BS ISO IEC 18477-1 pdf download.Information technology — Scalable compression and coding of continuous-tone still images
3 Terms and definitions
For the purposes of this document, the following definitions apply. 3.1 bit stream partially encoded or decoded sequence of bits comprising an entropy-coded segment 3.2 block 8 × 8 array of samples or an 8 × 8 array of DCT coefficient values of one component 3.3 byte group of 8 bits 3.4 coder embodiment of a coding process 3.5 coding encoding or decoding 3.6 compression reduction in the number of bits used to represent source image data 3.7 component two-dimensional array of samples having the same designation in the output or display device Note 1 to entry: An image typically consists of several components, e.g. red, green and blue. 3.8 continuous-tone image image whose components have more than one bit per sample 3.9 discrete cosine transform DCT either the forward discrete cosine transform or the inverse discrete cosine transform 3.10 downsampling procedure by which the spatial resolution of a component is reduced 3.11 entropy-coded (data) segment independently decodable sequence of entropy encoded bytes of compressed image data 3.12 entropy decoder embodiment of an entropy decoding procedure 3.13 entropy decoding lossless procedure which recovers the sequence of symbols from the sequence of bits produced by the entropy encoder 3.14 entropy encoder embodiment of an entropy encoding procedure 3.15 entropy encoding lossless procedure which converts a sequence of input symbols into a sequence of bits such that the average number of bits per symbol approaches the entropy of the input symbols 3.16 grayscale image continuous-tone image that has only one component 3.17 joint photographic experts group JPEG informal name of the committee which created this International Standard Note 1 to entry: The “joint” comes from the ITU-T and ISO/IEC collaboration. 3.18 legacy decoder embodiment of a decoding process conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 operating in baseline, sequential or progressive mode with a sample resolution of eight bits 3.19 marker two-byte code in which the first byte is hexadecimal FF and the second byte is a value between 1 and hexadecimal FE 3.20 marker segment marker and associated set of parameters 3.21 pixel collection of sample values in the spatial image domain having all the same sample coordinates Note 1 to entry: A pixel may consist of three samples describing its red, green and blue value. 3.22 precision number of bits allocated to a particular sample or DCT coefficient 3.23 procedure set of steps which accomplishes one of the tasks which comprise an encoding or decoding process 3.24 quantization value integer value used in the quantization procedure 3.25 quantize act of performing the quantization procedure for a DCT coefficient 3.26 sample one element in the two-dimensional array which comprises a component 3.27 sample grid common coordinate system for all samples of an image with the samples at the top left edge of the image having the coordinates (0, 0), the first coordinate increases towards the right, the second to the bottom 3.28 scan single pass through the data for one or more of the components in an image 3.29 scan header marker segment that contains a start-of-scan marker and associated scan parameters that are coded at the beginning of a scan 3.30 upsampling procedure by which the spatial resolution of a component is increased 3.31 vertical sampling factor relative number of vertical data units of a particular component with respect to the number of vertical data units in the other components in the frame
5 Conventions
5.1 Conformance language The keyword “reserved” indicates a provision that is not specified at this time, shall not be used, and may be specified in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never be specified in the future. 5.2 Operators NOTE Many of the operators used in this part of ISO/IEC 18477 are similar to those used in the C programming language.
BS ISO IEC 18477-1 pdf download
