We have been using High Definition in our vocabulary quite often. High Definition Television sets have been becoming most common in our homes. But, how many of us actually know what exactly it means? High Definition generally refers to a video of higher resolution than a standard. Any image with at least 720 horizontal lines is considered a high definition image. Any video which has lines more than 480 lines and less than 720 lines is called Quarter HD or qHD. A high definition television or computer monitor is required to view a high definition signal.
A regular digital television has 480 lines and a high definition television will have 720 or 1080 lines offering clarity and smoothness of images and video. There are basically two types of scanning system prevalent when it comes to high definition namely: progressive scanning denoted by p and interlaced scanning denoted by i. The Progressive scanning, while refreshing each image, redraws the entire image frame i.e. all the lines. The interlaced scanning refreshes the image in two steps. In the first image refresh operation, it draws the image field with odd numbered lines and in the second image refresh operation, it draws the remaining even numbered lines. While the image resolution is higher in case of interlaced scanning when the subject is not moving, the resolution is affected in case of moving subject.
Two interlaced fields form a single frame. When an interlaced video stream is used to transmit full frames, the techniques used are segmented frames and frame pull down. Number of frames or fields per second is denoted by Hz. A high definition signal with 1,280 × 720 pixels and progressing encoding with 60Hz is denoted by 720p60. It is not necessary to always specify a frame with a resolution. 50i refers to 50 interlaced fields per second or 25 progressive frames per second. Field rate 24p means 24 progressive scan frames per second.
An aspect ratio is a proportional relationship between width and height. While a standard definition television has an aspect ratio of 4:3, high definition television has an aspect ratio of 16:9. All the online video streaming services offer HD video offering lifelike experience, smooth and crystal clear picture with no blur. High Definition is the need and demand of today’s world. Not only professional organizations, but it is used in every aspect of life. Embrace it and feel the change.
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