New technologies need new cables. This article explains the important factors in choosing cables for HD and Blu-ray signals.
hd festival
HDTV broadcasts have five times as much bandwidth as normal standard-definition broadcasts.
The times are long past when the simple cinch connector and Scart cable were enough for video and audio. The old transmission types are simply no longer suitable for relaying modern, high-definition pictures and sound in their full glory. And while they might still be good enough for standard-definition signals, the high-definition sector needs to use better connections in order to maintain its superior quality.
Via modern cables, signals are sometimes transmitted not in their original resolution, but instead with a higher number of pixels, since many devices - such as DVD or Blu-ray players - up-scale PAL pictures to HD resolution. And signal-conversion also works the other way: You can view Blu-rays via the S-Video socket, and set-top boxes can output high-definition broadcasts via Scart. But the signals are then anything but HD - since a few years ago, therefore, digital connections have been the only way to go.
Bit rate and bandwidth:
To summarize once again: Traditional connections aren't suitable for HDTV, since they cannot transmit the full bit rates of the modern technologies. The larger amounts of information require faster and more powerful components. Let's look at an example of the arithmetic: If, for an analog signal, we take the horizontal deflection frequency (which roughly corresponds to the number of lines per second), standard TV reaches almost 16 kHz, HDTV around 32 kHz - progressive-scan PAL, however, also reaches this bandwidth. If you then multiply this by the number of oscillations necessary for each line in order to represent the roughly one thousand (960 to be precise) line pairs of HD, then you'll get a figure of around 60 MHz. Progressive-format standard signals, on the other hand, use around 13.5 MHz - that is, around a fifth of HD's bandwidth. Interlaced images in SDTV format get by on less than 7 MHz.
The situation is the same if you consider it in terms of bit rates: An uncompressed picture with eight bits per color requires around 250 MBit/s at PAL resolution; HDTV in 1080i format at 50 hertz, on the other hand, requires 1.25 Gbit/s, or almost 1.5 Gbit/s at 60 hertz. The bit rate then doubles for progressive-scan pictures - in a movie, for example - to around 3 Gbit/s at 1080p/60. For 24p, the lower frame rate means the bit rate drops to some 1.2 Gbit/s. 720p at 50 hertz uses around 1.1 Gbit/s, at 60 hertz around 1.3 Gbit/s.
In practice, the bit rates for digital transmissions are a third lower, since in most cases the signals are broadcast in YUV 4:2:2 - that is, with only half of the color resolution. The alternative RGB encoding, which uses the full bandwidth, is rare. The important point in practice is that higher bit rates and bandwidths require the cables to carry higher frequencies. Furthermore, the longer the cable, the more dampening the signal will suffer. What was OK for normal resolutions in the past can lead to errors in the high-definition era. At the same time, higher bandwidth also means a broader range for possible interfering frequencies.
Copy protection:
All sockets that receive or transmit video signals are - in theory at least - gateways for pirates and illegal copies. This topic becomes especially important when it comes to HD signals, since these signals more or less match the quality of original movie images.
Naturally, this is therefore one area on which the movie industry is keeping a close watch. TV broadcasters, too, are afraid of freeloaders that want to make money with their programs - from internet-based video recorders to people distributing their content by streaming it from abroad.
The reasons for the (sometimes excessive) vigilance are simple: movie productions cost more money than ever before, and programming costs are by far the biggest expense for TV channels. It seems pretty logical, therefore, that copy-protection measures are in place.
Pirates of the Caribbean
Pirates are only welcome if they're characters in the movie.
The foundations of today's copy-protection conditions were laid in 2002, when JVC wanted to introduce D-Theater, a system for distributing HDTV movies on D-VHS cassettes. This led to the creation of HDCP copy-protection for digital video signals - including the rules that, in 2006, culminated in an agreement on the provisional version of Blu-ray's content management (including AACS).
Here are the basics:
The only future-proof type of transmission is that via HDCP-secured interfaces - that is, via HDMI-compatible connections. The copy-protection is activated on request from the software (on the disc or via the HDTV transmission).
Analog transmission via YUV is tolerated, even without copy-protection. In this case, a maximum of 1080i or 720p is permitted; 1080p cannot be relayed as analog signals. If the software demands it, the analog outputs must be reduced to standard resolution or switched off completely.
From the year 2011, new players must only deliver HD signals via HDMI or other HDCP interfaces. The analog outputs will then be limited to 480i. From 2014, this will go one step further - then, all analog outputs must be switched off during playback of protected content.
Interfaces that can relay the original, protected files (such as Ethernet, Firewire, or USB) are blocked.
It's debatable whether all of these guidelines are justified. But in the end, the movie industry is just trying to prevent large-scale duplication. It remains to be seen whether this approach will actually work - no copy-protection in the world represents an insurmountable hurdle.
hd festival
HDTV broadcasts have five times as much bandwidth as normal standard-definition broadcasts.
The times are long past when the simple cinch connector and Scart cable were enough for video and audio. The old transmission types are simply no longer suitable for relaying modern, high-definition pictures and sound in their full glory. And while they might still be good enough for standard-definition signals, the high-definition sector needs to use better connections in order to maintain its superior quality.
Via modern cables, signals are sometimes transmitted not in their original resolution, but instead with a higher number of pixels, since many devices - such as DVD or Blu-ray players - up-scale PAL pictures to HD resolution. And signal-conversion also works the other way: You can view Blu-rays via the S-Video socket, and set-top boxes can output high-definition broadcasts via Scart. But the signals are then anything but HD - since a few years ago, therefore, digital connections have been the only way to go.
Bit rate and bandwidth:
To summarize once again: Traditional connections aren't suitable for HDTV, since they cannot transmit the full bit rates of the modern technologies. The larger amounts of information require faster and more powerful components. Let's look at an example of the arithmetic: If, for an analog signal, we take the horizontal deflection frequency (which roughly corresponds to the number of lines per second), standard TV reaches almost 16 kHz, HDTV around 32 kHz - progressive-scan PAL, however, also reaches this bandwidth. If you then multiply this by the number of oscillations necessary for each line in order to represent the roughly one thousand (960 to be precise) line pairs of HD, then you'll get a figure of around 60 MHz. Progressive-format standard signals, on the other hand, use around 13.5 MHz - that is, around a fifth of HD's bandwidth. Interlaced images in SDTV format get by on less than 7 MHz.
The situation is the same if you consider it in terms of bit rates: An uncompressed picture with eight bits per color requires around 250 MBit/s at PAL resolution; HDTV in 1080i format at 50 hertz, on the other hand, requires 1.25 Gbit/s, or almost 1.5 Gbit/s at 60 hertz. The bit rate then doubles for progressive-scan pictures - in a movie, for example - to around 3 Gbit/s at 1080p/60. For 24p, the lower frame rate means the bit rate drops to some 1.2 Gbit/s. 720p at 50 hertz uses around 1.1 Gbit/s, at 60 hertz around 1.3 Gbit/s.
In practice, the bit rates for digital transmissions are a third lower, since in most cases the signals are broadcast in YUV 4:2:2 - that is, with only half of the color resolution. The alternative RGB encoding, which uses the full bandwidth, is rare. The important point in practice is that higher bit rates and bandwidths require the cables to carry higher frequencies. Furthermore, the longer the cable, the more dampening the signal will suffer. What was OK for normal resolutions in the past can lead to errors in the high-definition era. At the same time, higher bandwidth also means a broader range for possible interfering frequencies.
Copy protection:
All sockets that receive or transmit video signals are - in theory at least - gateways for pirates and illegal copies. This topic becomes especially important when it comes to HD signals, since these signals more or less match the quality of original movie images.
Naturally, this is therefore one area on which the movie industry is keeping a close watch. TV broadcasters, too, are afraid of freeloaders that want to make money with their programs - from internet-based video recorders to people distributing their content by streaming it from abroad.
The reasons for the (sometimes excessive) vigilance are simple: movie productions cost more money than ever before, and programming costs are by far the biggest expense for TV channels. It seems pretty logical, therefore, that copy-protection measures are in place.
Pirates of the Caribbean
Pirates are only welcome if they're characters in the movie.
The foundations of today's copy-protection conditions were laid in 2002, when JVC wanted to introduce D-Theater, a system for distributing HDTV movies on D-VHS cassettes. This led to the creation of HDCP copy-protection for digital video signals - including the rules that, in 2006, culminated in an agreement on the provisional version of Blu-ray's content management (including AACS).
Here are the basics:
The only future-proof type of transmission is that via HDCP-secured interfaces - that is, via HDMI-compatible connections. The copy-protection is activated on request from the software (on the disc or via the HDTV transmission).
Analog transmission via YUV is tolerated, even without copy-protection. In this case, a maximum of 1080i or 720p is permitted; 1080p cannot be relayed as analog signals. If the software demands it, the analog outputs must be reduced to standard resolution or switched off completely.
From the year 2011, new players must only deliver HD signals via HDMI or other HDCP interfaces. The analog outputs will then be limited to 480i. From 2014, this will go one step further - then, all analog outputs must be switched off during playback of protected content.
Interfaces that can relay the original, protected files (such as Ethernet, Firewire, or USB) are blocked.
It's debatable whether all of these guidelines are justified. But in the end, the movie industry is just trying to prevent large-scale duplication. It remains to be seen whether this approach will actually work - no copy-protection in the world represents an insurmountable hurdle.
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