Which types of HDTV connections provide the best possible HDTV quality — online downloads, cable, satellite or broadcast? You might be surprised to hear that of the four choices, broadcast is often the best and online downloads usually the worst, with cable often better than satellite.
The problem is that HD hardware manufacturers and content distributors are playing a shell game with the numbers. Yes, you may have 1080p capable hardware, but the key measure I focus on for video quality is not resolution but bitrate, and there’s a lot of room to move in that department. So which is the best for HD delivery?
Full-bandwidth transmission of HDTV requires about 19.5Mbps, and optical media such as HD-DVD and Blu-Ray can provide around 36Mbps. But the reality of transmission, thanks to packet loss and multicasting, is that your HD signal could be anywhere from 7 to 18Mbps, tops, and sometimes even less.
Cable: While the signal in practice tops out at 18Mbps, not every channel provides content in that high a rate. HBO, for instance, specifically delivers content at CableLabs’ recommended 15Mbps so that it’s easy for cable providers to piggyback an 3Mbps Standard Definition (SD) signal alongside it.
Satellite: Satellite is often cheaper and provides the most channels, but you get what you pay for. Industry claims aside, satellite HD is often pejoratively referred to as “HD Lite.” And it’s not always reliable — everything from sun spots to ground interference can reduce your bit rate and introduce ugly artifacts into the picture.
Downloads: iTunes and Apple TV bitrates top out at 5Mbps, even for 720p HD content. And while there are true 19.5Mbps HD movies now available on torrent trackers, they run around 20GB each — and even if your broadband is super-fast, you can’t watch while you download.
Broadcast: This data from Smart Calibrations for average signal bit rate performance for both satellite and terrestrial broadcast in Dallas-Fort Worth provides a striking comparison — a quick scan shows that satellite signals average roughly 2-3Mbps lower bit rate than local networks. While the selection is limited, all it will cost you is the price of an antenna.
Verdict: In general, you’ll get the most bits for your buck, ironically enough, from your local TV station. And until FiOS is a viable option for most, it will probably stay that way. While cable and satellite providers are touting the switch to MPEG-4, variable bitrate encoding and other cures for picture quality, ultimately it all comes down to bandwidth. For more about comparitive HDTV quality, check out the AVS forums.