75 lines
2.4 KiB
Go
75 lines
2.4 KiB
Go
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package volcano
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import (
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"encoding/binary"
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"fmt"
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)
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// 标准 PCM WAV 头(44 字节)。
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// 文档 3.3 节:流式场景不推荐 wav(会多次返回 wav header),
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// 本项目策略:上游走 pcm,本地拼一次标准头,避免拼接过个 header。
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type wavHeader struct {
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// RIFF chunk descriptor
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ChunkID [4]byte // "RIFF"
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ChunkSize uint32 // 36 + SubChunk2Size
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Format [4]byte // "WAVE"
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// fmt sub-chunk
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Subchunk1ID [4]byte // "fmt "
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Subchunk1Size uint32 // 16 for PCM
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AudioFormat uint16 // 1 = PCM
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NumChannels uint16
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SampleRate uint32
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ByteRate uint32
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BlockAlign uint16
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BitsPerSample uint16
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// data sub-chunk
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Subchunk2ID [4]byte // "data"
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Subchunk2Size uint32
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}
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// WrapWAVHeader 把 PCM 原始字节封装成完整的 WAV 字节流。
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// sampleRate 决定 WAV 头里的采样率字段;pcm 视为 16-bit 单声道 little-endian。
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func WrapWAVHeader(pcm []byte, sampleRate int) ([]byte, error) {
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if sampleRate <= 0 {
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return nil, fmt.Errorf("invalid sample rate %d", sampleRate)
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}
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const channels uint16 = 1
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const bitsPerSample uint16 = 16
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blockAlign := channels * bitsPerSample / 8
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byteRate := uint32(sampleRate) * uint32(blockAlign)
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dataSize := uint32(len(pcm))
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hdr := wavHeader{
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ChunkID: [4]byte{'R', 'I', 'F', 'F'},
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ChunkSize: 36 + dataSize,
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Format: [4]byte{'W', 'A', 'V', 'E'},
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Subchunk1ID: [4]byte{'f', 'm', 't', ' '},
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Subchunk1Size: 16,
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AudioFormat: 1,
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NumChannels: channels,
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SampleRate: uint32(sampleRate),
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ByteRate: byteRate,
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BlockAlign: blockAlign,
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BitsPerSample: bitsPerSample,
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Subchunk2ID: [4]byte{'d', 'a', 't', 'a'},
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Subchunk2Size: dataSize,
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}
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out := make([]byte, 0, 44+len(pcm))
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out = append(out, hdr.ChunkID[:]...)
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out = binary.LittleEndian.AppendUint32(out, hdr.ChunkSize)
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out = append(out, hdr.Format[:]...)
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out = append(out, hdr.Subchunk1ID[:]...)
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out = binary.LittleEndian.AppendUint32(out, hdr.Subchunk1Size)
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out = binary.LittleEndian.AppendUint16(out, hdr.AudioFormat)
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out = binary.LittleEndian.AppendUint16(out, hdr.NumChannels)
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out = binary.LittleEndian.AppendUint32(out, hdr.SampleRate)
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out = binary.LittleEndian.AppendUint32(out, hdr.ByteRate)
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out = binary.LittleEndian.AppendUint16(out, hdr.BlockAlign)
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out = binary.LittleEndian.AppendUint16(out, hdr.BitsPerSample)
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out = append(out, hdr.Subchunk2ID[:]...)
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out = binary.LittleEndian.AppendUint32(out, hdr.Subchunk2Size)
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out = append(out, pcm...)
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return out, nil
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}
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