This isn't the most robust video converter for MP4, OGV, or webM, but it is FREE. You can't beat free. The codecs work fine and can help you be HTML5 compliant, however, you have little control over resolution, quality, and audio. If Mira video converter doesn't work for you, I would suggest trying movavi.com as your second option, but that costs around $50. That problem has far more controls over output.
It has worked very well for me on anything I've converted. Nice product