Image Processing Reference
In-Depth Information
Files and Storage Formats
Packing Your Bags
Squeezing everything you're bringing into your suitcase before a trip is not always easy.
There's always more that you want to put in, and before long it is overstuffed. Part of the
art of trouble-free travel is about packing what you need and not taking anything extra-
neous. The same is true for storing video in files effectively. A well-defined and structured
file format gives you everything you need without having to deal with loads of things that
you don't want.
Now Where Did I Put That Clip?
Movie data is often embedded into an interactive package or streamed over a networked
connection. At some time in its life, the video will be stored in a file container unless the
stream session is being encoded live. Some systems might create temporary structured
storage in memory that resembles the format used for file-based storage. The streamed file
may be stored at the receiving end by the client application.
This chapter looks at file structure and size and the implications of different kinds of
file-based storage. Choosing the right type of file ensures that you output files that are eas-
ily imported into other tools. Later on, Chapter 29 examines storage systems as part of the
systems-building process.
Basic Concept of Storing Video in Files
People have been storing video in files for a long time. In the very earliest days, the files
were just a digital version of storing the video on an analog tape. The file structures were
vestigial and the content was just a stream of video-intensity values. Storing video like this
takes up a lot of space because it is not compressed. In addition it is hard to edit the video
other than in a linear way. Storage like this is not very different from a straightforward
waveform recording. It is much like an audio track that is recorded as a series of samples,
except the video has a far higher sample rate.
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