int av_picture_crop(AVPicture *dst, const AVPicture *src,

                    enum PixelFormat pix_fmt, int top_band, int left_band)

{

    int y_shift;

    int x_shift;



    if (pix_fmt < 0 || pix_fmt >= PIX_FMT_NB)

        return -1;



    y_shift = av_pix_fmt_descriptors[pix_fmt].log2_chroma_h;

    x_shift = av_pix_fmt_descriptors[pix_fmt].log2_chroma_w;



    if (is_yuv_planar(&pix_fmt_info[pix_fmt])) {

    dst->data[0] = src->data[0] + (top_band * src->linesize[0]) + left_band;

    dst->data[1] = src->data[1] + ((top_band >> y_shift) * src->linesize[1]) + (left_band >> x_shift);

    dst->data[2] = src->data[2] + ((top_band >> y_shift) * src->linesize[2]) + (left_band >> x_shift);

    } else{

        if(top_band % (1<<y_shift) || left_band % (1<<x_shift))

            return -1;

        if(left_band) 

            return -1;

        dst->data[0] = src->data[0] + (top_band * src->linesize[0]) + left_band;

    }



    dst->linesize[0] = src->linesize[0];

    dst->linesize[1] = src->linesize[1];

    dst->linesize[2] = src->linesize[2];

    return 0;

}
