video files are series of still images played in sequence to give a sense of motion. Depending on size, quality and frame rate the video size can vary.
Size – Let us take 1400 as width and 1000 as height.
Quality – If images take 4 bytes memory space to store one point or pixel.
Frame rate – For illusion of a video we show 30 still images in one second.
Going by above data a 5 min video will take 1400(width) x 1000(height) x 4(bytes for one point) x 30(still images in a second) x 60(seconds in a min) x 5(minute) = 50400000000 bytes or 49218750 kilo bytes or 48065.2 mega bytes or 46.93 GB of space on your storage media !!!!This is a whole lot of space even in this age.
Consider how much space a 3 hour movie will take. And what does this means if it has to be transferred over a internet connection.
To solve this problem one uses something called CODEC which is acronym for COmpressor – DECompressor. We compress the video and then the player must understand the same logic for decompressing in order to play it. CODEC either compress the whole of individual images or use the fact that in most of the cases images in video depends on previous image. And if we can find out the difference in subsequent images and we superimpose the differences over the base image then whole video can be re created.
And this explain the realistic sizes of video files and the fact that we are able to see so much video on the web sites…