Composite literally means ‘made up of various elements’. CVS
has various elements like picture levels, sync pulses, etc. There are 4
types of CVS viz.:
1. CVS
for pedestal height
2. CVS
for blanking pulses
3. CVS
for horizontal sync detail
4. CVS
for vertical sync detail
Make sure you read the CVS in the order given above. Links to different CVS is given at end of this explanation.
If
in exam, a question comes as ‘Explain CVS’ then depending on the marks, explain anyone that you want to
explain. For 5 marks, write any from first three. I’d prefer first one as it’s easy whereas if the question is for 10 marks, go for the 4th one. The one that is explained below is the
first one.
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A video signal is nothing but sequence of images stitched together. A CVS contain many video signals which means a CVS has different brightness levels depending upon the scene.
As
video signals have various images, it is obvious that they will have various
colour components. So in a video signal, the maximum whitness to be handled is
known as Peak White level. This level is situated at 12.5% of the maximum value
of the signal. For example if a signal having 100 volts amplitude is
transmitted, then the peak white level for that signal will be at 12.5% of 100
= 12.5 volts.
Just
like the white level, a CVS has black and blank level also. Black level is at
72% and blank level is at 75% of the maximum value of the signal. The
synchronizing pulses, pulses that are used for keeping the horizontal and vertical oscillator in sync, are added at the blank level. The black level is used
for separating the blank level from the picture information.
The
difference between black level and blank level is known as pedestal and the
difference between pedestal and DC value of the signal is known as the pedestal
height. DC value of a signal is nothing but the average value of that signal.
To further elaborate the answer, you'll can add the details of horizontal and vertical sync pulses by stating their time duration, trace time, etc.
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ReplyDeleteNice work boss..in text this portion too difficult to understand . i used the same text .. but they elaborated a long till no one can understand nothing.. good job .. tnx
ReplyDelete