SILK fixes following last codec WG meeting

decoder:
- fixed incorrect scaling of filter states for the smallest quantization
  step sizes
- NLSF2A now limits the prediction gain of LPC filters

encoder:
- increased damping of LTP coefficients in LTP analysis
- increased white noise fraction in noise shaping LPC analysis
- introduced maximum total prediction gain.  Used by Burg's method to
  exit early if prediction gain is exceeded.  This improves packet
  loss robustness and numerical robustness in Burg's method
- Prefiltered signal is now in int32 Q10 domain, from int16 Q0
- Increased max number of iterations in CBR gain control loop from 5 to 6
- Removed useless code from LTP scaling control
- Optimization: smarter LPC loop unrolling
- Switched default win32 compile mode to be floating-point

resampler:
- made resampler have constant delay of 0.75 ms; removed delay
  compensation from silk code.
- removed obsolete table entries (~850 Bytes)
- increased downsampling filter order from 16 to 18/24/36 (depending on
  frequency ratio)
- reoptimized filter coefficients

1 files changed, 48 insertions, 166 deletions

diff --git a/silk/resampler_rom.c b/silk/resampler_rom.c
index 15473e09..9c4750c3 100644
--- a/silk/resampler_rom.c
+++ b/silk/resampler_rom.c
@@ -30,7 +30,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 /* Filter coefficients for IIR/FIR polyphase resampling     *
- * Total size: < 600 Words (1.2 kB)                         */
+ * Total size: 179 Words (358 Bytes)                        */
 
 #include "resampler_private.h"
 
@@ -39,32 +39,46 @@ const opus_int16 silk_resampler_down2_0 = 9872;
 const opus_int16 silk_resampler_down2_1 = 39809 - 65536;
 
 /* Tables for 2x upsampler, high quality */
-const opus_int16 silk_resampler_up2_hq_0[ 2 ] = {  4280, 33727 - 65536 };
-const opus_int16 silk_resampler_up2_hq_1[ 2 ] = { 16295, 54015 - 65536 };
-const opus_int16 silk_resampler_up2_hq_notch[ 4 ] = { 6554,  -3932,   6554,  30573 };
+const opus_int16 silk_resampler_up2_hq_0[ 3 ] = { 1746, 14986, 39083 - 65536 };
+const opus_int16 silk_resampler_up2_hq_1[ 3 ] = { 6854, 25769, 55542 - 65536 };
 
-/* Tables with IIR and FIR coefficients for fractional downsamplers (90 Words) */
-silk_DWORD_ALIGN const opus_int16 silk_Resampler_3_4_COEFS[ 2 + 3 * RESAMPLER_DOWN_ORDER_FIR / 2 ] = {
-    -20253, -13986,
-        86,      7,   -151,    368,   -542,    232,  11041,  21904,
-        39,     90,   -181,    216,    -17,   -877,   6408,  19695,
-         2,    113,   -108,      2,    314,   -977,   2665,  15787,
+/* Matlab code for the notch filter coefficients: */
+/* B = [1, 0.147, 1];  A = [1, 0.107, 0.89]; G = 0.93; freqz(G * B, A, 2^14, 16e3); axis([0, 8000, -10, 1]) */
+/* fprintf('\t%6d, %6d, %6d, %6d\n', round(B(2)*2^16), round(-A(2)*2^16), round((1-A(3))*2^16), round(G*2^15)) */
+const opus_int16 silk_resampler_up2_hq_notch[ 4 ] = { 9634,  -7012,   7209,  30474 };
+
+/* Tables with IIR and FIR coefficients for fractional downsamplers (123 Words) */
+silk_DWORD_ALIGN const opus_int16 silk_Resampler_3_4_COEFS[ 2 + 3 * RESAMPLER_DOWN_ORDER_FIR0 / 2 ] = {
+	-20694, -13867,
+	   -49,     64,     17,   -157,    353,   -496,    163,  11047,  22205,
+	   -39,      6,     91,   -170,    186,     23,   -896,   6336,  19928,
+	   -19,    -36,    102,    -89,    -24,    328,   -951,   2568,  15909,
+};
+
+silk_DWORD_ALIGN const opus_int16 silk_Resampler_2_3_COEFS[ 2 + 2 * RESAMPLER_DOWN_ORDER_FIR0 / 2 ] = {
+	-14457, -14019,
+	    64,    128,   -122,     36,    310,   -768,    584,   9267,  17733,
+	    12,    128,     18,   -142,    288,   -117,   -865,   4123,  14459,
+};
+
+silk_DWORD_ALIGN const opus_int16 silk_Resampler_1_2_COEFS[ 2 + RESAMPLER_DOWN_ORDER_FIR1 / 2 ] = {
+	   616, -14323,
+	   -10,     39,     58,    -46,    -84,    120,    184,   -315,   -541,   1284,   5380,   9024,
 };
 
-silk_DWORD_ALIGN const opus_int16 silk_Resampler_2_3_COEFS[ 2 + 2 * RESAMPLER_DOWN_ORDER_FIR / 2 ] = {
-    -13997, -14120,
-        60,   -174,     71,    298,   -800,    659,   9238,  17461,
-        48,    -40,   -150,    314,   -155,   -845,   4188,  14293,
+silk_DWORD_ALIGN const opus_int16 silk_Resampler_1_3_COEFS[ 2 + RESAMPLER_DOWN_ORDER_FIR2 / 2 ] = {
+	 16102, -15162,
+	   -13,      0,     20,     26,      5,    -31,    -43,     -4,     65,     90,      7,   -157,   -248,    -44,    593,   1583,   2612,   3271,
 };
 
-silk_DWORD_ALIGN const opus_int16 silk_Resampler_1_2_COEFS[ 2 + RESAMPLER_DOWN_ORDER_FIR / 2 ] = {
-      1233, -14293,
-       -91,    162,    169,   -342,   -505,   1332,   5281,   8742,
+silk_DWORD_ALIGN const opus_int16 silk_Resampler_1_4_COEFS[ 2 + RESAMPLER_DOWN_ORDER_FIR2 / 2 ] = {
+	 22500, -15099,
+	     3,    -14,    -20,    -15,      2,     25,     37,     25,    -16,    -71,   -107,    -79,     50,    292,    623,    982,   1288,   1464,
 };
 
-silk_DWORD_ALIGN const opus_int16 silk_Resampler_1_3_COEFS[ 2 + RESAMPLER_DOWN_ORDER_FIR / 2 ] = {
-     16306, -14409,
-        99,   -201,   -220,    -16,    572,   1483,   2433,   3043,
+silk_DWORD_ALIGN const opus_int16 silk_Resampler_1_6_COEFS[ 2 + RESAMPLER_DOWN_ORDER_FIR2 / 2 ] = {
+	 27540, -15257,
+	    17,     12,      8,      1,    -10,    -22,    -30,    -32,    -22,      3,     44,    100,    168,    243,    317,    381,    429,    455,
 };
 
 silk_DWORD_ALIGN const opus_int16 silk_Resampler_2_3_COEFS_LQ[ 2 + 2 * 2 ] = {
@@ -73,150 +87,18 @@ silk_DWORD_ALIGN const opus_int16 silk_Resampler_2_3_COEFS_LQ[ 2 + 2 * 2 ] = {
       1567,   8276,
 };
 
-/* Table with interplation fractions of 1/288 : 2/288 : 287/288 (432 Words) */
-silk_DWORD_ALIGN const opus_int16 silk_resampler_frac_FIR_144[ 144 ][ RESAMPLER_ORDER_FIR_144 / 2 ] = {
-    {  -25,    58, 32526},
-    {   -8,   -69, 32461},
-    {    8,  -195, 32393},
-    {   25,  -318, 32321},
-    {   41,  -439, 32244},
-    {   57,  -557, 32163},
-    {   72,  -673, 32079},
-    {   88,  -787, 31990},
-    {  103,  -899, 31897},
-    {  118, -1009, 31801},
-    {  133, -1116, 31700},
-    {  148, -1221, 31596},
-    {  162, -1324, 31488},
-    {  177, -1424, 31376},
-    {  191, -1522, 31260},
-    {  205, -1618, 31140},
-    {  218, -1712, 31017},
-    {  231, -1803, 30890},
-    {  245, -1893, 30759},
-    {  257, -1980, 30625},
-    {  270, -2065, 30487},
-    {  282, -2147, 30346},
-    {  295, -2228, 30201},
-    {  306, -2306, 30052},
-    {  318, -2382, 29900},
-    {  330, -2456, 29745},
-    {  341, -2528, 29586},
-    {  352, -2597, 29424},
-    {  362, -2664, 29259},
-    {  373, -2730, 29090},
-    {  383, -2793, 28918},
-    {  393, -2854, 28743},
-    {  402, -2912, 28565},
-    {  411, -2969, 28384},
-    {  421, -3024, 28199},
-    {  429, -3076, 28012},
-    {  438, -3126, 27822},
-    {  446, -3175, 27628},
-    {  454, -3221, 27432},
-    {  462, -3265, 27233},
-    {  469, -3307, 27031},
-    {  476, -3348, 26826},
-    {  483, -3386, 26619},
-    {  490, -3422, 26409},
-    {  496, -3456, 26196},
-    {  502, -3488, 25981},
-    {  508, -3518, 25763},
-    {  514, -3547, 25543},
-    {  519, -3573, 25320},
-    {  524, -3597, 25095},
-    {  529, -3620, 24867},
-    {  533, -3640, 24637},
-    {  538, -3659, 24405},
-    {  541, -3676, 24171},
-    {  545, -3691, 23934},
-    {  548, -3704, 23696},
-    {  552, -3716, 23455},
-    {  554, -3726, 23212},
-    {  557, -3733, 22967},
-    {  559, -3740, 22721},
-    {  561, -3744, 22472},
-    {  563, -3747, 22222},
-    {  565, -3748, 21970},
-    {  566, -3747, 21716},
-    {  567, -3745, 21460},
-    {  568, -3741, 21203},
-    {  568, -3735, 20944},
-    {  568, -3728, 20684},
-    {  568, -3719, 20422},
-    {  568, -3708, 20159},
-    {  568, -3697, 19894},
-    {  567, -3683, 19628},
-    {  566, -3668, 19361},
-    {  564, -3652, 19093},
-    {  563, -3634, 18823},
-    {  561, -3614, 18552},
-    {  559, -3594, 18280},
-    {  557, -3571, 18008},
-    {  554, -3548, 17734},
-    {  552, -3523, 17459},
-    {  549, -3497, 17183},
-    {  546, -3469, 16907},
-    {  542, -3440, 16630},
-    {  539, -3410, 16352},
-    {  535, -3379, 16074},
-    {  531, -3346, 15794},
-    {  527, -3312, 15515},
-    {  522, -3277, 15235},
-    {  517, -3241, 14954},
-    {  513, -3203, 14673},
-    {  507, -3165, 14392},
-    {  502, -3125, 14110},
-    {  497, -3085, 13828},
-    {  491, -3043, 13546},
-    {  485, -3000, 13264},
-    {  479, -2957, 12982},
-    {  473, -2912, 12699},
-    {  466, -2867, 12417},
-    {  460, -2820, 12135},
-    {  453, -2772, 11853},
-    {  446, -2724, 11571},
-    {  439, -2675, 11289},
-    {  432, -2625, 11008},
-    {  424, -2574, 10727},
-    {  417, -2522, 10446},
-    {  409, -2470, 10166},
-    {  401, -2417,  9886},
-    {  393, -2363,  9607},
-    {  385, -2309,  9328},
-    {  376, -2253,  9050},
-    {  368, -2198,  8773},
-    {  359, -2141,  8497},
-    {  351, -2084,  8221},
-    {  342, -2026,  7946},
-    {  333, -1968,  7672},
-    {  324, -1910,  7399},
-    {  315, -1850,  7127},
-    {  305, -1791,  6856},
-    {  296, -1731,  6586},
-    {  286, -1670,  6317},
-    {  277, -1609,  6049},
-    {  267, -1548,  5783},
-    {  257, -1486,  5517},
-    {  247, -1424,  5254},
-    {  237, -1362,  4991},
-    {  227, -1300,  4730},
-    {  217, -1237,  4470},
-    {  207, -1174,  4212},
-    {  197, -1110,  3956},
-    {  187, -1047,  3701},
-    {  176,  -984,  3448},
-    {  166,  -920,  3196},
-    {  155,  -856,  2946},
-    {  145,  -792,  2698},
-    {  134,  -728,  2452},
-    {  124,  -664,  2207},
-    {  113,  -600,  1965},
-    {  102,  -536,  1724},
-    {   92,  -472,  1486},
-    {   81,  -408,  1249},
-    {   70,  -345,  1015},
-    {   60,  -281,   783},
-    {   49,  -217,   553},
-    {   38,  -154,   325},
+/* Table with interplation fractions of 1/24, 3/24, 5/24, ... , 23/24 : 23/24 (46 Words) */
+silk_DWORD_ALIGN const opus_int16 silk_resampler_frac_FIR_12[ 12 ][ RESAMPLER_ORDER_FIR_12 / 2 ] = {
+	{  189,  -600,   617, 30567 },
+	{  117,  -159, -1070, 29704 },
+	{   52,   221, -2392, 28276 },
+	{   -4,   529, -3350, 26341 },
+	{  -48,   758, -3956, 23973 },
+	{  -80,   905, -4235, 21254 },
+	{  -99,   972, -4222, 18278 },
+	{ -107,   967, -3957, 15143 },
+	{ -103,   896, -3487, 11950 },
+	{  -91,   773, -2865,  8798 },
+	{  -71,   611, -2143,  5784 },
+	{  -46,   425, -1375,  2996 },
 };