Fffmpeg：从AVFrame中由YUV获取RGB

#define  SRC_FORMAT AV_PIX_FMT_YUV420P
#define DEST_FORMAT AV_PIX_FMT_BGR24
static        AVPicture   g_oPicture = {0};
static struct SwsContext* g_pScxt    = NULL;
void yuv2rgb(AVFrame* pFrame, uint8_t* pRgbBuffer)
{
    int width  = pFrame->width;
  int height = pFrame->height;
    if (g_pScxt == NULL)
    {
        g_pScxt = sws_getContext(width, height, SRC_FORMAT,
          width, height, DEST_FORMAT,
          SWS_POINT, NULL, NULL, NULL);
        //AVFrame需要填充，还是这个方便。 
        avpicture_alloc(&g_oPicture, DEST_FORMAT, width, height);
    }
    int num_bytes = av_image_get_buffer_size(DEST_FORMAT, width, height, 32);
    int retsws = sws_scale(g_pScxt, pFrame->data, pFrame->linesize, 0, height,
      g_oPicture.data, g_oPicture.linesize);
    //注意，RGB数据是这样复制的
  memcpy(pRgbBuffer, g_oPicture.data[0], num_bytes);
    //播放完毕后再释放。
    //avpicture_free(&g_oPicture);
    //sws_freeContext(g_pScxt);
}