ISO/IEC JTC 1/SC 29/WG 1 N234  
							    	     Date:   July 21, 1995

ISO/IEC JTC 1/SC 29/WG 1
(ITU-T SG8)

Coding of Still Pictures

JBIG                              JPEG
Joint Bi-level Image                     Joint Photographic 
 Experts Group                            Experts Group

TITLE:  		Invitation to Suggest Common Compression Coding Methods 			for use with all JBIG-2 Proposals

SOURCE:		SC29/WG1/JBIG

PROJECT:		JTC 1.29.10

STATUS:     		

REQUESTED
ACTION:		For Information

DISTRIBUTION:	WG1  Mailing List

Contact:
ISO/IEC JTC 1/SC 29/WG 1 Convenor - Eric Hamilton
C-Cube Microsystems, 1778 McCarthy Blvd., Milpitas CA  95035, USA
Tel:  +1 408 944 6335,   Fax:  +1 408 944 6314,   E-mail:  eric@c-cube.com 

ISO
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
ORGANIZATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG1
CODING OF STILL PICTURES

ISO/IEC JTC1/SC29WG1 N234
21 July, 1995

TITLE:  	Invitation to Suggest Common Compression Coding Methods for use 		with all  JBIG-2 Proposals
SOURCE:  	SC29/WG1/JBIG

INVITATION

The ISO/IEC SC29/WG1 working group invites suggestions for compression encoding and decoding methods, to code the intermediate results from all JBIG-2 proposals with one common datastream and decoder definition.  Suggested building blocks for such a common decoder are presented in Fig. 1.  Each block represents the need to define a noiseless decoder (and implicitly an encoder) subsystem for a common JBIG-2 decoder function.  Note that not all decoder subsystem functions will need to be used by each proposal received to date.

TEST DATA

Test data will be provided in a series of test ‘sets’, which are the intermediate results from one JBIG-2 proposal after it has been  applied to a JBIG-2 test imageplus a ‘trace file’, as produced by a JBIG-2 proposal or benchmark ‘test system’ selected by the JBIG-2 working group. 

The images provided for each test set will be as follows -

  (1) the original JBIG-2 test image
  (2) an image of all the marks processed for lossy coding, as presented and positioned by  	the given JBIG-2 test system.
  (3) an overlay image of all non-mark data, as determined by the JBIG-2 test system.

The trace file provided for each test set will be made up of an ordered record for each mark as processed for lossy coding, consisting of the following fields -

  (1) Bitmap Image Field - the lossy bitmap image for each mark and its bounding box dimensions, as prepared by the JBIG-2 test system.
  (2) Location Field - the absolute image location for the upper left corner of the above processed mark’s bounding box.
  (3) Matching Symbol Index Field - the Symbol Bitmap Library (207) index number use for regenerating the above processed mark bitmap, as assigned by the matching process in the JBIG-2 test system.
  (4) Library Symbol Flag Field - a flag indicating whether the bitmap for this mark is to be added to the decoder library.
  (5) Symbol Index Field - the Symbol Bitmap Library (207) index number used when adding the above processed mark to the library, as assigned by the JBIG-2 test system.
  (6) Symbol Refinement Flag Field - a flag indicating whether the bitmap for this mark is to be regenerated using the indexed Symbol Library bitmap, refined by additional decoded information from the Symbol Bitmap Refinement Decoder (203).

The marks and their record in the trace file will be ordered as prepared by the JBIG-2 test system for coding into a JBIG-2 datastream.  The presence of a mark record, will imply the need to code a mark index, possibly its bounding box dimensions and its bounding box location (if this is not null), for decoding by a Symbol Index Decoder (202) and Mark Location Decoder (204).

For a one-pass system the first sequential instance of a number in the Symbol Index Field will imply that the corresponding mark bitmap is to be encoded and then decoded by a Library Symbol Bitmap Decoder (201), for addition to the decoder’s symbol library.  This will be indicated by a ‘1’ in the Library Symbol Flag Field as well as a cross-check.

If the given mark bitmap does not exactly coincide with the library symbol to which it is matched, additional data may also be coded and a method suggested for refining the symbol to become the given mark bitmap if the test set specifies this requirement.  This requirement will be indicated by setting the Symbol Refinement Flag Field to ‘1’ in the corresponding test set record.  This additional data will have to be suggested and provided, for subsequent decoding and use by a Symbol Bitmap Refinement Decoder (203).  Note that in the general case, such refined mark bitmaps may also be added to the Symbol Bitmap Library (207) if the test set requires this by indicating a new number in the corresponding Symbol Index field (appropriate datastream signaling may also have to provided in the suggested coding method).  This additional requirement can also be inferred by referring to the Library Symbol Flag Field.

For a two-pass coding system, the initial mark records may contain null image locations, to indicate data used for pre-loading of a set of initial symbol bitmaps into the decoder’s symbol library via the Library Symbol Bitmap Decoder (201).

PAGE MAKEUP

A lossy image of the textual data will be prepared using a suggested method for encoding and then decoding the trace of processed marks (201, 202, 203, 204), as part of  a process called ‘page makeup’ (208, 209).  (This process does not require a full-page buffer, but does require a strip buffer of adequate height).  The lossy image of all processed marks provided in the test set can be used as a check against the above suggested method for assembling the mark bitmaps and locations into a lossy textual image (as a cross-check).

A method for coding an overlay image of all non-mark data in the original image will have to be suggested for a Non-mark Lossless Image Decoder (205).  This method should be demonstrated  using the overlay image provided in the test set.  The decoded overlay image results are to be combined with the above lossy mark image in the output Page Buffer (209).

A coding method will also have to be suggested for reconstructing the exact original image, using the lossy mark image and non-mark overlay image data in the Page Buffer (209), plus additional information received from a Lossless Refinement Decoder (206).

Note that for this process, no limit will be set for the memory size in the Symbol Bitmap Library (207).  However, recording of the maximum library memory used for each test set will be needed for evaluation of the suggested coding methods.

REQUESTED RESULTS

Suggested coding methods and datastream signaling for each decoder sub-system (201, 202, 203, 204, 205, 206) should be described in sufficient detail to be duplicated and independently tested.  Any headers necessary to define a complete working datastream will also have to be suggested.

For each test set, compressed byte counts should be reported as produced by each decoder sub-system used (including all bytes required for datastream signaling).  The combined compressed byte count should also be reported for the suggested overall method, implied by using all the subsystems required to (a) lossily and (b) losslessly encode each test set, (including any headers suggested).  In addition, the maximum memory size used for each test set should be reported.