基于ffmpeg的简单音视频播放器的demo

以下是基于ffmpeg的简单音视频播放器的demo的代码，使用C++语言编写：

#include <iostream>
#include <string>
#include <thread>
#include <chrono>

extern "C" {
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
#include <libavutil/imgutils.h>
}

using namespace std;

int main(int argc, char* argv[]) {
    if (argc != 2) {
        cout << "Usage: " << argv[0] << " filename" << endl;
        return 1;
    }

    // Initialize FFmpeg
    av_register_all();
    avcodec_register_all();

    // Open video file
    AVFormatContext* format_ctx = nullptr;
    if (avformat_open_input(&format_ctx, argv[1], nullptr, nullptr) != 0) {
        cerr << "Error: Failed to open file " << argv[1] << endl;
        return 1;
    }

    // Retrieve stream information
    if (avformat_find_stream_info(format_ctx, nullptr) < 0) {
        cerr << "Error: Failed to retrieve stream information" << endl;
        return 1;
    }

    // Find the first video stream
    int video_stream_index = -1;
    AVCodecParameters* codec_params = nullptr;
    AVCodec* codec = nullptr;
    AVCodecContext* codec_ctx = nullptr;
    for (int i = 0; i < format_ctx->nb_streams; i++) {
        codec_params = format_ctx->streams[i]->codecpar;
        if (codec_params->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream_index = i;
            codec = avcodec_find_decoder(codec_params->codec_id);
            if (codec == nullptr) {
                cerr << "Error: Unsupported codec" << endl;
                return 1;
            }
            codec_ctx = avcodec_alloc_context3(codec);
            if (codec_ctx == nullptr) {
                cerr << "Error: Failed to allocate codec context" << endl;
                return 1;
            }
            if (avcodec_parameters_to_context(codec_ctx, codec_params) < 0) {
                cerr << "Error: Failed to copy codec parameters to codec context" << endl;
                return 1;
            }
            if (avcodec_open2(codec_ctx, codec, nullptr) < 0) {
                cerr << "Error: Failed to open codec" << endl;
                return 1;
            }
            break;
        }
    }
    if (video_stream_index == -1) {
        cerr << "Error: Failed to find video stream" << endl;
        return 1;
    }

    // Allocate video frame and buffer
    AVFrame* frame = av_frame_alloc();
    if (frame == nullptr) {
        cerr << "Error: Failed to allocate video frame" << endl;
        return 1;
    }
    AVFrame* rgb_frame = av_frame_alloc();
    if (rgb_frame == nullptr) {
        cerr << "Error: Failed to allocate RGB video frame" << endl;
        return 1;
    }
    uint8_t* buffer = nullptr;
    int num_bytes = av_image_get_buffer_size(AV_PIX_FMT_RGB24, codec_ctx->width, codec_ctx->height, 1);
    buffer = (uint8_t*)av_malloc(num_bytes * sizeof(uint8_t));
    if (buffer == nullptr) {
        cerr << "Error: Failed to allocate buffer" << endl;
        return 1;
    }
    av_image_fill_arrays(rgb_frame->data, rgb_frame->linesize, buffer, AV_PIX_FMT_RGB24, codec_ctx->width, codec_ctx->height, 1);

    // Allocate SwsContext
    SwsContext* sws_ctx = sws_getContext(codec_ctx->width, codec_ctx->height, codec_ctx->pix_fmt, codec_ctx->width, codec_ctx->height, AV_PIX_FMT_RGB24, SWS_BILINEAR, nullptr, nullptr, nullptr);
    if (sws_ctx == nullptr) {
        cerr << "Error: Failed to allocate SwsContext" << endl;
        return 1;
    }

    // Initialize window and renderer
    SDL_Window* window = nullptr;
    SDL_Renderer* renderer = nullptr;
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        cerr << "Error: Failed to initialize SDL" << endl;
        return 1;
    }
    window = SDL_CreateWindow("Video Player", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, codec_ctx->width, codec_ctx->height, SDL_WINDOW_SHOWN);
    if (window == nullptr) {
        cerr << "Error: Failed to create window" << endl;
        return 1;
    }
    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    if (renderer == nullptr) {
        cerr << "Error: Failed to create renderer" << endl;
        return 1;
    }

    // Read packets from stream and decode
    AVPacket packet;
    while (av_read_frame(format_ctx, &packet) >= 0) {
        if (packet.stream_index == video_stream_index) {
            avcodec_send_packet(codec_ctx, &packet);
            while (avcodec_receive_frame(codec_ctx, frame) == 0) {
                sws_scale(sws_ctx, frame->data, frame->linesize, 0, frame->height, rgb_frame->data, rgb_frame->linesize);
                SDL_UpdateTexture(SDL_CreateTextureFromSurface(renderer, av_frame_get_surface(rgb_frame)), nullptr, nullptr, 0);
                SDL_RenderClear(renderer);
                SDL_RenderCopy(renderer, SDL_CreateTextureFromSurface(renderer, av_frame_get_surface(rgb_frame)), nullptr, nullptr);
                SDL_RenderPresent(renderer);
                this_thread::sleep_for(chrono::milliseconds(10));
            }
        }
        av_packet_unref(&packet);
    }

    // Clean up
    av_frame_free(&frame);
    av_frame_free(&rgb_frame);
    av_free(buffer);
    avcodec_free_context(&codec_ctx);
    avformat_close_input(&format_ctx);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

这个demo使用SDL库来显示视频，使用FFmpeg库来解码视频。在运行时需要提供一个视频文件的路径作为参数。可以根据需要进行修改和扩展。