Freesound Forums

How legal is get sounds parts of videos in internet. (no trailers or videos with designed sfx audio or music)
You go to a random video and record for example the birds sound or a weapon sound or other ambient sounds.

Example:
You go to random FPSRussia video for example this "https://www.youtube.com/watch?v=RSbNjXnLg5M" and go to 2:16 - 2:18 and get that weapon sound, now you edit the sound for example in audacity and use the sound/sfx in a commercial video game.

If you don't have permission to do this, then it is illegal. Unless the recording is described as in the public domain.

Permission could come in the form of a notice by the creator in conjunction with the media that expresses the usability of their recording. Or it could be that you have wrote a letter to them asking for permission. If no permissions are granted, then we have to assume that the recording is protected by copyrights.

Here's the grey area though... Copyrights expire after a certain amount of time based on whether the author has died, which means some material succumbs to the public domain:

In most other countries that are signatories to the Berne Convention, copyright term is based on the life of the author, and extends to 50 or 70 years beyond the death of the author. - Wikipedia.org