Multimedia is the seamless integration of text, graphics, animation, audio and video in a digital presentation. Media files are created as a continuous flow of content. These presentations can be linear, progressing from start to finish with minimal user control (video, audio recording) or non-linear offering higher level of user interactivity and control (games or learning objects). Multimedia content can be a simple video or audio stream or a convergence of text, images, video and sound with interactivity into a single content file commonly called a "movie".
These days it is very easy to create text, images, audio and video footage. There are multiple commercial and open source devices and software applications that can be used for audio/ video recording and editing and to capture and synchronize audio, video, text, slides and images to build rich multimedia presentations. Video and audio recordings can be captured by cameras built into phones, webcams and sound cards on computers. In addition both Windows (Movie Maker) and Mac (iMovie) operating systems come with tools to create, edit and publish content in different audio/video formats.
There are many content specific editing and creating software, authoring and development frameworks to build presentations for publication and distribution. Example include:
Digital multimedia is a continuous medium is represented by bitrate (number of bits per unit of playback time). Raw audio and video files are very large requiring great deal of resources both for storage transmission. A codec (compress/decompress) is software utility with an algorithm to compress audio and video data stream for storage and transmission and decompress it for playback. The goal of codec is to maintain audio and video quality. Codecs are mostly proprietary with their own algorithm for compression/decompression.
The quality of the compression is identified as lossy or lossless.
Multimedia can be audio only, video only, movie (synchronized audio and video) or a combination of audio, video, images and text (captions/ subtitles) and other meta data in a single presentation. The content is created to interface with specific codec. Commonly used standards for video compression are H.264(AVS) and WebM and for audio are AAC, ALAC, WMA and Vorbis.
Content format identifies the processing information needed for playback of media file. A container format is wrapper that contains different data types with information on how they interleave. Since audio and video streams use different codec algorithms, a container format is generally used to publish it as single file. Advanced container formats can have multiple audio, video, captions, meta data with synchronization information for playback. These are used for providing captioning and text descriptors.
Since multimedia is associated with a specific codec on creation, the playback device must also support the same codec leading to development of proprietary media players. While the media players support their proprietary media formats, new one support multiple formats.
Some of the common formats are:
Media like audio books, music, movies, games etc. continue to be distributed via storage media like DVD, CD-ROMS or Blue-ray disks etc. They can be viewed by standalone devices or by media players installed on computers.
On the web, the multimedia content can be embedded on a web page, download and stored on the user's computer for playback or streamed to media player on the user's computer from a remote location. Downloaded files are distributed by providing a link to the media file. This is the easiest way to distribute as it requires no additional hardware and software resources and the file is available to user for off-line viewing.
Streaming media is resources intensive requiring high speed network connection, storage space and hardware/software to manage and distribute the content called media servers. Streamed media can be either live or on-demand. Media used to deliver live events (webcast) is not usually stored but delivered to the user's media player as the content is being recorded. On-demand content is stored on a remote location and distributed as a continuous stream from a remote server to the media player on the user's device. This file is available to the user as long as it is exist on the server.
For on-demand streaming content can be embedded in the web page using <object> HTML code or streamed directly to the media player. Generally, the media player buffers some data before it starts playing. This is called progressive streaming. Examples of media server are:This service is very resource intensive and used mostly by business and education institutions who specialize in multimedia. For the individual online video sharing services (YouTube) have developed where an individual can upload videos for storage and distribution
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