Post by b_Pooly on Jul 3, 2008 16:39:00 GMT -5
Published: 7/3/08, 6:47 AM EDT
Over the past few years, we've seen the decline of analog signals in favor of the newer digital signal which offers better clarity and higher resolution. Here's a look at the differences and what's in store for the future.
Let's face it; television is an integral part of our daily lives. Studies done by A.C. Nielsen estimate that the average American spends about four hours a day (or 28 hours a week, or 2 months a year) watching TV. This means that people at the age of 65 will have watched television for 9 years of their life. These statistics demonstrate that the majority of Americans not only spend an inordinate amount of time watching television, but that they also spend considerable amounts of money on devices to enhance the picture quality.
Under a new law, defined by the Digital Transition Television and Public Safety in 2005, broadcasters must convert all of their signals to digital and cease the transmission of analog by February 17, 2009. This has caused television manufactures to produce TV sets that are capable of not only receiving analog, which has been used for over 50 years now, but also the newer digital signals. This will ensure the sets will continue to work after the new law is enacted.
How Analog Televisions Work
A video camera records photos in succession of still images over a period of time. Each photo is one frame and in North America it takes 30 frames to show one second of time. As the camera captures the scene, it records in rows of individual points, or pixels. Each pixel contains information for color (red, green and blue) and intensity. These rows, or lines, are combined with signals for horizontal and vertical synchronization. The lines are interlaced with the odd rows produced first followed by the even. These are called scan lines. This lets the television know where to reproduce the rows of pixels. This produces a composite. Composite video is where the color and intensity information is combined into one signal. The sound is transmitted separately.
The main drawback to analog is the amount of resolution that controls the clarity of detail in the signal. Resolution is determined by the number of pixels in the screen.
How Digital Television Works
In recent years, the FCC gave transmitters new frequencies for digital transmission. So now, each transmitter has an analog channel and a digital channel. The digital channels transport a 19.39 data flow of Megabits per second (Mbps) that the television receives and decodes. Each transmitter has a digital channel, but a channel can utilize sub-channels if the programmer wants it.
It works in the following way: a programmer can send a program to 19.39Mbps. That programmer can then divide the channel between different flows such as four flows of 4.85Mbps each. These flows are called sub-channels. For example, if the television channel is 53, then that channel can have three sub-channels each transporting a different program. These sub-channels would then be: 53.1, 53.2, and 53.3.
There are three formats in which the programmers can create sub-channels: 480p, 720p and 1080i.
480p contains 480 vertical scan lines with each frame drawn in sequence. The resolution can be 704x480 pixels for non-square sampling or 640x480 pixels for square sampling. The frame rates can be sent at 24, 30 or 60 progressive frames per second. The 16:9 aspect ratio is defined at 720x480 pixels using non-square, anamorphic sampling.
720p contains 720 vertical scan lines with each frame drawn in sequence. The resolution assumes a widescreen ratio of 16:9 at 1280x720 pixels. The frame rates can be sent in 24, 25, 30, 50, or 60 frames per second.
1080i contains 1080 vertical scan lines with each frame interlaced. This is the high-definition (HDTV) format. This resolution assumes a widescreen ratio of 16:9 at 1920x1080 pixels. The frame rates can be sent in 24, 30, or 60 frames per second.
AT&T U-Verse TV, cable, and satellite all are prepared to handle the digital conversion early next year. However, if you are still watching television without any of those services on a traditional analog television, you must start thinking about alternatives that will allow you to adapt to these changes. You could purchase one of those services or a new TV. The U.S. government is also offering a coupon to purchase a set-top box that will adapt to the digital signal, allowing you to still use your current TV.
I'm sure everyone knows all this by now, but in the off chance I may have missed something, I posted it anways.
Over the past few years, we've seen the decline of analog signals in favor of the newer digital signal which offers better clarity and higher resolution. Here's a look at the differences and what's in store for the future.
Let's face it; television is an integral part of our daily lives. Studies done by A.C. Nielsen estimate that the average American spends about four hours a day (or 28 hours a week, or 2 months a year) watching TV. This means that people at the age of 65 will have watched television for 9 years of their life. These statistics demonstrate that the majority of Americans not only spend an inordinate amount of time watching television, but that they also spend considerable amounts of money on devices to enhance the picture quality.
Under a new law, defined by the Digital Transition Television and Public Safety in 2005, broadcasters must convert all of their signals to digital and cease the transmission of analog by February 17, 2009. This has caused television manufactures to produce TV sets that are capable of not only receiving analog, which has been used for over 50 years now, but also the newer digital signals. This will ensure the sets will continue to work after the new law is enacted.
How Analog Televisions Work
A video camera records photos in succession of still images over a period of time. Each photo is one frame and in North America it takes 30 frames to show one second of time. As the camera captures the scene, it records in rows of individual points, or pixels. Each pixel contains information for color (red, green and blue) and intensity. These rows, or lines, are combined with signals for horizontal and vertical synchronization. The lines are interlaced with the odd rows produced first followed by the even. These are called scan lines. This lets the television know where to reproduce the rows of pixels. This produces a composite. Composite video is where the color and intensity information is combined into one signal. The sound is transmitted separately.
The main drawback to analog is the amount of resolution that controls the clarity of detail in the signal. Resolution is determined by the number of pixels in the screen.
How Digital Television Works
In recent years, the FCC gave transmitters new frequencies for digital transmission. So now, each transmitter has an analog channel and a digital channel. The digital channels transport a 19.39 data flow of Megabits per second (Mbps) that the television receives and decodes. Each transmitter has a digital channel, but a channel can utilize sub-channels if the programmer wants it.
It works in the following way: a programmer can send a program to 19.39Mbps. That programmer can then divide the channel between different flows such as four flows of 4.85Mbps each. These flows are called sub-channels. For example, if the television channel is 53, then that channel can have three sub-channels each transporting a different program. These sub-channels would then be: 53.1, 53.2, and 53.3.
There are three formats in which the programmers can create sub-channels: 480p, 720p and 1080i.
480p contains 480 vertical scan lines with each frame drawn in sequence. The resolution can be 704x480 pixels for non-square sampling or 640x480 pixels for square sampling. The frame rates can be sent at 24, 30 or 60 progressive frames per second. The 16:9 aspect ratio is defined at 720x480 pixels using non-square, anamorphic sampling.
720p contains 720 vertical scan lines with each frame drawn in sequence. The resolution assumes a widescreen ratio of 16:9 at 1280x720 pixels. The frame rates can be sent in 24, 25, 30, 50, or 60 frames per second.
1080i contains 1080 vertical scan lines with each frame interlaced. This is the high-definition (HDTV) format. This resolution assumes a widescreen ratio of 16:9 at 1920x1080 pixels. The frame rates can be sent in 24, 30, or 60 frames per second.
AT&T U-Verse TV, cable, and satellite all are prepared to handle the digital conversion early next year. However, if you are still watching television without any of those services on a traditional analog television, you must start thinking about alternatives that will allow you to adapt to these changes. You could purchase one of those services or a new TV. The U.S. government is also offering a coupon to purchase a set-top box that will adapt to the digital signal, allowing you to still use your current TV.
I'm sure everyone knows all this by now, but in the off chance I may have missed something, I posted it anways.
