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television channels frequency
TV and video is a term sometimes used interchangeably, but they differ in their technical sense. The video is the next visual television, whereas television is the combination of video and audio on a carrier frequency modulated (eg, a string television), so the signal can be delivered the receiver (TV or computer / PVR with a TV tuner). DVR resolutions differ from the two-way video is recorded.
Analog TV
Analog TV in NTSC, PAL or SECAM, analog cable, VHS tapes or regular using a signal which is fed directly to the electron beam on television. There are a number of details on how this is done, but in essence each line in each box corresponds to a specific portion in the time signal.
To record an analog signal few steps are necessary. A TV card plugs into a particular frequency and then it works like a frame grabber, breaking the lines in pixels individual and quantification in a format the computer can understand. Then the series of paintings, as well as audio are compressed (also sampled and quantized) in popular formats such as MPEG-2, or WMF, usually in software. Some TV tuner cards as DVR-250/350 TiVo or issue chip MPEG-2 or other compressed stream directly to the computer, using both the context and entering the compression hardware. This reduces much CPU load for an application usually cheaper.
Digital TV
Digital television contains audio visual and transmitted by air in a digital rather than analog. Recording digital TV is usually a direct input of the MPEG-2 During reception of binary data. No costly hardware required to quantify and compress the signal (such as television did in the studio). The MythTV DVR supports both international DVB signals and American while ATSC signals TiVo Series 3 supports only the ATSC signals. In the United States, the FCC has attempted to put a road block before DVRs flag with its regulation of broadcasting. "Digital Video Recorders who had not obtained prior approval from the FCC for implementing "effective" digital rights management has been forbidden to trade interstate, July 2005. The settlement was killed May 6, 2005.
DVD-based PVRs on the market from 2006 are not able to capture full range of available visual signal of high definition television (HDTV). This is largely because HDTV standards were completed in a few time after the standards for DVDs. However, on DVD PVR still be used (but with a reduced visual quality) with HDTV in high definition available today, and have also established a level / V.
Satellite or digital cable
Signal recording satellite or cable digital recorder digital video is more complex than recording analog signals or digital broadcasting. Because the MPEG-2 or MPEG-4 stream is usually encrypted to prevent people from seeing the content without paying the price (most often by subscription).
Cable or satellite-top box does two things. First, decode the signal. Second, it decodes the MPEG stream into analog, DVI or HDMI to the display signal to the television. In order to record cable / satellite digital signals you must get the signal after it is decrypted, but before it is decoded (between steps one two), thus the DVR set-top boxes work.
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Article Source: ArticlesBase.com – Easy Dvr Recording With Analog, Digital, or Satellite Television
