MobiTV said today that it now has 4 million subscribers, 1 million of whom signed up in the past 10 months.

The company formed in 1999 and began offering TV service for handsets in 2003.  Most of the content is clipped and edited versions of standard TV shows, although MobiTV also offers mobile-specific content as well as some interactive features.

The challenges of putting real and full TV shows on handsets are numerous.  The shortest shows are typically 30 minutes long, which means many minutes and battery life being consumed.  High-quality video is typically a bandwidth hog and most phones do not have the kind of sound quality that viewers expect for watching TV.

Currently the paid service works on select devices from Alltel, AT&T, Bell Canada, Sprint Nextel and Telus.  There are more than 50 channels available, officials said.

The company also said it’s seeing a large increase in unique daily users and viewing time.  But no forecasts were disclosed for other subscriber metrics.