FFMPEG scaling error-invalid dimension

Question

I'm working on a Project in FFMPEG, and right now i'm stuck on a Problem.

What i am trying to do is, convert a png pic in to a mpeg Video file. I've already managed to take informatin from the Picture, but somehow i cannot convert the Picture in YUV Format. It returns "0x0->0x0 is invalid scaling dimensions".

Here'S my code:

 AVFrame *pFrame;
AVFrame *pFrameYUV;
pFrame = av_frame_alloc();
pFrameYUV = av_frame_alloc();
int numBytes;//Groesse des Bildes
uint8_t *buffer= NULL;
numBytes=avpicture_get_size(AV_PIX_FMT_RGB24, pCodecCtx->width,pCodecCtx->height); 
buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t)); 

/*avpicture_fill((AVPicture *)pFrameYUV, buffer, AV_PIX_FMT_YUV420P,
                pCodecCtx->width, pCodecCtx->height);*/
av_image_fill_arrays(pFrameYUV->data,pFrameYUV->linesize,buffer,AV_PIX_FMT_YUV420P,pCodecCtx->width,pCodecCtx->height,32);


struct SwsContext *sws_ctx = NULL;

AVPacket packet;
// initialize SWS context for software scaling
sws_ctx=sws_getCachedContext(NULL,pFrame->width,pFrame->height,AV_PIX_FMT_RGB24,pFrameYUV->width,pFrameYUV->height,AV_PIX_FMT_YUV420P,0,0,0,0);
pFrameYUV->height= pFrame->height;
pFrameYUV->width= pFrame->width;

while (av_read_frame(pFormatCtx,&packet)>=0)
{
    if(packet.stream_index == videoStream)
    {
        avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet); 

        if(frameFinished)
        {

        sws_scale(sws_ctx, (uint8_t const * const *)pFrame->data,
          pFrame->linesize, 0, pCodecCtx->height,
          pFrameYUV->data, pFrameYUV->linesize);
        printf("%d",pFrameYUV->height);

    }
    }
    av_free_packet(&packet);
}

EDIT:

After the converting, i tried to encode the Frame in oa packet, but he size of the packet is 0. Code

AVPacket pkt;
av_init_packet(&pkt);
pkt.stream_index= st->index;
pkt.data= buffer;
pkt.size=numBytes;
int got_pkt;
test=avcodec_encode_video2(st->codec,&pkt,pFrameYUV,&got_pkt);

printf("%d",got_pkt);

Answer 1

These values pFrameYUV->height, pFrame->height, pFrameYUV->width, pFrame->width didn't set when calling sws_getCachedContext .

Do you mean the dimension not changing? If so, set them before sws_getCachedContext .

pFrameYUV->height = pFrame->height = pCodecCtx->height;
pFrameYUV->width = pFrame->width = pCodecCtx->width;
sws_ctx=sws_getCachedContext(NULL,pFrame->width,pFrame->height,AV_PIX_FMT_RGB24,pFrameYUV->width,pFrameYUV->height,AV_PIX_FMT_YUV420P,0,0,0,0);