--- asterisk-11.7.0.a/formats/format_g729.c	2012-04-29 21:50:57.000000000 +0200
+++ asterisk-11.7.0.b/formats/format_g729.c	2014-01-28 13:13:03.743740774 +0200
@@ -42,20 +42,34 @@
 
 /* Portions of the conversion code are by guido@sienanet.it */
 
-#define	BUF_SIZE	20	/* two G729 frames */
-#define	G729A_SAMPLES	160
+#define G729A_FRAME_SIZE    10
+#define G729A_FRAME_SAMPLES 80
+#define G729A_CNG_SIZE      2
+
+/* The original code assumed 20-byte frames, which isn't always true, consider
+ * for example a ptime=30, these are set up here to keep backwards compatible,
+ * and assumes two frames per packet as per previous. */
+#define G729A_BUF_SIZE     (G729A_FRAME_SIZE * 2)
+#define G729A_BUF_SAMPLES  (G729A_FRAME_SAMPLES * 2)
+
+struct ast_g729_pvt
+{
+	int detected_vad:1; /* simple flag indicating whether or not we detected and reported on VAD on this stream yet or not */
+	int warned_wrong_write_offset:1; /* Safety flag that if g729_write gets called and we're not on a G729A_FRAME_SIZE boundary, we can warn that there is a bug, just once */
+};
 
 static struct ast_frame *g729_read(struct ast_filestream *s, int *whennext)
 {
+	/* This assumes ptime=20, which is probably OK */
 	int res;
 	/* Send a frame from the file to the appropriate channel */
 	s->fr.frametype = AST_FRAME_VOICE;
 	ast_format_set(&s->fr.subclass.format, AST_FORMAT_G729A, 0);
 	s->fr.mallocd = 0;
-	s->fr.samples = G729A_SAMPLES;
-	AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, BUF_SIZE);
+	s->fr.samples = G729A_BUF_SAMPLES;
+	AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, G729A_BUF_SIZE);
 	if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) != s->fr.datalen) {
-		if (res && (res != 10))	/* XXX what for ? */
+		if (res && (res != G729A_FRAME_SIZE))	/* XXX what for ? */
 			ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
 		return NULL;
 	}
@@ -65,7 +79,15 @@
 
 static int g729_write(struct ast_filestream *fs, struct ast_frame *f)
 {
-	int res;
+	struct ast_g729_pvt* pvt = fs->_private;
+	int res, writelen = f->datalen;
+	int frame_has_cng = 0;
+	off_t position = ftello(fs->f);
+
+	ast_debug(4, "filestream(filename=%s,pos=%ld), frame(datalen=%d,samples=%d,ts=%ld,len=%ld,seqno=%d)\n",
+			fs->filename, position,
+			f->datalen, f->samples, f->ts, f->len, f->seqno);
+
 	if (f->frametype != AST_FRAME_VOICE) {
 		ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
 		return -1;
@@ -74,14 +96,30 @@
 		ast_log(LOG_WARNING, "Asked to write non-G729 frame (%s)!\n", ast_getformatname(&f->subclass.format));
 		return -1;
 	}
-	if (f->datalen % 10) {
-		ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 10\n", f->datalen);
+	if (f->datalen % G729A_FRAME_SIZE) {
+		if (f->datalen % G729A_FRAME_SIZE == G729A_CNG_SIZE) {
+			frame_has_cng = 1;
+			writelen -= G729A_CNG_SIZE;
+			if (!pvt->detected_vad) {
+				ast_log(LOG_WARNING, "Probable CNG parameter update detected, this is a bug in the sender who should not be sending CNG updates - try and switch off Voice Activity Detected (VAD) or Silence Suppression on the sender.\n");
+				pvt->detected_vad = 1;
+			}
+		} else {
+			ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of %d\n", f->datalen, G729A_FRAME_SIZE);
 		return -1;
 	}
-	if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
-			ast_log(LOG_WARNING, "Bad write (%d/10): %s\n", res, strerror(errno));
+	}
+	if (!pvt->warned_wrong_write_offset && position % G729A_FRAME_SIZE) {
+		ast_log(LOG_WARNING, "Writing a G729A frame to the wrong offset.  This is indicative of a bug, please contact jaco@uls.co.za for assistance.\n");
+		pvt->warned_wrong_write_offset = 1;
+	}
+	if ((res = fwrite(f->data.ptr, 1, writelen, fs->f)) != writelen) {
+			ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, writelen, strerror(errno));
 			return -1;
 	}
+	/* Pre-emptive seek G729A_CNG_SIZE bytes ahead in case of CNG */
+	if (frame_has_cng)
+		fseeko(fs->f, G729A_CNG_SIZE, SEEK_CUR);
 	return 0;
 }
 
@@ -94,7 +132,8 @@
 	fseeko(fs->f, 0, SEEK_END);
 	max = ftello(fs->f);
 	
-	bytes = BUF_SIZE * (sample_offset / G729A_SAMPLES);
+	/* Sample offset does not need to be a multiple of G729A_FRAME_SAMPLES in case of CNG having being received, the destination seek point, however, does */
+	bytes = sample_offset * G729A_FRAME_SIZE / G729A_FRAME_SAMPLES;
 	if (whence == SEEK_SET)
 		offset = bytes;
 	else if (whence == SEEK_CUR || whence == SEEK_FORCECUR)
@@ -106,6 +145,13 @@
 	}
 	/* protect against seeking beyond begining. */
 	offset = (offset < min)?min:offset;
+	ast_debug(4, "g729_seek(%s, %lu, %s), cur=%lu, offset=%lu\n",
+			fs->filename, sample_offset, whence == SEEK_SET ? "SEEK_SET" :
+				whence == SEEK_CUR ? "SEEK_CUR" :
+				whence == SEEK_FORCECUR ? "SEEK_FORCECUR" :
+				whence == SEEK_END ? "SEEK_END" : "SEEK_???",
+				cur,
+				offset);
 	if (fseeko(fs->f, offset, SEEK_SET) < 0)
 		return -1;
 	return 0;
@@ -131,7 +177,7 @@
 static off_t g729_tell(struct ast_filestream *fs)
 {
 	off_t offset = ftello(fs->f);
-	return (offset/BUF_SIZE)*G729A_SAMPLES;
+	return offset * G729A_FRAME_SAMPLES / G729A_FRAME_SIZE;
 }
 
 static struct ast_format_def g729_f = {
@@ -142,7 +188,8 @@
 	.trunc = g729_trunc,
 	.tell = g729_tell,
 	.read = g729_read,
-	.buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
+	.buf_size = G729A_BUF_SIZE + AST_FRIENDLY_OFFSET,
+	.desc_size = sizeof(struct ast_g729_pvt),
 };
 
 static int load_module(void)