diff --git a/stream/mts/psi/crc.go b/stream/mts/psi/crc.go
index a361307d..cd9a1199 100644
--- a/stream/mts/psi/crc.go
+++ b/stream/mts/psi/crc.go
@@ -37,13 +37,13 @@ import (
 func addCrc(out []byte) []byte {
 	t := make([]byte, len(out)+4)
 	copy(t, out)
-	updateCrc(t)
+	updateCrc(t[1:])
 	return t
 }
 
 // updateCrc updates the crc of bytes slice, writing the checksum into the last four bytes.
 func updateCrc(b []byte) {
-	crc32 := crc32_Update(0xffffffff, crc32_MakeTable(bits.Reverse32(crc32.IEEE)), b[1:len(b)-4])
+	crc32 := crc32_Update(0xffffffff, crc32_MakeTable(bits.Reverse32(crc32.IEEE)), b[:len(b)-4])
 	binary.BigEndian.PutUint32(b[len(b)-4:], crc32)
 }
 
diff --git a/stream/mts/psi/helpers.go b/stream/mts/psi/helpers.go
index 82d7ce72..174b289b 100644
--- a/stream/mts/psi/helpers.go
+++ b/stream/mts/psi/helpers.go
@@ -64,15 +64,14 @@ func UpdateTime(dst []byte, t uint64) error {
 	for i := range dst[TimeDataIndx : TimeDataIndx+TimeDataSize] {
 		dst[i+TimeDataIndx] = ts[i]
 	}
-	updateCrc(dst)
+	updateCrc(dst[1:])
 	return nil
 }
 
 // SyntaxSecLenFrom takes a byte slice representation of a psi and extracts
 // it's syntax section length
-func SyntaxSecLenFrom(p []byte) (l uint8) {
-	l = uint8(p[syntaxSecLenIndx]) - crcSize
-	return
+func SyntaxSecLenFrom(p []byte) int {
+	return int(((p[SyntaxSecLenIdx1] & SyntaxSecLenMask1) << 8) | p[SyntaxSecLenIdx2])
 }
 
 // TimeFrom takes a byte slice representation of a psi-pmt and extracts it's
@@ -112,7 +111,7 @@ func UpdateLocation(d []byte, s string) error {
 	for i := range loc {
 		loc[i] = 0
 	}
-	updateCrc(d)
+	updateCrc(d[1:])
 	return nil
 }
 
diff --git a/stream/mts/psi/psi.go b/stream/mts/psi/psi.go
index c2e30f9e..6a4a9103 100644
--- a/stream/mts/psi/psi.go
+++ b/stream/mts/psi/psi.go
@@ -70,8 +70,10 @@ const (
 
 // Other misc consts
 const (
-	syntaxSecLenIndx = 3
-	crcSize          = 4
+	SyntaxSecLenIdx1  = 2
+	SyntaxSecLenIdx2  = 3
+	SyntaxSecLenMask1 = 0x03
+	crcSize           = 4
 )
 
 const (
@@ -275,24 +277,40 @@ func (p *PSIBytes) descriptors() []byte {
 
 func (p *PSIBytes) createDescriptor(tag int, data []byte) {
 	curProgLen := p.ProgramInfoLen()
+	oldSyntaxSectionLen := SyntaxSecLenFrom(*p)
 	dataLen := len(data)
 
 	// Calculate the new descriptors index and length.
 	newDescIdx := DescriptorsIdx + curProgLen
 	newDescLen := dataLen + 2
-
 	// Copy data down from newDescIdx to create room for the new descriptor.
-	copy((*p)[newDescIdx+newDescLen:], (*p)[newDescIdx:dataLen-newDescLen])
-
+	copy((*p)[newDescIdx+newDescLen:], (*p)[newDescIdx:newDescIdx+newDescLen])
 	// Set the tag, data len and data of the new desriptor.
 	(*p)[newDescIdx] = byte(tag)
 	(*p)[newDescIdx+1] = byte(dataLen)
 	copy((*p)[newDescIdx+2:newDescIdx+2+dataLen], data)
 
 	// Update the program info length to account for the new descriptor.
-	newProgInfoLen := curProgLen + dataLen
-	(*p)[ProgramInfoLenIdx1] = byte(newProgInfoLen >> 8)
+	// TODO: put this in function set program info length
+	addedLen := dataLen + 2
+	newProgInfoLen := curProgLen + addedLen
+	(*p)[ProgramInfoLenIdx1] &= 0xff ^ ProgramInfoLenMask1
+	(*p)[ProgramInfoLenIdx1] |= byte(newProgInfoLen>>8) & ProgramInfoLenMask1
 	(*p)[ProgramInfoLenIdx2] = byte(newProgInfoLen)
+
+	// set section length
+	// TODO: put this in func set program info length
+	newSyntaxSectionLen := int(oldSyntaxSectionLen) + addedLen
+	(*p)[SyntaxSecLenIdx1] &= 0xff ^ SyntaxSecLenMask1
+	(*p)[SyntaxSecLenIdx1] |= byte(newSyntaxSectionLen>>8) & SyntaxSecLenMask1
+	(*p)[SyntaxSecLenIdx2] = byte(newSyntaxSectionLen)
+}
+
+func (p *PSIBytes) trimPadding() []byte {
+	sectionLength := SyntaxSecLenFrom(*p)
+	paddingIdx := (4 + sectionLength)
+	o := (*p)[:paddingIdx]
+	return o
 }
 
 func (d *Descriptor) update(data []byte) {