Apple Final Cut Express HD - Manual (Page 981)

Chapter 70 Learning About QuickTime 981
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How Is Information Stored in a QuickTime Movie?
QuickTime movie files store media data in separate tracks. You create a QuickTime
movie file by adding tracks that point to the media you want to use. The media may be
embedded in the file itself or in a reference movie in another file. This track architecture
is powerful and flexible, allowing you to store and synchronize multiple pieces of video
and audio media in a single file.
There are many types of tracks allowed in a QuickTime movie file. Here are a few
examples of what might be included in a QuickTime movie file used by
Final Cut Express HD:
 An audio track: This track contains audio media data of a certain duration, encoded
with a particular audio codec, sample rate and bit depth. The track may be mono or
contain two (stereo) or more interleaved channels of audio samples.
 A video track: This track contains video media data (a number of video frames) of a
certain duration (determined by the track’s frame rate), with particular horizontal and
vertical dimensions, and encoded with a particular video codec.
 A single still image: This track contains media for a single still image. The image
data has particular horizontal and vertical dimensions and is compressed with a
particular codec.
 A timecode track: A track that contains a number count and frame rate that
corresponds to the video frames in a video track. This track can be captured from a
video tape or created later in Final Cut Express HD.
 A text track: This track contains text information that changes at specified times. A
text track could contain subtitles, or marker notes about a video or audio track.
Codecs Supported in QuickTime
Because the QuickTime file format is so flexible, practically any kind of media can be
stored in a track of its kind. However, in order to play back media stored in a track, the
QuickTime framework installed on your computer must be able to recognize the type
of compression (codec) used to encode the data.
Compression is necessary for video and audio storage on computers because the data
rates would otherwise be prohibitively high. And no matter how large computer
storage devices become, compression is still desirable because it means faster transfer
time and storing more information with less data.
The QuickTime framework libraries support a remarkable number of video and audio
codec (compressor/decompressor) algorithms. The QuickTime frameworks are extensible,
so if a company invents a codec, the company can provide a QuickTime codec to support
it. Thus, if the media in a QuickTime file is not playing back because the format or codec
of the media is not recognized, you may be able to download and install it.