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在之前的学习中，通过AVFrame来保存为图片来认识了AVFrame，

[FFmpeg学习]从视频中获取图片_ffmpeg 获取图片-CSDN博客

在获取到AVFrame时，还可以调用SDL方法来进行展现，实现播放效果。

参考资料

SDL，ffmpeg实现简单视频播放器_ffmpeg sdl 播放器-CSDN博客

SDL2 简单介绍以及Windows开发环境搭建-CSDN博客

这里只显示了视频，没有处理声音，

// ffmpegTest.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//#include <iostream>/*
int main()
{std::cout << "Hello World!\n";
}*/extern "C" {
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include <libavutil/log.h>
#include <libavformat/avformat.h>
}using namespace std;//要使用FFmpeg库从MP4文件中提取一张图片，你需要使用FFmpeg的解码器来读取视频帧，并将其保存为图片。以下是一个简单的示例程序，演示如何使用FFmpeg库从MP4文件中提取一张图片：
#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  #include "SDL.h"int savePicture(AVFrame* pFrame, char* out_name) {//编码保存图片int width = pFrame->width;int height = pFrame->height;AVCodecContext* pCodeCtx = NULL;AVFormatContext* pFormatCtx = avformat_alloc_context();// 设置输出文件格式pFormatCtx->oformat = av_guess_format("mjpeg", NULL, NULL);// 创建并初始化输出AVIOContextif (avio_open(&pFormatCtx->pb, out_name, AVIO_FLAG_READ_WRITE) < 0) {printf("Couldn't open output file.");return -1;}// 构建一个新streamAVStream* pAVStream = avformat_new_stream(pFormatCtx, 0);if (pAVStream == NULL) {return -1;}AVCodecParameters* parameters = pAVStream->codecpar;parameters->codec_id = pFormatCtx->oformat->video_codec;parameters->codec_type = AVMEDIA_TYPE_VIDEO;parameters->format = AV_PIX_FMT_YUVJ420P;parameters->width = pFrame->width;parameters->height = pFrame->height;const AVCodec* pCodec = avcodec_find_encoder(pAVStream->codecpar->codec_id);  //查找编码器if (!pCodec) {printf("Could not find encoder\n");return -1;}pCodeCtx = avcodec_alloc_context3(pCodec);   //为AVCodecContext分配内存if (!pCodeCtx) {fprintf(stderr, "Could not allocate video codec context\n");exit(1);}if ((avcodec_parameters_to_context(pCodeCtx, pAVStream->codecpar)) < 0) {fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n",av_get_media_type_string(AVMEDIA_TYPE_VIDEO));return -1;}//  AVRational tmp = { 1, 25 };pCodeCtx->time_base = { 1, 25 };if (avcodec_open2(pCodeCtx, pCodec, NULL) < 0) {   //打开编码器printf("Could not open codec.");return -1;}int ret = avformat_write_header(pFormatCtx, NULL);if (ret < 0) {printf("write_header fail\n");return -1;}int y_size = width * height;//Encode// 给AVPacket分配足够大的空间AVPacket pkt;av_new_packet(&pkt, y_size * 3);// 编码数据ret = avcodec_send_frame(pCodeCtx, pFrame);if (ret < 0) {printf("Could not avcodec_send_frame.");return -1;}// 得到编码后数据ret = avcodec_receive_packet(pCodeCtx, &pkt);if (ret < 0) {printf("Could not avcodec_receive_packet");return -1;}ret = av_write_frame(pFormatCtx, &pkt);if (ret < 0) {printf("Could not av_write_frame");return -1;}av_packet_unref(&pkt);//Write Trailerav_write_trailer(pFormatCtx);avcodec_close(pCodeCtx);avio_close(pFormatCtx->pb);avformat_free_context(pFormatCtx);return 0;
}class SDLHandle
{
public:SDLHandle(int w, int h){m_rect.x = 0;m_rect.y = 0;m_rect.w = w;m_rect.h = h;SdlInit();}~SDLHandle(){if (m_pTexture){SDL_DestroyTexture(m_pTexture);}if (m_pRender){SDL_DestroyRenderer(m_pRender);}if (m_pWnd){SDL_DestroyWindow(m_pWnd);}SDL_Quit();}bool CreateSDLWindow(const char* title, Uint32 flag){m_pWnd = SDL_CreateWindow(title, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, m_rect.w, m_rect.h, flag);if (!m_pWnd){printf("CreateWindows error:%s.\n", SDL_GetError());return false;}m_pRender = SDL_CreateRenderer(m_pWnd, -1, 0);if (!m_pRender){return false;}m_pTexture = SDL_CreateTexture(m_pRender, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, m_rect.w, m_rect.h);if (!m_pTexture){return false;}return true;}void UpdateTexture(AVFrame* pFrame){if (!pFrame){return;}//SDL_UpdateTexture(m_pTexture, &m_rect, pFrame->data[0], pFrame->linesize[0]);SDL_UpdateYUVTexture(m_pTexture, &m_rect, pFrame->data[0], pFrame->linesize[0], pFrame->data[1], pFrame->linesize[1], pFrame->data[2], pFrame->linesize[2]);SDL_RenderClear(m_pRender);SDL_RenderCopy(m_pRender, m_pTexture, nullptr, &m_rect);SDL_RenderPresent(m_pRender);SDL_Delay(40);}
private:bool SdlInit(){if (SDL_Init(SDL_INIT_AUDIO | SDL_INIT_VIDEO | SDL_INIT_TIMER) < 0){printf("sdl_init error:%s\n", SDL_GetError());return false;}return true;}
private:SDL_Renderer* m_pRender = nullptr;SDL_Window* m_pWnd = nullptr;SDL_Texture* m_pTexture = nullptr;SDL_Rect m_rect;
};int getpic4() {std::string filename = "test.mp4";     // 输入MP4文件名std::string outputFilename = "output4.jpg";  // 输出图片文件名SDL_Window* pScreen = nullptr;      // 播放窗口SDL_Renderer* pRender = nullptr;    // 渲染器SDL_Texture* pSDLTexture = nullptr; // 纹理SDLHandle* m_pSDlHandle = nullptr;AVFormatContext* formatContext = nullptr;if (avformat_open_input(&formatContext, filename.c_str(), nullptr, nullptr) != 0) {std::cerr << "Error opening input file" << std::endl;return -1;}if (avformat_find_stream_info(formatContext, nullptr) < 0) {std::cerr << "Error finding stream information" << std::endl;avformat_close_input(&formatContext);return -1;}const AVCodec* codec = nullptr;int videoStreamIndex = -1;for (unsigned int i = 0; i < formatContext->nb_streams; i++) {if (formatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {videoStreamIndex = i;codec = avcodec_find_decoder(formatContext->streams[i]->codecpar->codec_id);break;}}if (videoStreamIndex == -1 || codec == nullptr) {std::cerr << "Error finding video stream or decoder" << std::endl;avformat_close_input(&formatContext);return -1;}AVCodecContext* codecContext = avcodec_alloc_context3(codec);if (codecContext == nullptr) {std::cerr << "Error allocating codec context" << std::endl;avformat_close_input(&formatContext);return -1;}if (avcodec_parameters_to_context(codecContext, formatContext->streams[videoStreamIndex]->codecpar) < 0) {std::cerr << "Error setting codec parameters" << std::endl;avcodec_free_context(&codecContext);avformat_close_input(&formatContext);return -1;}if (avcodec_open2(codecContext, codec, nullptr) < 0) {std::cerr << "Error opening codec" << std::endl;avcodec_free_context(&codecContext);avformat_close_input(&formatContext);return -1;}m_pSDlHandle = new SDLHandle(codecContext->width, codecContext->height);if (!m_pSDlHandle->CreateSDLWindow("SDL_TEXT", SDL_WINDOW_OPENGL)){printf("CreateSDLWindow error:%s\n", SDL_GetError());return -1;}AVPacket packet;av_init_packet(&packet);// 查找目标时间戳所对应的帧AVFrame* frame = av_frame_alloc();bool foundTargetFrame = false;int count = 0;while (av_read_frame(formatContext, &packet) >= 0) {if (packet.stream_index == videoStreamIndex) {int response = avcodec_send_packet(codecContext, &packet);if (response < 0) {std::cerr << "Error sending packet to decoder" << std::endl;break;}count++;response = avcodec_receive_frame(codecContext, frame);if (response == AVERROR(EAGAIN) || response == AVERROR_EOF) {continue;}else if (response < 0) {std::cerr << "Error receiving frame from decoder" << std::endl;break;}m_pSDlHandle->UpdateTexture(frame);}av_packet_unref(&packet);}if (!foundTargetFrame) {std::cerr << "Target frame not found" << std::endl;av_frame_free(&frame);avcodec_free_context(&codecContext);avformat_close_input(&formatContext);return -1;}// 清理资源av_frame_free(&frame);av_packet_unref(&packet);avcodec_free_context(&codecContext);return 1;
}#undef main
int main(int argc, char* argv[]) {av_log(NULL, AV_LOG_INFO, "...Hello world\n");getpic4();return 0;
}