There are several main sources for the high-definition version published online now:
First, Blu-ray and HD-DVD discs have 1080P progressive scanning, which is what we now call full HD (1920× 1080), and another is 1080i interlaced full HD.
The second is obtained by recording HDTV signals.
The third kind is taken by individual HD enthusiasts with their own HD cameras. Now there are a lot of high-definition camera equipment for sale in digital stores.
Do you know the HD Alliance Forum? This is a famous forum for HD enthusiasts. They like to post many high-definition movies and videos on it. At present, many online high-definition movie resources such as Thunder are generally produced by film and television exchange forums for members to communicate.
At present, there seems to be no software to restore DVD to 1080P. If there is, the cost is very high, and businesses will not do business at a loss.
In the 1980s and 1990s, the resolution of film was still very high, as long as your film quality was good.