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Codec
A codec is a software component capable of performing encoding and decoding of digital data.
Multimedia data contained in movie files is transformed into audio and video by one or several codecs.
Whether you can or cannot read a movie file depends on the codecs that are installed in the system.
Container
A container is a file format used to store multimedia information.
Most popular containers are...
avi |
AVI (Audio Video interleaved) |
Often used with DivX/XVID/3ivx video and mp3/ac3 audio, but not limited to them. |
mov |
QuickTime format |
The most universal container, can contain any kind of media. |
mp4 |
MPEG4 |
Audio/Video or audio only, can contain a variety of codecs, but usually MPEG4-Video or H264 with AAC audio. |
mpg |
MPEG |
Can be either MPEG-1 or MPEG-2. MPEG-2 can be a Transport or a Program stream and contain mp2 or AC3 audio. |
For more details about containers, see Wikipedia Container Format page.
RefMovie
RefMovie stands for reference movie.
Saving RefMovie is like regular QuickTime format saving, but without "flattening". It means that SimpleMovieX doesn't copy the media data, just the recipe to describe the movie. You can think of it as a kind of playlist where you can specify which chunks of movies are played in sequence. The main advantage is speed and low file size, the main drawback is fragility as if you move or delete any of the referenced media data, the RefMovie can be lost.
Keyframe
Some video codecs use temporal compression, where a frame makes reference to several others. A keyframe is a frame encoded without reference to any other frame. In general there is one keyframe for every 15 to 30 frames.
In digital video editing, keyframes are important as they represent the points where a video stream can easily be cut.
SimpleMovieX displays them in the keyframe indicator. MPEG and AVI movies can be edited and later saved natively if the editing points are keyframes. (See definition of Native Editing below)
Native editing is the a workflow where media quality, format and container are kept.
If you open an AVI movie, edit it and save the result back to AVI with the same quality, you've done native editing.
If you open an mp3 file, edit it and save as mov format (QuickTime container), this is not native as the container is not kept.
If you open a DivX AVI movie, edit it and export it back to DivX AVI, this is not native as the media has lost quality in the reenconding phase.
SimpleMovieX can edit natively mov, avi, mpeg and mp4 formats.
Movie and Track
Movie is the generic term for any file that SimpleMovieX can open and edit.
This includes, for example, audio-only sequences.
Movies are made of one or several tracks, each track carries a certain type of media. To get a list of tracks, do File>Get Info
A movie can contains several video tracks and audio tracks. Other types of tracks include Chapter tracks, Text tracks, and MPEG tracks that combine video and audio in one.