adpcm and mts: comments and pid change

codec/adpcm/adpcm.go

@@ -369,7 +369,7 @@ func capAdd16(a, b int16) int16 {
 // EncBytes will return the number of adpcm bytes that will be generated when encoding the given amount of pcm bytes (n).
 func EncBytes(n int) int {
 	// For 'n' pcm bytes, 1 sample is left uncompressed, the rest is compressed by a factor of 4
-	// and a start index and padding-flag byte are added.
+	// and a chunk length (4B), start index (1B) and padding-flag (1B) are added.
 	// Also if there are an even number of samples, there will be half a byte of padding added to the last byte.
 	if n%bytesPerEnc == 0 {
 		return (n-byteDepth)/compFact + headSize + 1

container/mts/encoder.go

@@ -44,7 +44,7 @@ import (
 const (
 	H264ID        = 27
 	H265ID        = 36
-	audioStreamID = 0xc0 // First audio stream ID.
+	audioStreamID = 0xc0 // ADPCM audio stream ID.
 )
 
 // Constants used to communicate which media codec will be packetized.
@@ -168,7 +168,7 @@ func NewEncoder(dst io.WriteCloser, rate float64, mediaType int) *Encoder {
 		Pil:    0,
 		Essd: &psi.ESSD{
 			St:   byte(sid),
-			Epid: 0x0100,
+			Epid: byte(mPid),
 			Esil: 0x00,
 		},
 	}