PGDEL/DECP05/Unit3/Ch03.09
Uttarakhand Open University
Post Graduate Diploma in e-Learning
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DECP 05: e-Content Creation
Multimedia Learning Resources
Audio Technologies - Tools
A broad range of digital audio technologies exist that enhance the delivery of multimedia audio through the web, CD-ROM and DVD-ROM, Internet streaming audio and other mechanisms. In years past, much audio technology was only commercially available. However, an impressive number of high quality digital audio tools have recently become available as free or open source software and with widespread availability through the WWW the benefits of such software are compelling.
Compression
Audio compression is a term used to describe two different processes to achieve reduced file size in an audio file. The first step is called encoding and it occurs when a set of algorithms are applied to convert the file to a specific format thereby reducing the size of the file. The second step is decoding, which is the process of uncompressing a sound file so that it can be played. The sound quality of digital audio files is determined largely by the ways that the sound file is encoded. Software encoders are programs that rely on codecs. Codec is short for Compression / Decompression and it refers to any technology that is used to compress and decompress data. For example, there are a variety of encoders that make use of certain codecs to produce MP3 files, and the quality of such codecs is an important determinant of sound quality.
Lossy vs. Lossless Compression
Encoders compress audio files through two different methods: lossy compression and lossless compression. Typically, lossy compression occurs when frequencies beyond the aural range of the average human ear are removed from the sound files, thereby reducing file size. Lossy compression, such as MP3 compression, often takes advantage of the ways that the human ear perceives sound to create compressed sound files that soundEncoders compress audio files through two different methods: lossy compression and lossless compression. Typically, lossy compression occurs when frequencies beyond the aural range of the average human ear are removed from the sound files, thereby reducing file size. Lossy compression, such as MP3 compression, often takes advantage of the ways that the human ear perceives sound to create compressed sound files that sound remarkably similar to the original even though they are not exact copies. Lossless compression occurs when no frequencies are removed from the sound file. Instead, other compression techniques are used to obtain a smaller file size and when the file is decoded, all the original data is restored. With lossless formats, the resulting audio file has the exact same sound quality of the original.
