  t13 = X[2] + X[5] - X[6] - X[9]  - X[14] - X[17];
+
+  MAD_F_ML0(hi, lo, t12, -MAD_F(0x0ec835e8));
+  MAD_F_MLA(hi, lo, t13,  MAD_F(0x061f78aa));
+
+  x[22] = x[31] = MAD_F_MLZ(hi, lo) + t0;
+
+  MAD_F_ML0(hi, lo, X[1],  -MAD_F(0x09bd7ca0));
+  MAD_F_MLA(hi, lo, X[7],   MAD_F(0x0216a2a2));
+  MAD_F_MLA(hi, lo, X[10], -MAD_F(0x0fdcf549));
+  MAD_F_MLA(hi, lo, X[16],  MAD_F(0x0cb19346));
+
+  t1 = MAD_F_MLZ(hi, lo) + t6;
+
+  MAD_F_ML0(hi, lo, X[0],   MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[3],  -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[5],  -MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[6],   MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[8],  -MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[9],   MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[11],  MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[15], -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x0f9ee890));
+
+  x[6]  = MAD_F_MLZ(hi, lo) + t1;
+  x[11] = -x[6];
+
+  MAD_F_ML0(hi, lo, X[0],  -MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[2],  -MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[3],   MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[5],   MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[6],   MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[8],  -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[9],  -MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[15],  MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[17],  MAD_F(0x04cfb0e2));
+
+  x[23] = x[30] = MAD_F_MLZ(hi, lo) + t1;
+
+  MAD_F_ML0(hi, lo, X[0],  -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[3],  -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[5],   MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[6],   MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[8],  -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[9],  -MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[11],  MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[15],  MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x0acf37ad));
+
+  x[18] = x[35] = MAD_F_MLZ(hi, lo) - t1;
+
+  MAD_F_ML0(hi, lo, X[4],   MAD_F(0x061f78aa));
+  MAD_F_MLA(hi, lo, X[13], -MAD_F(0x0ec835e8));
+
+  t7 = MAD_F_MLZ(hi, lo);
+
+  MAD_F_MLA(hi, lo, X[1],  -MAD_F(0x0cb19346));
+  MAD_F_MLA(hi, lo, X[7],   MAD_F(0x0fdcf549));
+  MAD_F_MLA(hi, lo, X[10],  MAD_F(0x0216a2a2));
+  MAD_F_MLA(hi, lo, X[16], -MAD_F(0x09bd7ca0));
+
+  t2 = MAD_F_MLZ(hi, lo);
+
+  MAD_F_MLA(hi, lo, X[0],   MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[3],  -MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[5],   MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[6],  -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[8],  -MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[9],   MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[12],  MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[15],  MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[17],  MAD_F(0x0f426cb5));
+
+  x[5]  = MAD_F_MLZ(hi, lo);
+  x[12] = -x[5];
+
+  MAD_F_ML0(hi, lo, X[0],   MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[2],  -MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[3],   MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[5],  -MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[6],  -MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[8],   MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[9],  -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[11],  MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[15],  MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x0bcbe352));
+
+  x[0]  = MAD_F_MLZ(hi, lo) + t2;
+  x[17] = -x[0];
+
+  MAD_F_ML0(hi, lo, X[0],  -MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[2],  -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[3],  -MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[5],   MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[6],   MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[8],   MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[9],   MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[14], -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[15], -MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x03768962));
+
+  x[24] = x[29] = MAD_F_MLZ(hi, lo) + t2;
+
+  MAD_F_ML0(hi, lo, X[1],  -MAD_F(0x0216a2a2));
+  MAD_F_MLA(hi, lo, X[7],  -MAD_F(0x09bd7ca0));
+  MAD_F_MLA(hi, lo, X[10],  MAD_F(0x0cb19346));
+  MAD_F_MLA(hi, lo, X[16],  MAD_F(0x0fdcf549));
+
+  t3 = MAD_F_MLZ(hi, lo) + t7;
+
+  MAD_F_ML0(hi, lo, X[0],   MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[3],  -MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[5],  -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[6],   MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[8],   MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[9],  -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[12],  MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[15], -MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x0ffc19fd));
+
+  x[8] = MAD_F_MLZ(hi, lo) + t3;
+  x[9] = -x[8];
+
+  MAD_F_ML0(hi, lo, X[0],  -MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[3],   MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[5],  -MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[6],  -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[8],   MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[9],   MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[14], -MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[15],  MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[17],  MAD_F(0x07635284));
+
+  x[21] = x[32] = MAD_F_MLZ(hi, lo) + t3;
+
+  MAD_F_ML0(hi, lo, X[0],  -MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[3],   MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[5],  -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[6],  -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[8],   MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[9],   MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[12],  MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[15], -MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x0898c779));
+
+  x[20] = x[33] = MAD_F_MLZ(hi, lo) - t3;
+
+  MAD_F_ML0(hi, lo, t14, -MAD_F(0x0ec835e8));
+  MAD_F_MLA(hi, lo, t15,  MAD_F(0x061f78aa));
+
+  t4 = MAD_F_MLZ(hi, lo) - t7;
+
+  MAD_F_ML0(hi, lo, t12, MAD_F(0x061f78aa));
+  MAD_F_MLA(hi, lo, t13, MAD_F(0x0ec835e8));
+
+  x[4]  = MAD_F_MLZ(hi, lo) + t4;
+  x[13] = -x[4];
+
+  MAD_F_ML0(hi, lo, t8,   MAD_F(0x09bd7ca0));
+  MAD_F_MLA(hi, lo, t9,  -MAD_F(0x0216a2a2));
+  MAD_F_MLA(hi, lo, t10,  MAD_F(0x0fdcf549));
+  MAD_F_MLA(hi, lo, t11, -MAD_F(0x0cb19346));
+
+  x[1]  = MAD_F_MLZ(hi, lo) + t4;
+  x[16] = -x[1];
+
+  MAD_F_ML0(hi, lo, t8,  -MAD_F(0x0fdcf549));
+  MAD_F_MLA(hi, lo, t9,  -MAD_F(0x0cb19346));
+  MAD_F_MLA(hi, lo, t10, -MAD_F(0x09bd7ca0));
+  MAD_F_MLA(hi, lo, t11, -MAD_F(0x0216a2a2));
+
+  x[25] = x[28] = MAD_F_MLZ(hi, lo) + t4;
+
+  MAD_F_ML0(hi, lo, X[1],  -MAD_F(0x0fdcf549));
+  MAD_F_MLA(hi, lo, X[7],  -MAD_F(0x0cb19346));
+  MAD_F_MLA(hi, lo, X[10], -MAD_F(0x09bd7ca0));
+  MAD_F_MLA(hi, lo, X[16], -MAD_F(0x0216a2a2));
+
+  t5 = MAD_F_MLZ(hi, lo) - t6;
+
+  MAD_F_ML0(hi, lo, X[0],   MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[3],   MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[5],   MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[6],   MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[8],  -MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[9],   MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[12],  MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[14], -MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[15],  MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x0d7e8807));
+
+  x[2]  = MAD_F_MLZ(hi, lo) + t5;
+  x[15] = -x[2];
+
+  MAD_F_ML0(hi, lo, X[0],   MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[2],   MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[3],   MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[5],   MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[6],  -MAD_F(0x00b2aa3e));
+  MAD_F_MLA(hi, lo, X[8],   MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[9],  -MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[11],  MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[14],  MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[15], -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[17],  MAD_F(0x0e313245));
+
+  x[3]  = MAD_F_MLZ(hi, lo) + t5;
+  x[14] = -x[3];
+
+  MAD_F_ML0(hi, lo, X[0],  -MAD_F(0x0ffc19fd));
+  MAD_F_MLA(hi, lo, X[2],  -MAD_F(0x0f9ee890));
+  MAD_F_MLA(hi, lo, X[3],  -MAD_F(0x0f426cb5));
+  MAD_F_MLA(hi, lo, X[5],  -MAD_F(0x0e313245));
+  MAD_F_MLA(hi, lo, X[6],  -MAD_F(0x0d7e8807));
+  MAD_F_MLA(hi, lo, X[8],  -MAD_F(0x0bcbe352));
+  MAD_F_MLA(hi, lo, X[9],  -MAD_F(0x0acf37ad));
+  MAD_F_MLA(hi, lo, X[11], -MAD_F(0x0898c779));
+  MAD_F_MLA(hi, lo, X[12], -MAD_F(0x07635284));
+  MAD_F_MLA(hi, lo, X[14], -MAD_F(0x04cfb0e2));
+  MAD_F_MLA(hi, lo, X[15], -MAD_F(0x03768962));
+  MAD_F_MLA(hi, lo, X[17], -MAD_F(0x00b2aa3e));
+
+  x[26] = x[27] = MAD_F_MLZ(hi, lo) + t5;
+}
+
+/*
+ * NAME:	III_imdct_l()
+ * DESCRIPTION:	perform IMDCT and windowing for long blocks
+ */
+static
+void III_imdct_l(mad_fixed_t const X[18], mad_fixed_t z[36],
+		 unsigned int block_type)
+{
+  unsigned int i;
+
+  /* IMDCT */
+
+  imdct36(X, z);
+
+  /* windowing */
+
+  switch (block_type) {
+  case 0:  /* normal window */
+# if defined(ASO_INTERLEAVE1)
+    {
+      register mad_fixed_t tmp1, tmp2;
+
+      tmp1 = window_l[0];
+      tmp2 = window_l[1];
+
+      for (i = 0; i < 34; i += 2) {
+	z[i + 0] = mad_f_mul(z[i + 0], tmp1);
+	tmp1 = window_l[i + 2];
+	z[i + 1] = mad_f_mul(z[i + 1], tmp2);
+	tmp2 = window_l[i + 3];
+      }
+
+      z[34] = mad_f_mul(z[34], tmp1);
+      z[35] = mad_f_mul(z[35], tmp2);
+    }
+# elif defined(ASO_INTERLEAVE2)
+    {
+      register mad_fixed_t tmp1, tmp2;
+
+      tmp1 = z[0];
+      tmp2 = window_l[0];
+
+      for (i = 0; i < 35; ++i) {
+	z[i] = mad_f_mul(tmp1, tmp2);
+	tmp1 = z[i + 1];
+	tmp2 = window_l[i + 1];
+      }
+
+      z[35] = mad_f_mul(tmp1, tmp2);
+    }
+# elif 1
+    for (i = 0; i < 36; i += 4) {
+      z[i + 0] = mad_f_mul(z[i + 0], window_l[i + 0]);
+      z[i + 1] = mad_f_mul(z[i + 1], window_l[i + 1]);
+      z[i + 2] = mad_f_mul(z[i + 2], window_l[i + 2]);
+      z[i + 3] = mad_f_mul(z[i + 3], window_l[i + 3]);
+    }
+# else
+    for (i =  0; i < 36; ++i) z[i] = mad_f_mul(z[i], window_l[i]);
+# endif
+    break;
+
+  case 1:  /* start block */
+    for (i =  0; i < 18; ++i) z[i] = mad_f_mul(z[i], window_l[i]);
+    /*  (i = 18; i < 24; ++i) z[i] unchanged */
+    for (i = 24; i < 30; ++i) z[i] = mad_f_mul(z[i], window_s[i - 18]);
+    for (i = 30; i < 36; ++i) z[i] = 0;
+    break;
+
+  case 3:  /* stop block */
+    for (i =  0; i <  6; ++i) z[i] = 0;
+    for (i =  6; i < 12; ++i) z[i] = mad_f_mul(z[i], window_s[i - 6]);
+    /*  (i = 12; i < 18; ++i) z[i] unchanged */
+    for (i = 18; i < 36; ++i) z[i] = mad_f_mul(z[i], window_l[i]);
+    break;
+  }
+}
+# endif  /* ASO_IMDCT */
+
+/*
+ * NAME:	III_imdct_s()
+ * DESCRIPTION:	perform IMDCT and windowing for short blocks
+ */
+static
+void III_imdct_s(mad_fixed_t const X[18], mad_fixed_t z[36])
+{
+  mad_fixed_t y[36], *yptr;
+  mad_fixed_t const *wptr;
+  int w, i;
+  register mad_fixed64hi_t hi;
+  register mad_fixed64lo_t lo;
+
+  /* IMDCT */
+
+  yptr = &y[0];
+
+  for (w = 0; w < 3; ++w) {
+    register mad_fixed_t const (*s)[6];
+
+    s = imdct_s;
+
+    for (i = 0; i < 3; ++i) {
+      MAD_F_ML0(hi, lo, X[0], (*s)[0]);
+      MAD_F_MLA(hi, lo, X[1], (*s)[1]);
+      MAD_F_MLA(hi, lo, X[2], (*s)[2]);
+      MAD_F_MLA(hi, lo, X[3], (*s)[3]);
+      MAD_F_MLA(hi, lo, X[4], (*s)[4]);
+      MAD_F_MLA(hi, lo, X[5], (*s)[5]);
+
+      yptr[i + 0] = MAD_F_MLZ(hi, lo);
+      yptr[5 - i] = -yptr[i + 0];
+
+      ++s;
+
+      MAD_F_ML0(hi, lo, X[0], (*s)[0]);
+      MAD_F_MLA(hi, lo, X[1], (*s)[1]);
+      MAD_F_MLA(hi, lo, X[2], (*s)[2]);
+      MAD_F_MLA(hi, lo, X[3], (*s)[3]);
+      MAD_F_MLA(hi, lo, X[4], (*s)[4]);
+      MAD_F_MLA(hi, lo, X[5], (*s)[5]);
+
+      yptr[ i + 6] = MAD_F_MLZ(hi, lo);
+      yptr[11 - i] = yptr[i + 6];
+
+      ++s;
+    }
+
+    yptr += 12;
+    X    += 6;
+  }
+
+  /* windowing, overlapping and concatenation */
+
+  yptr = &y[0];
+  wptr = &window_s[0];
+
+  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));
+    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;
+}