This came up a few weeks ago.[1] MPEG-LA's patent portfolio isn't that strong any more. MPEG-LA has a long list of patents, but most of them have expired. The key patents on video compression involved motion estimation, and those expired this year. MPEG-LA got their twenty years of patent protection, and it's over.
The remaining patents are mostly on things you don't need for Internet video. US #6,181,712, has to do with multiplexing two unrelated video streams into one. Broadcasters and cable systems do this, but Internet video does not. US #6,160,849 only applies to compression of interlaced video, which nobody uses on line. US #7,627,041 is about dealing with missing header data due to transmission noise. US #5,878,080 is about backwards-compatible multichannel (>2 channels) audio, also seldom used on-line. US #6,185,539 is for video with overcompressed extra-low-quality audio. So is US #6,009,399.
As I pointed out last time, it's time for a hard look at this patent situation. You can probably do a patent-free MPEG-4 video decoder and encoder for Internet video now. You might have to leave out some newer features nobody uses.
[1] https://news.ycombinator.com/item?id=10042469
[2] http://scratchpad.wikia.com/wiki/MPEG_patent_lists