change zmqInput buffering handling

1 files changed, 52 insertions, 14 deletions

diff --git a/src/dabInputZmq.cpp b/src/dabInputZmq.cpp
index 09b4688..b560313 100644
--- a/src/dabInputZmq.cpp
+++ b/src/dabInputZmq.cpp
@@ -121,13 +121,39 @@ int dabInputZmqReadFrame(dabInputOperations* ops, void* args, void* buffer, int
     int rc;
     dabInputZmqData* input = (dabInputZmqData*)args;
 
-    // Get new ZMQ messages
-    if (input->frame_buffer.size() < INPUT_ZMQ_MAX_BUFFER_SIZE) {
-        rc = dabInputZmqReadFromSocket(input, size);
-    }
-    else {
+    /* We must *always* read data from the ZMQ socket,
+     * to make sure that ZMQ internal buffers are emptied
+     * quickly. It's the only way to control the buffers
+     * of the whole path from encoder to our frame_buffer.
+     */
+    rc = dabInputZmqReadFromSocket(input, size);
+
+    /* Notify of a buffer overrun, and drop some frames */
+    if (input->frame_buffer.size() >= INPUT_ZMQ_MAX_BUFFER_SIZE) {
         global_stats.notifyOverrun(input->uri);
-        rc = 0;
+
+        /* If the buffer is really too full, we drop as many frames as needed
+         * to get down to the prebuffering size. We would like to have our buffer
+         * filled to the prebuffering length.
+         */
+        if (input->frame_buffer.size() >= 1.5*INPUT_ZMQ_MAX_BUFFER_SIZE) {
+            size_t over_max = input->frame_buffer.size() - INPUT_ZMQ_PREBUFFERING;
+
+            while (over_max--) {
+                input->frame_buffer.pop_front();
+            }
+        }
+        else {
+            /* Our frame_buffer contains DAB logical frames. Five of these make one
+             * AAC superframe.
+             *
+             * Dropping this superframe amounts to dropping 120ms of audio. */
+            input->frame_buffer.pop_front();
+            input->frame_buffer.pop_front();
+            input->frame_buffer.pop_front();
+            input->frame_buffer.pop_front();
+            input->frame_buffer.pop_front();
+        }
     }
 
     if (input->prebuffering > 0) {
@@ -136,6 +162,8 @@ int dabInputZmqReadFrame(dabInputOperations* ops, void* args, void* buffer, int
         if (input->prebuffering == 0)
             etiLog.log(info, "inputZMQ %s input pre-buffering complete\n",
                 input->uri.c_str());
+
+        /* During prebuffering, give a zeroed frame to the mux */
         global_stats.notifyUnderrun(input->uri);
         memset(buffer, 0, size);
         return size;
@@ -149,12 +177,16 @@ int dabInputZmqReadFrame(dabInputOperations* ops, void* args, void* buffer, int
                 input->uri.c_str());
         // reset prebuffering
         input->prebuffering = INPUT_ZMQ_PREBUFFERING;
+
+        /* We have no data to give, we give a zeroed frame */
         global_stats.notifyUnderrun(input->uri);
         memset(buffer, 0, size);
         return size;
     }
     else
     {
+        /* Normal situation, give a frame from the frame_buffer */
+
         char* newframe = input->frame_buffer.front();
         memcpy(buffer, newframe, size);
         delete[] newframe;
@@ -179,20 +211,24 @@ int dabInputZmqReadFromSocket(dabInputZmqData* input, int framesize)
         if (errno != EAGAIN) {
             etiLog.log(error, "Failed to receive zmq message: %s\n", zmq_strerror(errno));
         }
+        zmq_msg_close(&msg);
         return 0;
     }
 
     char* data = (char*)zmq_msg_data(&msg);
 
-    if (nBytes == 5*framesize) // five frames per superframe
+    /* TS 102 563, Section 6:
+     * Audio super frames are transported in five successive DAB logical frames
+     * with additional error protection.
+     */
+    if (nBytes == 5*framesize)
     {
         if (input->frame_buffer.size() > INPUT_ZMQ_MAX_BUFFER_SIZE) {
-            etiLog.log(warn, "inputZMQ %s input buffer full (%d), dropping frame !\n",
-                input->frame_buffer.size(), input->uri.c_str());
+            etiLog.level(warn) <<
+                "inputZMQ " << input->uri <<
+                " buffer full (" << input->frame_buffer.size() << "),"
+                " dropping incoming superframe !";
             nBytes = 0;
-
-            // we actually drop 2 frames
-            input->frame_buffer.pop_front();
         }
         else {
             // copy the input frame blockwise into the frame_buffer
@@ -207,8 +243,10 @@ int dabInputZmqReadFromSocket(dabInputZmqData* input, int framesize)
     }
     else
     {
-        etiLog.log(error, "ZMQ Wrong data size: recv'd %d, need %d \n",
-                nBytes, 5*framesize);
+        etiLog.level(error) <<
+            "inputZMQ " << input->uri <<
+            " wrong data size: recv'd" << nBytes <<
+            ", need " << 5*framesize << ".";
         nBytes = 0;
     }