Using HDMI cable adapter, only my older videos play back perfectly.

All videos are perfect on my iPad Mini's own screen. No exceptions.

However, on my HDTV, connected via Apple's Lightning HDMI cable adapter, only my older videos play back perfectly. Newer ones have only about one-third width, like squished in, fun-house mirror style. Why? Did I upset some setting? (Not an iOS 7 issue. This problem started much earlier.)

The iPad Mini is about a year old. Videos I recorded in March and April (I think) play back perfectly on the TV. Videos I recorded this summer and afterward, have a squished look when I play them back on the TV. Oddly, when I swipe across all my pictures and videos, the videos' "key frame" appears normal. It's only when I tap the PLAY icon that the video starts and does not fill the screen. The picture is so squished it is essentially useless.

All still photos are normal, as are other videos. Something may be changed about how the newer videos are being stored. What?!?!