Media items can be found easily from the Internet, it doesn't mean it is legal to use it without permission. Beware of the videos/images may have been uploaded to a website without the copyright owner's permission, this is an 'infringing content' and should not be re-used.
Find and use media items which are copyright-free or released under a Creative Commons License that allows non-commercial derivative use.
Or, find and use material that you have paid for.
"This library contains digital movies uploaded by Archive users which range from classic full-length films, to daily alternative news broadcasts, to cartoons and concerts. Many of these videos are available for free download"
Browse the Creative Commons licensed videos on Vimeo. Learn about what you can and can't do with other people’s videos on Vimeo to help you share, rework and reuse legally.
If you are going to limit the use YouTube video with Creative Commons license, please:
A non-profit organization enables sharing and using of creative materials
"Download thousands of historic media files for your creative projects" -- Registration is required
Click "Tools" > Selects"Usage rights" > Select license
"Many Flickr users have chosen to offer their work under a Creative Commons license, and you can browse or search through content under each type of license".
Patent Information Library Guide
This LibGuide provides general information about patent such as what is a patent, where to apply it in China, Europe, Hong Kong SAR and USA. It also lists the useful databases and internet resources.
"This library contains recordings ranging from alternative news programming, to Grateful Dead concerts, to Old Time Radio shows, to book and poetry readings, to original music uploaded by our users. Many of these audios and MP3s are available for free download"
"The music is absolutely royalty-free. Our artists are not members of collecting societies (like GEMA, SUISA....) and the music is therefore not registered there. Our artists upload their music under a Creative Commons license."
"Freesound is a collaborative database of Creative Commons Licensed sounds. Browse, download and share sounds" Includes sound effects.
Has a good collection of attribution-only or inexpensive music. Excellent search interface by "mood", tempo, etc.
Classical music - lots of it creative commons licensed (no charge) for non-profit use
Sound effects - thousands for free, mostly attribution only.
"You are allowed to use the sounds on our website free of charge and royalty free in your projects but you are NOT allowed to post the sounds on any web site for others to download, link directly to individual sound files, or sell the sounds to anyone else." Read the Terms of Use before using.
There are some sources of "stock music" sites that sell music, but often not "famous" artists. You can search by genre or style of music and then check on the price of the licenses (prices seem to range from USD 5 to higher).
In Hong Kong there are a number of licensing groups you can try to contact; but they are not instantaneous. You may need a few weeks to settle the licensing issues.