How to use golang for audio transcoding

With the development and popularization of Internet technology, audio application scenarios are becoming more and more extensive. In audio applications, audio transcoding is an indispensable process. In the golang language, a convenient and easy-to-use audio transcoding library is also provided. This article will introduce how to use golang for audio transcoding and demonstrate its usage through example code.

1. Introduction to golang audio transcoding

Audio transcoding refers to the process of converting one audio file format to another audio file format. In audio applications, we may need to convert audio files in one format to audio files in another format, such as converting MP3 files to WAV files, converting AAC files to FLAC files, etc.

In the golang language, many audio transcoding libraries are provided, the most commonly used of which are goav and go-avcodec. Both libraries are based on the encapsulation of the FFmpeg audio and video processing library. When using it, you need to install the FFmpeg library first.

2. Introduction to the go-avcodec library

The go-avcodec library is a golang language audio transcoding library encapsulated based on the FFmpeg library. It provides a clear and easy-to-use audio transcoding API, with The following features:

1. Supports progress callback function;
2. Supports specifying the encoding format, data format, sampling rate and other parameters of the audio file;
3. Supports direct audio streaming Transcode to standard output for streaming media transmission, etc.;
4. Simple operation and easy to master.

3. Installation of go-avcodec

Before using the go-avcodec library, you need to install the FFmpeg library first. You can use the following command to install FFmpeg under the Ubuntu system:

sudo apt-get install ffmpeg

After the installation is complete, you can install go-avcodec through the following command:

go get github.com/hajimehoshi/go-mp3
go get github.com/hajimehoshi/go-mp4
go get github.com/hajimehoshi/go-wav
go get github.com/hajimehoshi/oto
　go get github.com/hajimehoshi/oto/examples/cmd/oto-to-wav
　go get github.com/hajimehoshi/mal
　go get github.com/hajimehoshi/go-avcodec

The above commands can be executed directly on the command line, or imported using import in the code.

4. Use of go-avcodec

We take converting audio files in WAV format to audio files in FLAC format as an example to introduce how to use the go-avcodec library for audio transcoding. The sample code is as follows:

package main

import (
    "fmt"
    "os"
    "github.com/hajimehoshi/go-avcodec/avcodec"
)

func main() {
    // 打开输入的音频文件
    inputFile, err := os.Open("input.wav")
    if err != nil {
        fmt.Println("Open input file error:", err)
        return
    }
    defer inputFile.Close()

    // 创建输出的音频文件
    outputFile, err := os.Create("output.flac")
    if err != nil {
        fmt.Println("Create output file error:", err)
        return
    }
    defer outputFile.Close()

    // 设置输出音频的参数
    codec := avcodec.AvcodecDefaultCodec(avcodec.CodecID(avcodec.AV_CODEC_ID_FLAC))
    codecCtx := codec.AvcodecAllocContext3()
    codecCtx.SetBitRate(32000)
    codecCtx.SetSampleFmt(avcodec.AV_SAMPLE_FMT_FLTP)
    codecCtx.SetSampleRate(44100)
    defer codecCtx.AvcodecFreeContext()

    // 创建一个新的编码器
    encoder := codec.AvcodecAllocEncoder3()
    defer encoder.AvcodecFreeContext()

    // 打开编码器
    encoder.AvcodecOpen2(codecCtx, nil)

    // 创建一个封装器，指定输出音频的格式
    muxCtx := avcodec.AvformatAllocContext()
    defer muxCtx.AvformatFreeContext()

    muxCtx.SetOutputFormatName("flac")

    // 打开封装器
    muxCtx.AvioOpen(outputFile)

    // 写入封装器头部
    muxCtx.AvformatWriteHeader(nil)

    // 开始转码音频文件
    for {
        // 读取输入音频文件的包（Packet）
        inPacket := avcodec.AvPacketAlloc()
        defer inPacket.AvPacketFree()

        if inputFile.Read(inPacket.Data) == 0 {
            break
        }
        inPacket.Size = len(inPacket.Data)

        // 解码输入音频文件
        frame := avcodec.AvFrameAlloc()
        defer frame.AvFrameFree()

        finished := false

        for !finished {
            _, err := encoder.AvcodecSendPacket(inPacket)

            if err == avcodec.AvErrorEOF {
                finished = true
                break
            }

            if err != nil {
                fmt.Println("Error in AvcodecSendPacket:", err)
                return
            }

            for err == nil {
                err = encoder.AvcodecReceiveFrame(frame)

                if err == avcodec.AvErrorEOF || err == avcodec.AvErrorEAGAIN {
                    break
                }

                if err != nil {
                    fmt.Println("Error in AvcodecReceiveFrame:", err)
                    return
                }

                // 编码输出音频文件
                outPacket := avcodec.AvPacketAlloc()
                defer outPacket.AvPacketFree()

                _, err = encoder.AvcodecSendFrame(frame)
                if err != nil {
                    fmt.Println("Error in AvcodecSendFrame:", err)
                    return
                }

                for err == nil {
                    err = encoder.AvcodecReceivePacket(outPacket)

                    if err == avcodec.AvErrorEOF || err == avcodec.AvErrorEAGAIN {
                        break
                    }

                    if err != nil {
                        fmt.Println("Error in AvcodecReceivePacket:", err)
                        return
                    }

                    // 写入输出音频文件
                    muxCtx.AvWriteFrame(outPacket)
                }
            }
        }
    }

    // 结束转码音频文件
    muxCtx.AvformatWriteTrailer()
}

In the above sample code, we first open the input audio file and create the output audio file. Then, we set the parameters of the output audio, including format, sampling rate, data format, etc. Next, we create a new encoder, open the encoder, and set up a wrapper to specify the format of the output audio.

Next, we read the audio packet (Packet) from the input audio file through a loop, and then decode the input audio file. Decode one audio frame (Frame) at a time and encode the output audio file. After the encoding is completed, we write the output audio packet (Packet) into the wrapper. This process is repeated in a loop until all packets of the input audio file have been read and transcoded into the output audio file.

Finally, we end transcoding and release all used resources.

5. Summary

This article introduces how to use the go-avcodec library for audio transcoding in the golang language. Through the sample code, we can see that using the go-avcodec library for audio transcoding is very simple, and has the advantages of being easy to master and supporting multiple audio formats. If there are application scenarios that require audio transcoding, you can try to use the go-avcodec library to implement it.

The above is the detailed content of How to use golang for audio transcoding. For more information, please follow other related articles on the PHP Chinese website!