stream/mts: fixing discontinuities that could be caused by ringbuffer

revid/mtsSender_test.go

@@ -0,0 +1,39 @@
+/*
+NAME
+  mtsSender_test.go
+
+DESCRIPTION
+  mtsSender_test.go contains tests that validate the functionalilty of the
+  mtsSender under senders.go. Tests include checks that the mtsSender is
+  segmenting sends correctly, and also that it can correct discontinuities.
+
+AUTHORS
+  Saxon A. Nelson-Milton <saxon@ausocean.org>
+
+LICENSE
+  mtsSender_test.go is Copyright (C) 2017-2019 the Australian Ocean Lab (AusOcean)
+
+  It is free software: you can redistribute it and/or modify them
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with revid in gpl.txt.  If not, see http://www.gnu.org/licenses.
+*/
+package revid
+
+import "testing"
+
+func TestSegment(t *testing.T) {
+
+}
+
+func TestDiscontinuity(t *testing.T) {
+
+}

revid/senders.go

@@ -114,6 +114,7 @@ type mtsSender struct {
 	buf      []byte
 	pkt      [mts.PacketSize]byte
 	fail     bool
+	discard  bool
 	repairer *mts.DiscontinuityRepairer
 	chunk    *ring.Chunk
 }
@@ -136,6 +137,25 @@ func (s *mtsSender) load(c *ring.Chunk) error {
 // in s.buf is sent, otherwise the packet is added to s.buf.
 func (s *mtsSender) send() error {
 	copy(s.pkt[:], s.chunk.Bytes())
+	p := (*packet.Packet)(&s.pkt)
+	pid := p.PID()
+	cc := p.ContinuityCounter()
+
+	if s.discard {
+		if pid != mts.PatPid {
+			return nil
+		}
+		s.discard = false
+	}
+
+	if pid == mts.VideoPid {
+		if cc != s.repairer.expectedCC(pid) {
+			s.discard = true
+			s.buf = s.buf[:0]
+			return nil
+		}
+	}
+
 	if s.fail || (((*packet.Packet)(&s.pkt)).PID() == mts.PatPid && len(s.buf) != 0) {
 		err := s.fixAndSend()
 		if err != nil {

stream/mts/discontinuity.go

@@ -80,7 +80,7 @@ func (dr *DiscontinuityRepairer) Repair(d []byte) error {
 
 // expectedCC returns the expected cc. If the cc hasn't been used yet, then 16
 // and false is returned.
-func (dr *DiscontinuityRepairer) expectedCC() (byte, bool) {
+func (dr *DiscontinuityRepairer) expectedCC(pid int) (byte, bool) {
 	if dr.expCC == 16 {
 		return 16, false
 	}