Synchronizing the Analog Signal
Video images are generated from a source, such as a camera or computer, and viewed on a source, such as a monitor. In order for the viewed image to be seen in exactly the same way and the same time frame as the generated or original image, there has to be a method for synchronizing the elements of the image. Synchronizing an image is a critical part of the analog video process.
Synchronizing Generators A synchronizing generator, or sync generator as it is called, is the heart of the analog video system. The sync generator creates a seriesof pulses that drive all the different equipment in the entire video facility, from cameras to monitors. When viewing analog signals, the synchronizing pulses also drive the monitors.
The heart of the sync generator is an oscillator that puts out a signal called the color subcarrier, which is the reference signal that carries the color information portion of the signal (discussed in more detail later in this chapter). The frequency of the color subcarrier is 3,579,545 cycles per second, rounded off and more commonly referred to as simply 3.58. Starting with this basic signal, the sync generator, through a process of electronic multiplication and division, outputs other frequencies in order to create the other pulses that are necessary for driving video equipment. These pulses include horizontal and vertical synchronizing pulses, horizontal and vertical drive pulses, horizontal and vertical blanking pulses, and equalizing pulses.
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These pulses are often combined so that one signal will contain multiple synchronizing components. Combination signals are referred to as composite signals. Terms such as composite blanking and composite video refer to such signals.
Synchronizing Pulses
The sync generator puts out both horizontal and vertical synchronizing pulses. These synchronizing pulses ensure that all of the equipment within the system is in time or synchronized. Horizontal and vertical synchronizing pulses are part of the composite signal, so they can be easily fed to any piece of equipment that requires async reference signal.
Horizontal synchronizing pulses appear at the beginning of each line of video. They assure that monitors and receivers are in synchronization on a line-by-line basis with the information that the camera is creating. Vertical synchronizing pulses appear during the vertical interval, which will be discussed later in this chapter. These pulses assure that the retrace is taking place properly, so that the gun is inits proper position for painting the beginning of the next field.
The composite sync signal ensures that each piece of equipment is operating within the system on a line-by-line, field-by-field basis.
If equipment is not synchronized, switching between images can cause the image in the monitor to lose stability. Dissolves and special effects can change color or shift position. Character generators or computer-generated images might appear in a different position in the image from where they were originally placed.
The sync generator puts out both horizontal and vertical synchronizing pulses. These synchronizing pulses ensure that all of the equipment within the system is in time or synchronized. Horizontal and vertical synchronizing pulses are part of the composite signal, so they can be easily fed to any piece of equipment that requires async reference signal.
Horizontal synchronizing pulses appear at the beginning of each line of video. They assure that monitors and receivers are in synchronization on a line-by-line basis with the information that the camera is creating. Vertical synchronizing pulses appear during the vertical interval, which will be discussed later in this chapter. These pulses assure that the retrace is taking place properly, so that the gun is inits proper position for painting the beginning of the next field.
The composite sync signal ensures that each piece of equipment is operating within the system on a line-by-line, field-by-field basis.
If equipment is not synchronized, switching between images can cause the image in the monitor to lose stability. Dissolves and special effects can change color or shift position. Character generators or computer-generated images might appear in a different position in the image from where they were originally placed.
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