Radio Collector's Afficionado's Resource

History

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The initial DVR was tested on July 8, 1965, when CBS explored the possiblenesses of instant freeze-frame and rewind for sporting event broadcasts. Ampex freed the basi mercantile hard disk video recorder in 1967. The HS-100 recorded analog video onto a digital hard disk and could store a greatest or most complete or best possible of only 30 seconds.

Hard disk-based DVRs

The two early buyer DVRs, ReplayTV and TiVo, were launched at the 1999 Consumer Electronics Show in Las Vegas. Although ReplayTV won the “Best of Show” award in the video category, it was TiVo that went on to much dandier mercantile success. The appliances have regularly invented complementary abilities, such as recording onto DVDs, mercantile skip, sharing of recordings over the Internet, and programming and remote control facilities using PDAs, networked PCs, or Web browsers.

This makes the “time shifting” feature (traditionally done by a VCR) much more convenient, and also allows for “trick modes” such as pausing live TV, instant replay of interesting scenes, and skipping advertising. Most DVRs use the MPEG format for encoding analog video signals.

The two buyer DVR brands in the United States are the TiVo and DNNA’s ReplayTV. In the UK TiVo has a little presence; Thomson, Topfield, Fusion, Pace and Humax likewise supply digital terrestrial (DTT) DVRs. BSkyB markets a ordinary combined EPG and DVR as Sky+.South African based Africa Satellite TV beamer Multichoice not long back launched their PVR which is available on their Dstv platform.

Many satellite and cable companies are incorporating DVR functions into their set-top box, such as with DirecTiVo, DishPlayer/DishDVR, Scientific Atlanta Explorer 8xxx, Motorola 6xxx from Comcast, Moxi Media Center by Digeo (available through Charter, Adelphia, Sunflower, Bend Broadband, and soon Comcast and other cable companies), or Sky+. In this case there is no encoding necessary in the DVR, as the satellite signal is already a digitally encoded MPEG stream. The DVR plainly stores the digital stream directly to disk. Having the broadcaster involved with (subsidizing) the design of the DVR–and directly recording encrypted digital streams–can lead to features such as the capacity to use interactional TV on recorded shows, pre-loading of programs. It can, however, also strength the manufacturer to utilise non-skippable advertisements and automatically-expiring recordings.

Software is available for transferring programs recorded on DVR hardware to or from PC’s (e.g., TiVoToGo and DVArchive).

PCs

Software and hardware is available which may turn personal computers running Microsoft Windows, Linux and Macintosh into PVRs, and is a general option for home-theater PC (HTPC) enthusiasts.

Linux

There are a heap of open source and GPL-licensed DVR apps available for Linux:

• MythTV
• Freevo
• DVR
• VDR
• KnoppMyth – provides an out of the box MythTV based PVR solution

Commercial Linux version available from SageTV based on Gentoo Linux. Brightbox, a buyer electronics device, uses SageTV.

Macintosh

Elgato makes a series of DVR gadgets called EyeTV (400 / 500 / DTT etc.). The software supplied with each device (but available separately) is also called EyeTV. Elgato have not long back freed version 2.3 of their EyeTV software, with a redesigned interface, better program guide (built into the program) and a ‘One Click’ to iPod video feature. Miglia also makes DVR hardware that runs the EyeTV software, as well as DVR appliances that use other software.

Other DVR productions include myTV.PVR from EskapeLabs and ConvertX PVR from Plextor. MythTV (see above) likewise runs beneath OS X, but most recording gadgets are presently only supported beneath Linux. Precompiled binaries are available for the MythTV front-end, permitting a Mac to watch video from (and control) a MythTV server running underneath Linux.

Apple provides apps in the FireWire software developer kit which concede any Macintosh with a FireWire port to record the MPEG2 transport stream from a FireWire equipped cable box (e.g., Motorola 62xx, including HD streams). Applications may likewise change channels on the cable box by way of the firewire interface. Only broadcast channels may be recorded as the rest of the channels are encrypted. iRecord is a free scheduled-recording program derived from this SDK.

Windows

Microsoft Windows has assorted free DVR apps including GB-PVR, Got All Media and MediaPortal. DScaler has likewise DVR support in works.

There likewise are various proprietary apps including SageTV, SnapStream Beyond TV, ChrisTV, Showshifter, Meedio (now a dead product – Yahoo! purchased most of the company’s engineering science and discontinued the Meedio line, and rebranding the software Yahoo! Go – TV, which is now a free product), InterVideo WinDVR, Recordit Plus and the R5000-HD.

There is likewise a discerned version of Microsoft Windows called Windows XP Media Center Edition which has DVR capabilities.

And Microsoft Windows Vista will include in it is popular version the Media Center functionalities.

Source video

Television and video are terms that are from time to time employed interchangeably, but differ in their technical definitions. Video is the visual part of television, whereas television is the combining of video and audio modulated onto a carrier frequency (i.e., a television channel), so that multiple frequencies (i.e., multiple channels) may be transmitted at the same time.

Analog television

Analog television in NTSC, PAL or SECAM formats, analog cable, or regular VHS tapes use a signal that is fed directly to the electron beam within the television set. There are a number of details on how this is done, but in essence each line in each frame corresponds to a specific fraction of time within the signal.

To record an analog signal a few steps are required. A TV tuner card tunes into a peculiar frequency and then functions as a frame grabber, breaking the lines into person pixels and quantizing them into a format that a computer may comprehend. Then the series of frames along with the audio (also sampled and quantized) are compressed into a manageable format, like MPEG-2, or WMF, normally in software. Some TV tuner cards like the DVR-250/350 or the TiVo chip deliver an MPEG-2 or other compressed stream directly to the computer, performing both the frame grabbing and compression in silico. This mainly reduces the load on the CPU permitting an overall for less implementation.

Analog Broadcast Copy Protection

Many mass-produced buyer DVRs apply a copy-protection system called CGMS-A (Copy Generation Management System–Analog). This encodes a pair of bits in the VBI of the analog video signal that specify one of the following settings:

• Copying is freely permitted
• Copying is prohibited
• Only one copy of this material may be made
• This is a copy of material for which only one copy was permitted to be made, so no further copies are allowed.

CGMS-A info may be present in analog broadcast TV signals, and is preserved when the signal is recorded and played back by analog VCRs, which of course don’t grasp the significations of the bits. But the limitations still come into effect when you try to copy the tape onto a Player.

Digital television

Digital television is audio/visual signals that are broadcast over the air in a digital rather than analog format. Recording digital TV is in general a straightforward capture of the binary MPEG-2 data being received. No highpriced hardware is required to quantize and compress the signal (as the television broadcaster has already done this in the studio). The MythTV DVR supports both international DVB signals and American ATSC signals while the HDTV Tivo supports only the ATSC signals. In the U.S., the FCC attempted to place a road-block before digital DVRs with it is “Broadcast flag” regulation. Digital video recorders which had not won prior approval from the FCC for implementing “effective” digital rights management would have been banned from interstate commerce as of July 2005. The regulation was struck down on May 6, 2005.

DVD-based PVRs available on the market as of 2006 are not competent of capturing the full range of the visual signal available with high definition television (HDTV). This is for the most part because HDTV standards were finalized at a later time than the standards for DVDs. However, DVD-based PVRs may still be applied (albeit at scaled down visual quality) with HDTV since presently available HDTV sets likewise have popular A/V connections.

Satellite or Digital Cable

Recording satellite or digital cable signals on a digital video recorder is more complex than recording analog signals or broadcast digital signals. This is so because the MPEG-2 or MPEG-4 stream is normally encrypted to prevent people from looking at the content without paying for it (usually thru subscription).

The satellite or cable set-top box does two things. First, it decrypts the signal. Second, it decodes the MPEG stream into an analog, DVI, or HDMI signal for watching on 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 and two); this is how DVRs built into set-top boxes work.

An substitute is that galore satellite or (more commonly) cable set-top boxes have a FireWire port that may be connected to a computer. The recorded MPEG stream may be relayed to the computer thru this FireWire port; though it may be done live, this is more commonly employed for transferring shows from a set-top box with built-in DVR. (For instructions on doing this on a ordinary set-top box with DVR, please see the Wikibook entry How to use a Motorola DVR; galore of the ideas there may utilize to other set-top boxes as well.)

DVD

Many DVD-based DVRs are equipped with two DVD drives or an further and added internal hard drive. This arrangement may be used to copy content from a source DVD, which is disallowed in the US under the Digital Millennium Copyright Act if the disc is encrypted. Most such DVRs will accordingly not grant recording of video streams from encrypted movie discs.

Digital camcorders

Some DVD-based DVRs integrate a Firewire connector which may be used to capture digital video from a MiniDV or Digital 8 camcorder, perchance recording a simple DVD as the camcorder is played back. Some editing of the resulting DVD is normally possible, such as adding chapter points.

Security applications

Digital video recorders set up for physical security apps record video signals from closed circuit television cameras for detection and documentation purposes. Many are designed to record audio as well. DVRs have evolved into appliances that are feature rich and provide services that exceed the simple recording of video images that was antecedently done through VCRs. A DVR CCTV scheme provides a multitude of progressed functions over VCR engineering science including video searches by event, time, date and camera. There is also much more control over quality and frame rate permitting disk space usage to be optimized and the DVR may also be set to overwrite the oldest security footage must the disk become full. In galore DVR security schemes remote access to security footage using a PC may likewise be achieved by connecting the DVR to a LAN network or the internet.

Security DVRs may be categorized as being either PC based or embedded. A PC based DVR’s architecture is a classical personal computer with video capture cards designed to capture video images. An embedded type DVR is specifically designed as a digital video recorder with it is operating scheme and application software contained in firmware or read only memory.

Hardware Features

Hardware features of security DVRs vary amongst manufacturers and may include but are not inevitably fixed to:

• Designed for rack mounting or desktop configurations.
• Single or multiple video inputs with connector types consistent with the analogue or digital video provided such as coaxial cable, twisted pair or optical fiber cable. The most mutual number of inputs are 1, 4, 8, 16 and 32. Systems may be set up with a very huge number of inputs by networking or bussing person DVRs together.
• Looping video outputs for each input which duplicates the corresponding input video signal and connector type. These output signals are applied by other video instrumentation such as matrix switchers, multiplexers, and video monitors.
• Controlled outputs to external video display monitors.
• Front panel switches and indicators that grant the respective features of the machine to be controlled.
• Network connections consistent with the network type and applied to control features of the recorder and to send and/or receive video signals.
• Connections to external control gadgets such as keyboards.
• A connection to external pan-tilt-zoom drives that position cameras.
• Internal CD, DVD, VCR gadgets distinctively for archiving video.
• Connections to external storage media.
• Alarm event inputs from external security detection devices, commonly one per video input.
• Alarm event outputs from internal detection features such as motion detection or loss of video.

Software Features

Software features vary among manufacturers and may include but are not inevitably fixed to:

• User selectable effigy capture rates either on an all input basis or input by input basis. The capture rate feature may be programmed to mechanically adjust the capture rate on the occurrence of an external alarm or an internal event
• Selectable effigy solution either on an all input basis or input by input basis. The effigy solution feature may be programmed to mechanically adjust the effigy solution on the occurrence of an external alarm or an internal event.
• Motion detection: Provided on an input by input basis, this feature detects motion detection in the total effigy or a user definable part of the effigy and commonly provides sensitivity settings. Detection causes an internal event that may be output to external instrumentation and/or be used to trigger changes in other internal features.
• Lack of motion detection. Provided on an input by input basis, this feature detects the motion of an object into the field of view and remaining still for a user definable time. Detection causes an internal event that may be output to external instrumentation and/or employed to trigger changes in other internal features.
• Direction of motion detection. Provided on an input by input basis, this feature detects the direction of motion in the effigy that has been determined by the user as an unacceptable occurrence. Detection causes an internal event that may be output to external instrumentation and/or be employed to trigger changes in other internal features.
• Routing of input video to video monitors based on user inputs or mechanically on alarms or events.
• Input, time and date stamping.
• Alarm and event logging on suitable video inputs.
• Alarm and event search.
• One or more sound recording channels.
• Archival.
• Remote control.