Software: MediaInfo

Currently, MediaInfo is probably the best free & open-source utility for extracting technical info (metadata) from multimedia files (most frequently, containers with audio and video streams).
It's quite portable (runs on various Linux distributions, MS Windows, Apple Mac OS X, FreeBSD etc.; released regularly in source and compiled binary forms) and comes with CLI and GUI interfaces.

External links:

• MediaInfo on MediaArea (official website)
• MediaInfo on SourceForge (project page)
  • (redirect to the official website)
• MediaInfo - Wikipedia