Index: ulaw.c
===================================================================
--- ulaw.c	(revision 44743)
+++ ulaw.c	(working copy)
@@ -27,6 +27,7 @@
 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 
 #include "asterisk/ulaw.h"
+#include "asterisk/logger.h"
 
 #define ZEROTRAP    /*!< turn on the trap as per the MIL-STD */
 #define BIAS 0x84   /*!< define the add-in bias for 16 bit samples */
@@ -78,6 +79,20 @@
 	return ulawbyte;
 }
 
+static inline short ulaw2linear(unsigned char ulaw)
+{
+	short mu,e,f,y;
+	static short etab[]={0,132,396,924,1980,4092,8316,16764};
+
+	mu = 255-ulaw;
+	e = (mu & 0x70)/16;
+	f = mu & 0x0f;
+	y = f * (1 << (e + 3));
+	y += etab[e];
+	if (mu & 0x80) y = -y;
+	return y;
+}
+
 /*!
  * \brief  Set up mu-law conversion table
  */
@@ -85,21 +100,50 @@
 {
 	int i;
 	for(i = 0;i < 256;i++) {
-		short mu,e,f,y;
-		static short etab[]={0,132,396,924,1980,4092,8316,16764};
-
-		mu = 255-i;
-		e = (mu & 0x70)/16;
-		f = mu & 0x0f;
-		y = f * (1 << (e + 3));
-		y += etab[e];
-		if (mu & 0x80) y = -y;
-	        __ast_mulaw[i] = y;
+		__ast_mulaw[i] = ulaw2linear(i);
 	}
 	/* set up the reverse (mu-law) conversion table */
 	for(i = -32768; i < 32768; i++) {
 		__ast_lin2mu[((unsigned short)i) >> 2] = linear2ulaw(i);
 	}
 
+#ifdef TEST_CODING_TABLES
+	for (i = -32767; i < 32768; ++i)
+	{
+		unsigned char e1 = linear2ulaw(i);
+		short d1 = ulaw2linear(e1);
+		unsigned char e2 = AST_LIN2MU(i);
+		short d2 = ulaw2linear(e2);
+		short d3 = AST_MULAW(e1);
+		
+		if (e1 != e2 || d1 != d3 || d2 != d3)
+		{
+			ast_log(LOG_ERROR, "u-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n",
+					i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2);
+		}
+	}
+#endif // TEST_CODING_TABLES
+
+#ifdef TEST_TANDEM_TRANSCODING
+	// tandem transcoding test
+	for (i = -32767; i < 32768; ++i)
+	{
+		unsigned char e1 = AST_LIN2MU(i);
+		short d1 = AST_MULAW(e1);
+		unsigned char e2 = AST_LIN2MU(d1);
+		short d2 = AST_MULAW(e2);
+		unsigned char e3 = AST_LIN2MU(d2);
+		short d3 = AST_MULAW(e3);
+		
+		if (i < 0 && e1 == 0x7f && e2 == 0xff && e3 == 0xff)
+			continue; // known and normal negative 0 case
+
+		if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3)
+		{
+			ast_log(LOG_ERROR, "u-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n",
+					i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3);
+		}
+	}
+#endif // TEST_TANDEM_TRANSCODING
 }
 
Index: alaw.c
===================================================================
--- alaw.c	(revision 44743)
+++ alaw.c	(working copy)
@@ -27,6 +27,7 @@
 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 
 #include "asterisk/alaw.h"
+#include "asterisk/logger.h"
 
 #define AMI_MASK 0x55
 
@@ -93,8 +94,42 @@
 	  /* set up the reverse (mu-law) conversion table */
 	for(i = -32768; i < 32768; i++)
 	   {
		__ast_lin2a[((unsigned short)i) >> 3] = linear2alaw(i);
 	   }
 
+#ifdef TEST_CODING_TABLES
+	for (i = -32767; i < 32768; ++i)
+	{
+		unsigned char e1 = linear2alaw(i);
+		short d1 = alaw2linear(e1);
+		unsigned char e2 = AST_LIN2A(i);
+		short d2 = alaw2linear(e2);
+		short d3 = AST_ALAW(e1);
+		
+		if (e1 != e2 || d1 != d3 || d2 != d3)
+		{
+			ast_log(LOG_ERROR, "a-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n",
+					i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2);
+		}
+	}
+#endif // TEST_CODING_TABLES
+
+#ifdef TEST_TANDEM_TRANSCODING
+	// tandem transcoding test
+	for (i = -32767; i < 32768; ++i)
+	{
+		unsigned char e1 = AST_LIN2A(i);
+		short d1 = AST_ALAW(e1);
+		unsigned char e2 = AST_LIN2A(d1);
+		short d2 = AST_ALAW(e2);
+		unsigned char e3 = AST_LIN2A(d2);
+		short d3 = AST_ALAW(e3);
+		
+		if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3)
+		{
+			ast_log(LOG_ERROR, "a-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n",
+					i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3);
+		}
+	}
+#endif // TEST_TANDEM_TRANSCODING
 }
-