BD and DVD both have dips and bumps. The difference between the two is that the dips and bumps in BD are smaller and closer together. A blue laser is used to read the comic. The BD has spiral tracks running from the center of the disc to the edges. Information is stored in these tracks in audio and video form. The blue laser used to read this information has a wavelength of about 405 nanometers and must be much more precise than that of a DVD because the dips and bumps are smaller and closer together. Figure 2: Different lasers reading a DVD and a BD. Figure 2 shows an image of a DVD and a BD. As can be seen on the DVD, the dips and bumps are larger and the laser is therefore less precise than that of the BD. Blu-Ray disc can run MPEG-4 and MPEG-2 encoded formats. BD is also used for data storage, 1080p HD video and audio playback, 3D stereo and it has many other uses. DVD player is not only used to read the data present in a DVD but also to write the content to a DVD. As stated earlier, a DVD has dips and bumps like a BD in its tracks that contain information. This information can be video, audio or a mixture of both. When a DVD player reads this data, the smooth surface of the disc is read as "0" and the valleys are read as "1". It reads the DVD and converts the data into binary code. Unlike a BD, a DVD uses a red laser with a wavelength of around 600 nanometers. That's 180 nanometers less than a CD but 200 more than a BD. This allows it to have a higher density of pits and bumps than a CD but lower than a BD. Originally only single-layer DVDs were released, but later dual-layer discs were released. Single-layer drives can hold up to 4.7 GB of data and dual-layer drives can hold up to 17 GB of data. A DVD does not have the capacity to contain high definition movies. An MPEG-2 compression system is therefore introduced. As the data is used, it will be encoded onto the DVD as part of the changing images. This must be successfully decoded and decompressed by the DVD player..