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How can we look the same, but be so different? DVD vs Blu-ray

A guest blog from Eber Legarreta of YesVideo consumer services addresses the issue of Blu-ray. With the recent discontinuation of the Sony VRD-MC6 and VRD-MC10 DVD recorders and a move by Sony to a Blu-ray recorder, VBD-MA1, we thought this article may be of interest to the Legal Videographers that read the YesLaw blog.


How can we look the same, but be so different?

The differences between a DVD and Blu-ray disc

Authored by: Eber Legarreta, YesVideo consumer division 

Side by side, DVD and Blu-ray discs look identical. The main visible difference is the color on the bottom recordable surface of each disc. A DVD is bluish purple, and a Blu-ray is dark gray. While they may look the very similar, these two disc formats are unique in their capacity and function.

Disc Capacity

Capacity is one of the main differences between the two disc formats.

Single layer DVD:              4.7 GB

Single layer Blu-ray:        25 GB

Both discs are 8 cm in diameter, but a Blu-ray disc can hold five times as much information as a DVD. This is due to two key characteristics of each format –the compression of the information stored in each disc, and the laser that reads each format.

Data Compression – packing it all in!

A Blu-ray disc stores data in a far more compressed space than a DVD disc. Ever packed luggage for a long vacation? Pile all your clothes in one suitcase, and the zipper barely closes – that’s a DVD. Fold, organize and compress the same pile of clothes in the same suitcase. You have room left over, and the zipper closes just fine – that’s a Blu-ray disc. This compression (at a microscopic scale!) is what allows a Blu-ray disc to hold so much more data than a DVD.


The Lasers – Red vs Blue

Due to the compression of data in Blu-ray, the laser required to read these discs also needs to be more concentrated. The red lasers used to read DVDs can’t read Blu-ray discs because they are not concentrated enough to process the tiny data particles of a Blu-ray disc. This is similar to trying to read very small text without a magnifying glass.

The blue lasers used to read Blu-ray discs are focused to read the compressed data, as well as the data on a DVD disc. This is why most Blu-ray players are able to play both DVD and Blu-ray discs, but DVD players are limited to only playing DVDs.


So…Blu-ray is the best format, right?

Overall, Blu-ray is a major upgrade over DVDs and there are many technical details to support this.

From a video standpoint, they allow the storage and playback of large, rich, high-definition video – which looks amazing on an HD display. However, not all video is recorded in high definition.

For all the standard definition video out there (which is the majority of personal video recorded before 2008), DVD is a perfect media format. SD video doesn’t require the capacity and HD-playback capabilities of a Blu-ray disc. And while Blu-ray and HD televisions have recently become more affordable, not everyone has the equipment to play Blu-ray discs.  (YesLaw note: The Sony VBD-MA1 records DVD in addition to the added capability of Blu ray).

So hold on to your DVD players. Whether they are on your living room or your computer, DVDs have not gone away just yet.

Brian Clune has over 24 years in court reporting and legal support services. His focus is on the development and adoption of new technology to better serve clients in the legal sector. "Compete with better service and with new services that better serve clients."

Posted in Legal Video

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