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Avidemux is a simple tool for simple video processing tasks. The keyword here is simple: it does not offer tools like a timeline, multitrack 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:

  1. 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.

  2. 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.

  3. 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. See the Video filters chapter for more details.

When you are done with cutting, setting encoders or filters, save the resulting video file using the Save button (Ctrl+S).

In addition, there are other small features you can use, like saving or replacing the audio track from the video, joining several video files or saving a snapshot of your video.

To encode or not to encode

Avidemux works in two basic modes: copy mode and encoding mode.

Copy mode

When the audio or video encoder is set to Copy, it means no reencoding takes place, and the audio or video track from the input file is just copied to the resulting file as-is. This means it is very fast (usually a couple of minutes at most), and there is no quality loss.

Use the copy mode when:

  1. you just want to cut out parts from the video, without changing the output format
  2. you want to append several files (using either File→Append or the automatic appending that Avidemux provides) – if the resolution (width, height), video format, audio format, audio bitrate and sampling rate is the same for all files, you can use the copy mode
  3. you want to fix constant audio/video desync (using the Shift option in the audio section)
  4. you want to perform technical changes like saving the video to a different container

Encoding mode

When you select an audio or video encoder, the audio or video track is reencoded. If the compression is lossy (with most encoders it is), this implies quality loss. Encoding is also much slower than copying. Depending on the speed of your computer, it can take hours to complete.

Use the encoding mode when:

  1. you want to perform audio or video format conversion
  2. you want to compress the file to a smaller size (at the expense of quality)
  3. you have to do precise cutting that's not possible to do on keyframes
  4. you want to use filters (it is impossible to filter audio or video without reencoding it)
  5. you want to join several files with differing properties (different formats, different resolution etc.)

Basic terms

Since Avidemux is a tool that does not do things automagically for you and only executes the steps you directly tell it to perform, you should really understand what you are doing and why. Before you use Avidemux, you should understand basic characteristics of multimedia files, such as:

  • Container format: audio and video tracks are stored in a single file, in a container. The container format does not influence the audio or video quality, it is only a way of storing video and audio in a single file. In Avidemux, the container format is selected in the (Output) Format section at the left.
    Note: Always select an appropriate container format for the file you are saving! See the Output formats chapter for more details. You should also add a suitable extension to the file name when you save the video, like .avi for the AVI container format, or .mkv for the Matroska container format. Avidemux version 2.5 or older does not add the extensions automatically!
  • Video format: this is the way the video stream is encoded in the file, usually in compressed form. Modern compression fomats usually offer better quality/size ratio than old ones. Common video formats include H.264, MPEG-4 Part 2 or MPEG-2 Part 2.
  • Audio format: the way the audio stream is stored in the file. Common audio formats include AAC, MP3, MP2, Vorbis or PCM (uncompressed).
    Note: Do not confuse audio and video formats with audio and video codecs. Codecs are tools used for encoding and decoding, while formats are methods of encoding the data. See the Common myths chapter for more details.
  • Encoder: this is a tool used for encoding the audio or video stream into the desired format. Some encoders are better than others – even if there are multiple encoders for the same format, one of them may offer higher quality at the same size. In Avidemux, you can select the software encoder in the Video and Audio sections. Of course, the selected encoder then implies the output format as well.
  • Decoder: a tool used for decoding the input video or audio stream. Avidemux uses internal built-in decoders. If it does not have an appropriate decoder for the video or audio format, there will be no video or audio.

So, what does this all mean? Let's see a couple of use cases:

  • You want to cut out unwanted parts from a video, losslessly (in copy mode). You have to know the source audio and video format. Avidemux can show you the file properties using the Info button after you open it. Then you select an appropriate container format that's suitable for the video and audio format combination (typically the same container format that's used for the source file), leave audio and video encoders at Copy, do the editing, and finally save the file.
  • You have a Matroska (*.mkv) file with H.264 video and AAC audio. The Matroska container format is not supported (and therefore not playable) by default on Microsoft Windows, Mac OS X (without additional software) or various hardware devices, but H.264 and AAC is! This means you can open the file in Avidemux, change the output format to MP4 (which is the container format supported by default on those platforms), and save it in copy mode. Audio and video tracks will be left untouched, so it will be quick and lossless. Only the wrapper, the container, will be different. If the H.264 video was encoded with basic features supported on those platforms, the file should now be playable there.
  • You have a video saved from a DVB-T recorder, DVD or other sources and want to archive it in a more compact form. So after you open the file and do some editing, select a video encoder with the best quality/size ratio, that is x264, configure it, add video filters like deinterlace, crop and resize to make the video more compressible, select Matroska or MP4 as the container format and save the file. You may even save the original audio track in copy mode if you want to avoid any quality loss, as audio in DVB-T or DVD is already compressed and does not take as much space as video.
using/quickstart.txt · Last modified: 2012/11/11 08:51 (external edit)