How “H” is Online HDTV?

MultiMedia Intelligence issued a press release last week, announcing a new research report on peer-to-peer use of the Internet for for video content and its impact on connection bandwidths and the new data transfer caps being implemented by Comcast on all residential accounts.

The release gives a lot of good information, even if you don’t spend thousands for the full report. Buried in the release are some tidbits that are especially interesting. For example, it lists the bandwidth rates for a number of “high definition” video streams. Blu-ray is designed to deliver a maximum bit rate of 40 Mbps, presumably for one of its 1080p modes. The ATSC specification for HD over-the-air broadcasts tops out at 19.39 Mbps. (1080i and 720p images have about the same bandwidth requirements.) If you compress the signals more, however, you can squeeze the video into smaller bandwidth streams. Here are some Internet sources of video, and their bandwidth requirements for HD streams:

Apple iTunes: 4 Mbps
Hulu: 2.5 Mbps
Vudu: 4.0 to 4.5 Mbps
XBox Live: 6.8 Mbps

Clearly, these are designed to fit within the 5 Mbps bandwidth limits of many home broadband services. Few services offer the 20 Mbps needed to receive ATSC-quality signals without further compression. The result is that you won’t see the same HD quality on these online services as you would watching an over-the-air broadcast.

In time, we’ll see residential broadband rates increase, such as through Verizon’s FiOS fiber optic service, and then we can expect services to provide the same quality HD video streams that we now get over-the-air. Until then, we’ll have to settle for the more compressed versions that are available now.