1、Union internationale des telecommunications Place des Nations 1211 GENEVE 20 Suisse Switzerland Suiza COVERING NOTE GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Geneva, 9 June 2005 ITU TELECOMMUNICATION STANDARDIZATION SECTOR Subject: Erratum 1 (06/2005) to ITU-T Recommendation T.44 (01
2、/2005), Mixed Raster Content (MRC) Modify the note in Table 1/T.44 “Mask (even-numbered layer) coder octet(s)“ as follows: NOTE New bi-level coders (i.e., a 5th, 6th and 7th coder) would be assigned bit numbers 4, 5 and 6 respectively. Bit 7, the extend bit, would be set when adding another octet to
3、 accommodate additional coders, such as an 8th which would be assigned to bit number 8. Modify “Table 2/T.44 Image (odd-numbered layer) coder octet(s)“ as follows: Octet bit number Coder used LSB 0 T.81 (JPEG) coding and ITU-T Rec. T.42/LAB 1 T.82 (JBIG1) coding applying ITU-T Recs T.43 and T.42/LAB
4、 2 T.45 “Run-length Colour Encoding“ and ITU-T Rec. T.42/LAB, Annex B/T.44 is required (Note 1) 3 T.81 (JPEG) coding and ITU-T Rec. T.42/YCC 4 T.82 (JBIG1) coding applying ITU-T Recs T.43 and T.42/YCC 5 T.45 “Run-length Colour Encoding“ and ITU-T Rec. T.42/YCC, Annex B/T.44 is required (Note 1) 6 Re
5、served MSB 7 Extend, add another octet that follows immediately NOTE 1 Coding scheme(s) referencing this Note shall use the SLC (Start of Layer Coded data) marker segment, defined in the Layer Data Structure clause of Annex A/T.44. This means that Mode 1 shall not be used with the referencing coding
6、 scheme. NOTE 2 New multi-level coders (i.e., 4th through 7th coder) would be assigned bit numbers 2 through 6 respectively. Bit 7, the extend bit, would be set when adding another octet to accommodate additional coders, such as an 8th which would be assigned to bit number 8. NOTE 3 In Mode 1, the i
7、mage code shall use either LAB (bits 0, 1 and 2) or YCC (bits 3, 4 and 5), but not both. Therefore, if any of bits 0, 1 or 2 is set, bits 3, 4 and 5 shall not be set. Conversely, if any of bits 3, 4 or 5 is set, bits 0, 1 and 2 shall not be set. 2 In Clause A.9.1 “Overview“, change paragraphs order
8、as follows: A.9.1 Overview The MRC image data consist of a series of: markers; parameters; data that specify the image coder, image size, bit resolution and spatial resolution; coded image data. The conventions of Annex B/T.81 are used broadly here. The JPEG registration body, per ITU-T Rec. T.86, h
9、as been used to register the marker code, APP13, classified as an application marker. Markers and/or marker segments used in association with the coding methods (i.e., encoder marker and/or marker segments) may be defined outside of this Recommendation (i.e., foreign encoder markers and/or marker se
10、gments). Foreign encoder markers and/or marker segments may be located within or outside of the data stream. A foreign encoder marker located outside the data stream shall be of the APPn form (i.e., an XFF octet followed by an octet not equal to X00 or XFF and optionally preceded by extra XFF octet
11、codes). Structure of a foreign encoder marker segment located outside the data stream shall be as follows: APPn, Length of segment, identifier, parameter and/or data. The MRC page structure for this application has the following elements: Parameters, markers, and entropy-coded data segments. Paramet
12、ers and markers are often organized into marker segments. Parameters are integers of length , 1, 2 or more octets. Markers are assigned two or more octet codes, an XFF octet followed by an octet not equal to X00 or XFF and optionally preceded by extra XFF octet codes. This application defines marker
13、 segments to denote the start of page (SOP), optional marker segments, the start of a stripe (SOSt), the start of layer coded data (SLC), encoder marker segments and end of header (EOH). The MRC Magic Number (JPEG SOI) is used immediately preceding the application marker as part of the SOP marker se
14、gment. The JPEG EOI is used as a termination number located directly after the last SOP parameter. The end of a page (EOP) is defined as XFFD9FFD9. These markers are inserted by the encoder, and understood by the decoder in addition to all markers used for the coding methods such as the SOI of ITU-T
15、 Rec. T.81. Markers and/or marker segments used in association with the coding methods (i.e., encoder marker and/or marker segments) may be defined outside of this Recommendation (i.e., foreign encoder markers and/or marker segments). Foreign encoder markers and/or marker segments may be located wit
16、hin or outside of the data stream. A foreign encoder marker located outside the data stream shall be of the APPn form (i.e., an XFF octet followed by an octet not equal to X00 or XFF and optionally preceded by extra XFF octet codes). Structure of a foreign encoder marker segment located outside the data stream shall be as follows: APPn, Length of segment, identifier, parameter and/or data.
