From 6aa882b515f5d86c8c64e254b087cafbaae881ce Mon Sep 17 00:00:00 2001 From: Holger Hans Peter Freyther Date: Tue, 3 Aug 2010 14:35:50 +0000 Subject: mgcp: Allow switching the audio streams, patch the header Patch the sequence number, the SSRC and the timestamp to allow to mix various voice streams, e.g. toggling the loop during the call. --- openbsc/src/mgcp/mgcp_network.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) (limited to 'openbsc/src') diff --git a/openbsc/src/mgcp/mgcp_network.c b/openbsc/src/mgcp/mgcp_network.c index d2dbeebe4..b5e2cddf8 100644 --- a/openbsc/src/mgcp/mgcp_network.c +++ b/openbsc/src/mgcp/mgcp_network.c @@ -97,6 +97,7 @@ int mgcp_send_dummy(struct mgcp_endpoint *endp) static void patch_and_count(struct mgcp_rtp_state *state, int payload, char *data, int len) { uint16_t seq; + uint32_t timestamp; struct rtp_hdr *rtp_hdr; if (len < sizeof(*rtp_hdr)) @@ -104,15 +105,36 @@ static void patch_and_count(struct mgcp_rtp_state *state, int payload, char *dat rtp_hdr = (struct rtp_hdr *) data; seq = ntohs(rtp_hdr->sequence); + timestamp = ntohl(rtp_hdr->timestamp); if (!state->initialized) { - state->seq_no = seq; + state->seq_no = seq - 1; + state->ssrc = state->orig_ssrc = rtp_hdr->ssrc; state->initialized = 1; - } else if (state->seq_no + 1u != seq) - state->lost_no = abs(seq - (state->seq_no + 1)); + state->last_timestamp = timestamp; + } else if (state->ssrc != rtp_hdr->ssrc) { + state->ssrc = rtp_hdr->ssrc; + state->seq_offset = (state->seq_no + 1) - seq; + state->timestamp_offset = state->last_timestamp - timestamp; + LOGP(DMGCP, LOGL_NOTICE, "The SSRC changed... SSRC: %u offset: %d\n", + state->ssrc, state->seq_offset); + } + + /* apply the offset and store it back to the packet */ + seq += state->seq_offset; + rtp_hdr->sequence = htons(seq); + rtp_hdr->ssrc = state->orig_ssrc; + timestamp += state->timestamp_offset; + rtp_hdr->timestamp = htonl(timestamp); + + /* seq changed, now compare if we have lost something */ + if (state->seq_no + 1u != seq) + state->lost_no = abs(seq - (state->seq_no + 1)); state->seq_no = seq; + state->last_timestamp = timestamp; + if (payload < 0) return; -- cgit v1.2.3