客户端播放视频

一、以下是一个简单的代码示例，展示了如何使用FFmpeg API播放TCP视频流

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#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/avutil.h>

int main(int argc, char* argv[]) {
    AVFormatContext* pFormatCtx = NULL;
    int videoStream;
    AVCodecContext* pCodecCtx = NULL;
    AVCodec* pCodec = NULL;
    AVFrame* pFrame = NULL;
    AVPacket packet;

    // 初始化FFmpeg
    avformat_network_init();

    // 打开视频流
    if (avformat_open_input(&pFormatCtx, "udp://10.0.3.1:1234", NULL, NULL) != 0) {
        return -1; // Couldn't open stream
    }

    // 获取流信息
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        return -1; // Couldn't find stream information
    }

    // 查找视频流
    videoStream = -1;
    for (int i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStream = i;
            break;
        }
    }
    if (videoStream == -1) {
        return -1; // Didn't find a video stream
    }

    // 获取解码器参数
    AVCodecParameters* pCodecPar = pFormatCtx->streams[videoStream]->codecpar;

    // 找到解码器
    pCodec = avcodec_find_decoder(pCodecPar->codec_id);
    if (pCodec == NULL) {
        return -1; // Codec not found
    }

    // 分配解码器上下文
    pCodecCtx = avcodec_alloc_context3(pCodec);
    if (!pCodecCtx) {
        return -1; // Could not allocate codec context
    }

    // 从参数复制解码器上下文
    if (avcodec_parameters_to_context(pCodecCtx, pCodecPar) < 0) {
        return -1; // Could not copy codec context
    }

    // 打开解码器
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        return -1; // Could not open codec
    }

    // 分配视频帧
    pFrame = av_frame_alloc();

    // 读取帧并解码
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        if (packet.stream_index == videoStream) {
            if (avcodec_send_packet(pCodecCtx, &packet) == 0) {
                while (avcodec_receive_frame(pCodecCtx, pFrame) == 0) {
                    // 在这里显示视频帧
                    // display_frame(pFrame);
                }
            }
        }
        av_packet_unref(&packet);
    }

    // 清理
    av_frame_free(&pFrame);
    avcodec_free_context(&pCodecCtx);
    avformat_close_input(&pFormatCtx);

    return 0;
}

二、C语言使用FFMPEG与SDL播放视频流

播放成功，但是播放的视频速度不对。

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#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/avutil.h>
#include <libswscale/swscale.h>
#include <SDL2/SDL.h>
#undef main
int main(int argc, char* argv[]) {
    AVFormatContext* pFormatCtx = NULL;
    int videoStream;
    AVCodecContext* pCodecCtx = NULL;
    AVCodec* pCodec = NULL;
    AVFrame* pFrame = NULL;
    AVFrame* pFrameRGB = NULL;
    AVPacket packet;
    struct SwsContext* sws_ctx = NULL;
    uint8_t* buffer = NULL;
    int numBytes;

    SDL_Window* screen = NULL;
    SDL_Renderer* renderer = NULL;
    SDL_Texture* texture = NULL;
    SDL_Rect rect;

    // 初始化FFmpeg
    avformat_network_init();

    // 初始化SDL
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
        exit(1);
    }

    // 打开视频流
    if (avformat_open_input(&pFormatCtx, "http://cc.weichennet.com/26%20%E5%AE%9E%E6%88%98%E8%BF%87TP%E4%B8%B6NP%20%E8%BF%87%E5%9B%BE%E6%A0%87.mp4", NULL, NULL) != 0) {
        return -1; // Couldn't open stream
    }

    // 获取流信息
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        return -1; // Couldn't find stream information
    }

    // 查找视频流
    videoStream = -1;
    for (int i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStream = i;
            break;
        }
    }
    if (videoStream == -1) {
        return -1; // Didn't find a video stream
    }

    // 获取解码器参数
    AVCodecParameters* pCodecPar = pFormatCtx->streams[videoStream]->codecpar;

    // 找到解码器
    pCodec = avcodec_find_decoder(pCodecPar->codec_id);
    if (pCodec == NULL) {
        return -1; // Codec not found
    }

    // 分配解码器上下文
    pCodecCtx = avcodec_alloc_context3(pCodec);
    if (!pCodecCtx) {
        return -1; // Could not allocate codec context
    }

    // 从参数复制解码器上下文
    if (avcodec_parameters_to_context(pCodecCtx, pCodecPar) < 0) {
        return -1; // Could not copy codec context
    }

    // 打开解码器
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        return -1; // Could not open codec
    }

    // 分配视频帧
    pFrame = av_frame_alloc();
    pFrameRGB = av_frame_alloc();
    if (pFrameRGB == NULL) {
        return -1;
    }

    // 确定所需的缓冲区大小并分配缓冲区
    numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height, 32);
    buffer = (uint8_t*)av_malloc(numBytes * sizeof(uint8_t));
    av_image_fill_arrays(pFrameRGB->data, pFrameRGB->linesize, buffer, AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height, 32);

    // 初始化SWS上下文以进行软件缩放
    sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
        pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24,
        SWS_BILINEAR, NULL, NULL, NULL);

    // 创建SDL窗口
    screen = SDL_CreateWindow("FFmpeg Video Player",
        SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED,
        pCodecCtx->width,
        pCodecCtx->height,
        SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
    if (!screen) {
        fprintf(stderr, "SDL: could not set video mode - exiting\n");
        exit(1);
    }

    renderer = SDL_CreateRenderer(screen, -1, 0);
    texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB24, SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height);

    // 读取帧并解码
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        if (packet.stream_index == videoStream) {
            if (avcodec_send_packet(pCodecCtx, &packet) == 0) {
                while (avcodec_receive_frame(pCodecCtx, pFrame) == 0) {
                    // 转换图像格式
                    sws_scale(sws_ctx, (uint8_t const* const*)pFrame->data,
                        pFrame->linesize, 0, pCodecCtx->height,
                        pFrameRGB->data, pFrameRGB->linesize);

                    // 在这里显示视频帧
                    SDL_UpdateTexture(texture, NULL, pFrameRGB->data[0], pFrameRGB->linesize[0]);
                    SDL_RenderClear(renderer);
                    SDL_RenderCopy(renderer, texture, NULL, NULL);
                    SDL_RenderPresent(renderer);
                }
            }
        }
        av_packet_unref(&packet);

        // 处理SDL事件
        SDL_Event event;
        SDL_PollEvent(&event);
        switch (event.type) {
        case SDL_QUIT:
            SDL_DestroyTexture(texture);
            SDL_DestroyRenderer(renderer);
            SDL_DestroyWindow(screen);
            SDL_Quit();
            av_free(buffer);
            av_frame_free(&pFrameRGB);
            av_frame_free(&pFrame);
            avcodec_free_context(&pCodecCtx);
            avformat_close_input(&pFormatCtx);
            return 0;
            break;
        default:
            break;
        }
    }

    // 清理
    av_free(buffer);
    av_frame_free(&pFrameRGB);
    av_frame_free(&pFrame);
    avcodec_free_context(&pCodecCtx);
    avformat_close_input(&pFormatCtx);

    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(screen);
    SDL_Quit();

    return 0;
}

三、修复播放速度的问题

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#include <stdio.h>
#include <stdlib.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/avutil.h>
#include <libavutil/frame.h>  // av_frame_get_best_effort_timestamp is declared here
#include <libavutil/time.h>
#include <libswscale/swscale.h>
#include <SDL2/SDL.h>

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


#undef main
int main(int argc, char* argv[]) {
    AVFormatContext* pFormatCtx = NULL;
    int videoStream;
    AVCodecContext* pCodecCtx = NULL;
    AVCodec* pCodec = NULL;
    AVFrame* pFrame = NULL;
    AVFrame* pFrameRGB = NULL;
    AVPacket packet;
    struct SwsContext* sws_ctx = NULL;
    uint8_t* buffer = NULL;
    int numBytes;
    double pts, actual_delay;
    int64_t start_time, frame_time;

    SDL_Window* screen = NULL;
    SDL_Renderer* renderer = NULL;
    SDL_Texture* texture = NULL;

    // Initialize FFmpeg
    avformat_network_init();

    // Initialize SDL
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
        exit(1);
    }

    // Open video stream
    const char* inputURL = "http://cc.weichennet.com/26%20%E5%AE%9E%E6%88%98%E8%BF%87TP%E4%B8%B6NP%20%E8%BF%87%E5%9B%BE%E6%A0%87.mp4";
    if (avformat_open_input(&pFormatCtx, inputURL, NULL, NULL) != 0) {
        fprintf(stderr, "Could not open stream.\n");
        exit(1);
    }

    // Get stream info
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        fprintf(stderr, "Couldn't find stream information.\n");
        exit(1);
    }

    // Find the first video stream
    videoStream = -1;
    for (int i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStream = i;
            break;
        }
    }
    if (videoStream == -1) {
        fprintf(stderr, "Didn't find a video stream.\n");
        exit(1);
    }

    // Get codec parameters
    AVCodecParameters* pCodecPar = pFormatCtx->streams[videoStream]->codecpar;
    // Find the decoder for the video stream
    pCodec = avcodec_find_decoder(pCodecPar->codec_id);
    if (pCodec == NULL) {
        fprintf(stderr, "Codec not found.\n");
        exit(1);
    }

    // Allocate codec context
    pCodecCtx = avcodec_alloc_context3(pCodec);
    if (!pCodecCtx) {
        fprintf(stderr, "Could not allocate codec context.\n");
        exit(1);
    }

    // Copy codec parameters to context
    if (avcodec_parameters_to_context(pCodecCtx, pCodecPar) < 0) {
        fprintf(stderr, "Could not copy codec context.\n");
        exit(1);
    }

    // Open codec
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        fprintf(stderr, "Could not open codec.\n");
        exit(1);
    }

    // Allocate video frames
    pFrame = av_frame_alloc();
    pFrameRGB = av_frame_alloc();
    if (!pFrameRGB) {
        fprintf(stderr, "Could not allocate RGB frame.\n");
        exit(1);
    }

    // Determine required buffer size and allocate buffer
    numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGB24, pCodecCtx->width,
        pCodecCtx->height, 32);
    buffer = (uint8_t*)av_malloc(numBytes * sizeof(uint8_t));
    av_image_fill_arrays(pFrameRGB->data, pFrameRGB->linesize, buffer, AV_PIX_FMT_RGB24,
        pCodecCtx->width, pCodecCtx->height, 32);

    // Initialize SWS context for software scaling
    sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
        pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24,
        SWS_BILINEAR, NULL, NULL, NULL);

    // Create SDL window
    screen = SDL_CreateWindow("FFmpeg Video Player",
        SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED,
        pCodecCtx->width,
        pCodecCtx->height,
        SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
    if (!screen) {
        fprintf(stderr, "SDL: could not set video mode - %s\n", SDL_GetError());
        exit(1);
    }

    renderer = SDL_CreateRenderer(screen, -1, 0);
    texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB24, SDL_TEXTUREACCESS_STREAMING,
        pCodecCtx->width, pCodecCtx->height);

    // Get start time
    start_time = av_gettime();

    // Read frames and decode
   // Inside the main decoding loop:
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        if (packet.stream_index == videoStream) {
            if (avcodec_send_packet(pCodecCtx, &packet) == 0) {
                while (avcodec_receive_frame(pCodecCtx, pFrame) == 0) {
                    // Convert the image
                    sws_scale(sws_ctx,
                        (uint8_t const* const*)pFrame->data,
                        pFrame->linesize,
                        0,
                        pCodecCtx->height,
                        pFrameRGB->data,
                        pFrameRGB->linesize);

                    // Update texture
                    SDL_UpdateTexture(texture, NULL, pFrameRGB->data[0], pFrameRGB->linesize[0]);
                    SDL_RenderClear(renderer);
                    SDL_RenderCopy(renderer, texture, NULL, NULL);
                    SDL_RenderPresent(renderer);

                    // Timing control
                    pts = pFrame->best_effort_timestamp * av_q2d(pFormatCtx->streams[videoStream]->time_base);
                    frame_time = start_time + (int64_t)(pts * 1000000);
                    actual_delay = frame_time - av_gettime();
                    if (actual_delay > 0) {
                        av_usleep((unsigned)actual_delay);
                    }
                }
            }
        }
        av_packet_unref(&packet);

        // Handle SDL events
        SDL_Event event;
        SDL_PollEvent(&event);
        if (event.type == SDL_QUIT) {
            break;
        }
    }

end:
    // Cleanup
    av_free(buffer);
    av_frame_free(&pFrameRGB);
    av_frame_free(&pFrame);
    avcodec_free_context(&pCodecCtx);
    avformat_close_input(&pFormatCtx);

    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(screen);
    SDL_Quit();

    return 0;
}