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Rich Braun wrote: > I wrote: >> A terabyte can hold 55 hours of raw video > > I didn't do the math right, an hour of standard broadcast high-def is 7.4G so > a terabyte holds 135 hours. (For home videos, at least with the Sony > camcorderI use, an hour is about 13G so a TB is 76 hours.) Sorry 'bout the > error. The size of an hour of standard broadcast can vary. The maximum data rate of the ATSC data stream is 18Mbps, or 2.2MB per second, which comes to 8,100MB (about 8 gigabytes) per hour. Not all stations send a maximum rate data stream, and some multicast so the bandwidth to capture a single broadcast is lower. And at least two local DTV stations, WUNI-DT and WUTF-DT, only broadcast a single standard-definition signal; both of them use a data rate of about 8Mbps. (Those are Spanish-language stations and their parent networks do not yet provide HD content. Their Mexican supplier, Televisa, does, so we'll probably see HD on Univision and Telefutura someday.) Cable and satellite systems generally use lower data rates than broadcast ATSC does, so you'll be able to store more hours of video if you record from one of those sources. On the other hand, it won't look as good; the HD video from the broadcasts of the major networks is very good indeed, at least on the programs that provide good source material. Dramas and single-camera comedies shot on film are excellent; multi-camera comedies, game shows, and reality shows shot on video are more variable, and some are still SD. The flagship late night shows (Letterman and Leno) are also very good; they were among the very first shows to be broadcast in HD. For now at least, some daytime shows are also shot in HD video and broadcast that way, but I'm not convinced that will last; I suspect that the long-term course of broadcast television will be multicasting during the day, with HD content reserved for prime time, sports, and the major late-night programs. Locally, Channel 5 is doing local news in HD; none of the other stations are. The data rate of the most common types of digital camcorders (MiniDV, Digital8, and the most common variant of HDV) is 25Mbps, which is indeed about 13 gigabytes per hour. AVCHD cameras (most of the new flash and hard disk based cameras) use lower data rates (but use MPEG4 encoding instead of MPEG2) and most offer more than one choice, so you get a quality vs. recording time tradeoff.
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