Fix IndexPid.

container/mts/mpegts.go

@@ -221,7 +221,7 @@ func LastPid(d []byte, pid uint16) (pkt []byte, i int, err error) {
 // along with optional metadata if present. Commonly used to find a
 // PAT immediately followed by a PMT.
 func IndexPid(d []byte, pids ...uint16) (idx int, m map[string]string, err error) {
-	prev := 0
+	idx = -1
 	for _, pid := range pids {
 		pkt, i, _err := FindPid(d, pid)
 		if err != nil {
@@ -231,16 +231,13 @@ func IndexPid(d []byte, pids ...uint16) (idx int, m map[string]string, err error
 		if pid == PmtPid {
 			m, _ = metaFromPMT(pkt)
 		}
-		if prev == 0 {
+		if idx == -1 {
 			idx = i
-			prev = i
-			continue
-		}
-		if i != prev+PacketSize {
+		} else if i != 0 {
 			err = errors.New("PIDs not consecutive")
 			return
 		}
-		prev = i
+		d = d[i+PacketSize:]
 	}
 	return
 }