One of the most common questions about Blu Ray and DVD is, Whats the Difference? and the truth is that there are several. Just as the digital disc replaced VHS tapes with better sound and sharper image quality, the Blu Ray is expected to replace the DVDs with better audio and visual performance and more.

To start, the storage capacity of the current single layer DVD is 4.7GB, and the dual layer is 8.5GB. The Blu Ray discs have 25GB and 50GB, respectively. More storage capacity means more of the movie can fit onto one disc, and there is loads more room for bonus features and interactive extras on the BD (Blu ray) disc. The laser wavelength of the digital video disc (DVD) is 650nm (red laser) while the BD is at 405nm (blue laser). Both kinds of discs have the same diameters and the same thickness, at 120mm and 1.2mm respectively.

What many find interesting about the difference between the DVD disc and the Blu ray format is that while the DVD has a protective layer that is 0.6mm thick, the BD has a layer for protection that is only 0.1mm thick. However, while the digital video disc has no hard coating to help protect it, the BD does. There is a difference in track pitch in the two kinds of formats; the Blu ray has a track pitch of 0.32 ?m while the DVD disc has a track pitch of 0.74 ?m. In addition, the BD has a data transfer rate for downloads of 36.0Mbps (1x) while the digital video disc has a data transfer rate of only 11.08Mbps (1x). For audio and video transfers, the transfer rate for BD is 54.0Mbps (1.5x) and the audio/video transfer rate for the digital disc is only 10.08Mbps (<1x).

There are more differences between these two popular formats as well. The video resolution for the Blu ray format is 1920x1080, or 1080p, while the max resolution for DVDs is 720x480/720x576, or only 480i/576i. The video codecs are much more expansive on the BD as well. While both formats have video codecs of MPEG 2, that is all that digital discs feature. The BD, however, also boasts MPEG 4 AVC and SMPTE VC 1.

The video bit rate on the Blu ray format is 40.0Mbps, while the DVDs trail way behind at only 9.8Mbps. As far as audio goes, the audio codecs for the two formats are somewhat similar, but once again BD beats digital. They both have linear PCM and Dolby Digital, but while that is the extent of the capabilities for the DVD, the Blu ray also includes Dolby TrueHD, DTS Digital Surround, and DTS HD.