ISO/IEC 13818-4:1998

INTERNATIONAL ISO/IEC
STANDARD 13818-4
First edition
1998-12-01
Information technology — Generic coding
of moving pictures and associated audio
information —
Part 4:
Conformance testing
Technologies de l'information — Codage générique des images animées
et des informations sonores associées —
Partie 4: Essais de conformité
Reference number
B C
Contents
Foreword . iv
Introduction. v
1 General. 1
1.1 Scope . 1
1.2 Normative references. 1
2 Technical elements . 2
2.1 Definitions. 2
2.2 Abbreviations and symbols . 12
2.2.1 Arithmetic operators. 13
2.2.2 Logical operators . 13
2.2.3 Relational operators. 13
2.2.4 Bitwise operators. 14
2.2.5 Assignment. 14
2.2.6 Mnemonics. 14
2.2.7 Constants . 15
2.3 Systems. 16
2.3.1 System bitstream characteristics . 16
2.3.1.1 General system bitstream characteristics. 16
2.3.1.2 Transport Stream specific characteristics. 16
2.3.1.3 Program Stream specific characteristics. 16
2.3.2 System bitstream tests. 17
2.3.2.1 Tests of Transport Streams . 17
2.3.2.2 Tests of Program Streams . 29
2.3.2.3 Tests of timing accuracy . 32
2.3.2.4 Buffer overflow/underflow tests for Transport Streams . 34
2.3.3 General system decoder capabilities. 35
2.3.3.1 Handling of decoder discontinuities . 35
2.3.3.2 Presentation timing . 36
2.3.3.3 Presentation synchronisation . 36
2.3.3.4 Support of variable bitrate within a program . 36
2.3.3.5 General capabilities for program acquisition . 37
2.3.3.6 Private data handling . 37
2.3.3.7 Support of trick modes . 37
2.3.3.8 Systems decoder requirements for forward compatibility . 38
2.3.4 Procedures to test system decoder conformance . 38
2.4 Video . 39
2.4.1 Definition of video bitstream compliance. 39
2.4.1.1 Requirements and restrictions related to profile-and-level. 39
2.4.1.2 Additional restrictions on bitstream applied by the encoder . 40
2.4.1.3 Encoder requirements and recommendations . 40
2.4.2 Procedure for testing bitstream compliance . 40
2.4.3 Definition of video decoder compliance. 41
2.4.3.1 Requirement on arithmetic accuracy (without IDCT). 42
2.4.3.2 Requirement on arithmetic accuracy (with IDCT) . 42
2.4.3.3 Requirement on output of the decoding process and timing . 42
2.4.3.4 Requirement for compatibility with ISO/IEC 11172-2 (MPEG-1 video) . 43
2.4.3.5 Requirements for compatibility between various profile-and-level combinations . 43
2.4.3.6 Requirement for forward compatibility of future extensions. 43
2.4.3.7 Requirements related to zero byte stuffing, user data and reserved extensions. 43
2.4.3.8 Recommendations . 44
2.4.4 Procedure to test decoder compliance. 44
2.4.4.1 Static tests . . 44
©  ISO/IEC 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
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ISO/IEC Copyright Office • Case postale 56 • CH-1211 Genève 20 • Switzerland
Printed in Switzerland
ii
© ISO/IEC ISO/IEC 13818-4:1998(E)
2.4.4.2 Dynamic tests .44
2.4.4.3 Specification of the test bitstreams.44
2.4.4.4 Implementation of the static test .50
2.4.4.5 Implementation of the dynamic test.51
2.4.4.6 Decoder conformance.51
2.4.5 Conformance of scalable bitstreams and decoders.53
2.4.5.1 Definition of scalable video bitstream hierarchy compliance .53
2.4.5.2 Procedure for testing bitstream compliance.54
2.4.5.3 Definition of video decoder compliance.54
2.4.5.4 Procedure to test decoder compliance .54
2.5 Audio .55
2.5.1 Audio bitstreams.55
2.5.1.1 Extension of ISO/IEC 11172-3 audio coding to lower sampling frequencies .55
2.5.1.2 Low bit rate coding of Multichannel Audio .55
2.5.2 Audio bitstream tests.56
2.5.2.1 Extension of ISO/IEC 11172-3 audio coding to lower sampling frequencies .56
2.5.2.2 Low bit rate coding of Multichannel Audio .57
2.5.3 Audio decoder characteristics .59
2.5.3.1 Extension of ISO/IEC 11172-3 audio coding to lower sampling frequencies .59
2.5.3.2 Low bit rate coding of Multichannel Audio .59
2.5.4 Audio decoder tests.61
2.5.4.1 Calculation for RMS .62
2.5.4.2 Descriptions of the audio test bitstreams.62
Annex A (informative) Systems test bitstreams.67
Annex B (informative) Systems decoder characteristics beyond conformance .68
B.1 Number of PIDs that can be processed.68
B.2 Error handling.68
B.3 Program acquisition .68
B.4 Input processing capabilities .69
B.5 Presentation Timing .69
Annex C (informative) Video test bitstreams .70
Annex D (informative) Audio test bitstreams.71
Annex E (informative) Patent statements .72
Bibliography .74
iii
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the
development of International Standards through technical committees established by the respective organization to deal with
particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft
International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting a vote.
International Standard ISO/IEC 13818-4 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 13818 consists of the following parts, under the general title Information technology — Generic coding of moving
pictures and associated audio information:
— Part 1: Systems
— Part 2: Video
— Part 3: Audio
— Part 4: Conformance testing
— Part 5: Software simulation
— Part 6: Extensions for DSM-CC
— Part 7: Advanced Audio Coding (AAC)
— Part 9: Extension for real time interface for systems decoders
— Part 10: Conformance extensions for Digital Storage Media Command and Control (DSM-CC)
The electronic file directory “bitstreams” forms an integral part of this part of ISO/IEC 13818.
Annexes A to E of this part of ISO/IEC 13818 are for information only.
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© ISO/IEC ISO/IEC 13818-4:1998(E)
Introduction
Parts 1, 2 and 3 of ISO/IEC 13818 specify a multiplex structure and coded representations of audio-visual information. Parts 1,
2 and 3 of ISO/IEC 13818 allow for large flexibility, achieving suitability of ISO/IEC 13818 for many different applications.
The flexibility is obtained by including parameters in the bitstream that define the characteristics of coded bitstreams.
Examples are the audio sampling frequency, picture size, picture rate and bitrate parameters.
This part of ISO/IEC 13818 specifies how tests can be designed to verify whether bitstreams and decoders meet the
requirements as specified in parts 1, 2 and 3 of ISO/IEC 13818. These tests can be used for various purposes such as:
— manufacturers of encoders, and their customers, can use the tests to verify whether the encoder produces valid
bitstreams.
— manufacturers of decoders and their customers can use the tests to verify whether the decoder meets the requirements
specified in parts 1, 2 and 3 of ISO/IEC 13818 for the claimed decoder capabilities.
v
INTERNATIONAL STANDARD  © ISO/IEC ISO/IEC 13818-4:1998(E)
Information technology — Generic coding of moving
pictures and associated audio information —
Part 4:
Conformance testing
1 General
1.1 Scope
This part of ISO/IEC 13818 specifies how tests can be designed to verify whether bitstreams and decoders meet requirements
specified in parts 1, 2 and 3 of ISO/IEC 13818. In this part of ISO/IEC 13818, encoders are not addressed specifically. An
encoder may be said to be an ISO/IEC 13818 encoder if it generates bitstreams compliant with the syntactic and semantic
bitstream requirements specified in parts 1, 2 and 3 of ISO/IEC 13818.
Characteristics of coded bitstreams and decoders are defined for parts 1, 2 and 3 of ISO/IEC 13818. The characteristics of a
bitstream define the subset of the standard that is exploited in the bitstream. Examples are the applied values or range of the
picture size and bitrate parameters. Decoder characteristics define the properties and capabilities of the applied decoding
process. An example of a property is the applied arithmetic accuracy. The capabilities of a decoder specify which coded
bitstreams the decoder can decode and reconstruct, by defining the subset of the standard that may be exploited in decodable
bitstreams. A bitstream can be decoded by a decoder if the characteristics of the coded bitstream are within the subset of the
standard specified by the decoder capabilities.
Procedures are described for testing conformance of bitstreams and decoders to the requirements defined in parts 1, 2 and 3 of
ISO/IEC 13818. Given the set of characteristics claimed, the requirements that must be met are fully determined by parts 1, 2
and 3 of ISO/IEC 13818. This part of ISO/IEC 13818 summarises the requirements, cross references them to characteristics,
and defines how conformance with them can be tested. Guidelines are given on constructing tests to verify bitstream and
decoder conformance. This document gives guidelines on how to construct bitstream test suites to check or verify decoder
conformance. In addition, some test bitstreams implemented according to those guidelines are provided in the electronic file
directory called “Test bitstreams”.
1.2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO/IEC 13818. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties
to agreements based on this part of ISO/IEC 13818 are encouraged to investigate the possibility of applying the most recent
editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International
Standards.
ISO 639:1988, Code for the representation of names of languages.
ISO/IEC 8859-1:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin
alphabet No. 1.
ISO/IEC 10918-1:1994, Information technology — Digital compression and coding of continuous-tone still images:
Requirements and guidelines. (See also ITU-T Rec. T.81.)
ISO/IEC 11172-1:1993, Information technology — Coding of moving pictures and associated audio for digital
storage media at up to about 1,5 Mbit/s — Part 1: Systems.
ISO/IEC 11172-2:1993, Information technology — Coding of moving pictures and associated audio for digital
storage media at up to about 1,5 Mbit/s — Part 2: Video.
ISO/IEC 11172-3:1993, Information technology — Coding of moving pictures and associated audio for digital
storage media at up to about 1,5 Mbit/s — Part 3: Audio.
ISO/IEC 11172-4:1995, Information technology — Coding of moving pictures and associated audio for digital
storage media at up to about 1,5 Mbit/s — Part 4: Conformance testing.
ISO/IEC 13818-1:1996, Information technology — Generic coding of moving pictures and associated audio
information: Systems.
ISO/IEC 13818-2:1996, Information technology — Generic coding of moving pictures and associated audio
information: Video.
ISO/IEC 13818-3:1998, Information technology — Generic coding of moving pictures and associated audio
information — Part 3: Audio
.
Recommendations and reports of the CCIR, 1990.
XVIIth Plenary Assembly, Dusseldorf, 1990 Volume XI - Part 1.
Broadcasting Service (Television) Rec. 601-2, Encoding parameters of digital television for studios.
CCIR Volume X and XI Part 3 Recommendation 648: Recording of audio signals.
CCIR Volume X and XI Part 3 Report 955-2: Sound broadcasting by satellite for portable and mobile receivers,
including Annex IV Summary description of advanced digital system II.
IEEE Standard Specifications for the Implementations of 8 by 8 Inverse Discrete Cosine Transform, IEEE Std 1180-
1990, December 6, 1990.
IEC 461:1986, Time and control code for video tape recorders.
IEC 908:198, Compact disk digital audio system.
ITU-T Recommendation H.261 (Formerly CCITT Recommendation H.261) “Codec for audiovisual services at px64
kbit/s” Geneva, 1990.
2 Technical elements
2.1 Definitions
For the purposes of this part of ISO/IEC 13818, the following definitions apply.
2.1.1 16x8 prediction [video]: A prediction mode similar to field-based prediction but where the predicted block size is
16x8 luminance samples.
2.1.2 AC coefficient [video]: Any DCT coefficient for which the frequency in one or both dimensions is non-zero.
2.1.3 access unit [systems]: A coded representation of a presentation unit. In the case of audio, an access unit is the coded
representation of an audio frame.
In the case of video, an access unit includes all the coded data for a picture, and any stuffing that follows it, up to but not
including the start of the next access unit. If a picture is not preceded by a group_start_code or a sequence_header_code, the
access unit begins with the picture start code. If a picture is preceded by a group_start_code and/or a sequence_header_code,
the access unit begins with the first byte of the first of these start codes. If it is the last picture preceding a
sequence_end_code in the bitstream all bytes between the last byte of the coded picture and the sequence_end_code
(including the sequence_end_code) belong to the access unit.
2.1.4 adaptive bit allocation [audio]: The assignment of bits to subbands in a time and frequency varying fashion
according to a psychoacoustic model.
2.1.5 adaptive multichannel prediction [audio]: A method of multichannel data reduction exploiting statistical inter-
channel dependencies.
2.1.6 adaptive noise allocation [audio]: The assignment of coding noise to frequency bands in a time and frequency
varying fashion according to a psychoacoustic model.
2.1.7 adaptive segmentation [audio]: A subdivision of the digital representation of an audio signal in variable segments of
time.
2.1.8 alias [audio]: Mirrored signal component resulting from sub-Nyquist sampling.
2.1.9 analysis filterbank [audio]: Filterbank in the encoder that transforms a broadband PCM audio signal into a set of
subsampled subband samples.
© ISO/IEC ISO/IEC 13818-4:1998(E)
2.1.10 ancillary data [audio]: part of the bitstream that might be used for transmission of ancillary data.
2.1.11 audio access unit [audio]: For Layers I and II, an audio access unit is defined as the smallest part of the encoded
bitstream which can be decoded by itself, where decoded means "fully reconstructed sound". For Layer III, an audio access
unit is part of the bitstream that is decodable with the use of previously acquired main information.
2.1.12 audio buffer [audio]: A buffer in the system target decoder for storage of compressed audio data.
2.1.13 audio sequence [audio]
: A non-interrupted series of audio frames (base frames plus optional extension frames) in
which the following parameters are not changed:
- ID
- Layer
- Sampling Frequency
For Layer I and II, a decoder is not required to support a continuously variable bitrate (change in the bitrate index) of the
base stream. Such a relaxation of requirements does not apply to the extension stream.
2.1.14 B-field picture [video]: A field structure B-Picture.
2.1.15 B-frame picture [video]: A frame structure B-Picture.
2.1.16 B-picture; bidirectionally predictive-coded picture [video]: A picture that is coded using motion compensated
prediction from past and/or future reference fields or frames.
2.1.17 backward compatibility: A newer coding standard is backward compatible with an older coding standard if
decoders designed to operate with the older coding standard are able to continue to operate by decoding all or part of a
bitstream produced according to the newer coding standard.
2.1.18 backward motion vector [video]: A motion vector that is used for motion compensation from a reference frame or
reference field at a later time in display order.
2.1.19 backward prediction [video]: Prediction from the future reference frame (field).
2.1.20 Bark [audio]: Unit of critical band rate. The Bark scale is a non-linear mapping of the frequency scale over the audio
range closely corresponding with the frequency selectivity of the human ear across the band.
2.1.21 base layer [video]: First, independently decodable layer of a scalable hierarchy.
2.1.22 big picture [video]: A coded picture that would cause VBV buffer underflow as defined in C.7 Annex C of ISO/IEC
13818-2. Big pictures can only occur in sequences where low_delay is equal to 1. “Skipped picture” is a term that is
sometimes used to describe the same concept.
2.1.23 bitrate [audio]: The rate at which the compressed bitstream is delivered to the input of a decoder.
2.1.24 bitstream; stream
: An ordered series of bits that forms the coded representation of the data.
2.1.25 bitstream verifier [video]: A process by which it is possible to test and verify that all the requirements specified in
ISO/IEC 13818-2 are met by the bitstream.
2.1.26 block [video]: An 8-row by 8-column matrix of samples, or 64 DCT coefficients (source, quantised or dequantised).
2.1.27 block companding [audio]: Normalising of the digital representation of an audio signal within a certain time period.
2.1.28 bottom field [video]
: One of two fields that comprise a frame. Each line of a bottom field is spatially located
immediately below the corresponding line of the top field.
2.1.29 bound [audio]: The lowest subband in which intensity stereo coding is used.
2.1.30 byte aligned
: A bit in a coded bitstream is byte-aligned if its position is a multiple of 8-bits from the first bit in the
stream.
2.1.31 byte: Sequence of 8-bits.
2.1.32 centre channel [audio]: An audio presentation channel used to stabilise the central component of the frontal stereo
image.
2.1.33 channel [audio]: A sequence of data representing an audio signal being transported.
2.1.34 chroma simulcast [video]: A type of scalability (which is a subset of SNR scalability) where the enhancement layer
(s) contain only coded refinement data for the DC coefficients, and all the data for the AC coefficients, of the chrominance
components.
2.1.35 chrominance format [video]: Defines the number of chrominance blocks in a macroblock.
2.1.36 chrominance component [video]: A matrix, block or single sample representing one of the two colour difference
signals related to the primary colours in the manner defined in the bitstream. The symbols used for the chrominance signals
are Cr and Cb.
2.1.37 coded audio bitstream [audio]: A coded representation of an audio signal as specified in part 3 of ISO/IEC 13818.
2.1.38 coded B-frame [video]: A B-frame picture or a pair of B-field pictures.
2.1.39 coded frame [video]
: A coded frame is a coded I-frame, a coded P-frame or a coded B-frame.
2.1.40 coded I-frame [video]: An I-frame picture or a pair of field pictures, where the first field picture is an I-picture and
the second field picture is an I-picture or a P-picture.
2.1.41 coded order [video]
: The order in which the pictures are transmitted and decoded. This order is not necessarily the
same as the display order.
2.1.42 coded P-frame [video]: A P-frame picture or a pair of P-field pictures.
2.1.43 coded picture [video]: A coded picture is made of a picture header, the optional extensions immediately following it,
and the following picture data. A coded picture may be a coded frame or a coded field.
2.1.44 coded representation: A data element as represented in its encoded form.
2.1.45 coded video bitstream [video]: A coded representation of a series of one or more pictures as defined in ISO/IEC
13818-2.
2.1.46 coding parameters [video]: The set of user-definable parameters that characterise a coded bitstream. Bitstreams are
characterised by coding parameters. Decoders are characterised by the bitstreams that they are capable of decoding.
2.1.47 component [video]: A matrix, block or single sample from one of the three matrices (luminance and two
chrominance) that make up a picture.
2.1.48 compression: Reduction in the number of bits used to represent an item of data.
2.1.49 constant bitrate: Operation where the bitrate is constant from start to finish of the coded bitstream.
2.1.50 constrained parameters [video]: The values of the set of coding parameters defined in 2.4.3.2 of ISO/IEC 11172-2.
2.1.51 constrained system parameter stream; CSPS [systems]: A Program Stream for which the constraints defined in
subclause 2.7.9 of ISO/IEC 13818-1 apply.
2.1.52 CRC: The Cyclic Redundancy Check to verify the correctness of data.
2.1.53 critical band [audio]: Psychoacoustic measure in the spectral domain which corresponds to the frequency selectivity
of the human ear. This selectivity is expressed in Bark.
2.1.54 critical band rate [audio]: Psychoacoustic function of frequency. At a given audible frequency, it is proportional to
the number of critical bands below that frequency. The units of the critical band rate scale are Barks.
2.1.55 data element: An item of data as represented before encoding and after decoding.
2.1.56 data partitioning [video]: A method for dividing a bitstream into two separate bitstreams for error resilience
purposes. The two bitstreams have to be recombined before decoding.
2.1.57 DC coefficient [video]
: The DCT coefficient for which the frequency is zero in both dimensions.
2.1.58 DCT coefficient [video]: The amplitude of a specific cosine basis function.
2.1.59 de-emphasis [audio]: Filtering applied to an audio signal after storage or transmission to undo a linear distortion due
to emphasis.
2.1.60 decoded stream: The decoded reconstruction of a compressed bitstream.
2.1.61 decoder input buffer [video]: The first-in first-out (FIFO) buffer specified in the video buffering verifier.
2.1.62 decoder: An embodiment of a decoding process.
2.1.63 decoder sub-loop [video]: Stages within encoder which produce numerically identical results to the decode process
described in ISO/IEC 13818-2, clause 7. Encoders capable of producing more than just I-pictures embed a decoder sub-loop
to create temporal predictions and to model the behaviour of downstream decoders.
2.1.64 decoding (process): The process defined in ISO/IEC 13818 parts 1, 2 and 3 that reads an input coded bitstream and
outputs decoded pictures or audio samples.
© ISO/IEC ISO/IEC 13818-4:1998(E)
2.1.65 decoding time-stamp; DTS [systems]: A field that may be present in a PES packet header that indicates the time that
an access unit is decoded in the system target decoder.
2.1.66 dequantisation: The process of rescaling the quantised DCT coefficients after their representation in the bitstream
has been decoded and before they are presented to the inverse DCT.
2.1.67 digital storage media; DSM: A digital storage or transmission device or system.
2.1.68 discrete cosine transform; DCT
: Either the forward discrete cosine transform or the inverse discrete cosine
transform. The DCT is an invertible, discrete orthogonal transformation.
2.1.69 display aspect ratio [video]: The ratio height/width (in SI units) of the intended display.
2.1.70 display order [video]
: The order in which the decoded pictures are displayed. Normally this is the same order in
which they were presented at the input of the encoder.
2.1.71 display process [video]: The (non-normative) process by which reconstructed frames are displayed.
2.1.72 downmix [audio]: A matrixing of n channels to obtain less than n channels.
2.1.73 drift [video]: Accumulation of mismatch between the reconstructed output produced by the hypothetical decoder sub-
loop embedded within an encoder (see definition of "decoder sub-loop") and the reconstructed outputs produced by a
(downstream) decoder.
2.1.74 DSM-CC: digital storage media command and control.
2.1.75 dual channel mode [audio]: A mode, where two audio channels with independent programme contents (e.g.
bilingual) are encoded within one bitstream. The coding process is the same as for the stereo mode.
2.1.76 dual-prime prediction [video]: A prediction mode in which two forward field-based predictions are averaged. The
predicted block size is 16x16 luminance samples. Dual-prime prediction is only used in interlaced P-pictures.
2.1.77 dynamic crosstalk [audio]: A method of multichannel data reduction in which stereo-irrelevant signal components
are copied to another channel.
2.1.78 dynamic transmission channel switching [audio]
: A method of multichannel data reduction by allocating the most
orthogonal signal components to the transmission channels.
2.1.79 editing: The process by which one or more coded bitstreams are manipulated to produce a new coded bitstream.
Conforming edited bitstreams must meet the requirements defined in parts 1, 2, and 3 of ISO/IEC 13818.
2.1.80 Elementary Stream Clock Reference; ESCR [systems]: A time stamp in the PES Stream from which decoders of
PES streams may derive timing.
2.1.81 elementary stream; ES [systems]
: A generic term for one of the coded video, coded audio or other coded bitstreams
in PES packets. One elementary stream is carried in a sequence of PES packets with one and only one stream_id.
2.1.82 emphasis [audio]: Filtering applied to an audio signal before storage or transmission to improve the signal-to-noise
ratio at high frequencies.
2.1.83 encoder: An embodiment of an encoding process.
2.1.84 encoding (process): A process, not specified in ISO/IEC 13818, that reads a stream of input pictures or audio
samples and produces a valid coded bitstream as defined in parts 1, 2, and 3 of ISO/IEC 13818.
2.1.85 enhancement layer [video]: A relative reference to a layer (above the base layer) in a scalable hierarchy. For all
forms of scalability, its decoding process can be described by reference to the lower layer decoding process and the
appropriate additional decoding process for the enhancement layer itself.
2.1.86 entitlement control message; ECM [systems]: Entitlement Control Messages are private conditional access
information which specify control words and possibly other, typically stream-specific, scrambling and/or control parameters.
2.1.87 entitlement management message; EMM [systems]: Entitlement Management Messages are private conditional
access information which specify the authorisation levels or the services of specific decoders. They may be addressed to
single decoders or groups of decoders.
2.1.88 entropy coding: Variable length lossless coding of the digital representation of a signal to reduce redundancy.
2.1.89 event [systems]: An event is defined as a collection of elementary streams with a common time base, an associated
start time, and an associated end time.
2.1.90 evil bitstreams: Bitstreams orthogonal to reality.
2.1.91 extension bitstream [audio]: Information contained in an optional additional bit stream related to the audio base bit
stream at the system level, to support bit rates beyond those defined in ISO/IEC 11172-3. The optional extension bit stream
contains the remainder of the multichannel and multilingual data.
2.1.92 fast reverse playback [video]: The process of displaying the picture sequence in the reverse of display order faster
than real-time.
2.1.93 fast forward playback [video]: The process of displaying a sequence, or parts of a sequence, of pictures in display-
order faster than real-time.
2.1.94 FFT: Fast Fourier Transformation. A fast algorithm for performing a discrete Fourier transform (an orthogonal
transform).
2.1.95 field [video]: For an interlaced video signal, a “field” is the assembly of alternate lines of a frame. Therefore an
interlaced frame is composed of two fields, a top field and a bottom field.
2.1.96 field period [video]: The reciprocal of twice the frame rate.
2.1.97 field picture; field structure picture [video]: A field structure picture is a coded picture with picture_structure is
equal to "Top field" or "Bottom field".
2.1.98 field-based prediction [video]
: A prediction mode using only one field of the reference frame. The predicted block
size is 16x16 luminance samples. Field-based prediction is not used in progressive frames.
2.1.99 filterbank [audio]: A set of band-pass filters covering the entire audio frequency range.
2.1.100 fixed segmentation [audio]: A subdivision of the digital representation of an audio signal into fixed segments of
time.
2.1.101 flag: A variable which can take one of only the two values defined in this specification.
2.1.102 FLC: Fixed Length Code.
2.1.103 forbidden: The term "forbidden", when used in the clauses defining the coded bitstream, indicates that the value shall
never be used. This is usually to avoid emulation of start codes.
2.1.104 forced updating [video]: The process by which macroblocks are intra-coded from time-to-time to ensure that
mismatch errors between the inverse DCT processes in encoders and decoders cannot build up excessively.
2.1.105 forward compatibility: A newer coding standard is forward compatible with an older coding standard if decoders
designed to operate with the newer coding standard are able to decode bitstreams of the older coding standard.
2.1.106 forward motion vector [video]: A motion vector that is used for motion compensation from a reference frame or
reference field at an earlier time in display order.
2.1.107 forward prediction [video]: Prediction from the past reference frame (field).
2.1.108 frame [audio]: A part of the audio bit stream that corresponds to audio PCM samples from an Audio Access Unit.
2.1.109 frame [video]: A frame contains lines of spatial information of a video signal. For progressive video, these lines
contain samples starting from one time instant and continuing through successive lines to the bottom of the frame. For
interlaced video a frame consists of two fields, a top field and a bottom field. One of these fields may be temporally located
one field period later than the other.
2.1.110 frame period [video]: The reciprocal of the frame rate.
2.1.111 frame picture; frame structure picture [video]: A frame structure picture is a coded picture with picture_structure
is equal to "Frame".
2.1.112 frame rate [video]: The rate at which frames are be output from the decoding process.
2.1.113 frame reordering [video]: The process of reordering the reconstructed frames when the coded order is different from
the display order. Frame reordering occurs when B-frames are present in a bitstream. There is no frame reordering when
decoding low delay bitstreams.
2.1.114 frame-based prediction [video]: A prediction mode using both fields of the reference frame.
2.1.115 free format [audio]: Any bitrate other than the defined bitrates that is less than the maximum valid bitrate for each
layer.
2.1.116 future reference frame (field) [video]: A future reference frame(field) is a reference frame(field) that occurs at a
later time than the current picture in display order.
© ISO/IEC ISO/IEC 13818-4:1998(E)
2.1.117 granules [Layer II] [audio]: The set of 3 consecutive subband samples from all 32 subbands that are considered
together before quantisation. They correspond to 96 PCM samples.
2.1.118 granules [Layer III] [audio]: 576 frequency lines that carry their own side information.
2.1.119 group of pictures [video]: A notion defined only in ISO/IEC 11172-2 (MPEG-1 Video). In ISO/IEC 13818-2, a
similar functionality can be achieved by the mean of inserting group of pictures headers.
2.1.120 Hann window [audio]
: A time function applied sample-by-sample to a block of audio samples before Fourier
transformation.
2.1.121 header: A block of data in the coded bitstream containing the coded representation of a number of data elements
pertaining to the coded data that follow the header in the bitstream.
2.1.122 Huffman coding: A specific method for entropy coding.
2.1.123 hybrid filterbank [audio]: A serial combination of subband filterbank and MDCT.
2.1.124 hybrid scalability [video]: Hybrid scalability is the combination of two (or more) types of scalability.
2.1.125 I-field picture [video]: A field structure I-Picture.
2.1.126 I-frame picture [video]: A frame structure I-Picture.
2.1.127 I-picture; intra-coded picture [video]: A picture coded using information only from itself.
2.1.128 IDCT: Inverse Discrete Cosine Transform.
2.1.129 IMDCT [audio]: Inverse Modified Discrete Cosine Transform.
2.1.130 intensity stereo [audio]: A method of exploiting stereo irrelevance or redundancy in stereophonic audio programmes
based on retaining at high frequencies only the energy envelope of the right and left channels.
2.1.131 interlace [video]: The property of conventional television frames where alternating lines of the frame represent
different instances in time. In an interlaced frame
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