Why are DVDs limited to 2 hours?
Technically there is no limit to the amount of video which can fit on one DVD. By definition, the video signal must be digitally compressed before it is placed on the disc. By controlling the compression of the video signal, you control both the quality and amount of video which can fit on a disc. But there is a pretty steep trade-off. With higher compression, more video can fit onto a disc, but it will be of a lower quality. Conversely, for the highest quality video, the lowest compression setting must be used, which also limits how much video will fit. Fitting two hours on a disc balances the two considerations. The video is still of a very high quality.
