Standardized routines for forking processes (keeps all the specialized code in one...
[asterisk/asterisk.git] / include / asterisk / alaw.h
old mode 100755 (executable)
new mode 100644 (file)
index 6feb07a..0ef42be
 #ifndef _ASTERISK_ALAW_H
 #define _ASTERISK_ALAW_H
 
-/*! Init the ulaw conversion stuff */
-/*!
- * To init the ulaw to slinear conversion stuff, this needs to be run.
+
+/*! \brief
+ * To init the alaw to slinear conversion stuff, this needs to be run.
  */
-extern void ast_alaw_init(void);
+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 */
-/*!
-  */
+/*! \brief converts signed linear to alaw */
+#ifndef G711_NEW_ALGORITHM
 extern unsigned char __ast_lin2a[8192];
+#else
+extern unsigned char __ast_lin2a[AST_ALAW_TAB_SIZE];
+#endif
 
 /*! help */
 extern short __ast_alaw[256];
 
+#ifndef G711_NEW_ALGORITHM
 #define AST_LIN2A(a) (__ast_lin2a[((unsigned short)(a)) >> 3])
+#else
+#define AST_LIN2A_LOOKUP(mag)                                                  \
+       __ast_lin2a[(mag) >> AST_ALAW_BIT_LOSS]
+
+/*! \brief 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 */