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How to implement audio processing for web applications using Golang
- 王林Original
- 2023-06-25 09:50:25992browse
With the development of the Internet, audio processing has become an increasingly important task. Implementing audio processing is a necessary skill for web applications. As a fast and efficient programming language, Golang can also be used to implement audio processing for web applications.
In this article, we will introduce how to use Golang to implement audio processing for web applications, including audio file upload, audio format conversion, and audio feature extraction.
1. Audio file upload
Before implementing audio processing, you first need to upload audio files. The third-party package gin can be used in Golang to achieve rapid development of web applications.
In order to implement file upload, you first need to add the input tag in the HTML code to implement the file upload page, as shown below:
<html>
<head>
<title>音频文件上传</title>
</head>
<body>
<form enctype="multipart/form-data" action="/upload" method="post">
<input type="file" name="file" />
<input type="submit" value="上传" />
</form>
</body>
</html>Then, you can use gin to implement file upload in Golang The processing function is as follows:
func uploadFile(c *gin.Context) {
file, err := c.FormFile("file")
if err != nil {
log.Println(err)
c.String(http.StatusBadRequest, "Bad request")
return
}
// 保存上传的文件
err = c.SaveUploadedFile(file, file.Filename)
if err != nil {
log.Println(err)
c.String(http.StatusInternalServerError, "Internal server error")
return
}
c.String(http.StatusOK, fmt.Sprintf("'%s' uploaded!", file.Filename))
}2. Audio format conversion
Before audio processing is implemented, the format of the uploaded audio file needs to be converted so that it can be used by subsequent processing functions used. You can use the third-party package goav in Golang to implement audio format conversion.
First, you need to install FFmpeg for goav. In Ubuntu system, you can use the following command to install:
sudo apt install ffmpeg
Then, you can use goav to convert audio formats in Golang, such as converting MP3 format to WAV The format is as follows:
func convertAudioFormat(inputFile string, outputFile string) error {
ctx := avutil.AvAllocContext()
defer avutil.AvFree(ctx)
// 打开输入音频文件
if avformat.AvformatOpenInput(&ctx, inputFile, nil, nil) != 0 {
return errors.New("无法打开输入音频文件")
}
defer avformat.AvformatCloseInput(ctx)
// 检索音频流信息
if avformat.AvformatFindStreamInfo(ctx, nil) < 0 {
return errors.New("无法获取音频流信息")
}
// 寻找音频流索引
audioIndex := -1
for i := 0; i < int(ctx.NbStreams()); i++ {
if ctx.Streams()[i].CodecParameters().CodecType() == avcodec.AVMEDIA_TYPE_AUDIO {
audioIndex = i
break
}
}
if audioIndex < 0 {
return errors.New("音频流不存在")
}
// 打开音频解码器
codecParams := ctx.Streams()[audioIndex].CodecParameters()
codec := avcodec.AvcodecFindDecoder(codecParams.CodecId())
if codec == nil {
return errors.New("无法打开音频解码器")
}
if codec.AvcodecOpen(codecParams) != 0 {
return errors.New("无法打开音频解码器")
}
defer codec.AvcodecClose()
// 打开输出音频文件
outctx := avformat.AvformatAllocContext()
defer avformat.AvformatFreeContext(outctx)
if avformat.AvformatAllocOutputContext2(&outctx, nil, "wav", outputFile) != 0 {
return errors.New("无法打开输出音频文件")
}
defer func() {
avio.AvioClose(outctx.Pb())
avformat.AvformatFreeContext(outctx)
}()
// 写入音频流头部信息
stream := avformat.AvformatNewStream(outctx, nil)
defer avutil.AvFree(stream.CodecParameters())
if avcodec.AvCodecParametersCopy(stream.CodecParameters(), codecParams) != 0 {
return errors.New("无法复制音频参数")
}
// 写入文件头部信息
if outctx.Format().Flags()&avformat.AVFMT_NOFILE == 0 {
if avio.AvioOpen(&outctx.Pb(), outputFile, avutil.AVIO_FLAG_WRITE) < 0 {
return errors.New("无法打开输出文件")
}
}
if avformat.AvformatWriteHeader(outctx, nil) < 0 {
return errors.New("无法写入文件头部信息")
}
// 转换音频格式并写入文件
packet := avcodec.AvPacketAlloc()
defer avcodec.AvPacketUnref(packet)
for {
frame, err := codec.AvcodecReceiveFrame(packet)
if err != nil {
if err == avutil.ErrEOF || err == avutil.ErrEAGAIN {
break
} else {
return errors.New("无法接收音频帧")
}
}
if frame.Pts() != avutil.AvNoPts && codec.Avctx().TimeBase().Den() > 0 {
frame.SetPts(avutil.AvRescaleQ(frame.Pts(), codec.Avctx().TimeBase(), stream.TimeBase()))
}
if frame.PktDts() != avutil.AvNoPts && codec.Avctx().TimeBase().Den() > 0 {
frame.SetPktDts(avutil.AvRescaleQ(frame.PktDts(), codec.Avctx().TimeBase(), stream.TimeBase()))
}
if frame.PktPts() != avutil.AvNoPts && codec.Avctx().TimeBase().Den() > 0 {
frame.SetPktPts(avutil.AvRescaleQ(frame.PktPts(), codec.Avctx().TimeBase(), stream.TimeBase()))
}
if avcodec.AvCodecSendFrame(codec, frame) != 0 {
return errors.New("无法发送音频帧")
}
for {
err := avcodec.AvCodecReceivePacket(codec, packet)
if err != nil {
if err == avutil.ErrEOF || err == avutil.ErrEAGAIN {
break
} else {
return errors.New("无法接收音频数据包")
}
}
packet.SetStreamIndex(stream.Index())
if avformat.AvInterleavedWriteFrame(outctx, packet) < 0 {
return errors.New("无法写入音频数据包")
}
avcodec.AvPacketUnref(packet)
}
avutil.AvFrameFree(&frame)
}
// 写入文件尾部信息
if avformat.AvWriteTrailer(outctx) < 0 {
return errors.New("无法写入文件尾部信息")
}
return nil
}3. Audio feature extraction
Finally, we need to implement some audio feature extraction algorithms in order to process audio files.
For example, you can use the go-dsp package to implement short-time Fourier transform (STFT) to convert audio files into spectrograms. As shown below:
func stft(signal []float64, windowSize int, overlap float64) [][]complex128 {
hopSize := int(float64(windowSize) * (1.0 - overlap))
fftSize := windowSize / 2
stftMatrix := make([][]complex128, 0)
for i := 0; i+windowSize < len(signal); i += hopSize {
segment := signal[i : i+windowSize]
window := dsp.NewWindow(windowSize, dsp.Hamming)
fftIn := make([]complex128, windowSize)
for j := range segment {
fftIn[j] = complex(segment[j], 0)
}
window.Apply(fftIn)
fftOut := make([]complex128, fftSize)
for j := range fftOut {
fftOut[j] = 0
}
fft.FFT(fftOut, fftIn)
stftRow := make([]complex128, fftSize)
for j := range stftRow {
stftRow[j] = fftOut[j]
}
stftMatrix = append(stftMatrix, stftRow)
}
return stftMatrix
}In addition, you can also use the go-dsp package to implement other audio feature extraction algorithms, such as MFCC (Mel Cepstrum Coefficient) or ZCR (Zero Crossing Rate), etc.
To sum up, this article introduces how to use Golang to implement audio processing for web applications, including audio file upload, audio format conversion, and audio feature extraction. These skills can help developers developing web applications better process audio data and provide users with a better user experience.
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