video Understanding a media presentation
Remarks
Video playback is front and center in a large range of modern solutions, with the software and standards evolving rapidly. To understand what makes up a media presentation, you must first understand the multiple aspects involved in working with video:
- Raw color information captured from the physical world is commonly encoded using a codec - an algorithm whose purpose is to represent this data in a compressed form, often sacrificing some visual detail in favor of greater compression.
- For playback, the inverse algorithm is executed - the data is decoded to once again become raw color information that can be supplied to an output device (e.g. a monitor).
- Between encoding and decoding, the compressed data is packaged for storage, which may involve combining tracks of different types into a single file or the segmentation of content into a large number of small segments.
- The video is delivered to the end-user's device using a delivery technology, which can be as simple as a file download over HTTP or considerably more complex, involving live feedback from the network infrastructure and automatic adaptation of quality levels.
- Premium content is usually encrypted before packaging and can only be played back in a player equipped with a DRM technology that ensures decryption key security during use and actively protects against output capture.
While the visual portion is obviously dominant in visibility, audio and text also play a key role in media presentations, providing multilanguage features that make content accessible to a wide audience. In most workflows, audio and text tracks are handled in a manner equivalent to video tracks, being encoded, decoded, packaged and delivered along the same lines.
All of these aspects - and more - impact the composition, formatting and use of a media presentation. They must be understood as a whole in order to make effective use of media technologies.
