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// Copyright 2021, Chef. All rights reserved.
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// https://github.com/q191201771/lal
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//
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// Use of this source code is governed by a MIT-style license
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// that can be found in the License file.
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//
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// Author: Chef (191201771@qq.com)
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package aac
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import (
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"github.com/q191201771/lal/pkg/base"
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"github.com/q191201771/naza/pkg/nazaerrors"
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"github.com/q191201771/naza/pkg/nazabits"
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)
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// TODO(chef) 这个文件的部分内容可以考虑放到package base中
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// SequenceHeaderContext
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//
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// <spec-video_file_format_spec_v10.pdf>, <Audio tags, AUDIODATA>, <page 10/48>
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// ----------------------------------------------------------------------------
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// soundFormat [4b] 10=AAC
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// soundRate [2b] 3=44kHz. AAC always 3
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// soundSize [1b] 0=snd8Bit, 1=snd16Bit
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// soundType [1b] 0=sndMono, 1=sndStereo. AAC always 1
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// aacPackageType [8b] 0=seq header, 1=AAC raw
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type SequenceHeaderContext struct {
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SoundFormat uint8 // [4b]
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SoundRate uint8 // [2b]
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SoundSize uint8 // [1b]
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SoundType uint8 // [1b]
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AacPacketType uint8 // [8b]
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}
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// Unpack
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//
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// @param b: rtmp/flv的message/tag的payload的前2个字节。
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//
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// 函数调用结束后，内部不持有该内存块
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func (shCtx *SequenceHeaderContext) Unpack(b []byte) {
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br := nazabits.NewBitReader(b)
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shCtx.SoundFormat, _ = br.ReadBits8(4)
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shCtx.SoundRate, _ = br.ReadBits8(2)
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shCtx.SoundSize, _ = br.ReadBits8(1)
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shCtx.SoundType, _ = br.ReadBits8(1)
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shCtx.AacPacketType, _ = br.ReadBits8(8)
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}
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// MakeAudioDataSeqHeaderWithAsc
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//
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// @param asc: 函数调用结束后，内部不持有该内存块
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//
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// @return out: 内存块为独立新申请；函数调用结束后，内部不持有该内存块
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func MakeAudioDataSeqHeaderWithAsc(asc []byte) (out []byte, err error) {
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if len(asc) < minAscLength {
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return nil, nazaerrors.Wrap(base.ErrShortBuffer)
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}
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// 注意，前两个字节是SequenceHeaderContext，后面跟着asc
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out = make([]byte, 2+len(asc))
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out[0] = 0xaf
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out[1] = 0
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copy(out[2:], asc)
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return
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}
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// MakeAudioDataSeqHeaderWithAdtsHeader
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//
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// @param adtsHeader: 函数调用结束后，内部不持有该内存块
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//
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// @return out: 内存块为独立新申请；函数调用结束后，内部不持有该内存块
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func MakeAudioDataSeqHeaderWithAdtsHeader(adtsHeader []byte) (out []byte, err error) {
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var asc []byte
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if asc, err = MakeAscWithAdtsHeader(adtsHeader); err != nil {
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return nil, err
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}
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return MakeAudioDataSeqHeaderWithAsc(asc)
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}
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