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How DVRs Work
by James Bickers


 Introduction to How DVRs Work
The Basics
Pausing Live TV?
Search Tools
› Quality and Capacity
Ongoing Costs
Controversy Brewing
Lots More Information

Quality and Capacity
DVRs advertise anywhere from 30-hour to 320-hour recording capabilities. It's worth noting that these units can record programs at varying levels of quality -- and the advertised capacity usually refers to the number of hours it can hold at the lowest quality setting.

As an example, TiVo can record programs at four different quality levels: basic, medium, high, or best. A 30-hour TiVo unit can hold 30 hours at the basic quality level, but only about nine hours at the best setting. The hard drive in a 30-hour TiVo is approximately 30 gigabytes in size; on the basic setting, one hour translates to 1 gigabyte, while at the highest setting one hour uses 4 gigabytes.

So what's the difference? If you've ever seen full-motion video on the Web, you know how images can get blocky and distorted. This happens on DVR recordings made at low quality levels, particularly if there is a lot of movement in the image. As a result, different quality settings are good for different types of programs: While an old black-and-white movie or a talk show will look just fine at the basic level, a fast-moving sports program or action movie will be almost unwatchable. So bear this in mind if you're thinking of buying a DVR primarily to support your sports habit -- better go for the higher capacity unit.

File Sizes
In Sony's Giga Pocket system, the files for each recorded program are stored on the computer's normal hard disk. If you have a drive with 60 free gigabytes of space, then Giga Pocket can use those 60 gigabytes to store TV programs. The amount of space that a program consumes on the hard disk depends on both the length of the program and the recording quality. Giga Pocket offers three quality modes:
  • LP - Stored as a highly compressed MPEG-1 file
  • SP - Stored as a moderately compressed MPEG-2 file
  • HQ - Stored as a high-quality MPEG-2 file
In HQ mode, a one-hour program consumes about 3.35 gigabytes. In SP mode, a one-hour program consumes about 1.7 gigabytes. In LP mode, a one-hour program consumes about 0.6 gigabytes.

In other words, you can store about 18 hours of video on 60 gigabytes of space in HQ mode. In SP mode, you can store about 36 hours. In LP mode, you can store about 100 hours.

In terms of quality, LP mode has a noticeable grain to it, but it is watchable. SP mode looks good. HQ mode seems like overkill -- there's not a noticeable difference between SP and HQ when you are watching a program recorded from cable. Perhaps if you were recording an s-video signal coming in from a DVD player or camcorder and you wanted to preserve all the detail, HQ mode would be good for that.

Just like on a computer hard drive, deleting a program from a DVR doesn't actually delete the program itself -- it simply erases the file system's reference to where it is stored and how long it is, making it effectively gone. The raw program data remains on the drive until it is overwritten by a new recording.

Lowest Price
1.ReplayTV 5504 $139.95
2.Pioneer DVR-810H DVD Recorder with TiVo service $685.00
3.ReplayTV DIGITAL NETWORK Replay TV 5508 80 Hours $249.00
4.Hughes DIRECTV Satellite Receiver With TiVo Series 2- HDVR2 Up To 35 Hours of Digital Recording $99.00
5.Pioneer Elite DVR-57H DVD Recorder w/HDD and Tivo $1027.00

 

 
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Table of Contents:
Introduction to How DVRs Work
The Basics
Pausing Live TV?
Search Tools
› Quality and Capacity
Ongoing Costs
Controversy Brewing
Lots More Information


 
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