Avidemux

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Avidemux is a free open-source program designed for multi-purpose video editing and processing, which can be used on almost all known operating systems and computer platforms.Avidemux is a simple tool for simple video processing tasks. It does not offer tools like a timeline, multi-track editing, you cannot freely move or splice audio and video clips from various sources. However, Avidemux allows you to do elementary things in a very straightforward way.

When you open a video file using the Open button (Ctrl+O) on the main toolbar, there are 3 basic things you can do with it in Avidemux: 

• Cutting:
  Why: For example, cutting out ads from a TV recording, or saving only a small part of a video you are interested in. How: Select a portion of the video with the mark A and mark B buttons, and either delete, copy, paste or save that part. If you do not reencode the video (that is, if the encoder is set to Copy), make sure all segments start with keyframes, or the resulting video will be broken at cut points. See the Cutting chapter for more details.
• Encoding:
  Why: You may want to convert the video to a different video format that your hardware or software players understands, or you just want to compress the video to a smaller size, for archiving or publishing it on the Internet. How: Encoding in Avidemux means selecting an encoder that does the video compression. That is, the drop-down menu on the left cannot be set to Copy. See the Main window chapter for more details.
• Filtering:
  Why: Basic filters applied to the picture like deinterlacing or resizing come in handy for various format conversions. Other filters may be used for adding subtitles to the picture, color correction etc. How: Filters require reencoding. So you have to select an encoder first, then you can add filters using the Filters button.