diff --git a/container/mts/encoder.go b/container/mts/encoder.go
index e9efbd97..96cde642 100644
--- a/container/mts/encoder.go
+++ b/container/mts/encoder.go
@@ -120,8 +120,11 @@ const (
 	// the current presentation timestamp.
 	ptsOffset = 700 * time.Millisecond
 
-	// pcrFreq is the base Program Clock Reference frequency.
-	pcrFreq = 90000 // Hz
+	// PCRFreq is the base Program Clock Reference frequency.
+	PCRFreq = 90000 // Hz
+
+	// PTSFreq is the presentation timestamp frequency.
+	PTSFreq = 90000
 )
 
 // Encoder encapsulates properties of an mpegts generator.