The final type of digital video connection is IEEE 1394, which is the same connector found on many newer PCs. Digital camcorders, high-definition digital VCRs, and some cable or satellite set-top boxes use 1394 to carry a compressed digital video signal and digital audio signal between devices. One potentially confusing issue is that there are different "flavors" of 1394—although there's only one type of cable and one type of connector. The connection used on digital camcorders and most PCs is sometimes referred to as 1394 data and the one used between certain digital video components, such as digital VCRs, and some TVs is 1394 video and the two are not compatible. In other words, if you plugged a 1394 cable from a camcorder into a Tivo-like PVR (hard disk-based video recorder) or other digital video device, the two won't be able to communicate with each other because they used different signal formats. Similarly, if you try to attach a 1394-equipped PC into a TV with a 1394 port, that won't work either. If you're going to work with 1394 devices, you'll need to find out which "type" of 1394 connection it actually uses. Unfortunately, that isn't always easy to do, so you may have to do some research if you have any questions about your own gear.

The primary difference between 1394 and DVI or HDMI (other than the different physical connector) is that DVI and HDMI carry an uncompressed video signal, whereas 1394 compresses the video along the cable and then decompresses (technically speaking it "decodes" the MPEG2 video stream) on the receiving device. The issue here is that this can add cost to the receiving devices. On the other hand, 1394 signals can be carried over a network, whereas DVI and HDMI cannot—they can only be use directly from one point to another. One other difference is that IEEE 1394 uses the 5C copy-protection scheme, which is different than the HDCP copy-protection technology found in DVI/HDCP and HDMI. 1394 can co-exist side-by-side with HDMI, just as you might simultaneously use both component video and S-video analog video signals within your home theater/entertainment system. Most newer products have moved away from 1394 and focus more on HDMI so in scouting out gear, be sure to look for HDMI inputs and/or outputs.

Table 2 lists all the connection types for video connections in order of quality (from worst to best) showing the types of signals that each can carry.

SIGNAL

SIGNAL CONTENT

TYPES OF SIGNALS CARRIED

ANALOG

RF

Low-quality video and mono audio

Standard definition TV from cable or satellite, interlaced DVD, VCR, videogame

Composite

Standard video

Standard definition TV from cable or satellite, interlaced DVD, VCR, videogame

S-Video

Better video

Standard definition TV from cable or satellite, interlaced DVD, VCR, videogame

Component

Highest quality analog video

High definition TV, progressive scan DVD, standard definition TV from cable or satellite, interlaced DVD, VCR, videogame

DIGITAL

1394 (aka Firewire, iLink)

Compressed digital video, multi-channel digital audio, 5C copy protection

High definition TV, progressive scan DVD, standard definition TV from cable or satellite, interlaced DVD

DVI

Uncompressed digital video

High definition TV, progressive scan DVD, standard definition TV from cable or satellite, interlaced DVD

DVI/HDCP

Uncompressed digital video, HDCP copy protection

High definition TV, progressive scan DVD, standard definition TV from cable or satellite, interlaced DVD

HDMI

Uncompressed digital video, HDCP copy protection, multi-channel digital audio

High definition TV, progressive scan DVD, standard definition TV from cable or satellite, interlaced DVD

 

One important takeaway from this discussion is that you should always use the best connection type available to you. For example, if your satellite or cable box offers component video, S-Video and composite video, you should use the component video connections (which may require buying new cables) if at all possible. Similarly, if you have a choice between any analog output and digital one, choose the digital one. Note, however, that you only maintain the quality of the video signal if all the pieces in the chain support it. So, if your display doesn't offer HDMI inputs, then you can't use HDMI video cables to connect between your device and your display. Instead, you'll need to drop down to the next best choice available on both—typically component video—to make the connections.


 

 
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