mgcp/rtp: Fix RTP timestamps if enabled
This forces the output timing to fulfill
dTS = dSegNo * fixedPacketDuration
where dSegNo = seqNo - lastSeqNo.
If timestamp patching is enabled, the output timestamp will be set
to lastTimestamp + dTS. This kind of relative updating is used to
handle seqNo- and timestamp-wraparounds properly.
The updating of timestamp and SSRC has been separated and the patch
field of mgcp_rtp_state has been renamed to patch_ssrc to reflect
it's semantics more closely. The offset fields are now used always
and will change the corresponding header field if they are != 0.
Ticket: OW#1065
Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index 79c9e1a..6463ae0 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -278,7 +278,7 @@
state->timestamp_offset =
(state->out_stream.last_timestamp + tsdelta) -
timestamp;
- state->patch = 1;
+ state->patch_ssrc = 1;
ssrc = state->orig_ssrc;
if (rtp_end->force_constant_ssrc != -1)
rtp_end->force_constant_ssrc -= 1;
@@ -300,7 +300,7 @@
seq, timestamp, "input",
&state->in_stream.last_tsdelta);
- if (state->patch)
+ if (state->patch_ssrc)
ssrc = state->orig_ssrc;
}
@@ -308,15 +308,37 @@
state->in_stream.last_timestamp = timestamp;
state->in_stream.last_seq = seq;
- /* apply the offset and store it back to the packet */
- if (state->patch) {
- seq += state->seq_offset;
- rtp_hdr->sequence = htons(seq);
+ if (rtp_end->force_constant_timing &&
+ state->out_stream.ssrc == ssrc && state->packet_duration) {
+ int delta_seq = seq + state->seq_offset - state->out_stream.last_seq;
+ int timestamp_offset =
+ state->out_stream.last_timestamp - timestamp +
+ delta_seq * state->packet_duration;
+ if (state->timestamp_offset != timestamp_offset) {
+ state->timestamp_offset = timestamp_offset;
+
+ LOGP(DMGCP, LOGL_NOTICE,
+ "Timestamp patching enabled on 0x%x SSRC: %u "
+ "SeqNo delta: %d, TS offset: %d, "
+ "from %s:%d in %d\n",
+ ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
+ delta_seq, state->timestamp_offset,
+ inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
+ endp->conn_mode);
+ }
+ }
+
+ /* Store the updated SSRC back to the packet */
+ if (state->patch_ssrc)
rtp_hdr->ssrc = htonl(ssrc);
- timestamp += state->timestamp_offset;
- rtp_hdr->timestamp = htonl(timestamp);
- }
+ /* Apply the offset and store it back to the packet.
+ * This won't change anything if the offset is 0, so the conditional is
+ * omitted. */
+ seq += state->seq_offset;
+ rtp_hdr->sequence = htons(seq);
+ timestamp += state->timestamp_offset;
+ rtp_hdr->timestamp = htonl(timestamp);
/* Check again, whether the timestamps are still valid */
if (state->out_stream.ssrc == ssrc)