Golang and FFmpeg: Technology for real-time video streaming transcoding and encapsulation

Golang and FFmpeg: Real-time video stream transcoding and encapsulation technology requires specific code examples

Overview:
In today's Internet era, video has become an integral part of people's lives. However, due to the inconsistency of video formats and differences in network environments, there are often some problems in directly transmitting videos over the network, such as slow transmission speeds and reduced video quality. To solve these problems, we can use video transcoding and encapsulation technology to encode and decode the video stream and encapsulate it into a format suitable for network transmission. This article will introduce how to use Golang and FFmpeg to implement real-time video stream transcoding and encapsulation technology, and give specific code examples.

Technical background:
Golang is a powerful programming language. It has the characteristics of high concurrency, simplicity and ease of use, and fast compilation. It is suitable for network programming. FFmpeg is a cross-platform audio and video processing tool that can handle almost all common audio and video formats. Combining Golang and FFmpeg, we can achieve efficient video stream transcoding and encapsulation.

Specific implementation steps:

1. Introduce necessary libraries
   First, introduce FFmpeg-related libraries into Golang. In Golang, you can use cgo to call C language libraries. You can obtain FFmpeg related libraries through the go get command.
2. Open the video input stream
   Use FFmpeg's avformat_open_input function to open the video input stream. This function needs to pass in the address of the input stream, the encapsulation format of the input stream, and other related parameters.
3. Find video stream information
   Use FFmpeg's avformat_find_stream_info function to find relevant information about the input stream, such as video stream format, encoder, frame rate, etc. This function will fill in the relevant information of the AVFormatContext structure.
4. Open the video output stream
   Use FFmpeg's avformat_alloc_output_context2 function to create the context of the video output stream. This function needs to pass in the encapsulation format of the output stream and the output file name.
5. Add video stream information
   Copy the input stream information to the output stream.
6. Open the output file
   Use FFmpeg's avio_open2 function to open the output file. This function requires the context of the output stream, the output file name, and other related parameters.
7. Encoding and Encapsulation
   Loop to read each frame data of the video stream, and then encode the frame data. Video frames can be encoded using FFmpeg's avcodec_encode_video2 function. After the encoding is completed, use FFmpeg's av_interleaved_write_frame function to write the encoded data to the output file.
8. Close the input and output stream
   After the video stream traversal is completed, use FFmpeg's av_write_trailer function to complete the video encapsulation. Finally, close the input and output streams and release resources.

Specific code examples:

package main

// 导入FFmpeg相关的头文件
/*
#cgo LDFLAGS: -lavformat -lavcodec -lavutil
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
*/
import "C"

import (
    "fmt"
)

func main() {
    // 输入文件名和输出文件名
    inputFileName := "input.mp4"
    outputFileName := "output.mp4"

    // 打开输入文件流
    var inputFormatCtx *C.AVFormatContext
    if C.avformat_open_input(&inputFormatCtx, C.CString(inputFileName), nil, nil) != 0 {
        fmt.Printf("Failed to open input file
")
        return
    }

    // 查找视频流信息
    if C.avformat_find_stream_info(inputFormatCtx, nil) < 0 {
        fmt.Printf("Failed to find stream information
")
        return
    }

    // 打开输出文件流
    var outputFormatCtx *C.AVFormatContext
    C.avformat_alloc_output_context2(&outputFormatCtx, nil, nil, C.CString(outputFileName))
    if outputFormatCtx == nil {
        fmt.Printf("Failed to allocate output format context
")
        return
    }

    // 复制视频流信息到输出流
    for i := C.uint(0); i < inputFormatCtx.nb_streams; i++ {
        stream := inputFormatCtx.streams[i]
        outputStream := C.avformat_new_stream(outputFormatCtx, stream.codec.codec)
        if outputStream == nil {
            fmt.Printf("Failed to allocate output stream
")
            return
        }

        // 复制流的参数
        if C.avcodec_parameters_copy(outputStream.codecpar, stream.codecpar) < 0 {
            fmt.Printf("Failed to copy codec parameters
")
            return
        }
    }

    // 打开输出文件
    if C.avio_open(&outputFormatCtx.pb, C.CString(outputFileName), C.AVIO_FLAG_WRITE) < 0 {
        fmt.Printf("Failed to open output file
")
        return
    }

    // 写入文件头部
    if C.avformat_write_header(outputFormatCtx, nil) < 0 {
        fmt.Printf("Failed to write header
")
        return
    }

    // 读取视频流数据并进行编码处理
    packet := C.AVPacket{}
    for C.av_read_frame(inputFormatCtx, &packet) == 0 {
        stream := inputFormatCtx.streams[packet.stream_index]
        outStream := outputFormatCtx.streams[packet.stream_index]

        // 编码帧数据
        if C.avcodec_send_packet(stream.codec, &packet) < 0 || C.avcodec_receive_packet(stream.codec, &packet) < 0 {
            fmt.Printf("Error while encoding
")
            return
        }

        packet.stream_index = outStream.index
        packet.pts = C.AV_NOPTS_VALUE
        packet.dts = C.AV_NOPTS_VALUE

        // 封装编码后的数据
        if C.av_interleaved_write_frame(outputFormatCtx, &packet) < 0 {
            fmt.Printf("Error while writing frame
")
            return
        }

        C.av_packet_unref(&packet)
    }

    // 结束封装
    C.av_write_trailer(outputFormatCtx)

    // 关闭输入输出流
    C.avformat_close_input(&inputFormatCtx)
    if outputFormatCtx != nil && outputFormatCtx.pb != nil {
        C.avio_close(outputFormatCtx.pb)
    }
    C.avformat_free_context(outputFormatCtx)

    fmt.Printf("Done
")
}

Summary:
By using Golang and FFmpeg, we can easily achieve transcoding and encapsulation of real-time video streams. This article gives specific code examples and outlines the implementation steps. However, in actual projects, more details may need to be considered, such as exception handling, concurrency processing, etc. I hope this article can be helpful to beginners of real-time video streaming transcoding and encapsulation technology, and I also hope it can provide everyone with a learning direction and ideas.

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