使用ffmpeg4.0.2win64版本，在vs2015环境下使用c++写一个h264转yuv420p的小demo

下面是一个使用 C 语言写的使用 FFmpeg 4.0.2 Win64 版本在 Visual Studio 2015 环境下的 H.264 转 YUV420P 的小 demo：

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>

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

    AVFormatContext *pFormatCtx = avformat_alloc_context();
    if (avformat_open_input(&pFormatCtx, "input.h264", NULL, NULL) != 0)
    {
        printf("Couldn't open input stream.\n");
        return -1;
    }

    if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
    {
        printf("Couldn't find stream information.\n");
        return -1;
    }

    int 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)
    {
        printf("Couldn't find a video stream.\n");
        return -1;
    }

    AVCodecParameters *pCodecPar = pFormatCtx->streams[videoStream]->codecpar;
    AVCodec *pCodec = avcodec_find_decoder(pCodecPar->codec_id);
    if (pCodec == NULL)
    {
        printf("Couldn't find codec.\n");
        return -1;
    }

    AVCodecContext *pCodecCtx = avcodec_alloc_context3(pCodec);
    if (avcodec_parameters_to_context(pCodecCtx, pCodecPar) < 0)
    {
        printf("Couldn't copy codec context.\n");
        return -1;
    }

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
    {
        printf("Couldn't open codec.\n");
        return -1;
    }

    AVFrame *pFrame = av_frame_alloc();
    AVFrame *pFrameYUV = av_frame_alloc();
    uint8_t *out_buffer = (uint8_t *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1));
    av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, out_buffer, AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);