BD and DVD both have pits and bumps. The difference between the two is that the BD pits and bumps are smaller and packed closer together. A blue laser is used to read the BD. The BD has spiral tracks running from the center of the disc out to the edges. The information is stored in these tracks in the form of audio and video. The blue laser used to read this information has a wavelength of approximately 405 nanometers and must be much more accurate than that of a DVD as the pits and bumps are smaller and closer together.
Figure 2: Different lasers reading a DVD and BD.
Figure 2 present an image of a DVD and a BD. As can be seen on the DVD, the pits and bumps are larger and so the laser is less accurate than that of the BD. Blu-Ray disc can run formats that are encoded in MPEG-4 and MPEG-2. BD is also used for data storage, playing 1080p HD video and audio, 3-D Stereophonic and it has many other uses.
The DVD player is not only used for playing the data present in a DVD, but also to write the content onto a DVD. As told earlier, a DVD has pits and bumps like a BD in its tracks which hold information. This information can be a video, audio or mixture of both. When a DVD player reads this data, the smooth surface of the disk is taken as “0” and the pits are read as “1”. It reads the DVD and converts the data to binary code. Unlike a BD, a DVD uses a red laser with a wavelength of roughly 600 nanometers. This is 180 nanometers less than a CD however 200 more than a BD. This enables it to have a higher density of pits and bumps than a CD but less than a BD. Originally only single layer DVDs were released but then double layer discs were later released. Single layer discs can hold up to 4.7 GB of data and double layered discs can hold up to 17 GB of data. A DVD does not have the capacity to hold hi-def movies. So a MPEG-2 compression system is introduced. As this is used, the data will be encoded onto the DVD as elements of the changing frames. This has to be successfully decoded and decompressed by the DVD player.
CD has the capacity to store audio, images and data. Standard CDs have a diameter of 120 millimeters and can hold up to about 80 minutes of uncompressed audio or 700 MiB (actually about 703 MiB or...