add aac utilities

pkg/aac/aac.go

@@ -0,0 +1,2 @@
+// Package aac contains utilities to work with the MPEG-AAC codec.
+package aac

pkg/aac/adts.go

@@ -0,0 +1,136 @@
+package aac
+
+import (
+	"fmt"
+)
+
+// ADTSPacket is an ADTS packet
+type ADTSPacket struct {
+	Type         int
+	SampleRate   int
+	ChannelCount int
+	AU           []byte
+}
+
+// DecodeADTS decodes an ADTS stream into ADTS packets.
+func DecodeADTS(byts []byte) ([]*ADTSPacket, error) {
+	// refs: https://wiki.multimedia.cx/index.php/ADTS
+
+	var ret []*ADTSPacket
+
+	for len(byts) > 0 {
+		syncWord := (uint16(byts[0]) << 4) | (uint16(byts[1]) >> 4)
+		if syncWord != 0xfff {
+			return nil, fmt.Errorf("invalid syncword")
+		}
+
+		protectionAbsent := byts[1] & 0x01
+		if protectionAbsent != 1 {
+			return nil, fmt.Errorf("CRC is not supported")
+		}
+
+		pkt := &ADTSPacket{}
+
+		pkt.Type = int((byts[2] >> 6) + 1)
+
+		switch MPEG4AudioType(pkt.Type) {
+		case MPEG4AudioTypeAACLC:
+
+		default:
+			return nil, fmt.Errorf("unsupported object type: %d", pkt.Type)
+		}
+
+		sampleRateIndex := (byts[2] >> 2) & 0x0F
+
+		switch {
+		case sampleRateIndex <= 12:
+			pkt.SampleRate = sampleRates[sampleRateIndex]
+
+		default:
+			return nil, fmt.Errorf("invalid sample rate index: %d", sampleRateIndex)
+		}
+
+		channelConfig := ((byts[2] & 0x01) << 2) | ((byts[3] >> 6) & 0x03)
+
+		switch {
+		case channelConfig >= 1 && channelConfig <= 7:
+			pkt.ChannelCount = channelCounts[channelConfig-1]
+
+		default:
+			return nil, fmt.Errorf("invalid channel configuration: %d", channelConfig)
+		}
+
+		frameLen := int(((uint16(byts[3])&0x03)<<11)|
+			(uint16(byts[4])<<3)|
+			((uint16(byts[5])>>5)&0x07)) - 7
+
+		// fullness := ((uint16(byts[5]) & 0x1F) << 6) | ((uint16(byts[6]) >> 2) & 0x3F)
+
+		frameCount := byts[6] & 0x03
+		if frameCount != 0 {
+			return nil, fmt.Errorf("multiple frame count not supported")
+		}
+
+		if len(byts[7:]) < frameLen {
+			return nil, fmt.Errorf("invalid frame length")
+		}
+
+		pkt.AU = byts[7 : 7+frameLen]
+		byts = byts[7+frameLen:]
+
+		ret = append(ret, pkt)
+	}
+
+	return ret, nil
+}
+
+// EncodeADTS encodes ADTS packets into an ADTS stream.
+func EncodeADTS(pkts []*ADTSPacket) ([]byte, error) {
+	var ret []byte
+
+	for _, pkt := range pkts {
+		sampleRateIndex := func() int {
+			for i, s := range sampleRates {
+				if s == pkt.SampleRate {
+					return i
+				}
+			}
+			return -1
+		}()
+
+		if sampleRateIndex == -1 {
+			return nil, fmt.Errorf("invalid sample rate: %d", pkt.SampleRate)
+		}
+
+		channelConfig := func() int {
+			for i, co := range channelCounts {
+				if co == pkt.ChannelCount {
+					return i + 1
+				}
+			}
+			return -1
+		}()
+
+		if channelConfig == -1 {
+			return nil, fmt.Errorf("invalid channel count: %d", pkt.ChannelCount)
+		}
+
+		frameLen := len(pkt.AU) + 7
+
+		fullness := 0x07FF // like ffmpeg does
+
+		header := make([]byte, 7)
+		header[0] = 0xFF
+		header[1] = 0xF1
+		header[2] = uint8(((pkt.Type - 1) << 6) | (sampleRateIndex << 2) | ((channelConfig >> 2) & 0x01))
+		header[3] = uint8((channelConfig&0x03)<<6 | (frameLen>>11)&0x03)
+		header[4] = uint8((frameLen >> 3) & 0xFF)
+		header[5] = uint8((frameLen&0x07)<<5 | ((fullness >> 6) & 0x1F))
+		header[6] = uint8((fullness & 0x3F) << 2)
+		ret = append(ret, header...)
+
+		ret = append(ret, pkt.AU...)
+	}
+
+	return ret, nil
+}

pkg/aac/adts_test.go

@@ -0,0 +1,68 @@
+package aac
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var casesADTS = []struct {
+	name string
+	byts []byte
+	pkts []*ADTSPacket
+}{
+	{
+		"single",
+		[]byte{0xff, 0xf1, 0x4c, 0x80, 0x1, 0x3f, 0xfc, 0xaa, 0xbb},
+		[]*ADTSPacket{
+			{
+				Type:         2,
+				SampleRate:   48000,
+				ChannelCount: 2,
+				AU:           []byte{0xaa, 0xbb},
+			},
+		},
+	},
+	{
+		"multiple",
+		[]byte{
+			0xff, 0xf1, 0x50, 0x40, 0x1, 0x3f, 0xfc, 0xaa,
+			0xbb, 0xff, 0xf1, 0x4c, 0x80, 0x1, 0x3f, 0xfc,
+			0xcc, 0xdd,
+		},
+		[]*ADTSPacket{
+			{
+				Type:         2,
+				SampleRate:   44100,
+				ChannelCount: 1,
+				AU:           []byte{0xaa, 0xbb},
+			},
+			{
+				Type:         2,
+				SampleRate:   48000,
+				ChannelCount: 2,
+				AU:           []byte{0xcc, 0xdd},
+			},
+		},
+	},
+}
+
+func TestDecodeADTS(t *testing.T) {
+	for _, ca := range casesADTS {
+		t.Run(ca.name, func(t *testing.T) {
+			pkts, err := DecodeADTS(ca.byts)
+			require.NoError(t, err)
+			require.Equal(t, ca.pkts, pkts)
+		})
+	}
+}
+
+func TestEncodeADTS(t *testing.T) {
+	for _, ca := range casesADTS {
+		t.Run(ca.name, func(t *testing.T) {
+			byts, err := EncodeADTS(ca.pkts)
+			require.NoError(t, err)
+			require.Equal(t, ca.byts, byts)
+		})
+	}
+}

pkg/aac/mpeg4audioconfig.go

@@ -1,4 +1,4 @@
-package rtpaac
+package aac
 
 import (
 	"bytes"

pkg/aac/mpeg4audioconfig_test.go

@@ -1,4 +1,4 @@
-package rtpaac
+package aac
 
 import (
 	"testing"

pkg/h264/h264.go

@@ -1,2 +1,2 @@
-// Package h264 contains utilities to work with H264 streams.
+// Package h264 contains utilities to work with the H264 codec.
 package h264

track.go

@@ -9,8 +9,8 @@ import (
 
 	psdp "github.com/pion/sdp/v3"
 
+	"github.com/aler9/gortsplib/pkg/aac"
 	"github.com/aler9/gortsplib/pkg/base"
-	"github.com/aler9/gortsplib/pkg/rtpaac"
 	"github.com/aler9/gortsplib/pkg/sdp"
 )
 
@@ -244,8 +244,8 @@ func (t *Track) ExtractConfigH264() (*TrackConfigH264, error) {
 
 // NewTrackAAC initializes an AAC track.
 func NewTrackAAC(payloadType uint8, conf *TrackConfigAAC) (*Track, error) {
-	mpegConf, err := rtpaac.MPEG4AudioConfig{
-		Type:              rtpaac.MPEG4AudioType(conf.Type),
+	mpegConf, err := aac.MPEG4AudioConfig{
+		Type:              aac.MPEG4AudioType(conf.Type),
 		SampleRate:        conf.SampleRate,
 		ChannelCount:      conf.ChannelCount,
 		AOTSpecificConfig: conf.AOTSpecificConfig,
@@ -332,7 +332,7 @@ func (t *Track) ExtractConfigAAC() (*TrackConfigAAC, error) {
 				return nil, fmt.Errorf("invalid AAC config (%v)", tmp[1])
 			}
 
-			var mpegConf rtpaac.MPEG4AudioConfig
+			var mpegConf aac.MPEG4AudioConfig
 			err = mpegConf.Decode(enc)
 			if err != nil {
 				return nil, fmt.Errorf("invalid AAC config (%v)", tmp[1])