Issue 688: UDP packet has timestamp field

docs/sphinx/internals/timestamps.rst

@@ -8,11 +8,12 @@ Timestamps
 Types of timestamps
 ===================
 
-:doc:`Packets and frames </internals/packets_frames>` have three major types of timestamps:
+:doc:`Packets and frames </internals/packets_frames>` have four major types of timestamps:
 
 * STS - stream timestamp
 * CTS - capture timestamp
 * RTS - receive timestamp
+* QTS - queue timestamp
 
 **Stream timestamp** (STS) describes position of the first sample in packet or frame using abstract stream clock.
 
@@ -37,6 +38,10 @@ The clock for RTS is the same as for CTS: local Unix-time UTC clock, counting na
 
 This timestamp is used only on receiver and only for packets.
 
+**Queue timestamp** (QTS) is the time when the packet was transferred to a local queue of a sink-thread. The main difference with RTS is thread-switch time.
+
+This timestamp is used only on receiver and only for packets.
+
 Use of timestamps
 =================
 

src/internal_modules/roc_packet/router.cpp

@@ -55,6 +55,10 @@ status::StatusCode Router::write(const PacketPtr& packet) {
 
     if (Route* route = find_route_(packet->flags())) {
         if (allow_route_(*route, *packet)) {
+            if (packet->udp()) {
+                packet->udp()->queue_ts = core::timestamp(core::ClockUnix);
+            }
+
             return route->writer->write(packet);
         }
     }

src/internal_modules/roc_packet/target_libuv/roc_packet/udp.cpp

@@ -13,7 +13,8 @@ namespace roc {
 namespace packet {
 
 UDP::UDP()
-    : receive_timestamp(0) {
+    : receive_timestamp(0)
+    , queue_ts(0) {
     memset(&request, 0, sizeof(request));
 }
 

src/internal_modules/roc_packet/target_libuv/roc_packet/udp.h

@@ -33,6 +33,13 @@ struct UDP {
     //! Packet receive timestamp (RTS), nanoseconds since Unix epoch.
     core::nanoseconds_t receive_timestamp;
 
+    //! Timestamp in ns since unix-epoch. It points to a moment when
+    //! the packet was transferred to a sink-thread, that "consumes"
+    //! this packet. The reason to have it separate is that this
+    //! allows us to account additional jitter introduced by
+    //! thread-switch time.
+    core::nanoseconds_t queue_ts;
+
     //! Sender request state.
     uv_udp_send_t request;
 

src/tests/roc_rtp/test_link_meter.cpp

@@ -29,9 +29,10 @@ packet::PacketPtr new_packet(packet::seqnum_t sn) {
     packet::PacketPtr packet = packet_factory.new_packet();
     CHECK(packet);
 
-    packet->add_flags(packet::Packet::FlagRTP);
+    packet->add_flags(packet::Packet::FlagRTP | packet::Packet::FlagUDP);
     packet->rtp()->payload_type = PayloadType_L16_Stereo;
     packet->rtp()->seqnum = sn;
+    packet->udp()->queue_ts = 666;
 
     return packet;
 }