Copyright, IPR and Consent
Digital media makes it very easy to copy video and audio clips and distribute them across the Internet. If you are going to do this you need to make sure you are not in breach of copyright, otherwise you could be breaking the law and liable to prosecution or a large bill for royalties
In general, unless a web site explicitly says that the content is copyright free, then you need to obtain permission before you download anything for reuse. However, if a clip is viewable from a web address (URL) without having to enter a username and password, then you can put links to it from your own material. What you cannot do is download, copy, edit or further redistribute it. There is a lot of software available that makes it possible to capture streamed media at high quality, however note that this is probably illegal.
Another issue with certain video material is consent. If you are distributing video material of your research subjects, members of the public, medical or veterinary patients, do you have the specific consent of the subject or their owner for the material to be distributed in this way? Normally this consent should be given in writing, signed and dated.
The laws governing these issues will of course vary from country to country, so you will need to seek further advice if you want to use material you have captured from the Web, digitised from a VHS tape, or that contains footage of people who may not have given consent for their image to be used in this way.