[PATCH 4/5] mgcp/rtp: Compute delta timestamp based on wallclock

Currently, when the SSRC changes within a stream and SSRC fixing is enabled, the RTP timestamp between the last packet the has been received with the old SSRC and the first packet of the new SSRC is always incremented by one packet duration. This can lead to audio muting (at least with the nanoBTS) when the wallclock interval between these packets is too large (> 1s). This patch change the implementation to base the RTP timestamp offset on the wallclock interval that has passed between these two packets. Ticket: OW#466 Sponsored-by: On-Waves ehf --- openbsc/include/openbsc/mgcp_internal.h | 1 + openbsc/src/libmgcp/mgcp_network.c | 12 ++++++++++-- openbsc/tests/mgcp/mgcp_test.ok | 16 ++++++++-------- 3 files changed, 19 insertions(+), 10 deletions(-) diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h index 28ea678..9b97165 100644 --- a/openbsc/include/openbsc/mgcp_internal.h +++ b/openbsc/include/openbsc/mgcp_internal.h @@ -46,6 +46,7 @@ struct mgcp_rtp_stream_state { uint32_t last_timestamp; uint32_t err_ts_counter; int32_t last_tsdelta; + uint32_t last_arrival_time; }; struct mgcp_rtp_state { diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c index 39d5807..5363fb8 100644 --- a/openbsc/src/libmgcp/mgcp_network.c +++ b/openbsc/src/libmgcp/mgcp_network.c @@ -415,10 +415,17 @@ void mgcp_patch_and_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *sta state->in_stream.ssrc = ssrc; if (rtp_end->force_constant_ssrc) { - const int16_t delta_seq = 1; + int16_t delta_seq; + /* Always increment seqno by 1 */ state->seq_offset = - (state->out_stream.last_seq + delta_seq) - seq; + (state->out_stream.last_seq + 1) - seq; + + /* Estimate number of packets that would have been sent */ + delta_seq = + (arrival_time - state->in_stream.last_arrival_time + + state->packet_duration/2) / + state->packet_duration; adjust_rtp_timestamp_offset(endp, state, rtp_end, addr, delta_seq, timestamp); @@ -452,6 +459,7 @@ void mgcp_patch_and_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *sta /* Save before patching */ state->in_stream.last_timestamp = timestamp; state->in_stream.last_seq = seq; + state->in_stream.last_arrival_time = arrival_time; if (rtp_end->force_aligned_timing && state->out_stream.ssrc == ssrc && state->packet_duration) diff --git a/openbsc/tests/mgcp/mgcp_test.ok b/openbsc/tests/mgcp/mgcp_test.ok index 7883574..e383fb5 100644 --- a/openbsc/tests/mgcp/mgcp_test.ok +++ b/openbsc/tests/mgcp/mgcp_test.ok @@ -167,14 +167,14 @@ In TS: 36888, dTS: 160, Seq: 25 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 Stats: Jitter = 27, Transit = 4294967216 In TS: 160000, dTS: 0, Seq: 1000 -Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 -Stats: Jitter = 765, Transit = 11760 +Out TS change: 12000, dTS: 12000, Seq change: 1, TS Err change: in +0, out +0 +Stats: Jitter = 25, Transit = 4294967216 In TS: 160160, dTS: 160, Seq: 1001 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 -Stats: Jitter = 718, Transit = 11759 +Stats: Jitter = 24, Transit = 4294967215 In TS: 160320, dTS: 160, Seq: 1002 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 -Stats: Jitter = 673, Transit = 11759 +Stats: Jitter = 22, Transit = 4294967215 Testing packet error detection. Output SSRC changed to 11223344 In TS: 0, dTS: 0, Seq: 0 @@ -447,12 +447,12 @@ In TS: 36888, dTS: 160, Seq: 25 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 Stats: Jitter = 25, Transit = 4294967136 In TS: 160000, dTS: 0, Seq: 1000 -Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 -Stats: Jitter = 763, Transit = 11680 +Out TS change: 12000, dTS: 12000, Seq change: 1, TS Err change: in +0, out +0 +Stats: Jitter = 23, Transit = 4294967136 In TS: 160160, dTS: 160, Seq: 1001 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 -Stats: Jitter = 716, Transit = 11679 +Stats: Jitter = 22, Transit = 4294967135 In TS: 160320, dTS: 160, Seq: 1002 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0 -Stats: Jitter = 671, Transit = 11679 +Stats: Jitter = 21, Transit = 4294967135 Done -- 1.7.9.5