From 868d01527cafc7ec6baabb5a92a0379726769d61 Mon Sep 17 00:00:00 2001
From: Saxon <saxon@ausocean.org>
Date: Fri, 10 May 2019 14:18:55 +0930
Subject: [PATCH] container/mts/mpegts.go: wrote GetPTSRange func This func
 will return the first and last PTS from an MPEGTS clip by finding the first
 access unit, and then by moving backward from the end of the clip to find the
 start of the final PES packet.

---
 container/mts/mpegts.go | 44 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/container/mts/mpegts.go b/container/mts/mpegts.go
index ed8cbe02..4d8ec4a8 100644
--- a/container/mts/mpegts.go
+++ b/container/mts/mpegts.go
@@ -33,6 +33,7 @@ import (
 	"fmt"
 
 	"github.com/Comcast/gots/packet"
+	"github.com/Comcast/gots/pes"
 )
 
 // General mpegts packet properties.
@@ -315,3 +316,46 @@ func DiscontinuityIndicator(f bool) Option {
 		p[DiscontinuityIndicatorIdx] |= DiscontinuityIndicatorMask & set
 	}
 }
+
+// GetPTSRange retreives the first and last PTS of an MPEGTS clip.
+func GetPTSRange(clip []byte) (pts [2]uint64, err error) {
+	// Find the first video packet.
+	pkt, _, err := FindPid(clip, videoPid)
+	if err != nil {
+		return [2]uint64{}, err
+	}
+
+	// Get the payload of the packet, which will be the start of the PES packet.
+	var _pkt packet.Packet
+	copy(_pkt[:], pkt)
+	payload, err := packet.Payload(&_pkt)
+	if err != nil {
+		return [2]uint64{}, err
+	}
+
+	// Get the the first PTS from the PES header.
+	_pes, err := pes.NewPESHeader(payload)
+	if err != nil {
+		return [2]uint64{}, err
+	}
+	pts[0] = _pes.PTS()
+
+	// Get the final PTS and calculate PTS immediately after.
+	for i := len(clip) - PacketSize; i >= 0; i -= PacketSize {
+		copy(_pkt[:], clip[i:i+PacketSize])
+		if packet.PayloadUnitStartIndicator(&_pkt) {
+			payload, err = packet.Payload(&_pkt)
+			if err != nil {
+				return [2]uint64{}, err
+			}
+			_pes, err = pes.NewPESHeader(payload)
+			if err != nil {
+				return [2]uint64{}, err
+			}
+			pts[1] = _pes.PTS()
+			return
+		}
+	}
+
+	return [2]uint64{}, errors.New("could only find one access unit in mpegts clip")
+}