container/mts: added some commenting

container/mts/payload.go

@@ -184,6 +184,8 @@ var (
 	errMetaUpperBound = errors.New("meta 'to' cannot be found")
 )
 
+// BytesForMetaInterval will return the media data as a slice between two meta
+// values 'from' and 'to', of key 'key'. The meta values must not be the same.
 func (c *Clip) BytesForMetaInterval(key, from, to string) ([]byte, error) {
 	// First check that the interval makes sense.
 	if from == to {

container/mts/payload_test.go

@@ -316,6 +316,8 @@ func TestBytesForPTSInterval(t *testing.T) {
 	}
 }
 
+// TestBytesForMetaInterval checks that we can correctly get media data between
+// two meta values using BytesForMetaInterval.
 func TestBytesForMetaInterval(t *testing.T) {
 	const (
 		numOfTestFrames = 10