From 830b3a1f60efc37c911bfebb65a313425b00bfff Mon Sep 17 00:00:00 2001
From: aler9 <46489434+aler9@users.noreply.github.com>
Date: Fri, 19 Jan 2024 18:24:05 +0100
Subject: [PATCH] support MPEG-2 audio
 (https://github.com/bluenviron/gortsplib/issues/486)

---
 pkg/codecs/mpeg1audio/frame_header.go      | 189 ++++++++++++++-------
 pkg/codecs/mpeg1audio/frame_header_test.go | 176 ++++---------------
 2 files changed, 161 insertions(+), 204 deletions(-)

diff --git a/pkg/codecs/mpeg1audio/frame_header.go b/pkg/codecs/mpeg1audio/frame_header.go
index 987065a..5e4c7a1 100644
--- a/pkg/codecs/mpeg1audio/frame_header.go
+++ b/pkg/codecs/mpeg1audio/frame_header.go
@@ -5,45 +5,115 @@ import (
 )
 
 // http://www.mp3-tech.org/programmer/frame_header.html
-var bitrates = map[uint8]map[uint8]int{
-	2: {
-		0b1:    32000,
-		0b10:   48000,
-		0b11:   56000,
-		0b100:  64000,
-		0b101:  80000,
-		0b110:  96000,
-		0b111:  112000,
-		0b1000: 128000,
-		0b1001: 160000,
-		0b1010: 192000,
-		0b1011: 224000,
-		0b1100: 256000,
-		0b1101: 320000,
-		0b1110: 384000,
+var bitrates = [][][]int{
+	// MPEG-1
+	{
+		// layer 1
+		{},
+		// layer 2
+		{
+			32000,
+			48000,
+			56000,
+			64000,
+			80000,
+			96000,
+			112000,
+			128000,
+			160000,
+			192000,
+			224000,
+			256000,
+			320000,
+			384000,
+		},
+		// layer 3
+		{
+			32000,
+			40000,
+			48000,
+			56000,
+			64000,
+			80000,
+			96000,
+			112000,
+			128000,
+			160000,
+			192000,
+			224000,
+			256000,
+			320000,
+		},
 	},
-	3: {
-		0b1:    32000,
-		0b10:   40000,
-		0b11:   48000,
-		0b100:  56000,
-		0b101:  64000,
-		0b110:  80000,
-		0b111:  96000,
-		0b1000: 112000,
-		0b1001: 128000,
-		0b1010: 160000,
-		0b1011: 192000,
-		0b1100: 224000,
-		0b1101: 256000,
-		0b1110: 320000,
+	// MPEG-2
+	{
+		// layer 1
+		{},
+		// layer 2
+		{
+			8000,
+			16000,
+			24000,
+			32000,
+			40000,
+			48000,
+			56000,
+			64000,
+			80000,
+			96000,
+			112000,
+			128000,
+			144000,
+			160000,
+		},
+		// layer 3
+		{
+			8000,
+			16000,
+			24000,
+			32000,
+			40000,
+			48000,
+			56000,
+			64000,
+			80000,
+			96000,
+			112000,
+			128000,
+			144000,
+			160000,
+		},
 	},
 }
 
-var sampleRates = map[uint8]int{
-	0:    44100,
-	0b1:  48000,
-	0b10: 32000,
+var sampleRates = [][]int{
+	// MPEG-1
+	{
+		44100,
+		48000,
+		32000,
+	},
+	// MPEG-2
+	{
+		22050,
+		24000,
+		16000,
+	},
+}
+
+var samplesPerFrame = [][]int{
+	// MPEG-1
+	{
+		384,
+		1152,
+		1152,
+	},
+	// MPEG-2
+	{
+		384,
+		1152,
+		576,
+	},
 }
 
 // ChannelMode is a channel mode of a MPEG-1/2 audio frame.
@@ -80,27 +150,30 @@ func (h *FrameHeader) Unmarshal(buf []byte) error {
 	}
 
 	h.MPEG2 = ((buf[1] >> 3) & 0x01) == 0
-	h.Layer = 4 - ((buf[1] >> 1) & 0b11)
 
-	switch {
-	case !h.MPEG2 && h.Layer == 2:
-	case !h.MPEG2 && h.Layer == 3:
-	default:
-		return fmt.Errorf("unsupported MPEG version or layer: %v %v", h.MPEG2, h.Layer)
+	var mpegIndex int
+	if h.MPEG2 {
+		mpegIndex = 1
+	} else {
+		mpegIndex = 0
+	}
+
+	h.Layer = 4 - ((buf[1] >> 1) & 0b11)
+	if h.Layer <= 1 || h.Layer >= 4 {
+		return fmt.Errorf("unsupported MPEG layer: %v", h.Layer)
 	}
 
-	bitrateIndex := buf[2] >> 4
-	var ok bool
-	h.Bitrate, ok = bitrates[h.Layer][bitrateIndex]
-	if !ok {
+	bitrateIndex := (buf[2] >> 4)
+	if bitrateIndex == 0 || bitrateIndex >= 15 {
 		return fmt.Errorf("invalid bitrate")
 	}
+	h.Bitrate = bitrates[mpegIndex][h.Layer-1][bitrateIndex-1]
 
 	sampleRateIndex := (buf[2] >> 2) & 0b11
-	h.SampleRate, ok = sampleRates[sampleRateIndex]
-	if !ok {
+	if sampleRateIndex >= 3 {
 		return fmt.Errorf("invalid sample rate")
 	}
+	h.SampleRate = sampleRates[mpegIndex][sampleRateIndex]
 
 	h.Padding = ((buf[2] >> 1) & 0b1) != 0
 	h.ChannelMode = ChannelMode(buf[3] >> 6)
@@ -108,7 +181,7 @@ func (h *FrameHeader) Unmarshal(buf []byte) error {
 	return nil
 }
 
-// FrameLen returns the length of the frame associated to the header.
+// FrameLen returns the length of the frame associated with the header.
 func (h FrameHeader) FrameLen() int {
 	if h.Padding {
 		return (144 * h.Bitrate / h.SampleRate) + 1
@@ -118,16 +191,12 @@ func (h FrameHeader) FrameLen() int {
 
 // SampleCount returns the number of samples contained into the frame.
 func (h FrameHeader) SampleCount() int {
-	/*
-		MPEG-1:
-		* layer 1: 384
-		* layer 2: 1152
-		* layer 3: 1152
-
-		MPEG-2:
-		* layer 1: 384
-		* layer 2: 1152
-		* layer 3: 576
-	*/
-	return 1152
+	var mpegIndex int
+	if h.MPEG2 {
+		mpegIndex = 1
+	} else {
+		mpegIndex = 0
+	}
+
+	return samplesPerFrame[mpegIndex][h.Layer-1]
 }
diff --git a/pkg/codecs/mpeg1audio/frame_header_test.go b/pkg/codecs/mpeg1audio/frame_header_test.go
index 3becfbb..ebf3e78 100644
--- a/pkg/codecs/mpeg1audio/frame_header_test.go
+++ b/pkg/codecs/mpeg1audio/frame_header_test.go
@@ -11,47 +11,13 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 		name        string
 		enc         []byte
 		dec         FrameHeader
+		frameLen    int
 		sampleCount int
 	}{
 		{
-			"mp2 32k",
+			"mpeg-1 layer 2 32k",
 			[]byte{
-				0xff, 0xfd, 0x48, 0x00, 0x11, 0x11, 0x25, 0x24,
-				0x9b, 0x6d, 0xb4, 0x92, 0x24, 0x9a, 0xaa, 0xaa,
-				0xaa, 0xaa, 0xaa, 0xaf, 0xff, 0xff, 0xff, 0xff,
-				0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-				0xff, 0xff, 0xff, 0xff, 0xff, 0xf6, 0xb5, 0xad,
-				0x6b, 0x5f, 0x3e, 0x7c, 0xf9, 0x6c, 0x5b, 0x16,
-				0xc5, 0xb1, 0x6c, 0x5b, 0x1f, 0x3e, 0x7c, 0xf9,
-				0xad, 0x6b, 0x5a, 0xd6, 0xb5, 0xad, 0x7c, 0xf9,
-				0xf3, 0xe5, 0xb1, 0x6c, 0x5b, 0x16, 0xc5, 0xb1,
-				0x6c, 0x7c, 0xf9, 0xf3, 0xe6, 0xb5, 0xad, 0x6b,
-				0x5a, 0xd6, 0xb5, 0xf3, 0xe7, 0xcf, 0x96, 0xc5,
-				0xb1, 0x6c, 0x5b, 0x16, 0xc5, 0xb1, 0xf3, 0xe7,
-				0xcf, 0x9a, 0xd6, 0xb5, 0xad, 0x6b, 0x5a, 0xd7,
-				0xcf, 0x9f, 0x3e, 0x5b, 0x16, 0xc5, 0xb1, 0x6c,
-				0x5b, 0x16, 0xc7, 0xcf, 0x9f, 0x3e, 0x6b, 0x5a,
-				0xd6, 0xb5, 0xad, 0x6b, 0x5f, 0x3e, 0x7c, 0xf9,
-				0x6c, 0x5b, 0x16, 0xc5, 0xb1, 0x6c, 0x5b, 0x1f,
-				0x3e, 0x7c, 0xf9, 0xad, 0x6b, 0x5a, 0xd6, 0xb5,
-				0xad, 0x7c, 0xf9, 0xf3, 0xe5, 0xb1, 0x6c, 0x5b,
-				0x16, 0xc5, 0xb1, 0x6c, 0x7c, 0xf9, 0xf3, 0xe6,
-				0xb5, 0xad, 0x6b, 0x5a, 0xd6, 0xb5, 0xf3, 0xe7,
-				0xcf, 0x96, 0xc5, 0xb1, 0x6c, 0x5b, 0x16, 0xc5,
-				0xb1, 0xf3, 0xe7, 0xcf, 0x9a, 0xd6, 0xb5, 0xad,
-				0x6b, 0x5a, 0xd7, 0xcf, 0x9f, 0x3e, 0x5b, 0x16,
-				0xc5, 0xb1, 0x6c, 0x5b, 0x16, 0xc7, 0xcf, 0x9f,
-				0x3e, 0x6b, 0x5a, 0xd6, 0xb5, 0xad, 0x6b, 0x5f,
-				0x3e, 0x7c, 0xf9, 0x6c, 0x5b, 0x16, 0xc5, 0xb1,
-				0x6c, 0x5b, 0x1f, 0x3e, 0x7c, 0xf9, 0xad, 0x6b,
-				0x5a, 0xd6, 0xb5, 0xad, 0x7c, 0xf9, 0xf3, 0xe5,
-				0xb1, 0x6c, 0x5b, 0x16, 0xc5, 0xb1, 0x6c, 0x7c,
-				0xf9, 0xf3, 0xe6, 0xb5, 0xad, 0x6b, 0x5a, 0xd6,
-				0xb5, 0xf3, 0xe7, 0xcf, 0x96, 0xc5, 0xb1, 0x6c,
-				0x5b, 0x16, 0xc5, 0xb1, 0xf3, 0xe7, 0xcf, 0x9a,
-				0xd6, 0xb5, 0xad, 0x6b, 0x5a, 0xd7, 0xcf, 0x9f,
-				0x3e, 0x5b, 0x16, 0xc5, 0xb1, 0x6c, 0x5b, 0x16,
-				0xc7, 0xcf, 0x9f, 0x3e, 0x6b, 0x5a, 0xd0, 0x00,
+				0xff, 0xfd, 0x48, 0x00, 0x00,
 			},
 			FrameHeader{
 				Layer:       2,
@@ -59,29 +25,13 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 				SampleRate:  32000,
 				ChannelMode: ChannelModeStereo,
 			},
+			288,
 			1152,
 		},
 		{
-			"mp3 32k",
+			"mpeg-1 layer 3 32k",
 			[]byte{
-				0xff, 0xfb, 0x18, 0x64, 0x00, 0x0f, 0xf0, 0x00,
-				0x00, 0x69, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00,
-				0x0d, 0x20, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01,
-				0xa4, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x34,
-				0x80, 0x00, 0x00, 0x04, 0x4c, 0x41, 0x4d, 0x45,
-				0x33, 0x2e, 0x31, 0x30, 0x30, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x4c, 0x41, 0x4d, 0x45, 0x33, 0x2e, 0x31,
-				0x30, 0x30, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
+				0xff, 0xfb, 0x18, 0x64, 0x00,
 			},
 			FrameHeader{
 				Layer:       3,
@@ -89,56 +39,13 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 				SampleRate:  32000,
 				ChannelMode: ChannelModeJointStereo,
 			},
+			144,
 			1152,
 		},
 		{
-			"mp3 32k mono",
+			"mpeg-1 layer 3 32k mono",
 			[]byte{
-				0xff, 0xfb, 0x68, 0xc4, 0xdc, 0x80, 0x16, 0x25,
-				0xcd, 0x5f, 0xbd, 0xa5, 0x80, 0x2a, 0x92, 0xbb,
-				0x2b, 0xf5, 0xb6, 0x21, 0x3c, 0x7f, 0xdb, 0x79,
-				0x6b, 0xab, 0x6f, 0x8d, 0x5f, 0x37, 0xfc, 0xa6,
-				0x6c, 0x82, 0xbe, 0xb2, 0x49, 0xb3, 0xe3, 0x55,
-				0x53, 0xa1, 0x41, 0x90, 0x38, 0xc6, 0xae, 0xcf,
-				0x79, 0x3b, 0xff, 0x33, 0x7c, 0xe7, 0xae, 0x76,
-				0xa6, 0x66, 0x36, 0x8a, 0xc6, 0x74, 0xd1, 0xeb,
-				0x37, 0x67, 0x4e, 0x86, 0x5c, 0xd9, 0x09, 0x4a,
-				0x8a, 0x73, 0x74, 0x6b, 0xa2, 0x33, 0x9b, 0x99,
-				0x8e, 0xe8, 0x3b, 0x16, 0xb1, 0x39, 0x24, 0x00,
-				0x91, 0x0d, 0x66, 0x93, 0x68, 0x02, 0x9f, 0x33,
-				0x40, 0xd0, 0xf6, 0x53, 0x18, 0x19, 0x2f, 0xd3,
-				0x36, 0x2b, 0x01, 0xa5, 0x6c, 0xf3, 0x52, 0xab,
-				0x2c, 0xf9, 0x5a, 0x2e, 0xd4, 0x64, 0xd0, 0xb8,
-				0x03, 0x4a, 0x87, 0xca, 0x6d, 0xc5, 0x43, 0x6a,
-				0x1a, 0x57, 0x1f, 0x0f, 0x5b, 0x56, 0xd4, 0x0a,
-				0x2b, 0xbf, 0x45, 0xd1, 0xdf, 0x96, 0xf2, 0xef,
-				0xda, 0xd9, 0xd6, 0x74, 0x9b, 0x45, 0x38, 0xac,
-				0x15, 0x90, 0xce, 0xbf, 0x6a, 0xea, 0x5c, 0x74,
-				0x50, 0x8f, 0xb3, 0x23, 0xf9, 0x35, 0x58, 0x90,
-				0x1f, 0x4e, 0x7e, 0x59, 0x28, 0x6a, 0xb1, 0x25,
-				0x54, 0x8a, 0x1e, 0x6a, 0x12, 0x23, 0x0e, 0x9f,
-				0x18, 0x27, 0x56, 0x14, 0x7d, 0x7b, 0xf5, 0x9b,
-				0xbe, 0xc5, 0x76, 0x1e, 0x20, 0x90, 0x62, 0xa8,
-				0xd3, 0x57, 0xe9, 0x7a, 0xe2, 0xa4, 0x60, 0xfd,
-				0xad, 0x94, 0x82, 0x9e, 0xa2, 0x6c, 0x58, 0xe8,
-				0x7a, 0x8f, 0xa2, 0x73, 0xab, 0xfb, 0xfe, 0x9b,
-				0xf9, 0xbe, 0x2b, 0xfe, 0x7d, 0x62, 0x74, 0xc6,
-				0x6a, 0x45, 0xcd, 0x62, 0xe2, 0x34, 0x8f, 0x1e,
-				0x91, 0xc1, 0xab, 0x2d, 0x7f, 0xf3, 0xef, 0x30,
-				0x70, 0xa0, 0x99, 0x6b, 0xc1, 0xb8, 0x3c, 0x3e,
-				0x6f, 0xfa, 0xea, 0x00, 0x14, 0x52, 0xd1, 0x2d,
-				0xa1, 0x29, 0x3e, 0x63, 0xa9, 0x01, 0xa3, 0x80,
-				0xa1, 0x81, 0xc5, 0x0a, 0x55, 0xb2, 0x26, 0xb9,
-				0xa7, 0x5a, 0x5f, 0x0a, 0x6e, 0x49, 0x31, 0xcd,
-				0x26, 0x3f, 0x2b, 0x2d, 0x0f, 0xbd, 0x51, 0xe1,
-				0x71, 0xd2, 0x61, 0x49, 0x01, 0xab, 0xbe, 0x3f,
-				0x42, 0x6e, 0x95, 0x97, 0x73, 0x7f, 0x0e, 0xdd,
-				0x38, 0xde, 0x66, 0x27, 0xa0, 0x8d, 0xf8, 0xeb,
-				0x75, 0xb0, 0xbf, 0xf8, 0x7d, 0xd7, 0x1a, 0x31,
-				0x2d, 0xb6, 0xf9, 0x60, 0xf9, 0x6e, 0xb5, 0xe7,
-				0x87, 0x5e, 0x19, 0xa0, 0x3a, 0x38, 0x6d, 0x74,
-				0xd9, 0x50, 0x2d, 0x44, 0xd4, 0xa9, 0xec, 0x2e,
-				0xa3, 0x1a, 0xc3, 0x4b, 0x3e, 0xc2, 0xc5, 0x7d,
+				0xff, 0xfb, 0x68, 0xc4, 0x00,
 			},
 			FrameHeader{
 				Layer:       3,
@@ -146,38 +53,13 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 				SampleRate:  32000,
 				ChannelMode: ChannelModeMono,
 			},
+			360,
 			1152,
 		},
 		{
-			"mp3 44.1k",
+			"mpeg-1 layer 3 44.1k",
 			[]byte{
-				0xff, 0xfa, 0x52, 0x04, 0xa9, 0xbe, 0xe4, 0x8f,
-				0xf0, 0xfd, 0x02, 0xdc, 0x80, 0x00, 0x30, 0x00,
-				0x22, 0xc1, 0x5b, 0x90, 0x14, 0x23, 0x24, 0x05,
-				0x58, 0x3f, 0x72, 0x02, 0x84, 0xc4, 0xc0, 0xc5,
-				0x07, 0xae, 0x40, 0x21, 0xbc, 0x98, 0x90, 0xfa,
-				0x3a, 0x2d, 0xda, 0x07, 0xe1, 0x4d, 0xa9, 0x9a,
-				0xb8, 0xa2, 0x3b, 0x20, 0xc1, 0xc1, 0xba, 0x08,
-				0x94, 0x30, 0x8b, 0xc5, 0x69, 0x51, 0x95, 0xd5,
-				0xd7, 0x42, 0x91, 0x65, 0x09, 0xfb, 0x7e, 0x7e,
-				0xd9, 0xcf, 0x7f, 0x77, 0x45, 0x03, 0x8d, 0x5c,
-				0xcd, 0x52, 0x82, 0x19, 0xbc, 0x94, 0x8c, 0x78,
-				0x13, 0xe0, 0x94, 0xc2, 0x96, 0x62, 0x82, 0x20,
-				0xb9, 0xf1, 0x3a, 0x05, 0xfa, 0x94, 0x06, 0xbd,
-				0xf6, 0x67, 0xa3, 0xca, 0xa5, 0x3a, 0xd5, 0xb5,
-				0x34, 0xa9, 0xe8, 0x7e, 0x9f, 0x2f, 0x53, 0xde,
-				0x8b, 0xd6, 0x3c, 0x2f, 0x2d, 0xb4, 0x56, 0x0c,
-				0xc5, 0x3e, 0x7a, 0xa7, 0x81, 0x5c, 0x35, 0x60,
-				0xb3, 0x0c, 0x28, 0x2c, 0x08, 0x06, 0xc0, 0xe0,
-				0x3c, 0x0a, 0xfa, 0x1a, 0x6f, 0x43, 0x55, 0xbe,
-				0x05, 0x5a, 0x53, 0xae, 0xcb, 0x74, 0xa9, 0xe8,
-				0x7e, 0x9f, 0x2f, 0x53, 0xde, 0x8b, 0xd6, 0x20,
-				0x36, 0xce, 0xcb, 0xcd, 0x95, 0x15, 0x08, 0xaa,
-				0x82, 0x13, 0x51, 0x48, 0xc1, 0x09, 0x28, 0x46,
-				0x11, 0x0b, 0x3b, 0x41, 0x34, 0x50, 0x24, 0x18,
-				0xa7, 0x72, 0x88, 0x99, 0x49, 0x17, 0x63, 0xac,
-				0xa7, 0x98, 0x7e, 0x81, 0x7b, 0x13, 0x9d, 0x7f,
-				0xd3,
+				0xff, 0xfa, 0x52, 0x04, 0x00,
 			},
 			FrameHeader{
 				Layer:       3,
@@ -186,23 +68,13 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 				Padding:     true,
 				ChannelMode: ChannelModeStereo,
 			},
+			209,
 			1152,
 		},
 		{
-			"mp3 48k",
+			"mpeg-1 layer 3 48k",
 			[]byte{
-				0xff, 0xfb, 0x14, 0x64, 0x00, 0x0f, 0xf0, 0x00,
-				0x00, 0x69, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00,
-				0x0d, 0x20, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01,
-				0xa4, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x34,
-				0x80, 0x00, 0x00, 0x04, 0x4c, 0x41, 0x4d, 0x45,
-				0x33, 0x2e, 0x31, 0x30, 0x30, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
-				0x55, 0xc0, 0x65, 0xf4, 0xa0, 0x31, 0x8f, 0xce,
-				0x8d, 0x46, 0xfc, 0x8c, 0x73, 0xb9, 0x34, 0x3e,
-				0xb5, 0x03, 0x39, 0xc0, 0x04, 0x01, 0x98, 0x44,
-				0x38, 0xe0, 0x98, 0x10, 0x9b, 0xa8, 0x0f, 0xa8,
+				0xff, 0xfb, 0x14, 0x64, 0x00,
 			},
 			FrameHeader{
 				Layer:       3,
@@ -210,6 +82,22 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 				SampleRate:  48000,
 				ChannelMode: ChannelModeJointStereo,
 			},
+			96,
+			1152,
+		},
+		{
+			"mpeg-2 layer 2 16khz",
+			[]byte{
+				0xff, 0xf5, 0x88, 0x4, 0x00,
+			},
+			FrameHeader{
+				MPEG2:       true,
+				Layer:       2,
+				Bitrate:     64000,
+				SampleRate:  16000,
+				ChannelMode: ChannelModeStereo,
+			},
+			576,
 			1152,
 		},
 	} {
@@ -218,7 +106,7 @@ func TestFrameHeaderUnmarshal(t *testing.T) {
 			err := h.Unmarshal(ca.enc)
 			require.NoError(t, err)
 			require.Equal(t, ca.dec, h)
-			require.Equal(t, len(ca.enc), h.FrameLen())
+			require.Equal(t, ca.frameLen, h.FrameLen())
 			require.Equal(t, ca.sampleCount, h.SampleCount())
 		})
 	}