This patch solves problem 1 in 8126; it should not slow down the alaw codec, but...

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@80166 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/include/asterisk/alaw.h b/include/asterisk/alaw.h
index 44b3bad86ead9e7343dcc9f68356602cbe8956c8..5f6c9a3731dcddab82ad6c1d9dd653c18e0fa97e 100644 (file)
--- a/include/asterisk/alaw.h
+++ b/include/asterisk/alaw.h
@@ -23,21 +23,69 @@
 #ifndef _ASTERISK_ALAW_H
 #define _ASTERISK_ALAW_H
 
+#define G711_FAST_AND_DIRTY 1
+/* #define G711_REDUCED_BRANCHING */
+
 /*! Init the ulaw conversion stuff */
 /*!
  * To init the ulaw to slinear conversion stuff, this needs to be run.
  */
 void ast_alaw_init(void);
 
+#define AST_ALAW_BIT_LOSS  4
+#define AST_ALAW_STEP      (1 << AST_ALAW_BIT_LOSS)
+#define AST_ALAW_TAB_SIZE  (32768 / AST_ALAW_STEP + 1)
+#define AST_ALAW_SIGN_BIT  0x80
+#define AST_ALAW_AMI_MASK  0x55
+
+
 /*! converts signed linear to mulaw */
 /*!
-  */
+ */
+#ifdef G711_FAST_AND_DIRTY
 extern unsigned char __ast_lin2a[8192];
+#else
+extern unsigned char __ast_lin2a[AST_ALAW_TAB_SIZE];
+#endif
 
 /*! help */
 extern short __ast_alaw[256];
 
+#ifdef G711_FAST_AND_DIRTY
 #define AST_LIN2A(a) (__ast_lin2a[((unsigned short)(a)) >> 3])
+#else
+#define AST_LIN2A_LOOKUP(mag)                                                  \
+       __ast_lin2a[(mag) >> AST_ALAW_BIT_LOSS]
+
+/*! convert signed linear sample to sign-magnitude pair for a-Law */
+static inline void ast_alaw_get_sign_mag(short sample, unsigned *sign, unsigned *mag)
+{
+       /* It may look illogical to retrive the sign this way in both cases,
+        * but this helps gcc eliminate the branch below and produces
+        * faster code */
+       *sign = ((unsigned short)sample >> 8) & AST_ALAW_SIGN_BIT;
+#if defined(G711_REDUCED_BRANCHING)
+       {
+               unsigned dual_mag = (-sample << 16) | (unsigned short)sample;
+               *mag = (dual_mag >> (*sign >> 3)) & 0xffffU;
+       }
+#else
+       if (sample < 0)
+               *mag = -sample;
+       else
+               *mag = sample;
+#endif /* G711_REDUCED_BRANCHING */
+       *sign ^= AST_ALAW_SIGN_BIT;
+}
+
+static inline unsigned char AST_LIN2A(short sample)
+{
+       unsigned mag, sign;
+       ast_alaw_get_sign_mag(sample, &sign, &mag);
+       return (sign | AST_LIN2A_LOOKUP(mag)) ^ AST_ALAW_AMI_MASK;
+}
+#endif
+
 #define AST_ALAW(a) (__ast_alaw[(int)(a)])
 
 #endif /* _ASTERISK_ALAW_H */

diff --git a/include/asterisk/ulaw.h b/include/asterisk/ulaw.h
index d9ab0d17878fa8a511eb504dd9c3d17d41d307bc..2c7940f260e9209279781bdd06d9bfba9cfe9a0a 100644 (file)
--- a/include/asterisk/ulaw.h
+++ b/include/asterisk/ulaw.h
@@ -23,21 +23,71 @@
 #ifndef _ASTERISK_ULAW_H
 #define _ASTERISK_ULAW_H
 
+#define G711_FAST_AND_DIRTY 1
+
+/* #define G711_REDUCED_BRANCHING */
+
 /*! Init the ulaw conversion stuff */
 /*!
  * To init the ulaw to slinear conversion stuff, this needs to be run.
  */
 void ast_ulaw_init(void);
 
+#define AST_ULAW_BIT_LOSS  3
+#define AST_ULAW_STEP      (1 << AST_ULAW_BIT_LOSS)
+#define AST_ULAW_TAB_SIZE  (32768 / AST_ULAW_STEP + 1)
+#define AST_ULAW_SIGN_BIT  0x80
+
 /*! converts signed linear to mulaw */
 /*!
   */
+#ifdef G711_FAST_AND_DIRTY
 extern unsigned char __ast_lin2mu[16384];
+#else
+extern unsigned char __ast_lin2mu[AST_ULAW_TAB_SIZE];
+#endif
 
 /*! help */
 extern short __ast_mulaw[256];
 
+#ifdef G711_FAST_AND_DIRTY
+
 #define AST_LIN2MU(a) (__ast_lin2mu[((unsigned short)(a)) >> 2])
+
+#else
+
+#define AST_LIN2MU_LOOKUP(mag)                                                                                 \
+       __ast_lin2mu[((mag) + AST_ULAW_STEP / 2) >> AST_ULAW_BIT_LOSS]
+
+
+/*! convert signed linear sample to sign-magnitude pair for u-Law */
+static inline void ast_ulaw_get_sign_mag(short sample, unsigned *sign, unsigned *mag)
+{
+       /* It may look illogical to retrive the sign this way in both cases,
+        * but this helps gcc eliminate the branch below and produces
+        * faster code */
+       *sign = ((unsigned short)sample >> 8) & AST_ULAW_SIGN_BIT;
+#if defined(G711_REDUCED_BRANCHING)
+       {
+               unsigned dual_mag = (-sample << 16) | (unsigned short)sample;
+               *mag = (dual_mag >> (*sign >> 3)) & 0xffffU;
+       }
+#else
+       if (sample < 0)
+               *mag = -sample;
+       else
+               *mag = sample;
+#endif /* G711_REDUCED_BRANCHING */
+}
+
+static inline unsigned char AST_LIN2MU(short sample)
+{
+       unsigned mag, sign;
+       ast_ulaw_get_sign_mag(sample, &sign, &mag);
+       return ~(sign | AST_LIN2MU_LOOKUP(mag));
+}
+#endif
+
 #define AST_MULAW(a) (__ast_mulaw[(a)])
 
 #endif /* _ASTERISK_ULAW_H */

diff --git a/main/alaw.c b/main/alaw.c
index 782419d9e6f4809ef22ca41417a1b71e1ff68717..b94772ea6b40041b17c5f7b1ae3154fab8ed40cb 100644 (file)
--- a/main/alaw.c
+++ b/main/alaw.c
@@ -71,7 +71,7 @@ static inline short int alaw2linear (unsigned char alaw)
     int seg;
 
     alaw ^= AMI_MASK;
-    i = ((alaw & 0x0F) << 4);
+    i = ((alaw & 0x0F) << 4) + 8 /* rounding error */;
     seg = (((int) alaw & 0x70) >> 4);
     if (seg)
         i = (i + 0x100) << (seg - 1);