13 December, 2005

Whats there in a VCD, DVD?

Digital video knocks you in different forms day-in and day-out. You have a VCD player, DVD player, DVD combo drive in PC, blah,blah, so many digital gizmos are available around us. Whats driving this industry? Lets take old days video, where we capture an image sequence in casette. Play it with VCR player. No trouble in it. Quality OK! Then came this new world, where contents are required to be available in all gizmos including ur tiny mobiles. So moving from analog to digital domain become inevitable. Suddenly all headaches arises. An analog image say a frame, when converted to digital domain, takes huge space. For example, your computer screen size image takes 460 KBytes (Dont get whats bytes measure all about, forget it). You can save 3 such frames in one floppy or 1500 frames in a CD. But you know what- 30 frames of image is required to be played in a screen to make it look like a real movie. (TV frame rate is 30). With 1500 frames which we stored in a CD, we can play it back for just 50 secons (not even a minute!!!). So....... how is that we can able to see a movie of 3 hrs duration stored in 2 VCDs or in one DVD. This magic is done by what we call coding and decoding. Video coding is logical science, can be picked up by any new entrant. Lets see an image sequence, you can see the adjacent frames of images dont change much other than few movements here and there. (Take for example, sequence of images of bird flying....most of the frames, the background gonna be sky, which remains almost stable, whereas the small bird alone change its position in continous frame). Got the place where we gonna hit the video codec?! This tells me that I need not transmit all background data again and again, I can post only the data which changes across frame. ( Wow, looks simple. Isnt it?) Video codecs born out of this simple catch. Now it has devolped into many generations. VCDs are first generation aka MPEG1, DVDs are second generation, aka MPEG2.....(btw, I am working in 4th generation and latest video codes in industry ;)) Most of the business in this industry revolves around the different algorithms implementation for different embedded devices. Electronic device makers buy different implementation from small players to big ones. [+] check this wiki entry


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4 comments:

karthik m said...

as all u techno savvy professionals keeps on advancing ur video codings and compressions... it will be a great boon for the movie freaks like me... with the entry of dvds(divx)... i would havent ben introduced to great movies(which will never hit the indian screen)... thanks to u IT people... and more thanks to movie pirates of the paris corner!!!

Nirek said...

ha ha ha....
dont see in pirated CDs da! our CM can arrest you in Kundaa's act! :)
video coding as such is very interesting science!

Ghost Particle said...

wow! okay, i have to confess, i neve knew that!

Nirek said...

@gp, Thanks bro!