Saturday, July 25, 2015

The high's and low's of videos

Everyone knows that a compressed image pixellates when enlarged, and that a compressed video doesn't look that good when seen on a larger screen. There is actually a very simple logic at play here. The reason is actually very simple...

(Image source: http://www.generalforum.com/images/hosted/bluray_vs_dvd_vs_vhs_01.jpg)


When we shoot one hour of full HD video, the frame size is 1920 X 1080 pixels, and the space occupied on the hard disk after it is transferred is about 50 GB. With SD footage the frame size is 720 X 576 pixels for PAl video (Standard Definition - fast becoming outdated) the captured video on the hard disk is about 12 GB. Of course it all depends on the codec you use for capturing the video.

The HD video is vibrant, crisp, and beautiful looking on your editing screen. If we make a blu-ray disk after the edit, it is almost as good as the original raw format because you can tranfer the edited video almost in its original format. The capacity of the double layer blu-ray disk is about 50 GB. So you can have a 2 hour movie in high resolution, maintaining most of its original richness.

So what happens in other formats?

The capacity of a VCD is 700 MB. Imagine what must be happening to the HD data and hence, its quality when you compress 25 GB to 700 MB! You have reduced the data to less than 3% of the original! Its like eating a sweet with very very less sugar. Besides, the frame size of a VCD video is 352 X 288 which is again less than 1/4th of the original 1920 X 1080. A DVD has a capacity of 4.7 can fit in a 2 hour PAL format movie with the frame size of 720 X 576 pixels. Though the picture quality if a DVD is much better thatn that of a VCD, you are still getting only 1/10th of the data. A little more sugar than the VCD sweet, but still, not the full dose.

What about online videos? Well, with the technology advances, we can view very good quality videos online, but they are still compressed enough to allow for streaming on the Internet. For a mobile phone, they are still compressed and a 3GP format will look horrible if blown up on a larger screen.

It's simple then, isnt it? More compression - less data - smaller file size, and bad picture quality. Do watch out for my upcoming video on resolution.