In electronic communications, an endec is a device which acts as both an encoder and a decoder on a signal or data stream, either with the same or separate circuitry or algorithm.

* A modem is an endec, likewise a modulator is an encoder and a demodulator is a decoder

The general difference between an endec and a codec ( compressor / decompressor ) is that hardware is usually considered to be an endec, while software is considered to be the codec.

* An Emergency Alert System unit is usually an endec, but sometimes just a decoder

* Hardware that encodes data bits to a run length limited line code, and decodes the line code back to data bits, is an endec.

* When implementing the Infrared Data Association ( IrDA ) protocol, often an endec is used between the UART and the optoelectronics.

In a simple model, often referred to as the transmission model or standard view of communication, information or content ( e. g. a message in natural language ) is sent in some form ( as spoken language ) from an emisor / sender / encoder to a destination / receiver / decoder.

Communication is usually described along a few major dimensions: Message ( what type of things are communicated ), source / emisor / sender / encoder ( by whom ), form ( in which form ), channel ( through which medium ), destination / receiver / target / decoder ( to whom ), and Receiver.

It is also often used as a component within lossy data compression technologies ( e. g. lossless mid / side joint stereo preprocessing by the LAME MP3 encoder and other lossy audio encoders ).

The key parts to be aware of are MPEG-4 part 2 ( including Advanced Simple Profile, used by codecs such as DivX, Xvid, Nero Digital and 3ivx and by QuickTime 6 ) and MPEG-4 part 10 ( MPEG-4 AVC / H. 264 or Advanced Video Coding, used by the x264 encoder, by Nero Digital AVC, by QuickTime 7, and by high-definition video media like Blu-ray Disc ).

The interrupt controller can be as simple as a 74LS148 priority encoder, or may be part of a VLSI peripheral chip such as the MC68901 Multi-Function Peripheral ( used in Atari TT030 ), which also provided a UART, timer, and parallel I / O.

Special-purpose I / O modules, such as timer modules or counter modules, can be used where the scan time of the processor is too long to reliably pick up, for example, counting pulses and interpreting quadrature from a shaft encoder.

Assumptions: speed at the encoder, is 500 kbit / s.

: Number of MBs transferred = encoder speed ( in bit / s ) × number of seconds × number of viewers / ( 8 * 1024 * 1024 )

* Other encoder / decoder implementation:

** Vorbis acceleration project-Optimized versions of aoTuV Vorbis encoder and other SSE / MultiThread optimizations

A vocoder (, short for voice encoder ) is an analysis / synthesis system, used to reproduce human speech.

The figure below is a rate 1 / 3 ( m / n ) encoder with constraint length ( k ) of 3.

Rate 1 / 3 non-recursive, non-systematic convolutional encoder with constraint length 3

Rate 1 / 2 recursive, systematic convolutional encoder with constraint length 4

Because the decoder is always one step behind in maintaining the table, it does not generate a table entry upon receiving the first code from the encoder, but will generate one for each succeeding code.

Therefore the encoder must emit extra CLEAR codes at intervals of 2 < sup > n </ sup > − 2 codes or less to make the decoder restart.

Both the encoder and decoder begin with a trivial model, yielding poor compression of initial data, but as they learn more about the data, performance improves.

The MPEG compression methodology is considered asymmetric as the encoder is more complex than the decoder.

The encoder needs to be algorithmic or adaptive whereas the decoder is ' dumb ' and carries out fixed actions.

The MPEG's ( ISO's ) approach to standardization is novel, because it is not the encoder that is standardized, but the way a decoder interprets the bitstream.

This gives scope for competition between different encoder designs, which means better designs can evolve and users have greater choice, because encoders of different levels of cost and complexity can exist, yet a compliant decoder operates with all of them.

An open source PNG encoder and decoder for C and C ++ with no external dependencies.

* PNGJ: A pure Java PNG encoder and decoder.

In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder.

In linear prediction coding, the all-pole filter replaces the bandpass filter bank of its predecessor and is used at the encoder to whiten the signal ( i. e., flatten the spectrum ) and again at the decoder to re-apply the spectral shape of the target speech signal.

Rather, when several consecutive bits have the same direction value, the encoder and decoder assume that slope overload is occurring, and the step size becomes progressively larger.

The decoder must have the same probability estimation the encoder used, which can either be sent in advance, derived from already transferred data or be part of the compressor and decompressor.

* DivX Pro Codec: An H. 264 decoder and encoder was added in version 7.

The last stable version of Speex encoder and decoder is 1. 1. 12.

It is critical that the encoder and decoder agree on which variety of LZW is being used: the size of the alphabet, the maximum code width, whether variable-width encoding is being used, the initial code size, whether to use the clear and stop codes ( and what values they have ).

In this way the decoder builds up a dictionary which is identical to that used by the encoder, and uses it to decode subsequent input values.

Thus the full dictionary does not need be sent with the encoded data ; just the initial dictionary containing the single-character strings is sufficient ( and is typically defined beforehand within the encoder and decoder rather than being explicitly sent with the encoded data.

If variable-width codes are being used, the encoder and decoder must be careful to change the width at the same points in the encoded data, or they will disagree about where the boundaries between individual codes fall in the stream.

The decoder is always one code behind the encoder in building the table, so when it sees the code for ω, it will generate an entry for code 2 < sup > p </ sup > − 1.

Since this is the point where the encoder will increase the code width, the decoder must increase the width here as well: at the point where it generates the largest code that will fit in p bits.