This change set fixes bug 8126 in trunk. It is implemented via compile time options, activated via the menuselect stuff, which defaults to the old way. non-zero sample data added. Translate tables expressed in microseconds instead of milliseconds, with 5-digit data now instead of 3, giving 2 more digits of precision.

git-svn-id: http://svn.digium.com/svn/asterisk/trunk@80113 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 49 insertions, 3 deletions

diff --git a/include/asterisk/alaw.h b/include/asterisk/alaw.h
index 44b3bad86..34968969d 100644
--- a/include/asterisk/alaw.h
+++ b/include/asterisk/alaw.h
@@ -23,21 +23,67 @@
 #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.
+ * To init the alaw to slinear conversion stuff, this needs to be run.
  */
 void ast_alaw_init(void);
 
-/*! converts signed linear to mulaw */
+#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 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]
+
+/*! 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 */