我们今天实现一个能够播放视频的播放器。

播放的是多媒体文件 比如 flv  mp4 m3u8等。、

要用到的知识是

https://blog.csdn.net/qq_15255121/article/details/116805910?spm=1001.2014.3001.5501   YUV播放器

https://blog.csdn.net/qq_15255121/article/details/116795766?spm=1001.2014.3001.5501  SDL 纹理

https://blog.csdn.net/qq_15255121/article/details/116720913?spm=1001.2014.3001.5501 SDL基础

播放多媒体文件，实际上对视频流进行解码，然后再进行播放。那么我们要用到下面这一节的知识

https://blog.csdn.net/qq_15255121/article/details/116330738   h264转yuv

 

下面的代码完全就是  h264转yuv 和 YUV播放器的结合。后续章节会对代码进行优化，使其成为真正的视频播放器。

#include <stdio.h>
#include <string.h>
#include <SDL2/SDL.h>
#include <stdlib.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/imgutils.h>
#include <libswscale/swscale.h>
//event message
#define QUIT_EVENT (SDL_USEREVENT + 2)

int thread_exit = 0;
static SDL_Window *win = NULL;
static SDL_Renderer *renderer = NULL;
static SDL_Texture *texture = NULL;
SDL_Rect rect;
static int w_width = 960;
static int w_height = 540;

int play(char *in_file)
{
    AVFormatContext *fmt_ctx = NULL;
    AVCodecContext *cod_ctx = NULL;
    AVCodec *cod = NULL;
    struct SwsContext *img_convert_ctx = NULL;
    int ret = 0;
    AVPacket packet;

    //第一步创建输入文件AVFormatContext
    fmt_ctx = avformat_alloc_context();
    if (fmt_ctx == NULL)
    {
        ret = -1;
        av_log(NULL, AV_LOG_ERROR, "alloc fail");
        goto __ERROR;
    }
    if (avformat_open_input(&fmt_ctx, in_file, NULL, NULL) != 0)
    {
        ret = -1;
        av_log(NULL, AV_LOG_ERROR, "open fail");
        goto __ERROR;
    }

    //第二步 查找文件相关流，并初始化AVFormatContext中的流信息
    if (avformat_find_stream_info(fmt_ctx, NULL) < 0)
    {
        ret = -1;
        av_log(NULL, AV_LOG_ERROR, "find stream fail");
        goto __ERROR;
    }

    av_dump_format(fmt_ctx, 0, in_file, 0);

    //第三步查找视频流索引和解码器
    int stream_index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &cod, -1);

    //第四步设置解码器上下文并打开解码器
    AVCodecParameters *codecpar = fmt_ctx->streams[stream_index]->codecpar;
    if (!cod)
    {
        ret = -1;
        av_log(NULL, AV_LOG_ERROR, "find codec fail");
        goto __ERROR;
    }
    cod_ctx = avcodec_alloc_context3(cod);
    avcodec_parameters_to_context(cod_ctx, codecpar);
    ret = avcodec_open2(cod_ctx, cod, NULL);
    if (ret < 0)
    {
        av_log(NULL, AV_LOG_ERROR, "can't open codec");
        goto __ERROR;
    }

    //创建packet,用于存储解码前的数据
    av_init_packet(&packet);

    //第六步创建Frame，用于存储解码后的数据
    AVFrame *frame = av_frame_alloc();
    frame->width = codecpar->width;
    frame->height = codecpar->height;
    frame->format = codecpar->format;
    av_frame_get_buffer(frame, 32);

    AVFrame *yuv_frame = av_frame_alloc();
    yuv_frame->width = codecpar->width;
    yuv_frame->height = codecpar->height;
    yuv_frame->format = AV_PIX_FMT_YUV420P;
    av_frame_get_buffer(yuv_frame, 32);

    // size_t writesize = av_image_get_buffer_size(frame->format, frame->width,frame->height, 32);
    //第七步重采样初始化与设置参数
    // uint8_t **data = (uint8_t **)av_calloc((size_t)out_channels, sizeof(*data))

    img_convert_ctx = sws_getContext(codecpar->width,
                                     codecpar->height,
                                     codecpar->format,
                                     codecpar->width,
                                     codecpar->height,
                                     AV_PIX_FMT_YUV420P,
                                     SWS_BICUBIC,
                                     NULL, NULL, NULL);

    //while循环，每次读取一帧，并转码
    //第八步 读取数据并解码,重采样进行保存
    int count = 0;
    while (av_read_frame(fmt_ctx, &packet) >= 0)
    {
        if (packet.stream_index != stream_index)
        {
            av_packet_unref(&packet);
            continue;
        }

        ret = avcodec_send_packet(cod_ctx, &packet);
        if (ret < 0)
        {
            ret = -1;
            av_log(NULL, AV_LOG_ERROR, "decode error");
            goto __ERROR;
        }

        while (avcodec_receive_frame(cod_ctx, frame) >= 0)
        {
            if (thread_exit)
            {
                goto __ERROR;
            }
            av_log(NULL, AV_LOG_INFO, "decode frame count = %d\n", count++);
            sws_scale(img_convert_ctx,
                      (const uint8_t **)frame->data,
                      frame->linesize,
                      0,
                      codecpar->height,
                      yuv_frame->data,
                      yuv_frame->linesize);
            SDL_UpdateYUVTexture(texture, NULL,
                                 yuv_frame->data[0],
                                 yuv_frame->linesize[0],
                                 yuv_frame->data[1],
                                 yuv_frame->linesize[1],
                                 yuv_frame->data[2],
                                 yuv_frame->linesize[2]);
            //FIX: If window is resize
            rect.x = 0;
            rect.y = 0;
            rect.w = w_width;
            rect.h = w_height;

            SDL_RenderClear(renderer);
            SDL_RenderCopy(renderer, texture, NULL, &rect);
            SDL_RenderPresent(renderer);
            SDL_Delay(40);
        }

        av_packet_unref(&packet);
    }

    while (1)
    {
        av_log(NULL, AV_LOG_INFO, "flush decode \n");
        ret = avcodec_send_packet(cod_ctx, NULL);
        if (ret < 0)
        {
            ret = -1;
            av_log(NULL, AV_LOG_ERROR, "flush decode error\n");
            goto __ERROR;
        }

        while (avcodec_receive_frame(cod_ctx, frame) >= 0)
        {
            if (thread_exit)
            {
                goto __ERROR;
            }
            av_log(NULL, AV_LOG_INFO, "flush decode frame count = %d", count++);
            sws_scale(img_convert_ctx,
                      (const uint8_t **)frame->data,
                      frame->linesize,
                      0,
                      codecpar->height,
                      yuv_frame->data,
                      yuv_frame->linesize);
            SDL_UpdateYUVTexture(texture, NULL,
                                 yuv_frame->data[0],
                                 yuv_frame->linesize[0],
                                 yuv_frame->data[1],
                                 yuv_frame->linesize[1],
                                 yuv_frame->data[2],
                                 yuv_frame->linesize[2]);
            //FIX: If window is resize
            rect.x = 0;
            rect.y = 0;
            rect.w = w_width;
            rect.h = w_height;

            SDL_RenderClear(renderer);
            SDL_RenderCopy(renderer, texture, NULL, &rect);
            SDL_RenderPresent(renderer);
        }
    }

__ERROR:
    if (fmt_ctx)
    {
        avformat_close_input(&fmt_ctx);
        avformat_free_context(fmt_ctx);
    }

    if (cod_ctx)
    {
        avcodec_close(cod_ctx);
        avcodec_free_context(&cod_ctx);
    }

    if (frame)
    {
        av_frame_free(&frame);
    }

    if (yuv_frame)
    {
        av_frame_free(&yuv_frame);
    }

    if (img_convert_ctx)
    {
        sws_freeContext(img_convert_ctx);
    }

    return ret;
}

int refresh_video_timer(void *file)
{

    play(file);

    //push quit event
    SDL_Event event;
    event.type = QUIT_EVENT;
    SDL_PushEvent(&event);

    return 0;
}

int main(int argc, char *argv[])
{

    FILE *video_fd = NULL;

    SDL_Event event;

    Uint32 pixformat = 0;

    SDL_Thread *timer_thread = NULL;

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

    //creat window from SDL
    win = SDL_CreateWindow("YUV Player",
                           SDL_WINDOWPOS_UNDEFINED,
                           SDL_WINDOWPOS_UNDEFINED,
                           w_width, w_height,
                           SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
    if (!win)
    {
        fprintf(stderr, "Failed to create window, %s\n", SDL_GetError());
        goto __FAIL;
    }

    renderer = SDL_CreateRenderer(win, -1, 0);

    //IYUV: Y + U + V  (3 planes)
    //YV12: Y + V + U  (3 planes)
    pixformat = SDL_PIXELFORMAT_IYUV;

    //create texture for render
    texture = SDL_CreateTexture(renderer,
                                pixformat,
                                SDL_TEXTUREACCESS_STREAMING,
                                w_width,
                                w_height);

    //创建AVFrame
    int ret = 0;

    if (ret < 0)
    {
        printf("av_frame_get_buffer fail error =  %s", av_err2str(ret));
        goto __FAIL;
    }

    //read block data

    timer_thread = SDL_CreateThread(refresh_video_timer,
                                    NULL,
                                    argv[1]);

    do
    {
        //Wait
        SDL_WaitEvent(&event);
        if (event.type == SDL_WINDOWEVENT)
        {
            //If Resize
            SDL_GetWindowSize(win, &w_width, &w_height);
        }
        else if (event.type == SDL_QUIT)
        {
            thread_exit = 1;
        }
        else if (event.type == QUIT_EVENT)
        {
            break;
        }
    } while (1);

__FAIL:

    SDL_Quit();

    return 0;
}