avctx->aspect_ratio = 4.0 / 3.0;
avctx->sample_aspect_ratio = (AVRational){4,3}; avctx->sample_aspect_ratio = av_div_q(avctx->sample_aspect_ratio, (AVRational){sys->width,sys->height});
static int dv_extract_video_info(uint8_t* frame, AVCodecContext* avctx){    const DVprofile* sys;     const uint8_t* vsc_pack;    int apt;    int size = 0;        sys = dv_frame_profile(frame);    if (sys) {        apt = frame[4] & 0x07;        avctx->frame_rate = sys->frame_rate;        avctx->frame_rate_base = sys->frame_rate_base;        avctx->width = sys->width;        avctx->height = sys->height;        avctx->pix_fmt = sys->pix_fmt;        vsc_pack = dv_extract_pack(frame, dv_video_control);        if (vsc_pack && (vsc_pack[2] & 0x07) == (apt?0x02:0x07))            avctx->aspect_ratio = 16.0 / 9.0;        else            avctx->aspect_ratio = 4.0 / 3.0;	size = sys->frame_size;    }    return size;}