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Most modern audio compression algorithms are based on modified discrete cosine transform (MDCT) coding and linear predictive coding (LPC). In hardware, audio codec refers to a single device that encodes analog audio as digital signals and decodes digital back into analog.
A lossless audio coding format reduces the total data needed to represent a sound but can be de-coded to its original, uncompressed form. A lossy audio coding format additionally reduces the bit resolution of the sound on top of compression, which results in far less data at the cost of irretrievably lost information.
A classic method is nonlinear PCM, such as the μ-law algorithm. Small signals are digitized with finer granularity than are large ones; the effect is to add noise that is proportional to the signal strength. Sun's Au file format for sound is a popular example of mu-law encoding. Using 8-bit mu-law encoding would cut the per-channel bitrate of ...
As the MP3 standard allows quite a bit of freedom with encoding algorithms, different encoders do feature quite different quality, even with identical bit rates. As an example, in a public listening test featuring two early MP3 encoders set at about 128 kbit/s , [ 75 ] one scored 3.66 on a 1–5 scale, while the other scored only 2.22.
For example, MP3 and AAC dominate the personal audio market in terms of market share, though many other formats are comparably well suited to fill this role from a purely technical standpoint. First public release date is first of either specification publishing or source releasing, or in the case of closed-specification, closed-source codecs ...
A dictionary coder, also sometimes known as a substitution coder, is a class of lossless data compression algorithms which operate by searching for matches between the text to be compressed and a set of strings contained in a data structure (called the 'dictionary') maintained by the encoder. When the encoder finds such a match, it substitutes ...
The metadata is stored in a vector of byte strings of arbitrary length and size. The size of the vector and the size of each string in bytes is limited to 2 32 − 1 (about 4.3 billion, or any positive integer that can be expressed in 32 bits). This vector is stored in the second header packet that begins a Vorbis bitstream.
Huffman coding is an entropy encoding method and variable-length code algorithm that assigns more common values with shorter binary codes that require fewer bits to store. Huffman coding works in the context of silence compression by assigning frequently occurring silence patterns with shorter binary codes, reducing data size.