Improve CPU performance of MG2 by using a counter instead of a history

git-svn-id: http://svn.digium.com/svn/zaptel/trunk@1025 5390a7c7-147a-4af0-8ec9-7488f05a26cb

1 files changed, 10 insertions, 10 deletions

diff --git a/mg2ec.h b/mg2ec.h
index fca3c21..a1d691e 100644
--- a/mg2ec.h
+++ b/mg2ec.h
@@ -158,8 +158,8 @@ struct echo_can_state {
 	int avg_Lu_i_toolow; 
 	int avg_Lu_i_ok;
 #endif 
-	short lastsig[256];
-	int lastpos;
+	short lastsig;
+	int lastcount;
 	int backup;
 #ifdef DC_NORMALIZE
 	int dc_estimate;
@@ -327,18 +327,18 @@ static inline short echo_can_update(struct echo_can_state *ec, short iref, short
   			ec->N_d);
 	rs >>= 15;
 
-	ec->lastsig[ec->lastpos++] = isig;
-	if (ec->lastpos >= 256)
-		ec->lastpos = 0;
-
-	for (k=0; k < 256; k++) {
-		if (isig != ec->lastsig[k])
-			break;
+	if (ec->lastsig == isig) {
+		ec->lastcount++;
+	} else {
+		ec->lastcount = 0;
+		ec->lastsig = isig;
 	}
 
 	if (isig == 0) {
 		u = 0;
-	} else if (k == 256) {
+	} else if (ec->lastcount > 255) {
+		/* We have seen the same input-signal more than 255 times,
+		 * we should pass it through uncancelled, as we are likely on hold */
 		u = isig;
 	} else {
 		if (rs < -32768) {