diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h
index 8b6a56b..0b52c1c 100644
--- a/openbsc/include/openbsc/mgcp_internal.h
+++ b/openbsc/include/openbsc/mgcp_internal.h
@@ -77,6 +77,10 @@
 
 	/* per endpoint data */
 	int payload_type;
+	uint32_t rate;
+	uint32_t frame_duration_num;
+	uint32_t frame_duration_den;
+	int  frames_per_packet;
 	char *fmtp_extra;
 
 	/*
diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index 72d0a5c..75d39c1 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -238,15 +238,30 @@
 		state->transit = arrival_time - timestamp;
 		state->out_stream = state->in_stream;
 	} else if (state->in_stream.ssrc != rtp_hdr->ssrc) {
+		int32_t tsdelta = state->out_stream.last_tsdelta;
+		if (tsdelta == 0) {
+			tsdelta = rtp_end->rate * rtp_end->frames_per_packet *
+				rtp_end->frame_duration_num /
+				rtp_end->frame_duration_den;
+			LOGP(DMGCP, LOGL_NOTICE,
+			     "Computed timestamp delta %d based on "
+			     "rate %d, num frames %d, frame duration %d/%d\n",
+			     tsdelta, rtp_end->rate, rtp_end->frames_per_packet,
+			     rtp_end->frame_duration_num,
+			     rtp_end->frame_duration_den);
+		}
 		state->in_stream.ssrc = rtp_hdr->ssrc;
 		state->seq_offset = (state->out_stream.last_seq + 1) - seq;
-		state->timestamp_offset = state->out_stream.last_timestamp - timestamp;
+		state->timestamp_offset =
+			(state->out_stream.last_timestamp + tsdelta) - timestamp;
 		state->patch = endp->allow_patch;
 		LOGP(DMGCP, LOGL_NOTICE,
-			"The SSRC changed on 0x%x SSRC: %u offset: %d from %s:%d in %d\n",
+			"The SSRC changed on 0x%x SSRC: %u offset: %d tsdelta: %d "
+			"from %s:%d in %d\n",
 			ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
-			state->seq_offset, inet_ntoa(addr->sin_addr),
-			ntohs(addr->sin_port), endp->conn_mode);
+			state->seq_offset, tsdelta,
+			inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
+			endp->conn_mode);
 
 		state->in_stream.last_tsdelta = 0;
 	} else {
diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index aec2cb0..7096495 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -40,6 +40,12 @@
 	for (line = strtok_r(NULL, "\r\n", &save); line;\
 	     line = strtok_r(NULL, "\r\n", &save))
 
+/* Assume audio frame length of 20ms */
+#define DEFAULT_RTP_AUDIO_FRAME_DUR_NUM 20
+#define DEFAULT_RTP_AUDIO_FRAME_DUR_DEN 1000
+#define DEFAULT_RTP_AUDIO_FRAMES_PER_PACKET 1
+#define DEFAULT_RTP_AUDIO_DEFAULT_RATE  8000
+
 static void mgcp_rtp_end_reset(struct mgcp_rtp_end *end);
 
 struct mgcp_parse_data {
@@ -965,6 +971,12 @@
 	end->local_alloc = -1;
 	talloc_free(end->fmtp_extra);
 	end->fmtp_extra = NULL;
+
+	/* Set default values */
+	end->frame_duration_num = DEFAULT_RTP_AUDIO_FRAME_DUR_NUM;
+	end->frame_duration_den = DEFAULT_RTP_AUDIO_FRAME_DUR_DEN;
+	end->frames_per_packet  = DEFAULT_RTP_AUDIO_FRAMES_PER_PACKET;
+	end->rate = DEFAULT_RTP_AUDIO_DEFAULT_RATE;
 }
 
 static void mgcp_rtp_end_init(struct mgcp_rtp_end *end)
diff --git a/openbsc/tests/mgcp/mgcp_test.c b/openbsc/tests/mgcp/mgcp_test.c
index b2d20b4..d36aaa8 100644
--- a/openbsc/tests/mgcp/mgcp_test.c
+++ b/openbsc/tests/mgcp/mgcp_test.c
@@ -417,7 +417,7 @@
 	struct mgcp_trunk_config trunk;
 	struct mgcp_endpoint endp;
 	struct mgcp_rtp_state state;
-	struct mgcp_rtp_end rtp;
+	struct mgcp_rtp_end *rtp = &endp.net_end;
 	struct sockaddr_in addr = {0};
 	char buffer[4096];
 
@@ -426,15 +426,21 @@
 	memset(&trunk, 0, sizeof(trunk));
 	memset(&endp, 0, sizeof(endp));
 	memset(&state, 0, sizeof(state));
-	memset(&rtp, 0, sizeof(rtp));
 
 	trunk.number_endpoints = 1;
 	trunk.endpoints = &endp;
-
-	rtp.payload_type = 98;
-	endp.allow_patch = 1;
 	endp.tcfg = &trunk;
 
+	/* This doesn't free endp but resets/frees all fields of the structure
+	 * and invokes mgcp_rtp_end_reset() for each mgcp_rtp_end. OTOH, it
+	 * expects valid pointer fields (either NULL or talloc'ed), so the
+	 * memset is still needed. It also requires that endp.tcfg and
+	 * trunk.endpoints are set up properly. */
+	mgcp_free_endp(&endp);
+
+	rtp->payload_type = 98;
+	endp.allow_patch = 1;
+
 	for (i = 0; i < ARRAY_SIZE(test_rtp_packets1); ++i) {
 		struct rtp_packet_info *info = test_rtp_packets1 + i;
 
@@ -442,7 +448,7 @@
 		OSMO_ASSERT(info->len >= 0);
 		memmove(buffer, info->data, info->len);
 
-		mgcp_patch_and_count(&endp, &state, &rtp, &addr,
+		mgcp_patch_and_count(&endp, &state, rtp, &addr,
 				     buffer, info->len);
 
 		printf("TS: %d, dTS: %d, TS Errs: in %d, out %d\n",
diff --git a/openbsc/tests/mgcp/mgcp_test.ok b/openbsc/tests/mgcp/mgcp_test.ok
index 8c3fa26..5666424 100644
--- a/openbsc/tests/mgcp/mgcp_test.ok
+++ b/openbsc/tests/mgcp/mgcp_test.ok
@@ -41,7 +41,7 @@
 TS: 1400, dTS: 120, TS Errs: in 4, out 4
 TS: 1560, dTS: 160, TS Errs: in 5, out 5
 TS: 1720, dTS: 160, TS Errs: in 5, out 5
-TS: 1720, dTS: 160, TS Errs: in 5, out 6
-TS: 1880, dTS: 160, TS Errs: in 5, out 6
-TS: 2040, dTS: 160, TS Errs: in 5, out 6
+TS: 1880, dTS: 160, TS Errs: in 5, out 5
+TS: 2040, dTS: 160, TS Errs: in 5, out 5
+TS: 2200, dTS: 160, TS Errs: in 5, out 5
 Done