Video with inconsistent exposed / rendered image sizes
HDV camera, right? It's not untypical for cameras to claim higher resolution than they actually scan. In such cases you have to look at the different aspect ratios involved: pixel, frame, display, sample. Here's a post that discusses this, or google "HDV aspect ratio". And here's a link to the spec from the HDV consortium.

It's essentially anamorphic. The ffmpeg or avconv docs should show how to extract and expand to 1920 in one step.