| slovo | definícia |
encoding
(mass) | encoding
- kódovanie, kódovacia stránka |
encoding
(encz) | encoding,kódování n: |
encoding
(wn) | encoding
n 1: the activity of converting data or information into code
[syn: encoding, encryption] |
| | podobné slovo | definícia |
encodings
(encz) | encodings,kódování n: pl. Michal Božoň |
basic encoding rules
(foldoc) | Basic Encoding Rules
ISO 8825
ITU X.209
X.209
(BER) ASN.1 encoding rules for
producing self-identifying and self-delimiting {transfer
syntax} for data structures described in ASN.1 notations.
BER is an self-identifying and self-delimiting encoding
scheme, which means that each data value can be identified,
extracted and decoded individually.
Huw Rogers once described BER as "a triumph of bloated theory
over clean implementation". He also criticises it as designed
around bitstreams with arbitrary boundaries between data which
can only be determined at a high level.
Documents: ITU-T X.690, ISO 8825-1.
See also CER, DER, PER.
(1998-05-28)
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canonical encoding rules
(foldoc) | Canonical Encoding Rules
CER
(CER) A restricted variant of BER for
producing unequivocal transfer syntax for data structures
described by ASN.1.
Whereas BER gives choices as to how data values may be
encoded, CER and DER select just one encoding from those
allowed by the basic encoding rules, eliminating all of the
options. They are useful when the encodings must be
preserved, e.g. in security exchanges.
CER and DER differ in the set of restrictions that they
place on the encoder. The basic difference between CER and
DER is that DER uses definitive length form and CER uses
indefinite length form.
Documents: ITU-T X.690, ISO 8825-1.
See also PER.
(1998-05-19)
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character encoding
(foldoc) | character encoding
character encoding scheme
(Or "character encoding scheme") A mapping between
binary data values and character code positions (or "code
points").
Early systems stored characters in a variety of ways,
e.g. four six-bit characters in a 24-bit word, but around
1960, eight-bit bytes started to become the most common data
storage layout, with each character stored in one byte,
typically in the ASCII character set.
In the case of ASCII, the character encoding is an
identity mapping: code position 65 maps to the byte value
65. This is possible because ASCII uses only code positions
representable as single bytes, i.e., values between 0 and
255. (US-ASCII only uses values 0 to 127, in fact.)
From the late 1990s, there was increased use of larger
character sets such as Unicode and many CJK {coded
character sets}. These can represent characters from many
languages and more symbols.
Unicode uses many more than the 256 code positions that can
be represented by one byte. It thus requires more complex
mappings: sometimes the characters are mapped onto pairs of
bytes (see DBCS). In many cases, this breaks programs that
assume a one-to-one mapping of bytes to characters, and so,
for example, treat any occurrance of the byte value 13 as a
carriage return. To avoid this problem, character encodings
such as UTF-8 were devised.
(2015-11-29)
|
character encoding scheme
(foldoc) | character encoding
character encoding scheme
(Or "character encoding scheme") A mapping between
binary data values and character code positions (or "code
points").
Early systems stored characters in a variety of ways,
e.g. four six-bit characters in a 24-bit word, but around
1960, eight-bit bytes started to become the most common data
storage layout, with each character stored in one byte,
typically in the ASCII character set.
In the case of ASCII, the character encoding is an
identity mapping: code position 65 maps to the byte value
65. This is possible because ASCII uses only code positions
representable as single bytes, i.e., values between 0 and
255. (US-ASCII only uses values 0 to 127, in fact.)
From the late 1990s, there was increased use of larger
character sets such as Unicode and many CJK {coded
character sets}. These can represent characters from many
languages and more symbols.
Unicode uses many more than the 256 code positions that can
be represented by one byte. It thus requires more complex
mappings: sometimes the characters are mapped onto pairs of
bytes (see DBCS). In many cases, this breaks programs that
assume a one-to-one mapping of bytes to characters, and so,
for example, treat any occurrance of the byte value 13 as a
carriage return. To avoid this problem, character encodings
such as UTF-8 were devised.
(2015-11-29)
|
distinguished encoding rules
(foldoc) | Distinguished Encoding Rules
DER
(DER) An X.690 encoding format (or
transfer syntax) for data structures described by ASN.1
that specifies exactly one way to encode a value thus ensuring
a unique, canonical, serialised representation. DER is a
restricted variant of BER. For example, DER has exactly one
way to encode a Boolean value. DER is used in
cryptography, e.g. for digital certificates such as
X.509.
(2016-05-05)
|
horizontal encoding
(foldoc) | horizontal encoding
An instruction set where each field (a bit or
group of bits) in an instruction word controls some
functional unit or gate directly, as opposed to {vertical
encoding} where instruction fields are decoded (by
hard-wired logic or microcode) to produce the control
signals. Horizontal encoding allows all possible combinations
of control signals (and therefore operations) to be expressed
as instructions whereas vertical encoding uses a shorter
instruction word but can only encode those combinations of
operations built into the decoding logic.
An instruction set may use a mixture of horizontal and
vertical encoding within each instruction. Because an
architecture using horizontal encoding typically requires more
instruction word bits it is sometimes known as a {very long
instruction word} (VLIW) architecture.
(1995-04-23)
|
huffman encoding
(foldoc) | Huffman coding
Huffman
Huffman code
Huffman encoding
A data compression technique which varies the
length of the encoded symbol in proportion to its information
content, that is the more often a symbol or token is used, the
shorter the binary string used to represent it in the
compressed stream. Huffman codes can be properly decoded
because they obey the prefix property, which means that no
code can be a prefix of another code, and so the complete set
of codes can be represented as a binary tree, known as a
Huffman tree. Huffman coding was first described in a seminal
paper by D.A. Huffman in 1952.
(1994-12-23)
|
manchester encoding
(foldoc) | Manchester encoding
A method of transmitting bits which
enables the receiver to easily synchronise with the sender.
A simple way of signalling bits might be to transmit a high
voltage for some period for a 1-bit and a low voltage for a 0
bit:
Bits Sent: 1 1 0 0
Signal: High ___________
Low |___________
Time: -> . . . . .
However, when several identical bits are sent in succession,
this provides no information to the receiver about when each
bit starts and stops.
Manchester encoding splits each bit period into two, and
ensures that there is always a transition between the signal
levels in the middle of each bit. This allows the receiver to
synchronise with the sender.
In normal Manchester encoding, a 1-bit is transmitted with a
high voltage in the first period, and a low voltage in the
second, and vice verse for the 0 bit:
Bits Sent: 1 1 0 0
Signal: High __ __ __ __
Low |__| |_____| |__|
Time: -> . ' . ' . ' . ' .
In Differential Manchester encoding, a 1-bit is indicated by
making the first half of the signal equal to the last half of
the previous bit's signal and a 0-bit is indicated by making
the first half of the signal opposite to the last half of the
previous bit's signal. That is, a zero bit is indicated by a
transition at the beginning of the bit.
Like normal Manchester encoding, there is always a transition
in the middle of the transmission of the bit.
Differential Manchester Encoding
Bits Sent: 1 1 0 0
Signal: High ____ __ __ __
Low |_____| |__| |__|
Time: -> . ' . ' . ' . ' .
With each bit period half as long, twice as much bandwidth
is required when using either of the Manchester encoding
schemes.
(1995-11-23)
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packed encoding rules
(foldoc) | Packed Encoding Rules
(PER) ASN.1 encoding rules for
producing a compact transfer syntax for data structures
described in ASN.1, defined in 1994.
PER provides a much more compact encoding then BER. It
tries to represents the data units using the minimum number of
bits. The compactness requires that the decoder knows the
complete abstract syntax of the data structure to be
decoded, however.
Documents: ITU-T X.691, ISO 8825-2.
(1998-05-19)
|
run-length encoding
(foldoc) | run-length encoding
RLE
A kind of compression algorithm which replaces sequences
("runs") of consecutive repeated characters (or other units of
data) with a single character and the length of the run. This
can either be applied to all input characters, including runs
of length one, or a special character can be used to introduce
a run-length encoded group. The longer and more frequent the
runs are, the greater the compression that will be achieved.
This technique is particularly useful for encoding black and
white images where the data units would be single bit
pixels.
(1994-10-27)
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subband encoding
(foldoc) | subband encoding
An audio compression technique where the sound is split into
frequency bands and then parts of the signal which the ear
cannot detect are removed, e.g. a quiet sound masked by a loud
one. The remaining signal is encoded using variable bit-rates
with more bits per sample being used in the mid frequency
range.
Subband encoding is used in MPEG-1.
(1994-11-02)
|
text encoding initiative
(foldoc) | Text Encoding Initiative
(TEI) A project working to establish
a standard for interchanging electronic text for scholarly
research. The TEI has adopted SGML and implemented the TEI
standard as an SGML Document Type Definition.
The TEI was incorporated as a not-for-profit consortium in
December 2000, with host sites in Bergen, Oxford, Virginia,
and Providence RI, USA.
(http://tei-c.org/).
See also Corpus Processing.
[Any connection with Computational Linguistics or {Natural
Language Processing}?]
(2001-03-23)
|
vertical encoding
(foldoc) | vertical encoding
An instruction set where a field (a bit or group
of bits) of the instruction word is decoded (either by
hard-wired logic or microcode) to generate signals to
control the functional units, as opposed to {horizontal
encoding} where the instruction word bits are used as the
control signals directly.
With vertical encoding, which combinations of signals and
operations are possible is dictated by the decoding logic; the
instruction field can only select one of these preprogrammed
combinations. This has the advantage that many control
signals can be generated based on only a few instruction word
bits and only valid combinations of control signals can be
generated, e.g. only one source driving a bus at once. An
instruction set may use a mixture of horizontal and vertical
encoding within each instruction.
(1995-04-23)
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