Add pre-roll burst config setting

This includes Common 306b5fc

4 files changed, 18 insertions, 13 deletions

diff --git a/doc/example.mux b/doc/example.mux
index 6682f0a..03fb3f0 100644
--- a/doc/example.mux
+++ b/doc/example.mux
@@ -50,6 +50,11 @@ general {
     ; your file is still valid.
     tist false
 
+    ; On startup, the timestamp is initialised to system time. If you want
+    ; to add an offset, uncomment the following line and give a number
+    ; in seconds.
+    ; tist_offset 0
+
     ; The URLs used to fetch the TAI bulletin can be overridden if needed.
     ; URLs are given as a pipe-separated list, and the default value is:
     ;tai_clock_bulletins "https://www.ietf.org/timezones/data/leap-seconds.list|https://raw.githubusercontent.com/eggert/tz/master/leap-seconds.list"
@@ -285,13 +290,15 @@ outputs {
     edi {
         ; Example EDI-over-TCP output
         ; If TIST is enabled, requires leap-second information
-        ;
-        ; When a new client connects, it will receive a pre-roll of 1.5x tist_offset seconds
-        ; worth of EDI data, so that it can quickly fill its buffers.
         destinations {
             example_tcp {
                 protocol tcp
                 listenport 13000
+                ; (Optional) When a new client connects, it will receive a pre-roll burst of EDI data, so that it can quickly fill
+                ; its buffers. The value given is the duration of the pre-roll in seconds.
+                ; It makes sense to have a value slightly larger than tist-offset to ensure the destination will receive
+                ; data that will allow it to start transmitting immediately.
+                ;preroll-burst 2.0
             }
         }
     }
diff --git a/lib/edioutput/EDIConfig.h b/lib/edioutput/EDIConfig.h
index a7225a7..1997210 100644
--- a/lib/edioutput/EDIConfig.h
+++ b/lib/edioutput/EDIConfig.h
@@ -53,6 +53,9 @@ struct udp_destination_t : public destination_t {
 struct tcp_server_t : public destination_t {
     unsigned int listen_port = 0;
     size_t max_frames_queued = 1024;
+
+    // The TCP Server output can preroll a fixed number of previous buffers each time a new client connects.
+    size_t tcp_server_preroll_buffers = 0;
 };
 
 // TCP client that connects to one endpoint
@@ -74,9 +77,6 @@ struct configuration_t {
     // Spread transmission of fragments in time. 1.0 = 100% means spreading over the whole duration of a frame (24ms)
     // Above 100% means that the fragments are spread over several 24ms periods, interleaving the AF packets.
 
-    // TCP Server output can preroll a fixed number of previous buffers each time a new client connects.
-    size_t tcp_server_preroll_buffers = 0;
-
     bool enabled() const { return destinations.size() > 0; }
 
     void print() const;
diff --git a/lib/edioutput/Transport.cpp b/lib/edioutput/Transport.cpp
index a870aa0..8ebb9fc 100644
--- a/lib/edioutput/Transport.cpp
+++ b/lib/edioutput/Transport.cpp
@@ -66,7 +66,7 @@ Sender::Sender(const configuration_t& conf) :
     edi_pft(m_conf)
 {
     if (m_conf.verbose) {
-        etiLog.level(info) << "Setup EDI Output, TCP output preroll " << m_conf.tcp_server_preroll_buffers;
+        etiLog.level(info) << "Setup EDI Output";
     }
 
     for (const auto& edi_dest : m_conf.destinations) {
@@ -82,7 +82,7 @@ Sender::Sender(const configuration_t& conf) :
         }
         else if (auto tcp_dest = dynamic_pointer_cast<edi::tcp_server_t>(edi_dest)) {
             auto dispatcher = make_shared<Socket::TCPDataDispatcher>(
-                    tcp_dest->max_frames_queued, m_conf.tcp_server_preroll_buffers);
+                    tcp_dest->max_frames_queued, tcp_dest->tcp_server_preroll_buffers);
 
             dispatcher->start(tcp_dest->listen_port, "0.0.0.0");
             tcp_dispatchers.emplace(tcp_dest.get(), dispatcher);
diff --git a/src/DabMux.cpp b/src/DabMux.cpp
index 4373265..f6a69bb 100644
--- a/src/DabMux.cpp
+++ b/src/DabMux.cpp
@@ -348,6 +348,9 @@ int main(int argc, char *argv[])
                         auto dest = make_shared<edi::tcp_server_t>();
                         dest->listen_port = pt_edi_dest.second.get<unsigned int>("listenport");
                         dest->max_frames_queued = pt_edi_dest.second.get<size_t>("max_frames_queued", 500);
+                        double preroll = pt_edi_dest.second.get<double>("preroll-burst", 0.0);
+                        dest->tcp_server_preroll_buffers = ceil(preroll / 24e-3);
+
                         edi_conf.destinations.push_back(dest);
                     }
                     else {
@@ -355,11 +358,6 @@ int main(int argc, char *argv[])
                     }
                 }
 
-                const auto tist_offset = pt.get<int>("general.tist_offset", 0);
-                // By keeping 1.5 x tist_offset worth of EDI in the pre-roll buffer, we ensure that a new client can
-                // immediately send out frames according to their timestamp.
-                edi_conf.tcp_server_preroll_buffers = ceil(1.5 * (tist_offset / 24e-3));
-
                 edi_conf.dump = pt_edi.get<bool>("dump", false);
                 edi_conf.enable_pft = pt_edi.get<bool>("enable_pft", false);
                 edi_conf.verbose = pt_edi.get<bool>("verbose", false);