+
+ // attempt to keep aspect during typical resolution switches
+ if (!old_aspect.num)
+ old_aspect = (AVRational){1, 1};
+ if (2 * new_w * s->height == new_h * s->width)
+ s->avctx->sample_aspect_ratio = av_mul_q(old_aspect, (AVRational){2, 1});
+ if (new_w * s->height == 2 * new_h * s->width)
+ s->avctx->sample_aspect_ratio = av_mul_q(old_aspect, (AVRational){1, 2});