Index: dsp.c
===================================================================
RCS file: /usr/cvsroot/asterisk/dsp.c,v
retrieving revision 1.42
diff -u -r1.42 dsp.c
--- dsp.c	15 May 2005 17:22:41 -0000	1.42
+++ dsp.c	19 May 2005 01:16:49 -0000
@@ -80,7 +80,7 @@
 	{ GSAMP_SIZE_CR, { 425 } },
 };
 
-#define DEFAULT_THRESHOLD	512
+#define DEFAULT_THRESHOLD	512	/* If energy is below this, consider it silence */
 
 #define BUSY_PERCENT		10	/* The percentage diffrence between the two last silence periods */
 #define BUSY_THRESHOLD		100	/* Max number of ms difference between max and min times in busy */
@@ -1114,18 +1114,20 @@
 	return __ast_dsp_call_progress(dsp, inf->data, inf->datalen / 2);
 }
 
-static int __ast_dsp_silence(struct ast_dsp *dsp, short *s, int len, int *totalsilence)
+static int __ast_dsp_energy(struct ast_dsp *dsp, short *s, int len, int *totalsilence)
 {
 	int accum;
 	int x;
-	int res = 0;
 
 	if (!len)
 		return 0;
+
 	accum = 0;
 	for (x=0;x<len; x++) 
 		accum += abs(s[x]);
 	accum /= len;
+
+	/* accumulated noise was below the threshold, therefore it is silence */
 	if (accum < dsp->threshold) {
 		dsp->totalsilence += len/8;
 		if (dsp->totalnoise) {
@@ -1138,7 +1140,6 @@
 #endif
 		}
 		dsp->totalnoise = 0;
-		res = 1;
 	} else {
 		dsp->totalnoise += len/8;
 		if (dsp->totalsilence) {
@@ -1162,10 +1163,23 @@
 		}
 		dsp->totalsilence = 0;
 	}
+
 	if (totalsilence)
 		*totalsilence = dsp->totalsilence;
-	return res;
+
+	return accum;
+}
+
+static int __ast_dsp_silence(struct ast_dsp *dsp, short *s, int len, int *totalsilence)
+{
+	int accum;
+	accum = __ast_dsp_energy(dsp, s, len, totalsilence);
+	if (accum < dsp->threshold)
+		return 1;
+	else
+		return 0;
 }
+
 #ifdef BUSYDETECT_MARTIN
 int ast_dsp_busydetect(struct ast_dsp *dsp)
 {
@@ -1297,9 +1311,27 @@
 	return __ast_dsp_silence(dsp, s, len, totalsilence);
 }
 
+int ast_dsp_energy(struct ast_dsp *dsp, struct ast_frame *f, int *totalsilence)
+{
+	short *s;
+	int len;
+	
+	if (f->frametype != AST_FRAME_VOICE) {
+		ast_log(LOG_WARNING, "Can't calculate voice energy on a non-voice frame\n");
+		return 0;
+	}
+	if (f->subclass != AST_FORMAT_SLINEAR) {
+		ast_log(LOG_WARNING, "Can only calculate voice energy on signed-linear frames :(\n");
+		return 0;
+	}
+	s = f->data;
+	len = f->datalen/2;
+	return __ast_dsp_energy(dsp, s, len, totalsilence);
+}
+
 struct ast_frame *ast_dsp_process(struct ast_channel *chan, struct ast_dsp *dsp, struct ast_frame *af)
 {
-	int silence;
+	int energy;
 	int res;
 	int digit;
 	int x;
@@ -1359,11 +1391,17 @@
 		ast_log(LOG_WARNING, "Inband DTMF is not supported on codec %s. Use RFC2833\n", ast_getformatname(af->subclass));
 		return af;
 	}
-	silence = __ast_dsp_silence(dsp, shortdata, len, NULL);
-	if ((dsp->features & DSP_FEATURE_SILENCE_SUPPRESS) && silence) {
-		memset(&dsp->f, 0, sizeof(dsp->f));
-		dsp->f.frametype = AST_FRAME_NULL;
-		return &dsp->f;
+	if (dsp->features & (DSP_FEATURE_SILENCE_DETECT | DSP_FEATURE_SILENCE_SUPPRESS)) {
+		energy = __ast_dsp_energy(dsp, shortdata, len, NULL);
+		af->energy = energy;
+		if (energy < dsp->threshold) {
+			if (dsp->features & DSP_FEATURE_SILENCE_SUPPRESS) {
+				af->frametype = AST_FRAME_CNG;
+			}
+			/* a silence frame should not be processed any further */
+			FIX_INF(af);
+			return af;
+		}
 	}
 	if ((dsp->features & DSP_FEATURE_BUSY_DETECT) && ast_dsp_busydetect(dsp)) {
 		chan->_softhangup |= AST_SOFTHANGUP_DEV;
@@ -1514,7 +1552,8 @@
 	if (dsp) {
 		memset(dsp, 0, sizeof(struct ast_dsp));
 		dsp->threshold = DEFAULT_THRESHOLD;
-		dsp->features = DSP_FEATURE_SILENCE_SUPPRESS;
+		/* No features are enabled at creation time */
+		dsp->features = 0;
 		dsp->busycount = DSP_HISTORY;
 		/* Initialize DTMF detector */
 		ast_dtmf_detect_init(&dsp->td.dtmf);
Index: frame.c
===================================================================
RCS file: /usr/cvsroot/asterisk/frame.c,v
retrieving revision 1.55
diff -u -r1.55 frame.c
--- frame.c	15 May 2005 05:46:34 -0000	1.55
+++ frame.c	19 May 2005 01:16:50 -0000
@@ -279,6 +279,7 @@
 		out->datalen = fr->datalen;
 		out->samples = fr->samples;
 		out->offset = fr->offset;
+		out->energy = fr->energy;
 		out->src = NULL;
 		out->data = fr->data;
 	} else {
@@ -334,6 +335,7 @@
 	out->delivery = f->delivery;
 	out->mallocd = AST_MALLOCD_HDR;
 	out->offset = AST_FRIENDLY_OFFSET;
+	out->energy = f->energy;
 	out->data = buf + sizeof(struct ast_frame) + AST_FRIENDLY_OFFSET;
 	if (srclen > 0) {
 		out->src = out->data + f->datalen;
Index: channels/chan_zap.c
===================================================================
RCS file: /usr/cvsroot/asterisk/channels/chan_zap.c,v
retrieving revision 1.447
diff -u -r1.447 chan_zap.c
--- channels/chan_zap.c	16 May 2005 19:15:56 -0000	1.447
+++ channels/chan_zap.c	19 May 2005 01:16:59 -0000
@@ -303,6 +303,15 @@
 /* When to send the CallerID signals (rings) */
 static int sendcalleridafter = DEFAULT_CIDRINGS;
 
+/* Whether to mark a voice frame as being silence (but still keeping the audio) */
+static int silencedetection = 0;
+
+/* Whether to convert silence frames to comfort noise generator (CNG) frames */
+static int silencesuppression = 0;
+
+/* What magic number to use for the silence detection accumulator in dsp.c */
+static int silencethreshold = 512;
+
 /* Protect the monitoring thread, so only one process can kill or start it, and not
    when it's doing something critical. */
 AST_MUTEX_DEFINE_STATIC(monlock);
@@ -631,6 +640,9 @@
 	int sigchecked;
 #endif	
 	int polarity;
+	int silencedetection;
+	int silencesuppression;
+	int silencethreshold;
 } *iflist = NULL, *ifend = NULL;
 
 static struct ast_channel *zt_request(const char *type, int format, void *data, int *cause);
@@ -4740,6 +4752,11 @@
 		if (ioctl(i->subs[index].zfd, ZT_TONEDETECT, &x))
 #endif		
 			features |= DSP_FEATURE_DTMF_DETECT;
+		if (i->silencedetection)
+			features |= DSP_FEATURE_SILENCE_DETECT;
+		if (i->silencesuppression) {
+			features |= DSP_FEATURE_SILENCE_SUPPRESS;
+		}
 		if (features) {
 			if (i->dsp) {
 				ast_log(LOG_DEBUG, "Already have a dsp on %s?\n", tmp->name);
@@ -4755,6 +4772,7 @@
 						features = 0;
 					}
 #endif
+					ast_dsp_set_threshold(i->dsp, i->silencethreshold);
 					ast_dsp_set_features(i->dsp, features);
 					ast_dsp_digitmode(i->dsp, DSP_DIGITMODE_DTMF | i->dtmfrelax);
 					if (!ast_strlen_zero(progzone))
@@ -6862,6 +6880,9 @@
 		tmp->answeronpolarityswitch = answeronpolarityswitch;
 		tmp->hanguponpolarityswitch = hanguponpolarityswitch;
 		tmp->sendcalleridafter = sendcalleridafter;
+		tmp->silencedetection = silencedetection;
+		tmp->silencesuppression = silencesuppression;
+		tmp->silencethreshold = silencethreshold;
 
 	}
 	if (tmp && !here) {
@@ -10359,7 +10380,13 @@
 				ast_copy_string(defaultcic, v->value, sizeof(defaultcic));
 			} else if (!strcasecmp(v->name, "defaultozz")) {
 				ast_copy_string(defaultozz, v->value, sizeof(defaultozz));
-			} 
+			} else if (!strcasecmp(v->name, "silencedetection")) {
+				silencedetection = ast_true(v->value);
+			} else if (!strcasecmp(v->name, "silencesuppression")) {
+				silencesuppression = ast_true(v->value);
+			} else if (!strcasecmp(v->name, "silencethreshold")) {
+				silencethreshold = atoi(v->value);
+			}
 		} else 
 			ast_log(LOG_WARNING, "Ignoring %s\n", v->name);
 		v = v->next;
Index: configs/zapata.conf.sample
===================================================================
RCS file: /usr/cvsroot/asterisk/configs/zapata.conf.sample,v
retrieving revision 1.47
diff -u -r1.47 zapata.conf.sample
--- configs/zapata.conf.sample	12 May 2005 15:04:55 -0000	1.47
+++ configs/zapata.conf.sample	19 May 2005 01:17:00 -0000
@@ -396,6 +396,24 @@
 ;callprogress=yes
 ;progzone=us
 ;
+; Frames of minimal noise energy can be turned into special Comfort Noise
+; Generation frames.  These frames can be useful to save bandwidth amongst other
+; things.  Setting "silencesuppression=yes" will turn this on.  Default is "no".
+;
+; silencesuppression=no
+;
+; Instead of converting the silence into CNG, it might be useful to simply
+; detect the energy in each frame for some other purpose.  Setting
+; "silencedetection=yes" will turn this on.  Default is "no".
+;
+; silencedetection=no
+;
+; Define the threshold for which frames below this amount of voice energy will
+; be considered silence.  Default is 512.  This option does nothing unless
+; "silencesuppression=yes"
+;
+; silencethreshold=512
+;
 ; For FXO (FXS signalled) devices, whether to use pulse dial instead of DTMF
 ;
 ;pulsedial=yes
Index: include/asterisk/dsp.h
===================================================================
RCS file: /usr/cvsroot/asterisk/include/asterisk/dsp.h,v
retrieving revision 1.6
diff -u -r1.6 dsp.h
--- include/asterisk/dsp.h	17 Nov 2004 05:55:26 -0000	1.6
+++ include/asterisk/dsp.h	19 May 2005 01:17:00 -0000
@@ -15,7 +15,8 @@
 #define _ASTERISK_DSP_H
 
 #define DSP_FEATURE_SILENCE_SUPPRESS	(1 << 0)
-#define DSP_FEATURE_BUSY_DETECT		(1 << 1)
+#define DSP_FEATURE_SILENCE_DETECT	(1 << 1)
+#define DSP_FEATURE_BUSY_DETECT		(1 << 2)
 #define DSP_FEATURE_DTMF_DETECT		(1 << 3)
 #define DSP_FEATURE_FAX_DETECT		(1 << 4)
 
@@ -65,6 +66,10 @@
 /* Return non-zero if this is silence.  Updates "totalsilence" with the total
    number of seconds of silence  */
 int ast_dsp_silence(struct ast_dsp *dsp, struct ast_frame *f, int *totalsilence);
+
+/* Return the amount of voice energy in a frame.  Updates "totalsilence" with the total
+   number of seconds of silence  */
+int ast_dsp_energy(struct ast_dsp *dsp, struct ast_frame *f, int *totalsilence);
 
 /* Return non-zero if historically this should be a busy, request that
   ast_dsp_silence has already been called */
Index: include/asterisk/frame.h
===================================================================
RCS file: /usr/cvsroot/asterisk/include/asterisk/frame.h,v
retrieving revision 1.52
diff -u -r1.52 frame.h
--- include/asterisk/frame.h	15 May 2005 04:48:30 -0000	1.52
+++ include/asterisk/frame.h	19 May 2005 01:17:00 -0000
@@ -45,6 +45,8 @@
 	int mallocd;				
 	/*! How far into "data" the data really starts */
 	int offset;				
+	/*! Set by the DSP to how ever much "noise power" is in the frame, only non-zero for frames run thru ast_dsp_process */
+	int energy;
 	/*! Optional source of frame for debugging */
 	const char *src;				
 	/*! Pointer to actual data */