Blu-ray is similar to PDD, another optical disc format introduced by Sony in 2003, but has a higher transfer speed: 88 Mbit / s, compared to only 36 Mbit / s for Blu-ray disc. To achieve this performance PDD uses advanced technology and expensive, which makes its market is limited to information archiving applications by companies, while Blu-ray is addressed much broader market of households.
Blu-ray’s main rival is HD DVD format. Like the DVD was the rival to VCD, and every one tried to use DVDs to store VHS movies using vhs to dvd.
On a 50 GB Blu-ray can store about 9 hours of video in HD (high definition) or approx. 23 hours of video SD (standard quality).
On average, a single-layer disc can store 135 minutes of HD video using MPEG-2 encoding and additional space can be used for 2 hours of footage of “bonus” with standard quality. A double layer disc will extend this number up to 3 hours in HD quality and 9 hours of bonus material in standard quality (SD).

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