1、INTERNATIONAL STANDARD ISO/IEC 11172-4 First edition 1995-03-I 5 Information technology - Coding of moving pictures and associated audio for digital storage media at up to about I,5 Mbit/s - Part 4: Compliance testing Technologies de /information - Codage de /image anim B-picture video: A picture th
2、at is coded using motion compensated prediction from a past and/or future reference picture. 2.1.14 bitrate: The rate at which the compressed bitstream is delivered from the storage medium to the input of a decoder. 2.1.15 bitstream characteristics compliance: The subset of the standard that is expl
3、oited by the encoder in generating the bitstream. For example, an encoder may apply syntactic and semantic constraints, such as restricted ranges of parameters, to produce a bitstream that exploits a subset of the capabilities supported by parts 1, 2 and 3 of ISO/IEC 11172. Examples are the applied
4、values or range of the picture size and bitrate parameters in video bitstreams. 2.1.16 bitstream compliance compliance: A bitstream is compliant, if the bitstream meets the syntactic and semantic bitstream requirements, specified in the normative clauses of parts 1, 2 and 3 of ISO/IEC 11172. 2.1.17
5、bitstream requirements compliance: Requirements for bitstreams defined in the normative clauses of parts 1,2 and 3 of ISO/IEC 11172. 2.1.18 block companding audio: Normalizing of the digital representation of an audio signal within a certain time period. 2.1.19 block video: An 8-row by 8-column orth
6、ogonal block of pels. 2.1.20 bound audio: The lowest subband in which intensity stereo coding is used. 2.1.21 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. 2.1.22 byte: Sequence of 8-bits. 2.1.23 channel: A digital
7、medium that stores or transports an ISO/IEC 11172 stream. 2.1.24 channel audio: The left and right channels of a stereo signal 2.1.25 chrominance (component) video: A matrix, block or single pel representing one of the two colour difference signals related to the primary colours in the manner define
8、d in CCIR Ret 601. The symbols used for the colour difference signals are Cr and Cb. 2.1.26 coded audio bitstream audio: A coded representation of an audio signal as specified in ISO/IEC 11172-3. 2.1.27 coded video bitstream video: A coded representation of a series of one or more pictures as specif
9、ied in ISO/IEC 11172-2. 2.1.28 coded order video: The order in which the pictures are stored and decoded. This order is not necessarily the same as the display order. 2.1.29 coded representation: A data element as represented in its encoded form. 2.1.30 coding parameters video: The set of user-defin
10、able parameters that characterize a coded video bitstream. Bitstreams are characterized by coding parameters. Decoders are characterized by the bitstreams that they are capable of decoding. 3 ISOAEC 11172-4: 1995 (E) 0 ISOAEC 2.1.31 component video: A matrix, block or single pel from one of the thre
11、e matrices (luminance and two chrominance) that make up a picture. 2.1.32 compression: Reduction in the number of bits used to represent an item of data. 2.1.33 constant bitrate coded video video: A compressed video bitstream with a constant average bitrate. 2.1.34 constant bitrate: Operation where
12、the bitrate is constant from start to finish of the compressed bitstream. 2.1.35 constrained parameters video: The values of the set of coding parameters defined in 2.4.3.2 of ISO/IEC 11172-2. 2.1.36 constrained system parameter stream (CSPS) system: An ISO/IEC 11172 multiplexed stream for which the
13、 constraints defined in 2.4.6 of this part of ISO/IEC 11172 apply. 2.1.37 CRC: Cyclic redundancy code. 2.1.38 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 critica
14、l band rate scale are Barks. 2.1.39 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. 2.1.40 data element: An item of data as represented before encoding and after decoding. 2.1.4
15、1 dc-coeffkient video: The DCT coefficient for which the frequency is zero in both dimensions. 2.1.42 dc-coded picture; D-picture video: A picture that is coded using only information from itself. Of the DCT coefficients in the coded representation, only the dc-coefficients are present. 2.1.43 DCT c
16、oefficient: The amplitude of a specific cosine basis function. 2.1.44 decoded stream: The decoded reconstruction of a compressed bitstream. 2.1.45 decoder characteristics compliance: The properties and capabilities of the decoding process applied in the decoder. 2.1.46 decoder compliance compliance:
17、 A decoder is compliant, if the decoder meets the decoder requirements, specified in the normative clauses of parts 1, 2 and 3 of ISO/IEC 11172, to decode compliant bitstreams within the subset of the standard defined by the specified capabilities of the decoder. 2.1.47 decoder input buffer video: T
18、he first-in first-out (FIFO) buffer specified in the video buffering verifier. 2.1.48 decoder input rate video: The data rate specified in the video buffering verifier and encoded in the coded video bitstream. 2.1.49 decoder: An embodiment of a decoding process. 2.1.50 decoding (process): The proces
19、s defined in ISO/IEC 11172 that reads an input coded bitstream and produces decoded pictures or audio samples. 2.1.51 decoder requirements compliance: Requirements for decoders defined in the normative clauses of parts 1, 2 and 3 of ISO/IEC 11172. 4 0 ISO/IEC ISOAEC 11172-4: 1995 (E) 2.1.52 decoding
20、 time-stamp; DTS system: A field that may be present in a packet header that indicates the time that an access unit is decoded in the system target decoder. 2.1.53 de-emphasis audio: Filtering applied to an audio signal after storage or transmission to undo a linear distortion due to emphasis. 2.1.5
21、4 dequantization video: The process of resealing the quantized DCT coefficients after their representation in the bitstream has been decoded and before they are presented to the inverse DCT. 2.1.55 digital storage media; DSM: A digital storage or transmission device or system 2.1.56 discrete cosine
22、transform; DCT video: Either the forward discrete cosine transform or the inverse discrete cosine transform. The DCT is an invertible, discrete orthogonal transformation. The inverse DCT is defined in annex A of ISO/IEC 11172-2. 2.1.57 display order video: The order in which the decoded pictures sho
23、uld be displayed. Normally this is the same order in which they were presented at the input of the encoder. 2.1.58 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 th
24、e stereo mode. 2.1.59 editing: The process by which one or more compressed bitstreams are manipulated to produce a new compressed bitstream. Conforming edited bitstreams must meet the requirements defined in ISOLEC 11172. 2.1.60 elementary stream system: A generic term for one of the coded video, co
25、ded audio or other coded bitstreams. 2.1.61 emphasis audio: Filtering applied to an audio signal before storage or transmission to improve the signal-to-noise ratio at high frequencies. 2.1.62 encoder: An embodiment of an encoding process. 2.1.63 encoding (process): A process, not specified in ISO/I
26、EC 11172, that reads a stream of input pictures or audio samples and produces a valid coded bitstream as defined in ISO/IEC 11172. 2.1.64 entropy coding: Variable length lossless coding of the digital representation of a signal to reduce redundancy. 2.1.65 fast forward playback video: The process of
27、 displaying a sequence, or parts of a sequence, of pictures in display-order faster than real-time. 2.1.66 FFT: Fast Fourier Transformation. A fast algorithm for performing a discrete Fourier transform (an orthogonal transform). 2.1.67 filterbank audio: A set of band-pass filters covering the entire
28、 audio frequency range. 2.1.68 fixed segmentation audio: A subdivision of the digital representation of an audio signal into fixed segments of time. 2.1.69 forbidden: The term “forbidden” when used in the clauses defining the coded bitstream indicates that the value shall never be used. This is usua
29、lly to avoid emulation of start codes. 2.1.70 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. 2.1.71 forward motion vector video: A motion
30、vector that is used for motion compensation from a reference picture at an earlier time in display order. ISOAEC 11172-4: 1995 (E) 0 ISOAEC 2.1.72 frame audio: A part of the audio signal that corresponds to audio PCM samples from an audio access unit. 2.1.73 free format audio: Any bitrate other than
31、 the defined bitrates that is less than the maximum valid bitrate for each layer. 2.1.74 future reference picture video: The future reference picture is the reference picture that occurs at a later time than the current picture in display order. 2.1.75 granules Layer II audio: The set of 3 consecuti
32、ve subband samples from all 32 subbands that are considered together before quantization. They correspond to 96 PCM samples. 2.1.76 granules Layer III audio: 576 frequency lines that carry their own side information. 2.1.77 group of pictures video: A series of one or more coded pictures intended to
33、assist random access. The group of pictures is one of the layers in the coding syntax defined in ISO/IEC 11172-2. 2.1.78 Hann window audio: A time function applied sample-by-sample to a block of audio samples before Fourier transformation. 2.1.79 Huffman coding: A specific method for entropy coding.
34、 2.1.80 hybrid filterbank audio: A serial combination of subband filterbank and MDCT. 2.1.81 IMDCT audio: Inverse Modified Discrete Cosine Transform. 2.1.82 intensity stereo audio: A method of exploiting stereo irrelevance or redundancy in stereophonic audio programmes based on retaining at high fre
35、quencies only the energy envelope of the right and left channels. 2.1.83 interlace video: The property of conventional television pictures where alternating lines of the picture represent different instances in time. 2.1.84 intra coding video: Coding of a macroblock or picture that uses information
36、only from that macroblock or picture. 2.1.85 intra-coded picture; I-picture video: A picture coded using information only from itself. 2.1.85a ISO/IEC 11172-1 decoder compliance: An embodiment of a decoding process for an ISO/IEC 11172- 1 bitstream. MPEG-system decoder is a synonym. 2.1.85b ISO/IEC
37、11172-2 decoder compliance: An embodiment of a decoding process for an ISO/IEC 11172-2 bitstream. MPEG-video decoder is a synonym. 2.1.85 ISO/IEC 11172-3 decoder compliance: An embodiment of a decoding process for an ISO/IEC 11172-3 bitstream. MPEG-audio decoder is a synonym. 2.1.86 ISO/IEC 11172 (m
38、ultiplexed) stream system: A bitstream composed of zero or more elementary streams combined in the manner defined in this part of ISO/IEC 11172. 2.1.87 joint stereo coding audio: Any method that exploits stereophonic irrelevance or stereophonic redundancy. 2.1.88 .joint stereo mode audio: A mode of
39、the audio coding algorithm using joint stereo coding. 2.1.89 layer audio: One of the levels in the coding hierarchy of the audio system defined in ISO/IEC 11172-3. 0 ISO/IEC ISO/IEC 11172-4: 1995 (E) 2.1.90 layer video and systems: One of the levels in the data hierarchy of the video and system spec
40、ifications defined in this part of ISO/IEC 11172 and ISO/IEC 11172-2. 2.1.91 luminance (component) video: A matrix, block or single pel representing a monochrome representation of the signal and related to the primary colours in the manner defined in CCIR Ret 601. The symbol used for luminance is Y.
41、 2.1.92 macroblock video: The four 8 by 8 blocks of luminance data and the two corresponding 8 by 8 blocks of chrominance data coming from a 16 by 16 section of the luminance component of the picture. Macroblock is sometimes used to refer to the pel data and sometimes to the coded representation of
42、the pel values and other data elements defined in the macroblock layer of the syntax defined in ISO/IEC 11172-2. The usage is clear from the context. 2.1.93 mapping audio: Conversion of an audio signal from time to frequency domain by subband filtering and/or by MDCT. 2.1.94 masking audio: A propert
43、y of the human auditory system by which an audio signal cannot be perceived in the presence of another audio signal . 2.1.95 masking threshold audio: A function in frequency and time below which an audio signal cannot be perceived by the human auditory system. 2.1.96 MDCT audio: Modified Discrete Co
44、sine Transform. 2.1.97 motion compensation video: The use of motion vectors to improve the efficiency of the prediction of pel values. The prediction uses motion vectors to provide offsets into the past and/or future reference pictures containing previously decoded pel values that are used to form t
45、he prediction error signal. 2.1.98 motion estimation video: The process of estimating motion vectors during the encoding process. 2.1.99 motion vector video: A two-dimensional vector used for motion compensation that provides an offset from the coordinate position in the current picture to the coord
46、inates in a reference picture. 2.1.100 MS stereo audio: A method of exploiting stereo irrelevance or redundancy in stereophonic audio programmes based on coding the sum and difference signal instead of the left and right channels. 2.1.101 non-intra coding video: Coding of a macroblock or picture tha
47、t uses information both from itself and from macroblocks and pictures occurring at other times. 2.1.102 non-tonal component audio: A noise-like component of an audio signal. 2.1.103 Nyquist sampling: Sampling at or above twice the maximum bandwidth of a signal. 2.1.104 pack system: A pack consists o
48、f a pack header followed by one or more packets. It is a layer in the system coding syntax described in this part of ISO/IEC 11172. 2.1.105 packet data system: Contiguous bytes of data from an elementary stream present in a packet. 2.1.106 packet header system: The data structure used to convey info
49、rmation about the elementary stream data contained in the packet data. 2.1.107 packet system: A packet consists of a header followed by a number of contiguous bytes from an elementary data stream. It is a layer in the system coding syntax described in this part of ISO/IEC 11172. 2.1.108 padding audio: A method to adjust the average length in time of an audio frame to the duration of the corresponding PCM samples, by conditionally addi
