写一个使用ffmpeg播放rtsp流，vs2019可以编译通过的播放器

好的，以下是一个使用FFmpeg播放RTSP流的简单示例程序（仅供参考）：

#include <iostream>
#include <string>
#include <Windows.h>
#include "ffmpeg.h"

#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avutil.lib")
#pragma comment(lib, "swscale.lib")
#pragma comment(lib, "swresample.lib")

using namespace std;

int main()
{
    av_register_all();
    avformat_network_init();

    AVFormatContext* formatCtx = NULL;
    AVCodecContext* codecCtx = NULL;
    AVCodec* codec = NULL;
    AVPacket packet;
    AVFrame* frame = NULL;
    int videoStreamIndex = -1;

    const char* rtspUrl = "rtsp://xxx.xxx.xxx.xxx:554/xxx";

    if (avformat_open_input(&formatCtx, rtspUrl, NULL, NULL) != 0)
    {
        cerr << "Failed to open input file" << endl;
        system("pause");
        return -1;
    }

    if (avformat_find_stream_info(formatCtx, NULL) < 0)
    {
        cerr << "Failed to retrieve stream information" << endl;
        system("pause");
        return -1;
    }

    for (unsigned int i = 0; i < formatCtx->nb_streams; i++)
    {
        if (formatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            videoStreamIndex = i;
            break;
        }
    }

    if (videoStreamIndex == -1)
    {
        cerr << "Failed to find video stream" << endl;
        system("pause");
        return -1;
    }

    codec = avcodec_find_decoder(formatCtx->streams[videoStreamIndex]->codecpar->codec_id);
    if (codec == NULL)
    {
        cerr << "Failed to find codec" << endl;
        system("pause");
        return -1;
    }

    codecCtx = avcodec_alloc_context3(codec);
    if (codecCtx == NULL)
    {
        cerr << "Failed to allocate codec context" << endl;
        system("pause");
        return -1;
    }

    if (avcodec_parameters_to_context(codecCtx, formatCtx->streams[videoStreamIndex]->codecpar) < 0)
    {
        cerr << "Failed to copy codec parameters to context" << endl;
        system("pause");
        return -1;
    }

    if (avcodec_open2(codecCtx, codec, NULL) < 0)
    {
        cerr << "Failed to open codec" << endl;
        system("pause");
        return -1;
    }

    frame = av_frame_alloc();
    if (frame == NULL)
    {
        cerr << "Failed to allocate frame" << endl;
        system("pause");
        return -1;
    }

    cout << "Starting playback..." << endl;

    AVPixelFormat dstFormat = AV_PIX_FMT_BGR24;
    int dstWidth = codecCtx->width;
    int dstHeight = codecCtx->height;
    int numBytes = av_image_get_buffer_size(dstFormat, dstWidth, dstHeight, 1);
    uint8_t* buffer = (uint8_t*)av_malloc(numBytes * sizeof(uint8_t));
    SwsContext* swsCtx = sws_getContext(codecCtx->width, codecCtx->height, codecCtx->pix_fmt, dstWidth, dstHeight, dstFormat, SWS_BILINEAR, NULL, NULL, NULL);

    while (av_read_frame(formatCtx, &packet) >= 0)
    {
        if (packet.stream_index == videoStreamIndex)
        {
            if (avcodec_send_packet(codecCtx, &packet) < 0)
            {
                cerr << "Error while sending a packet to the decoder" << endl;
                break;
            }

            while (avcodec_receive_frame(codecCtx, frame) == 0)
            {
                sws_scale(swsCtx, frame->data, frame->linesize, 0, codecCtx->height, &buffer, &dstWidth, &dstHeight);

                // TODO: 将 buffer 中的数据渲染到屏幕上

                av_frame_unref(frame);
            }
        }

        av_packet_unref(&packet);
    }

    av_frame_free(&frame);
    av_free(buffer);
    avcodec_close(codecCtx);
    avformat_close_input(&formatCtx);
    avformat_network_deinit();

    cout << "Playback finished" << endl;
    system("pause");
    return 0;
}

注意，在使用之前需要先下载、编译并链接FFmpeg库，这里不再赘述。此外，还需要自行完成视频数据的渲染部分。