Horizontal retrace occurs during the horizontal blanking period.
The horizontal blanking period can be viewed on a waveform monitor, which displays an electronic representation of the visual image (Figure 4.3A). (The waveform monitor is discussed in detail in Chapter 8.) Several critical synchronizing signals occur during this horizontal blanking period. These signals appear in the followingorder: the front porch, the horizontal synchronizing pulse, the breezeway, and color burst reference (see definitions of these terms below). The breezeway and color burst reference occur during the period of time referred to as the back porch.
The front porch is the period of time that begins at the end of active video. It initiates the retrace and is the beginning of the synchronizing period of time. A single scan line is defined as starting at the front porch and ending with active video before the next front porch begins.
Following the front porch is the horizontal synchronizing pulse. This pulse synchronizes the receiver with the originating source that
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created the image. Following the horizontal synchronizing pulse is the area known as the back porch. With the advent of color, the color burst signal was inserted in the back porch. The area betweenhorizontal sync and color burst on the back porch is called the breezeway. Following the end of the back porch, the active video scanning portion of the line begins.
Vertical Blanking
Vertical blanking is somewhat more complex. During the vertical blanking period, there are pre- and post-equalizing pulses and vertical sync pulses, as well as several lines of blanked video. These are full lines of video on which there is no active picture. The vertical blanking period can also be seen on a waveform monitor.
Vertical Synchronizing Pulses
Vertical synchronizing pulses, which are part of the broadcast signal, are used to drive the electron beam back to the beginning of the next field so that the horizontal trace can be initiated. There are six vertical synchronizing pulses that occur between fields to initiate this process. Vertical synchronizing pulses only occur between fields.
The horizontal blanking period can be viewed on a waveform monitor, which displays an electronic representation of the visual image (Figure 4.3A). (The waveform monitor is discussed in detail in Chapter 8.) Several critical synchronizing signals occur during this horizontal blanking period. These signals appear in the followingorder: the front porch, the horizontal synchronizing pulse, the breezeway, and color burst reference (see definitions of these terms below). The breezeway and color burst reference occur during the period of time referred to as the back porch.
The front porch is the period of time that begins at the end of active video. It initiates the retrace and is the beginning of the synchronizing period of time. A single scan line is defined as starting at the front porch and ending with active video before the next front porch begins.
Following the front porch is the horizontal synchronizing pulse. This pulse synchronizes the receiver with the originating source that
created the image. Following the horizontal synchronizing pulse is the area known as the back porch. With the advent of color, the color burst signal was inserted in the back porch. The area betweenhorizontal sync and color burst on the back porch is called the breezeway. Following the end of the back porch, the active video scanning portion of the line begins.Vertical Blanking
Vertical blanking is somewhat more complex. During the vertical blanking period, there are pre- and post-equalizing pulses and vertical sync pulses, as well as several lines of blanked video. These are full lines of video on which there is no active picture. The vertical blanking period can also be seen on a waveform monitor.
Vertical Synchronizing Pulses
Vertical synchronizing pulses, which are part of the broadcast signal, are used to drive the electron beam back to the beginning of the next field so that the horizontal trace can be initiated. There are six vertical synchronizing pulses that occur between fields to initiate this process. Vertical synchronizing pulses only occur between fields.
1 comments:
When multiplied by 13.5 MHz sample clock, the info for NTSC would be:
- Horizontal blanking: 147 pixels
- Front porch: 20 pixels
- Horizontal sync: 64 pixels
- Breezeway: 8 pixels
- Burst: 34 pixels
- Back porch (total): 63 pixels (including breezeway and burst)
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