According to copyright, changing mediums, say from VHS (videocassette) to DVD or streaming, is considered a derivative work. This is one of the privileges for holding copyright.
Here is an example. Suppose you want to digitize the library film The Secret of Marcel Duchamp. The library has it on VHS and you want to either make online clips for your home folder, or at least put it on DVD.
The first step would be to see if there are any license restrictions. Licenses can be more restrictive than copyright. In most cases, however, you are not going to find a license that discusses changing format. At this point you have to consider the issue of derivative works. If this VHS is available in the medium you want, then you would need to purchase it.
However, what about films that haven't been reformatted? Depending on how you use the film, you may be able to make a claim of fair use. There is one other possible argument, and that would be to create an archival copy if the medium is in an obsolete format. VHS is now considered obsolete, so that may be an option. There are likely to be restrictions on how this could be used.
Downloading media -
The issue with P2P sites is that the files are often illegal copies and represent a copyright violation.
How can I get caught?
When you use such services as BitTorrent and peer to peer
(P2P) to download and upload files, you are not anonymous.
Whenever you connect to the network, your computer is assigned
a unique IP address. This unique IP address is used to identify
your computer as the source of available files to all other
computers on P2P or BitTorrent. P2P allows your computer to
exchange files with other computers that are running similar
software. BitTorrent is a client-server service using a group
of computers called a “swarm” uploading/downloading
the same file. Files you download/upload can be traced back
to you.
How do I prevent copyright infringement?
If you have P2P or BitTorrent software installed on one or
more of your computers connected to the Internet, delete it,
or if you have a legal reason to use the software, delete
any unauthorized files in your "shared folder."
Also be aware that file sharing is one of the easiest ways
to send and receive viruses and/or spyware that will adversely
affect the performance of your machine and others on the network.