FFmpeg 将YUV数据转RGB

只要开始初始化一次，结束后释放就好，中间可以循环转码 

AVFrame    *m_pFrameRGB,*m_pFrameYUV;
uint8_t *m_rgbBuffer,*m_yuvBuffer;
struct SwsContext *m_img_convert_ctx;

void init（） //分配两个Frame，两段buff，一个转换上下文
{
　//为每帧图像分配内存
    m_pFrameYUV = av_frame_alloc();
    m_pFrameRGB = av_frame_alloc();

// width和heigt为传入的分辨率的大小，分辨率有变化时可以以最大标准申请
    int numBytes = avpicture_get_size(AV_PIX_FMT_RGB32, nwidth,nheight);
    m_rgbBuffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
    int yuvSize = nwidth * nheight * 3 /2;
    m_yuvBuffer = (uint8_t *)av_malloc(yuvSize);

    //特别注意sws_getContext内存泄露问题，
    //注意sws_getContext只能调用一次，在初始化时候调用即可，另外调用完后，在析构函数中使用sws_freeContext，将它的内存释放。
    //设置图像转换上下文
    m_img_convert_ctx = sws_getContext(nwidth, nheight, AV_PIX_FMT_YUV420P, 
　　　　　　　　　　　　　　　　　　　　　　　 nwidth, nheight, AV_PIX_FMT_RGB32, SWS_BICUBIC, NULL, NULL, NULL);
}

void play（char* pbuff_in,int nwidth,int nheight）
{ 
    avpicture_fill((AVPicture *) m_pFrameRGB, m_rgbBuffer, AV_PIX_FMT_RGB32,nwidth, nheight);
    avpicture_fill((AVPicture *) m_pFrameYUV, (uint8_t *)pbuff_in, AV_PIX_FMT_YUV420P, nwidth, nheight);
    //转换图像格式，将解压出来的YUV420P的图像转换为RGB的图像
    sws_scale(m_img_convert_ctx,
            (uint8_t const * const *) m_pFrameYUV->data,
            m_pFrameYUV->linesize, 0, nheight, m_pFrameRGB->data,
            m_pFrameRGB->linesize);
    //把这个RGB数据 用QImage加载
    QImage tmpImg((uchar *)m_rgbBuffer,nwidth,nheight,QImage::Format_RGB32);
     //把图像复制一份 传递给界面显示
    m_mapImage[nWindowIndex] = tmpImg.copy();
}

void release()
{
    av_frame_free(&m_pFrameYUV);
    av_frame_free(&m_pFrameRGB);
    av_free(m_rgbBuffer);
    av_free(m_yuvBuffer);
    sws_freeContext(m_img_convert_ctx);
}
 

另一种方法：

bool YV12ToBGR24_FFmpeg(unsigned char* pYUV,unsigned char* pBGR24,int width,int height)
{
    if (width < 1 || height < 1 || pYUV == NULL || pBGR24 == NULL)
        return false;
    //int srcNumBytes,dstNumBytes;
    //uint8_t *pSrc,*pDst;
    AVPicture pFrameYUV,pFrameBGR;
    
    //pFrameYUV = avpicture_alloc();
    //srcNumBytes = avpicture_get_size(PIX_FMT_YUV420P,width,height);
    //pSrc = (uint8_t *)malloc(sizeof(uint8_t) * srcNumBytes);
    avpicture_fill(&pFrameYUV,pYUV,PIX_FMT_YUV420P,width,height);

    //U,V互换
    uint8_t * ptmp=pFrameYUV.data[1];
    pFrameYUV.data[1]=pFrameYUV.data[2];
    pFrameYUV.data [2]=ptmp;

    //pFrameBGR = avcodec_alloc_frame();
    //dstNumBytes = avpicture_get_size(PIX_FMT_BGR24,width,height);
    //pDst = (uint8_t *)malloc(sizeof(uint8_t) * dstNumBytes);
    avpicture_fill(&pFrameBGR,pBGR24,PIX_FMT_BGR24,width,height);

    struct SwsContext* imgCtx = NULL;
    imgCtx = sws_getContext(width,height,PIX_FMT_YUV420P,width,height,PIX_FMT_BGR24,SWS_BILINEAR,0,0,0);

    if (imgCtx != NULL){
        sws_scale(imgCtx,pFrameYUV.data,pFrameYUV.linesize,0,height,pFrameBGR.data,pFrameBGR.linesize);
        if(imgCtx){
            sws_freeContext(imgCtx);
            imgCtx = NULL;
        }
        return true;
    }
    else{
        sws_freeContext(imgCtx);
        imgCtx = NULL;
        return false;
    }
}