New SBC analysis filter function to replace current broken code

This code is heavily based on the patch submitted by Jaska Uimonen.
Additional changes include preserving extra bits in the output of
filter function for better precision, support for both 16-bit and
32-bit fixed point implementation. Sign of some table values was
changed in order to preserve a regular code structure and have
multiply-accumulate oparations only. No additional optimizations
were applied as this code is intended to be some kind of "reference"
implementation. Platform specific optimizations may require
different tricks and can be branched off from this implementation.
Some extra information about this code can be found in linux-bluetooth
mailing list archive for December 2008.

1 files changed, 213 insertions, 34 deletions

diff --git a/sbc/sbc_tables.h b/sbc/sbc_tables.h
index f5daaa7f..8df8c1fe 100644
--- a/sbc/sbc_tables.h
+++ b/sbc/sbc_tables.h
@@ -40,40 +40,11 @@ static const int sbc_offset8[4][8] = {
 };
 
 
-#define SP4(val) (((int32_t)(val))/17658) /* Used to be #define SP4(val) ASR(val, SCALE_PROTO4_TBL) but causes wrong gain */
-#define SA4(val) ASR(val, SCALE_ANA4_TBL)
-#define SP8(val) (((int32_t)(val))/57740) /* Used to be #define SP8(val) ASR(val, SCALE_PROTO8_TBL) but causes wrong gain */
-#define SA8(val) ASR(val, SCALE_ANA8_TBL)
 #define SS4(val) ASR(val, SCALE_SPROTO4_TBL)
 #define SS8(val) ASR(val, SCALE_SPROTO8_TBL)
 #define SN4(val) ASR(val, SCALE_NPROTO4_TBL)
 #define SN8(val) ASR(val, SCALE_NPROTO8_TBL)
 
-static const int32_t _sbc_proto_4[20] = {
-	SP4(0x02cb3e8c), SP4(0x22b63dc0), SP4(0x002329cc), SP4(0x053b7548),
-	SP4(0x31eab940), SP4(0xec1f5e60), SP4(0xff3773a8), SP4(0x0061c5a7),
-	SP4(0x07646680), SP4(0x3f239480), SP4(0xf89f23a8), SP4(0x007a4737),
-	SP4(0x00b32807), SP4(0x083ddc80), SP4(0x4825e480), SP4(0x0191e578),
-	SP4(0x00ff11ca), SP4(0x00fb7991), SP4(0x069fdc58), SP4(0x4b584000)
-};
-
-static const int32_t _anamatrix4[4] = {
-	SA4(0x2d413cc0), SA4(0x3b20d780), SA4(0x40000000), SA4(0x187de2a0)
-};
-
-static const int32_t _sbc_proto_8[40] = {
-	SP8(0x02e5cd20), SP8(0x22d0c200), SP8(0x006bfe27), SP8(0x07808930),
-	SP8(0x3f1c8800), SP8(0xf8810d70), SP8(0x002cfdc6), SP8(0x055acf28),
-	SP8(0x31f566c0), SP8(0xebfe57e0), SP8(0xff27c437), SP8(0x001485cc),
-	SP8(0x041c6e58), SP8(0x2a7cfa80), SP8(0xe4c4a240), SP8(0xfe359e4c),
-	SP8(0x0048b1f8), SP8(0x0686ce30), SP8(0x38eec5c0), SP8(0xf2a1b9f0),
-	SP8(0xffe8904a), SP8(0x0095698a), SP8(0x0824a480), SP8(0x443b3c00),
-	SP8(0xfd7badc8), SP8(0x00d3e2d9), SP8(0x00c183d2), SP8(0x084e1950),
-	SP8(0x4810d800), SP8(0x017f43fe), SP8(0x01056dd8), SP8(0x00e9cb9f),
-	SP8(0x07d7d090), SP8(0x4a708980), SP8(0x0488fae8), SP8(0x0113bd20),
-	SP8(0x0107b1a8), SP8(0x069fb3c0), SP8(0x4b3db200), SP8(0x00763f48)
-};
-
 static const int32_t sbc_proto_4_40m0[] = {
 	SS4(0x00000000), SS4(0xffa6982f), SS4(0xfba93848), SS4(0x0456c7b8),
 	SS4(0x005967d1), SS4(0xfffb9ac7), SS4(0xff589157), SS4(0xf9c2a8d8),
@@ -116,11 +87,6 @@ static const int32_t sbc_proto_8_80m1[] = {
 	SS8(0x0d9daee0), SS8(0xeac182c0), SS8(0xfdf1c8d4), SS8(0xfff5bd1a)
 };
 
-static const int32_t _anamatrix8[8] = {
-	SA8(0x3b20d780), SA8(0x187de2a0), SA8(0x3ec52f80), SA8(0x3536cc40),
-	SA8(0x238e7680), SA8(0x0c7c5c20), SA8(0x2d413cc0), SA8(0x40000000)
-};
-
 static const int32_t synmatrix4[8][4] = {
 	{ SN4(0x05a82798), SN4(0xfa57d868), SN4(0xfa57d868), SN4(0x05a82798) },
 	{ SN4(0x030fbc54), SN4(0xf89be510), SN4(0x07641af0), SN4(0xfcf043ac) },
@@ -166,3 +132,216 @@ static const int32_t synmatrix8[16][8] = {
 	{ SN8(0xf9592678), SN8(0x018f8b84), SN8(0x07d8a5f0), SN8(0x0471ced0),
 	  SN8(0xfb8e3130), SN8(0xf8275a10), SN8(0xfe70747c), SN8(0x06a6d988) }
 };
+
+/* Uncomment the following line to enable high precision build of SBC encoder */
+
+/* #define SBC_HIGH_PRECISION */
+
+#ifdef SBC_HIGH_PRECISION
+#define FIXED_A int64_t /* data type for fixed point accumulator */
+#define FIXED_T int32_t /* data type for fixed point constants */
+#define SBC_FIXED_EXTRA_BITS 16
+#else
+#define FIXED_A int32_t /* data type for fixed point accumulator */
+#define FIXED_T int16_t /* data type for fixed point constants */
+#define SBC_FIXED_EXTRA_BITS 0
+#endif
+
+/* A2DP specification: Section 12.8 Tables
+ *
+ * Original values are premultiplied by 2 for better precision (that is the
+ * maximum which is possible without overflows)
+ *
+ * Note: in each block of 8 numbers sign was changed for elements 2 and 7
+ * in order to compensate the same change applied to cos_table_fixed_4
+ */
+#define SBC_PROTO_FIXED4_SCALE \
+	((sizeof(FIXED_T) * CHAR_BIT - 1) - SBC_FIXED_EXTRA_BITS + 1)
+#define F(x) (FIXED_A) ((x * 2) * \
+	((FIXED_A) 1 << (sizeof(FIXED_T) * CHAR_BIT - 1)) + 0.5)
+static const FIXED_T _sbc_proto_fixed4[40] = {
+	 F(0.00000000E+00),  F(5.36548976E-04),
+	-F(1.49188357E-03),  F(2.73370904E-03),
+	 F(3.83720193E-03),  F(3.89205149E-03),
+	 F(1.86581691E-03),  F(3.06012286E-03),
+
+	 F(1.09137620E-02),  F(2.04385087E-02),
+	-F(2.88757392E-02),  F(3.21939290E-02),
+	 F(2.58767811E-02),  F(6.13245186E-03),
+	-F(2.88217274E-02),  F(7.76463494E-02),
+
+	 F(1.35593274E-01),  F(1.94987841E-01),
+	-F(2.46636662E-01),  F(2.81828203E-01),
+	 F(2.94315332E-01),  F(2.81828203E-01),
+	 F(2.46636662E-01), -F(1.94987841E-01),
+
+	-F(1.35593274E-01), -F(7.76463494E-02),
+	 F(2.88217274E-02),  F(6.13245186E-03),
+	 F(2.58767811E-02),  F(3.21939290E-02),
+	 F(2.88757392E-02), -F(2.04385087E-02),
+
+	-F(1.09137620E-02), -F(3.06012286E-03),
+	-F(1.86581691E-03),  F(3.89205149E-03),
+	 F(3.83720193E-03),  F(2.73370904E-03),
+	 F(1.49188357E-03), -F(5.36548976E-04),
+};
+#undef F
+
+/*
+ * To produce this cosine matrix in Octave:
+ *
+ * b = zeros(4, 8);
+ * for i = 0:3
+ * for j = 0:7 b(i+1, j+1) = cos((i + 0.5) * (j - 2) * (pi/4))
+ * endfor
+ * endfor;
+ * printf("%.10f, ", b');
+ *
+ * Note: in each block of 8 numbers sign was changed for elements 2 and 7
+ *
+ * Change of sign for element 2 allows to replace constant 1.0 (not
+ * representable in Q15 format) with -1.0 (fine with Q15).
+ * Changed sign for element 7 allows to have more similar constants
+ * and simplify subband filter function code.
+ */
+#define SBC_COS_TABLE_FIXED4_SCALE \
+	((sizeof(FIXED_T) * CHAR_BIT - 1) + SBC_FIXED_EXTRA_BITS)
+#define F(x) (FIXED_A) ((x) * \
+	((FIXED_A) 1 << (sizeof(FIXED_T) * CHAR_BIT - 1)) + 0.5)
+static const FIXED_T cos_table_fixed_4[32] = {
+	 F(0.7071067812),  F(0.9238795325), -F(1.0000000000),  F(0.9238795325),
+	 F(0.7071067812),  F(0.3826834324),  F(0.0000000000),  F(0.3826834324),
+
+	-F(0.7071067812),  F(0.3826834324), -F(1.0000000000),  F(0.3826834324),
+	-F(0.7071067812), -F(0.9238795325), -F(0.0000000000), -F(0.9238795325),
+
+	-F(0.7071067812), -F(0.3826834324), -F(1.0000000000), -F(0.3826834324),
+	-F(0.7071067812),  F(0.9238795325),  F(0.0000000000),  F(0.9238795325),
+
+	 F(0.7071067812), -F(0.9238795325), -F(1.0000000000), -F(0.9238795325),
+	 F(0.7071067812), -F(0.3826834324), -F(0.0000000000), -F(0.3826834324),
+};
+#undef F
+
+/* A2DP specification: Section 12.8 Tables
+ *
+ * Original values are premultiplied by 4 for better precision (that is the
+ * maximum which is possible without overflows)
+ *
+ * Note: in each block of 16 numbers sign was changed for elements 4, 13, 14, 15
+ * in order to compensate the same change applied to cos_table_fixed_8
+ */
+#define SBC_PROTO_FIXED8_SCALE \
+	((sizeof(FIXED_T) * CHAR_BIT - 1) - SBC_FIXED_EXTRA_BITS + 2)
+#define F(x) (FIXED_A) ((x * 4) * \
+	((FIXED_A) 1 << (sizeof(FIXED_T) * CHAR_BIT - 1)) + 0.5)
+static const FIXED_T _sbc_proto_fixed8[80] = {
+	 F(0.00000000E+00),  F(1.56575398E-04),
+	 F(3.43256425E-04),  F(5.54620202E-04),
+	-F(8.23919506E-04),  F(1.13992507E-03),
+	 F(1.47640169E-03),  F(1.78371725E-03),
+	 F(2.01182542E-03),  F(2.10371989E-03),
+	 F(1.99454554E-03),  F(1.61656283E-03),
+	 F(9.02154502E-04),  F(1.78805361E-04),
+	 F(1.64973098E-03),  F(3.49717454E-03),
+
+	 F(5.65949473E-03),  F(8.02941163E-03),
+	 F(1.04584443E-02),  F(1.27472335E-02),
+	-F(1.46525263E-02),  F(1.59045603E-02),
+	 F(1.62208471E-02),  F(1.53184106E-02),
+	 F(1.29371806E-02),  F(8.85757540E-03),
+	 F(2.92408442E-03), -F(4.91578024E-03),
+	-F(1.46404076E-02),  F(2.61098752E-02),
+	 F(3.90751381E-02),  F(5.31873032E-02),
+
+	 F(6.79989431E-02),  F(8.29847578E-02),
+	 F(9.75753918E-02),  F(1.11196689E-01),
+	-F(1.23264548E-01),  F(1.33264415E-01),
+	 F(1.40753505E-01),  F(1.45389847E-01),
+	 F(1.46955068E-01),  F(1.45389847E-01),
+	 F(1.40753505E-01),  F(1.33264415E-01),
+	 F(1.23264548E-01), -F(1.11196689E-01),
+	-F(9.75753918E-02), -F(8.29847578E-02),
+
+	-F(6.79989431E-02), -F(5.31873032E-02),
+	-F(3.90751381E-02), -F(2.61098752E-02),
+	 F(1.46404076E-02), -F(4.91578024E-03),
+	 F(2.92408442E-03),  F(8.85757540E-03),
+	 F(1.29371806E-02),  F(1.53184106E-02),
+	 F(1.62208471E-02),  F(1.59045603E-02),
+	 F(1.46525263E-02), -F(1.27472335E-02),
+	-F(1.04584443E-02), -F(8.02941163E-03),
+
+	-F(5.65949473E-03), -F(3.49717454E-03),
+	-F(1.64973098E-03), -F(1.78805361E-04),
+	-F(9.02154502E-04),  F(1.61656283E-03),
+	 F(1.99454554E-03),  F(2.10371989E-03),
+	 F(2.01182542E-03),  F(1.78371725E-03),
+	 F(1.47640169E-03),  F(1.13992507E-03),
+	 F(8.23919506E-04), -F(5.54620202E-04),
+	-F(3.43256425E-04), -F(1.56575398E-04),
+};
+#undef F
+
+/*
+ * To produce this cosine matrix in Octave:
+ *
+ * b = zeros(8, 16);
+ * for i = 0:7
+ * for j = 0:15 b(i+1, j+1) = cos((i + 0.5) * (j - 4) * (pi/8))
+ * endfor endfor;
+ * printf("%.10f, ", b');
+ *
+ * Note: in each block of 16 numbers sign was changed for elements 4, 13, 14, 15
+ *
+ * Change of sign for element 4 allows to replace constant 1.0 (not
+ * representable in Q15 format) with -1.0 (fine with Q15).
+ * Changed signs for elements 13, 14, 15 allow to have more similar constants
+ * and simplify subband filter function code.
+ */
+#define SBC_COS_TABLE_FIXED8_SCALE \
+	((sizeof(FIXED_T) * CHAR_BIT - 1) + SBC_FIXED_EXTRA_BITS)
+#define F(x) (FIXED_A) ((x) * \
+	((FIXED_A) 1 << (sizeof(FIXED_T) * CHAR_BIT - 1)) + 0.5)
+static const FIXED_T cos_table_fixed_8[128] = {
+	 F(0.7071067812),  F(0.8314696123),  F(0.9238795325),  F(0.9807852804),
+	-F(1.0000000000),  F(0.9807852804),  F(0.9238795325),  F(0.8314696123),
+	 F(0.7071067812),  F(0.5555702330),  F(0.3826834324),  F(0.1950903220),
+	 F(0.0000000000),  F(0.1950903220),  F(0.3826834324),  F(0.5555702330),
+
+	-F(0.7071067812), -F(0.1950903220),  F(0.3826834324),  F(0.8314696123),
+	-F(1.0000000000),  F(0.8314696123),  F(0.3826834324), -F(0.1950903220),
+	-F(0.7071067812), -F(0.9807852804), -F(0.9238795325), -F(0.5555702330),
+	-F(0.0000000000), -F(0.5555702330), -F(0.9238795325), -F(0.9807852804),
+
+	-F(0.7071067812), -F(0.9807852804), -F(0.3826834324),  F(0.5555702330),
+	-F(1.0000000000),  F(0.5555702330), -F(0.3826834324), -F(0.9807852804),
+	-F(0.7071067812),  F(0.1950903220),  F(0.9238795325),  F(0.8314696123),
+	 F(0.0000000000),  F(0.8314696123),  F(0.9238795325),  F(0.1950903220),
+
+	 F(0.7071067812), -F(0.5555702330), -F(0.9238795325),  F(0.1950903220),
+	-F(1.0000000000),  F(0.1950903220), -F(0.9238795325), -F(0.5555702330),
+	 F(0.7071067812),  F(0.8314696123), -F(0.3826834324), -F(0.9807852804),
+	-F(0.0000000000), -F(0.9807852804), -F(0.3826834324),  F(0.8314696123),
+
+	 F(0.7071067812),  F(0.5555702330), -F(0.9238795325), -F(0.1950903220),
+	-F(1.0000000000), -F(0.1950903220), -F(0.9238795325),  F(0.5555702330),
+	 F(0.7071067812), -F(0.8314696123), -F(0.3826834324),  F(0.9807852804),
+	 F(0.0000000000),  F(0.9807852804), -F(0.3826834324), -F(0.8314696123),
+
+	-F(0.7071067812),  F(0.9807852804), -F(0.3826834324), -F(0.5555702330),
+	-F(1.0000000000), -F(0.5555702330), -F(0.3826834324),  F(0.9807852804),
+	-F(0.7071067812), -F(0.1950903220),  F(0.9238795325), -F(0.8314696123),
+	-F(0.0000000000), -F(0.8314696123),  F(0.9238795325), -F(0.1950903220),
+
+	-F(0.7071067812),  F(0.1950903220),  F(0.3826834324), -F(0.8314696123),
+	-F(1.0000000000), -F(0.8314696123),  F(0.3826834324),  F(0.1950903220),
+	-F(0.7071067812),  F(0.9807852804), -F(0.9238795325),  F(0.5555702330),
+	-F(0.0000000000),  F(0.5555702330), -F(0.9238795325),  F(0.9807852804),
+
+	 F(0.7071067812), -F(0.8314696123),  F(0.9238795325), -F(0.9807852804),
+	-F(1.0000000000), -F(0.9807852804),  F(0.9238795325), -F(0.8314696123),
+	 F(0.7071067812), -F(0.5555702330),  F(0.3826834324), -F(0.1950903220),
+	-F(0.0000000000), -F(0.1950903220),  F(0.3826834324), -F(0.5555702330),
+};
+#undef F