1、STD-SMPTE EL 23-ENGL 3977 8357403 U0028b7 2Db SMPTE ENGINEERING GUIDELINE EG 21-1997 Revision of EG 21-1993 Nomenclature for Television Digital Recording of 19-mm Type D-1 Component and Type D-2 Composite Formats I Scope This guideline explains terms as used in the docu- ments defining the D-1 and D
2、-2 digital television recording formats. 2 General definitions 2.1 D-1 format recorder: A 19-mm cassette- based digital recorder for component video and other television signals in accordance with ANSIEMPTE 227M. 2.2 D-2format recorder: A 19-mm cassette- based digital recorder for composite video an
3、d other television signals in accordance with ANSIISMPTE 247M. 2.3 programareas: That part of the tape on which is digitally recorded the program video and audio signals. 2.4 program area track pattern: T h e a rra n g e- ment of video and audio sectors on helical-scan tracks within the program area
4、. 3 Track pattern allocation -Video and audio segments 3.1 video segment: A video segment contains the digital video data originating from one con- tiguous portion of a television field. It is recorded within several video sectors, which are located in adjacent video tracks. 3.2 audio segment: An au
5、dio segment contains the digital audio data associated with one or more video segments. These data are written into several audio sectors. Audio sectors from different audio channels are interleaved and Page 1 of 5 pages written on adjacent helical tracks at the ends of video sectors. 4 Electrical s
6、ignal allocation 4.1 video and audio sectors: A sector is a struc- tured sequence of data which incorporates the video or audio data and appropriate synchroniz- ing and identification patterns, so that the video or audio data can be recovered from tape and identified for subsequent processing. 4.1.1
7、 preamble: A preamble consists of a runup sequence, a sync pattern, an identification pattern, and some fill data. 4.1.1.1 runupsequence: A runup sequence consists of a sequential bit pattern chosen to facilitate the locking of data-extraction circuits. 4.1.1.2 sync pattern: A sync pattern consists
8、of two consecutive bytes whose bit pattern is chosen to be a robust indication of the start of a sync block. 4.1.1.3 identification pattern: An identification pattern consists of two to four consecutive bytes providing a unique address of the position of a sync block within two to four frames of rec
9、orded data. It may be coded to remove direct current and provide error protection. 4.1.1.4 fill data: Fill data consists of a few bytes of a fixed pattern which is designed to provide a minimum separation on tape between the runup, sync pattern, and the first sync block. Fill data may also be record
10、ed in the edit gap between sectors in a track. Copyright O 1997 by the SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. HartsdaieA.ve., White Plains, NY 10607 (914) 761-1100 Approved September 18, 1997 STD-SMPTE EG 21-ENGL 1997 8357403 0002870 T28 9 EG 21 -1 997 4.1.2 sync block: A sync blo
11、ck consists of a sync pattern followed by an identification pattern followed by two inner code blocks. 5.6 bit rate: The rate at which encoded informa- tion is transmitted from one part of a system to another, expressed in bits per second. 4.1.2.1 inner code block: An inner code block consists of a
12、number of bytes of video data, audio data, or outer code check data, followed by a number of inner code check data. A D-2 inner code block may include an identification pattern. 5.6.1 In component digital video with a lumi- nance sampling frequency of 13.5 MHz and a color difference sampling frequen
13、cy of 6.75 MHz for each of the two color-difference channels and 8-bit PCM encoding of each sample, the bit rate is 216 million bits per second. 4.1.3 postamble: A postamble consists of a sync pattern followed by an identification pattern and, possibly, some fill data. 5 Subsets of binary data Usual
14、ly, for convenience in parallel digital processing, binary information is processed in groups of bits referred to in the literature as words or bytes. These terms have generally understood meanings but are not unambiguously defined. For the purpose of this terminology, the following definitions are
15、assumed: 5.1 bit: A contraction of binary and digit to define a unit of information. 5.2 bit-parallel: Refers to a set of concurrent data bits present on a like number of data lines used to carry information. Bit-parallel data bits may be acted upon concurrently as a group (word) or independently as
16、 individual data bits. 5.6.2 In composite digital video with a sampling frequency of 14.32 MHz (4f) and 8-bit PCM encoding of each sample, the bit rate is approxi- mately 114 million bits per second. 5.7 bus: A signal line or a set of signal lines used by an interface to which multiple devices are c
17、onnected and over which messages are carried. 5.8 unidirectional bus: A b u s u sed by a n y individual device for one-way transmission only; that is, either input only or output only. 5.9 positive binary: The condition where the most positive of the two possible signal levels is a logical 1. 5.10 c
18、lock: A source of accurately timed pulses used for synchronization in a digital computer or as a time base in a transmission system. 5.3 byte: A byte consists of eight bits of binary information. It may have an identity other than being a convenient processing unit (for example, see video data word)
19、, but generally this is not implicit. signal. Asynchronous clock in this application means that the clock Pulses are Synchronous in frequency and phase to the video horizontal rate for a component signal or the chrominance subcarrier frequency foracomposite 5.4 video data word: A video data word is
20、a byte in which the eight bits represent the possible 256 quantum levels of a video sample. 5.5 audio data word: An audio data word con- sists of 16 to 20 bits. In the most basic operating mode 16 bits represent the possible 216 quantum levels of an audio sample and four bits are used for auxiliary
21、signals. Other modes are defined in which either one, two, three, or four of the auxiliary signal bits are allocated to extend the dynamic range of the audio sample quantization. For convenience, the 20-bit word may be proc- essed in five words of four bits each. 5.11 data lines: Refers to the inter
22、connecting signal lines of the interface system. A single data line is defined as a pair of signal lines due to the balanced electrical specification of the system. The signal wires that make up a data line are usually twisted together for crosstalk considera- tions in conventional cable technology.
23、 5.12 data rate: The rate at which data is trans- ferred from one part of the system to another expressed in bits, bytes, or words per second. 2 I 5.13 ECL: Refers to emitter coupled logic. This logic is a nonsaturating form of digital logic Page 2 of 5 pages STD-SMPTE EG 21-ENGL 1777 M 8357401 0002
24、873 Yb4 = which eliminates transistor storage time, permit- ting very high speed operation. Standard ECL in this application means an integrated circuit de- vice of the ECL 10,000 series or equivalent. 5.14 interface system: The device-independent mechanical, electrical, and functional elements of a
25、n interface necessary to effect communica- tion among a set of devices. Cables, connector, driver and receiver circuits, signal line descrip- tions, timing and control conventions, and func- tional logic circuits are typical interface system elements. 5.15 LSB: Least significant bit of a data word.
26、5.16 MSB: Most significant bit of a data word. 5.17 parallel interface: Pertains to a transmis- sion system wherein all bits of a particular character are sent simultaneously. 5.18 serial interface: Pertains to a transmission system wherein all bits are sent in serial (series) order. 5.19 system: A
27、set of interconnected elements constituted to achieve a given objective by per- forming a specified function. 6 Error protection strategy 6.1 Various methods are used to reduce the effect of data errors on the objective and subjec- tive quality of the replayed video or audio. The appropriate combina
28、tion of methods to achieve an optimum result is generally known as the error protection strategy. 6.1.1 error correction: The use of mathemati- cally related check data, recorded with the video and audio data, to determine the precise value and location and, hence, enable correction of data errors.
29、6.1.2 error concealment: To replace the error sample with the interpolation of adjacent audio or video samples as an estimate of the value of data words previously detected to be in error, but which cannot be corrected. 6.1.3 source precoding: The mapping of video data words so that, for the most pr
30、obable EG 21-1997 distribution of data errors, there is a reduction in the peak error produced in a video sample. Source precoding is used in the type D-I format. Source precoding is not used in the type D-2 format. 7 Error protection - Data organization 7.1 Error correction for both video data and
31、audio data is of the product block type in which each data word is included in the computation of two sets of check data known as outer code check data and inner code check data, respec- tively. Additionally, the video and audio data are redistrib- uted from their naturally occurring sequences in or
32、der to reduce the effect of burst errors. Outer code check data are the first to be computed. Inner code check data are the second to be computed, and are applied to the outer code check data as well as to the video and audio data. 7.2 data sector array: For the application of product block error co
33、rrection, the video data words to be recorded in a video sector are con- sidered as a rectangular array with rows and columns. 7.2.1 outer code check data -outer code block: Outer code check data consists of a number of bytes computed from a column of the video data array and regarded as being appen
34、ded. 7.2.2 inner code check data - inner code block: Inner code check data consists of a number of bytes computed from a row of the array (or a row of the outer code check data) and appended to that subset. The resulting bytes are known as an inner code block. 7.2.3 product block: The array defined
35、by a number of inner code blocks or the correspond- ing outer code blocks is known as a product block. There are a number of such product blocks in each sector. 7.3 Video and audio data redistribution 7.3.1 interleaving: The systematic reordering of data so that originally adjacent bytes of data in
36、an error correcting code are separated on tape, Page 3 of 5 pages STD-SMPTE EG 21-ENGL 1797 8357Ll01, 0002872 BTO D EG 21-1997 thus reducing the effect of bursts of data errors on the error correcting capability. The separa- tion is known as the interleave distance. 7.3.2 shuffling: The systematic r
37、eordering of video or audio data words to increase the probability that uncorrectable samples are surrounded by error-free data words, for the application of error concealment. 8 Coding and modulation 8.1 channel coding: The process by which binary information obtained from the digital logic circuit
38、s, used in the processing of video and audio data, is converted to a waveform suitable for recording onto a magnetic medium. 8.2 randomization: The reduction of correlation in a serial bit sequence so that it statistically approximates a random sequence. 8.3 scrambling: Alternate term for randomiza-
39、 tion. 8.4 mapping: The recoding of data by computa- tion or look-up table, so that there is a defined one-to-one relationship between each original code word and the derived code word. 8.5 composite video signal (analog): The color- picture signal, encoded in the NTSC standard, including blanking a
40、nd all synchronizing signals. 8.6 composite encoded signal (digital): A digital representation of a composite video signal. 8.7 digitize: To sample. quantize, and code an analog signal. 8.8 PCM (pulse-code modulation): A format for representing information as a set of digital words. As used herein,
41、the process involves the conversion of a signal from analog to digital form by means of sampling, quantizing, and coding. The peak-to-peak amplitude range of the analog signal is divided into a finite number of discrete values each having its own value code. 8.9 linear PCM: Pertaining to quantizing
42、inter- vals that are equal throughout the range of the system. 8.10 quantization: The division of a continuous range of values into a finite number of distinct values. 8.11 sampling: The process of obtaining a series of discrete, instantaneous values of a signal at regular or intermittent intervals.
43、 8.12 SCH: An abbreviation for the timing rela- tionship between the color subcarrier burst and horizontal sync pulses of a composite color video signal. Zero SCH occurs when the positive going zero-crossings of a subcarrier with the same phase as the color burst are nominally coincident with the 50
44、% point on the leading edges of the even horizontal sync pulses in color field I. as shown in ITU-R BT.470. 9 Mechanical terms 9.1 basic dimension: A basic dimension is fundamental dimension to which no tolerance applicable. 9.2 derived dimension: A derived dimension a is obtained from other fundame
45、ntal dimensions by computation and is given for information purposes only. 9.3 reference dimension: A dimension usually without tolerance, used for informational pur- poses. It may be a dimension resulting from other values. 9.4 scanner: A mechanical assembly containing a drum, rotating pole tips, a
46、nd tape-guiding elements used to record and reproduce data. 9.5 drum: A cylindrical column around which the tape is at least partially wrapped in order to form a head-to-tape interface of a recording system. 9.6 effective diameter: The effective diameter is the diameter at the surface of tape wrappe
47、d around the drum which includes the drum diameter and the air film between drum and tape. i 9.7 helix angle: An angle formed between the path of the rotating pole tips and the tape refer- ence edge-guiding system on the scanner of the helical-scan recording system. Page 4 of 5 pages STD-SMPTE EG 21
48、-ENGL 1777 8357403 O002873 737 EG 21-1997 9.8 trackangle: An angle of the helical track record with respect to the reference edge of the tape. tape entrance and exit guides of the scanner in the recording system. 10 Editing definitions 9.9 effective wrap angle: An angle at the center of the drum sub
49、tended bv the start and endpoint of the track. 10.1 edit gap: The space between adjacent sec- tors, to which edit transitions must be confined, start Of the preamble. 10.2 cue track: The longitudinal track reserved for the recording of audio frequency signals which are to be used for editing reference pur- poses. 9.10 total wrap angle: An angle at the center between the end ofthe sector postamble and the of the drum subtended by the lines of contact between the drum and the reference edge of the tape. 9.11 center span tension: A calculated value of the tape tension at a point midway
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