How to implement video editing using Golang and FFmpeg

The method of using Golang and FFmpeg to implement video editing requires specific code examples

Overview:
Video editing is a common multimedia processing requirement, through editing Video can realize functions such as cropping, splicing, cutting and adding watermarks to videos. This article will introduce how to use Golang and FFmpeg libraries to implement video editing, and provide specific code examples.

Step 1: Install FFmpeg
First, we need to install FFmpeg. FFmpeg is an open source multimedia processing library that can be used on various platforms. For specific installation methods, please refer to the FFmpeg official website (https://ffmpeg.org/).
After the installation is complete, we need to add the FFmpeg executable file to the system environment variables so that we can call FFmpeg directly in the terminal or command line.

Step 2: Download Golang’s FFmpeg library
Golang’s FFmpeg library is a Go language library used to call FFmpeg functions. We need to introduce this library into the project. The library can be downloaded through the following commands:
go get github.com/giorgisio/goav/avcodec
go get github.com/giorgisio/goav/avformat
go get github.com/giorgisio/goav/ avutil
go get github.com/giorgisio/goav/swscale

Step 3: Code implementation of video clipping
The following is a sample code to implement video clipping using Golang and FFmpeg libraries:

package main

import (
    "fmt"
    "os"
    "strings"
    "sync"
    "time"

    "github.com/giorgisio/goav/avcodec"
    "github.com/giorgisio/goav/avformat"
)

func main() {
    start := time.Now()

    inputFileName := "input.mp4"
    outputFileName := "output.mp4"
    startTime := 10
    duration := 20

    // 初始化FFmpeg库
    avformat.AvRegisterAll()
    avcodec.AvcodecRegisterAll()

    // 打开输入文件
    inputFormatContext := avformat.AvformatAllocContext()
    if avformat.AvformatOpenInput(&inputFormatContext, inputFileName, nil, nil) != 0 {
        fmt.Println("Failed to open input file")
        os.Exit(1)
    }

    // 找到输入文件中的流信息
    if avformat.AvformatFindStreamInfo(inputFormatContext, nil) < 0 {
        fmt.Println("Failed to find stream info")
        os.Exit(1)
    }

    // 寻找视频流信息
    var videoStreamIndex int
    for i := 0; i < int(inputFormatContext.NbStreams()); i++ {
        if inputFormatContext.Streams()[i].CodecParameters().CodecType() == avformat.AVMEDIA_TYPE_VIDEO {
            videoStreamIndex = i
            break
        }
    }

    // 获取视频流的解码器上下文
    videoCodecContext := inputFormatContext.Streams()[videoStreamIndex].Codec()

    // 初始化解码器
    videoCodec := avcodec.AvcodecFindDecoder(videoCodecContext.CodecId())
    if videoCodec == nil {
        fmt.Println("Unsupported codec")
        os.Exit(1)
    }

    videoCodecContext.AvcodecOpen2(videoCodec, nil)

    // 创建输出文件
    outputFormatContext := avformat.AvformatAllocContext()
    if avformat.AvformatAllocOutputContext2(&outputFormatContext, nil, "", outputFileName) != 0 {
        fmt.Println("Failed to create output file")
        os.Exit(1)
    }

    // 添加视频流到输出文件
    outputVideoStream := outputFormatContext.AvformatNewStream(nil)
    if outputVideoStream == nil {
        fmt.Println("Failed to create output video stream")
        os.Exit(1)
    }

    // 复制输入视频流的参数到输出视频流
    outputVideoStream.SetCodecParameters(videoCodecContext.CodecParameters())

    // 写入输出文件头
    if avformat.AvformatWriteHeader(outputFormatContext, nil) != 0 {
        fmt.Println("Failed to write output file header")
        os.Exit(1)
    }

    // 读取和写入视频帧
    packets := avformat.AvPacketAlloc()
    frame := avutil.AvFrameAlloc()
    frameCount := 0
    for {
        // 从输入文件中读取一个packet
        if avformat.AvReadFrame(inputFormatContext, packets) < 0 {
            break
        }

        // 判断是否为视频流的packet
        if packets.StreamIndex() == videoStreamIndex {
            // 解码packet
            if avcodec.AvcodecSendPacket(videoCodecContext, packets) != 0 {
                fmt.Println("Failed to send packet to decoder")
                os.Exit(1)
            }

            for avcodec.AvcodecReceiveFrame(videoCodecContext, frame) == 0 {
                // 判断当前帧是否在指定的时间范围内
                currentTime := float64(frameCount) * avutil.AvQ2D(videoFormatContext.Streams()[videoStreamIndex].TimeBase())
                if currentTime >= float64(startTime) && currentTime <= float64(startTime+duration) {
                // 将剪辑好的帧写入输出文件
                if avcodec.AvcodecSendFrame(outputCodecContext, frame) != 0 {
                    fmt.Println("Failed to send framed to encoder")
                    os.Exit(1)
                }

                for {
                    if avcodec.AvcodecReceivePacket(outputCodecContext, packets) != 0 {
                        break
                    }

                    // 将packet写入输出文件
                    avformat.AvWriteFrame(outputFormatContext, packets)
                    avcodec.AvPacketUnref(packets)
                }
            }

            frameCount++
        }
    }

    // 写入输出文件尾部
    avformat.AvWriteTrailer(outputFormatContext)

    // 释放资源
    avutil.AvFrameFree(frame)
    avformat.AvformatCloseInput(&inputFormatContext)
    avformat.AvformatFreeContext(inputFormatContext)
    avformat.AvformatFreeContext(outputFormatContext)
    avcodec.AvcodecClose(videoCodecContext)
    avcodec.AvcodecFreeContext(videoCodecContext)

    fmt.Println("Video clipping completed in", time.Since(start))
}

The above code implements the basic functions of video editing. It first reads the frames of the video stream from the input file, and then writes the frames that need to be retained to the output file by judging the frame time. The functions provided by the FFmpeg library are used for reading, decoding, encoding and writing operations.

It should be noted that this example only edits a single video stream; if multiple video streams are involved, corresponding modifications need to be made based on the actual situation.

Conclusion:
This article introduces the method of using Golang and FFmpeg to implement video editing, and provides specific code examples. Readers can adjust and expand the code accordingly according to their own needs to achieve more complex and personalized video editing functions. At the same time, you can also learn more about video editing by reading the official FFmpeg documentation and Golang's FFmpeg library documentation.

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