Hello friends!
Welcome back. We hear the word video many times in our day to day life. We use it and enjoy it. Have you ever thought how these video are created and how it is possible to move a picture? Let us try to understand basics of video.
You all have seen photos, these are called still images. If these are brought in front of your eyes at very fast rate one after one with some mechanism it gives illusion of movement i.e. we will see these still images moving. These still images are called frames in technical language & rate at which these are shown is called video frame rate. Human eye is capable of seeing less than 25 different images per second, so video having rate more than 25 frame per sec. will be experienced as smoothly moving as we saw in movies. If a video displays less than the speed it will appears to be jerky i.e. interrupted as you experience when seeing a scratched and old CD.
There are three standards of video prevailing in world. These are 1. PAL (Phase Alternation Line) with 25 fps (frames per second) for Analog Video 2. NTSC (National Television System Committee) with 30 fps. PAL video format is widely used all over the world for TV signals. In the USA NTSC is being used. Third standard is Secam and it is less used for TV Signals
. You might have seen these words while changing setting of your Television set or VCD/DVD players.
The video is categorised in two types i.e. analogue and digital. Analog Video transmits and stores video data in continuous wave form (also called sinosuidal wave i.e.that can have any value at any instant) of red , blue and green, (RGB) colours. These colours are called primary colours as any colour can be obtained from the combination of these colours. To display changing images in TV , the signal is varied using different frequencies of each colour's wave. Analog video data is more prone to distortion.
In digital video analog signal is converted into two binary digits (0,1) as modern computerized devices can understand binary only, stored & displayed on screen repeatedly at very fast rate i.e. refresh rate. In this way we can say that digital video is the computer's understanding of analog video. However these days some application like games can be developed using digits directly i.e. analog signals are not required.
In our next post we will try to compare both these types of videos. Enjoy happy reading and viewing good videos till then. Don't forget to comment how you feel about this post. If you liked it, email to your friends also.
Rajesh Kumar
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