Convert multiple jpeg files to mp4 video using ffmpeg

This doesn't work:

ffmpeg -r 2 -f image2 -i %05d.jpg out.mp4

The video generated doesn't play in Chrome.

The problem is with the pixel format. This is the correct way to generate the video:

ffmpeg -r 2 -f image2 -i %05d.jpg -pix_fmt yuv420p out2.mp4