Alexey Khit
53 lines
1.1 KiB
Go
53 lines
1.1 KiB
Go
package aac
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import (
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"encoding/hex"
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"fmt"
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"github.com/AlexxIT/go2rtc/pkg/bits"
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"github.com/AlexxIT/go2rtc/pkg/core"
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)
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const (
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TypeAACMain = 1
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TypeAACLC = 2
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TypeESCAPE = 31
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)
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// streamtype=5 - audio stream
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const fmtp = "streamtype=5;profile-level-id=1;mode=AAC-hbr;sizelength=13;indexlength=3;indexdeltalength=3;config="
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var sampleRates = []uint32{96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350}
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func ConfigToCodec(conf []byte) *core.Codec {
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// https://en.wikipedia.org/wiki/MPEG-4_Part_3#MPEG-4_Audio_Object_Types
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rd := bits.NewReader(conf)
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codec := &core.Codec{
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FmtpLine: fmtp + hex.EncodeToString(conf),
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PayloadType: core.PayloadTypeRAW,
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}
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objType := rd.ReadBits(5)
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if objType == TypeESCAPE {
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objType = 32 + rd.ReadBits(6)
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}
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switch objType {
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case TypeAACLC:
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codec.Name = core.CodecAAC
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default:
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codec.Name = fmt.Sprintf("AAC-%X", objType)
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}
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if sampleRateIdx := rd.ReadBits8(4); sampleRateIdx < 12 {
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codec.ClockRate = sampleRates[sampleRateIdx]
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} else if sampleRateIdx == 0x0F {
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codec.ClockRate = rd.ReadBits(24)
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}
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codec.Channels = rd.ReadBits16(4)
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return codec
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}
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