Merge pull request #170 from morrowa/fix_ebp_group_parsing

Correct EBP group ID parsing to read 7-bit ID field
Comcast · Aug 16, 2022 · 975de6e · 975de6e
2 parents 4c4c4eb + 62fa5de
commit 975de6e
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Showing 6 changed files with 130 additions and 24 deletions.
diff --git a/ebp/baseebp.go b/ebp/baseebp.go
@@ -146,10 +146,10 @@ func (ebp *baseEbp) SetIsEmpty(value bool) {
 // but Stream Sync and SCTE-35 were the only two ever to get implemented. MK was the only Transcoder to implement SCTE-35 within the
 // Grouping ID section and we never leveraged that data on any downstream devices.
 func (ebp *baseEbp) StreamSyncSignal() uint8 {
-	// The first byte is Grouping ID, the second byte is the sync signal
-	if len(ebp.Grouping) == 2 && ebp.Grouping[0] == 0x80 {
-		return ebp.Grouping[1]
+	for _, groupID := range ebp.Grouping {
+		if groupID == StreamSynchronized || groupID == StreamNotSynchronized {
+			return groupID
+		}
 	}
-
 	return InvalidStreamSyncSignal
 }
diff --git a/ebp/cablelabsebp.go b/ebp/cablelabsebp.go
@@ -122,12 +122,15 @@ func readCableLabsEbp(data []byte) (ebp *cableLabsEbp, err error) {
 
 	if ebp.GroupingFlag() {
 		var group byte
-		group = data[index]
+		var groupExtFlag bool
+		groupExtFlag = data[index]&0x80 != 0
+		group = data[index] & 0x7F
 		ebp.Grouping = append(ebp.Grouping, group)
 		index += uint8(1)
 
-		for group&0x80 != 0 {
-			group = data[index]
+		for groupExtFlag {
+			groupExtFlag = data[index]&0x80 != 0
+			group = data[index] & 0x7F
 			ebp.Grouping = append(ebp.Grouping, group)
 			index += uint8(1)
 		}
@@ -182,11 +185,15 @@ func (ebp *cableLabsEbp) Data() []byte {
 
 	if ebp.GroupingFlag() {
 		for i := range ebp.Grouping {
-			ebp.Grouping[i] |= 0x80 // set flag because this is not the last ID
-			if i == len(ebp.Grouping)-1 {
-				ebp.Grouping[i] &= 0x7F // last index does not have this flag set
+			var group byte
+			if i < len(ebp.Grouping)-1 {
+				// add the ext flag for all but the last group
+				group = ebp.Grouping[i] | 0x80
+			} else {
+				// last group - no ext flag
+				group = ebp.Grouping[i]
 			}
-			binary.Write(data, ebpEncoding, ebp.Grouping[i])
+			binary.Write(data, ebpEncoding, group)
 		}
 	}
 

diff --git a/ebp/cablelabsebp_test.go b/ebp/cablelabsebp_test.go
@@ -1,7 +1,7 @@
 /*
 MIT License
 
-Copyright 2016 Comcast Cable Communications Management, LLC
+# Copyright 2016 Comcast Cable Communications Management, LLC
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -110,3 +110,49 @@ func TestCableLabsEBP(t *testing.T) {
 		)
 	}
 }
+
+func TestParseCableLabsEBPWithMultipleGroups(t *testing.T) {
+	var ebpBytes = []byte{0xdf, 0x11, 0x45, 0x42, 0x50, 0x30, 0x98, 0x80, 0xa3, 0xfe, 0x1d, 0xe6, 0xa1, 0x45, 0x18, 0xb8, 0x51, 0x00, 0x00}
+	ebp, err := readCableLabsEbp(ebpBytes)
+	if err != nil {
+		t.Logf("failed to parse CableLabs-style EBP: #{err}")
+		t.FailNow()
+	}
+	if ebp.StreamSyncSignal() != StreamSynchronized {
+		t.Errorf("Wrong stream sync signal (expected 0x1D, got #{ebp.StreamSyncSignal()})")
+	}
+	var expectedGroups = []uint8{0x00, 0x23, 0x7E, 0x1D}
+	if len(ebp.Grouping) != len(expectedGroups) {
+		t.Logf("Wrong number of group IDs (expected #{len(expectedGroups)}, got #{len(ebp.Grouping)}")
+		t.FailNow()
+	}
+	for i, gid := range expectedGroups {
+		other := ebp.Grouping[i]
+		if gid != other {
+			t.Errorf("Wrong group ID (expected #{gid}, got #{other})")
+		}
+	}
+}
+
+func TestParseCableLabsEBPWithSyncInMiddle(t *testing.T) {
+	var ebpBytes = []byte{0xdf, 0x12, 0x45, 0x42, 0x50, 0x30, 0x98, 0x80, 0xa3, 0xfe, 0x9d, 0x05, 0xe6, 0xa1, 0x45, 0x18, 0xb8, 0x51, 0x00, 0x00}
+	ebp, err := readCableLabsEbp(ebpBytes)
+	if err != nil {
+		t.Logf("failed to parse CableLabs-style EBP: #{err}")
+		t.FailNow()
+	}
+	if ebp.StreamSyncSignal() != StreamSynchronized {
+		t.Errorf("Wrong stream sync signal (expected 0x1D, got #{ebp.StreamSyncSignal()})")
+	}
+	var expectedGroups = []uint8{0x00, 0x23, 0x7E, 0x1D, 0x05}
+	if len(ebp.Grouping) != len(expectedGroups) {
+		t.Logf("Wrong number of group IDs (expected #{len(expectedGroups)}, got #{len(ebp.Grouping)}")
+		t.FailNow()
+	}
+	for i, gid := range expectedGroups {
+		other := ebp.Grouping[i]
+		if gid != other {
+			t.Errorf("Wrong group ID (expected #{gid}, got #{other})")
+		}
+	}
+}
diff --git a/v2/ebp/baseebp.go b/v2/ebp/baseebp.go
@@ -146,10 +146,10 @@ func (ebp *baseEbp) SetIsEmpty(value bool) {
 // but Stream Sync and SCTE-35 were the only two ever to get implemented. MK was the only Transcoder to implement SCTE-35 within the
 // Grouping ID section and we never leveraged that data on any downstream devices.
 func (ebp *baseEbp) StreamSyncSignal() uint8 {
-	// The first byte is Grouping ID, the second byte is the sync signal
-	if len(ebp.Grouping) == 2 && ebp.Grouping[0] == 0x80 {
-		return ebp.Grouping[1]
+	for _, groupID := range ebp.Grouping {
+		if groupID == StreamSynchronized || groupID == StreamNotSynchronized {
+			return groupID
+		}
 	}
-
 	return InvalidStreamSyncSignal
 }
diff --git a/v2/ebp/cablelabsebp.go b/v2/ebp/cablelabsebp.go
@@ -122,12 +122,15 @@ func readCableLabsEbp(data []byte) (ebp *cableLabsEbp, err error) {
 
 	if ebp.GroupingFlag() {
 		var group byte
-		group = data[index]
+		var groupExtFlag bool
+		groupExtFlag = data[index]&0x80 != 0
+		group = data[index] & 0x7F
 		ebp.Grouping = append(ebp.Grouping, group)
 		index += uint8(1)
 
-		for group&0x80 != 0 {
-			group = data[index]
+		for groupExtFlag {
+			groupExtFlag = data[index]&0x80 != 0
+			group = data[index] & 0x7F
 			ebp.Grouping = append(ebp.Grouping, group)
 			index += uint8(1)
 		}
@@ -182,11 +185,15 @@ func (ebp *cableLabsEbp) Data() []byte {
 
 	if ebp.GroupingFlag() {
 		for i := range ebp.Grouping {
-			ebp.Grouping[i] |= 0x80 // set flag because this is not the last ID
-			if i == len(ebp.Grouping)-1 {
-				ebp.Grouping[i] &= 0x7F // last index does not have this flag set
+			var group byte
+			if i < len(ebp.Grouping)-1 {
+				// add the ext flag for all but the last group
+				group = ebp.Grouping[i] | 0x80
+			} else {
+				// last group - no ext flag
+				group = ebp.Grouping[i]
 			}
-			binary.Write(data, ebpEncoding, ebp.Grouping[i])
+			binary.Write(data, ebpEncoding, group)
 		}
 	}
 

diff --git a/v2/ebp/cablelabsebp_test.go b/v2/ebp/cablelabsebp_test.go
@@ -1,7 +1,7 @@
 /*
 MIT License
 
-Copyright 2016 Comcast Cable Communications Management, LLC
+# Copyright 2016 Comcast Cable Communications Management, LLC
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -110,3 +110,49 @@ func TestCableLabsEBP(t *testing.T) {
 		)
 	}
 }
+
+func TestParseCableLabsEBPWithMultipleGroups(t *testing.T) {
+	var ebpBytes = []byte{0xdf, 0x11, 0x45, 0x42, 0x50, 0x30, 0x98, 0x80, 0xa3, 0xfe, 0x1d, 0xe6, 0xa1, 0x45, 0x18, 0xb8, 0x51, 0x00, 0x00}
+	ebp, err := readCableLabsEbp(ebpBytes)
+	if err != nil {
+		t.Logf("failed to parse CableLabs-style EBP: #{err}")
+		t.FailNow()
+	}
+	if ebp.StreamSyncSignal() != StreamSynchronized {
+		t.Errorf("Wrong stream sync signal (expected 0x1D, got #{ebp.StreamSyncSignal()})")
+	}
+	var expectedGroups = []uint8{0x00, 0x23, 0x7E, 0x1D}
+	if len(ebp.Grouping) != len(expectedGroups) {
+		t.Logf("Wrong number of group IDs (expected #{len(expectedGroups)}, got #{len(ebp.Grouping)}")
+		t.FailNow()
+	}
+	for i, gid := range expectedGroups {
+		other := ebp.Grouping[i]
+		if gid != other {
+			t.Errorf("Wrong group ID (expected #{gid}, got #{other})")
+		}
+	}
+}
+
+func TestParseCableLabsEBPWithSyncInMiddle(t *testing.T) {
+	var ebpBytes = []byte{0xdf, 0x12, 0x45, 0x42, 0x50, 0x30, 0x98, 0x80, 0xa3, 0xfe, 0x9d, 0x05, 0xe6, 0xa1, 0x45, 0x18, 0xb8, 0x51, 0x00, 0x00}
+	ebp, err := readCableLabsEbp(ebpBytes)
+	if err != nil {
+		t.Logf("failed to parse CableLabs-style EBP: #{err}")
+		t.FailNow()
+	}
+	if ebp.StreamSyncSignal() != StreamSynchronized {
+		t.Errorf("Wrong stream sync signal (expected 0x1D, got #{ebp.StreamSyncSignal()})")
+	}
+	var expectedGroups = []uint8{0x00, 0x23, 0x7E, 0x1D, 0x05}
+	if len(ebp.Grouping) != len(expectedGroups) {
+		t.Logf("Wrong number of group IDs (expected #{len(expectedGroups)}, got #{len(ebp.Grouping)}")
+		t.FailNow()
+	}
+	for i, gid := range expectedGroups {
+		other := ebp.Grouping[i]
+		if gid != other {
+			t.Errorf("Wrong group ID (expected #{gid}, got #{other})")
+		}
+	}
+}