[FFmpeg-user] output jpeg quality

[Green Koopa]

This creates one image for each second of video:
ffmpeg -i 00020.MTS -vf fps=fps=1 -f image2 stills-%03d.png

When I change the output format to jpeg, it does the same:
ffmpeg -i 00020.MTS -vf fps=fps=1 -f image2 stills-%03d.jpeg
But there is a problem. The quality of the jpegs begin okay, but quickly
deteriorate. By the tenth image or so, they are unusable. This seems
strange to me, but this is my first day with ffmpeg.

Same problem when I tried this:
ffmpeg -i 00020.MTS -vsync 1 -r 1 -f image2 stills-%03d.jpeg

I found -qmin 1 -qmax 1 in an old post. It helped all but the last two
images. I can just use png, but I was wondering what is going on here.
Thanks for any insight.

Console output and sample images:
https://googledrive.com/host/0B0-UKhirpea7Sml5OVJpc241bVE/

FFmpeg Win64 static build on 2014-01-22
http://ffmpeg.zeranoe.com/builds/