ffmpeg：sws_scale无法将图像从YUV转换为RGB

如何解决ffmpeg：sws_scale无法将图像从YUV转换为RGB

我正在尝试将图像从YUV420P转换为RGB24，下面是我提取帧并对其进行解码的代码，

帧提取

while(av_read_frame(avc,avpacket) == 0){
        if(avpacket->stream_index == videoStream){
            int res = avcodec_send_packet(avctx,avpacket);
            if(res == AVERROR(EAGAIN)){
                continue;
            }
            else if(res<0){
                std::cout<<"error reading packet\n";
                break;
            }
            else{
                AVFrame* avframeRGB = av_frame_alloc();
                res = avcodec_receive_frame(avctx,avframeRGB);
                if(res == AVERROR(EAGAIN)){
                    continue;
                }
                else if(res<0){
                    std::cout<<"Error reading frame";
                    break;
                }
                else{
                    ++i;
                    convertimage(&avframeRGB,avctx->pix_fmt,AV_PIX_FMT_RGB24);
                    displayImage(avframeRGB);
                }
            }
        }
    }

功能convertimage

void convertimage(AVFrame** frame,AVPixelFormat srcFmt,AVPixelFormat destFmt){
    AVFrame* tframe = *frame;
    struct SwsContext* swscaler = sws_getContext(tframe->width,tframe->height,srcFmt,tframe->width,destFmt,SWS_BILINEAR,NULL,NULL);
    AVFrame* tmp = av_frame_alloc();
    tmp->width = tframe->width;
    tmp->height = tframe->height;
    tmp->format = destFmt;
    if(av_frame_get_buffer(tmp,32) !=0)
        return;
    int res = sws_scale(swscaler,(uint8_t const * const*)tframe->data,tframe->linesize,tmp->data,tmp->linesize);
    *frame = tmp;
}

在调用convertimage之前 avframeRGB

data : {0x555555988ec0 '\020' <repeats 200 times>...,0x555555a6f940 '\200' <repeats 200 times>...,0x555555aa9440 '\200' <repeats 200 times>...,0x0,0x0}
height : 720
width : 1280

在调用convertimage之后

data : {0x7fffdde19040 "",0x0}
height : 0
width : 0

我无法理解为什么我的数据为NULL并且高度和宽度为0？

ffmpeg版本-4.3.2