How do they do it?
These days, a DVD player can be bought at any Wal-Mart or CVS for 15 to 20 bucks, but it wasn’t too long ago that people still needed to pay upwards of $300 to get their hands on one. So, how do these modern staples of film-watching and game-playing actually work? They’re actually surprisingly simple devices that are refinements of the original starting technology of the CD player from the 80s.
Optical media isn’t a new idea, per se; people had these discs since 1958, when David Gregg first established the patent for them. However, the idea of a DVD only came about when the size of the laser was adjusted and focused to make it capable of writing and reading in an even smaller amount of size on the disc. But that’s just the disc; let’s get to how the player actually works.
It all starts when you put the disc into the tray. If your tray is an opening and closing tray, it works with a small motor that pulls the tray in and sets the disc into the guide in the middle of the drive. If it’s a slot-loading tray, a more sophisticated “squeeze” system pulls your DVD in and locks it into place over the same guide as before.
Once your DVD is in the guide and everything’s been checked, the DVD is lifted by the guide and spun at incredible speeds. How fast, you ask? Somewhere between 600 and 2000 rotations per minute (RPM) – at the center, just due to physics, it spins faster than on the outside edges.
The DVD, now spinning, is exposed to the laser, which is shot onto the bottom side of the disc. There, the laser will reflect in two distinct ways, signifying a zero or a one. This reflection is detected by the disc drive and is relayed back to the processor, which then goes about interpreting the information.
Once the information goes through the processor and is properly interpreted, the signal is set out to the appropriate transfer cable. This means that for your component cables each take care of a specific part of the signal. The red cable receives the proper burst of red colors, similarly so for the green and blue.
In this way, a projector or television is able to only display the proper set of colors that correspond to the media on the actual disc. As amazing as that sounds, even the most nuanced of colors can be reproduced using those three basic colors found in a standard component cable.
The colors, which are sent out in the signal as bursts of different colors for every frame the picture is on-screen, are able to create elaborate images due to the amount of pixels located on the screen and the interlacing found in the video.
This is why, when people mention 1080p, or 1080 progressive scan, they’re talking about the way the screen is scanned and how many pixels are available. Specifically, at 1080p, you’re talking about a 1920 x 1080 resolution, resulting in a total number of pixels of just a little over 2 million on screen at a time. Each one of those is dependent on the video signal to tell it whether to be green, red, blue, or newer variations of cyan, magenta, etc.
Once the video is on-screen, the DVD also reads the audio, whose track runs along the same length as the DVD’s video track. This way, the audio and video are synchronized precisely. And that is how a DVD player takes the information stored on the disc and relays it back onto the screen along with audio.
For more on the basics of Home Theater technology read:
How to Burn AVI Files to DVD?