Add a tolerance period for sync-triggered audiohooks

so that if packetization of audio is close (but not equal)
we don't end up flushing the audiohooks over small
inconsistencies in synchronization.

Related to issue #13005, and solves the issue
for most people who were experiencing the problem.
However, a small number of people are still experiencing
the problem on long calls, so I am not closing
the issue yet



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@149204 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/audiohook.h

@@ -56,6 +56,8 @@ enum ast_audiohook_flags {
 	AST_AUDIOHOOK_TRIGGER_SYNC = (1 << 2),  /*!< Audiohook wants to be triggered when both sides have combined audio available */
 };
 
+#define AST_AUDIOHOOK_SYNC_TOLERANCE 100 /*< Tolerance in milliseconds for audiohooks synchronization */
+
 struct ast_audiohook;
 
 /*! \brief Callback function for manipulate audiohook type

main/audiohook.c

@@ -130,12 +130,19 @@ int ast_audiohook_write_frame(struct ast_audiohook *audiohook, enum ast_audiohoo
 	struct ast_slinfactory *factory = (direction == AST_AUDIOHOOK_DIRECTION_READ ? &audiohook->read_factory : &audiohook->write_factory);
 	struct ast_slinfactory *other_factory = (direction == AST_AUDIOHOOK_DIRECTION_READ ? &audiohook->write_factory : &audiohook->read_factory);
 	struct timeval *time = (direction == AST_AUDIOHOOK_DIRECTION_READ ? &audiohook->read_time : &audiohook->write_time), previous_time = *time;
+	int our_factory_ms;
+	int other_factory_samples;
+	int other_factory_ms;
 
 	/* Update last feeding time to be current */
 	*time = ast_tvnow();
 
+	our_factory_ms = ast_tvdiff_ms(*time, previous_time) + (ast_slinfactory_available(factory) / 8);
+	other_factory_samples = ast_slinfactory_available(other_factory);
+	other_factory_ms = other_factory_samples / 8;
+
 	/* If we are using a sync trigger and this factory suddenly got audio fed in after a lapse, then flush both factories to ensure they remain in sync */
-	if (ast_test_flag(audiohook, AST_AUDIOHOOK_TRIGGER_SYNC) && ast_slinfactory_available(other_factory) && (ast_tvdiff_ms(*time, previous_time) > (ast_slinfactory_available(other_factory) / 8))) {
+	if (ast_test_flag(audiohook, AST_AUDIOHOOK_TRIGGER_SYNC) && other_factory_samples && (our_factory_ms - other_factory_ms > AST_AUDIOHOOK_SYNC_TOLERANCE)) {
 		if (option_debug)
 			ast_log(LOG_DEBUG, "Flushing audiohook %p so it remains in sync\n", audiohook);
 		ast_slinfactory_flush(factory);