Remove packet pacing.

It's not obvious that it's useful, especially now that the writer
is split into multiple threads.  Do retain the dynamically computed
delay in case of audio congestion.

rtpwriter.go

@@ -17,8 +17,6 @@ type packetIndex struct {
 	seqno uint16
 	// the index in the cache
 	index uint16
-	// the expected delay until the next packet, in jiffies
-	delay uint32
 }
 
 // An rtpWriterPool is a set of rtpWriters
@@ -109,7 +107,7 @@ func (wp *rtpWriterPool) close() {
 
 // write writes a packet stored in the packet cache to all local tracks
 func (wp *rtpWriterPool) write(seqno uint16, index uint16, delay uint32, isvideo bool, marker bool) {
-	pi := packetIndex{seqno, index, delay}
+	pi := packetIndex{seqno, index}
 
 	var dead []*rtpWriter
 	for _, w := range wp.writers {
@@ -143,11 +141,6 @@ func (wp *rtpWriterPool) write(seqno uint16, index uint16, delay uint32, isvideo
 			timer := time.NewTimer(rtptime.ToDuration(
 				uint64(d), rtptime.JiffiesPerSec,
 			))
-			if pi.delay > d {
-				pi.delay -= d
-			} else {
-				pi.delay = 0
-			}
 
 			select {
 			case w.ch <- pi:
@@ -286,14 +279,6 @@ func rtpWriterLoop(writer *rtpWriter, conn *rtpUpConnection, track *rtpUpTrack)
 				continue
 			}
 
-			var delay time.Duration
-			if len(local) > 0 {
-				delay = rtptime.ToDuration(
-					uint64(pi.delay/uint32(len(local))),
-					rtptime.JiffiesPerSec,
-				)
-			}
-
 			kfNeeded := false
 			for _, l := range local {
 				err := l.WriteRTP(&packet)
@@ -304,9 +289,6 @@ func rtpWriterLoop(writer *rtpWriter, conn *rtpUpConnection, track *rtpUpTrack)
 					continue
 				}
 				l.Accumulate(uint32(bytes))
-				if delay > 0 {
-					time.Sleep(delay)
-				}
 			}
 
 			if kfNeeded {