Apparatus for compressing image data employing entropy encoding of data scanned from a plurality of spatial frequency bands

• US 5,537,493 A
• Filed: 06/29/1994
• Issued: 07/16/1996
• Est. Priority Date: 08/27/1993
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony United Kingdom Limited (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony United Kingdom Limited (Sony Group Corp.)
• Inventors: Wilkinson, James H.
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Johns, Andrew W.
• Application Number:
  US08/267,679
• Time in Patent Office: 748 Days
• Field of Search: 382/233, 382/240, 382/245, 382/246, 382/248, 358/261.1, 358/427, 358/432, 358/433, 348/398, 348/403, 348/437, 348/438
• US Class Current: 382/240
• CPC Class Codes: H04N 19/129 Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/1883 the unit relating to sub-band structure, e.g. hierarchical level, directional tree, e.g. low-high [LH], high-low [HL], high-high [HH]
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/64 characterised by ordering of coefficients or of bits for transmission
• CPC Class Codes: H04N 19/645 by grouping of coefficients into blocks after the transform
• CPC Class Codes: H04N 19/65 using error resilience
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/89 involving methods or arrangements for detection of transmission errors at the decoder

Abstract

A data compression technique is described for use in systems employing frequency separation, such as wavelet separation, in which the sub bands (0 to 9) have different numbers of frequency component values therein. The sub bands are scanned to form a stream of data for feeding to an entropy encoder (30) in an order in which a number of samples from each sub band are taken in turn, that number being proportional to how many frequency values are in the particular sub band.

Claims

1. Apparatus for compressing image data, said apparatus comprising:

(i) means for frequency separating input image data into a plurality of spatial frequency bands, at least some lower spatial frequency bands containing fewer frequency component values than at least some higher spatial frequency bands;

(ii) means for scanning frequency component values from said plurality of spatial frequency bands with a repeating scan pattern to form a scanned data stream, said scan pattern being such that a number of frequency component values are read from corresponding spatial positions within each given spatial frequency band, said number being proportional to how many frequency component values are in said given spatial frequency band, successive ones of said repeating scanning pattern corresponding to non spatially adjacent positions within said image data; and

(iii) means for entropy encoding said scanned data stream to form compressed image data.

2. Apparatus for compressing image data, said apparatus comprising:

(i) means for frequency separating input image data into a plurality of spatial frequency bands, at least some lower spatial frequency bands containing fewer frequency component values than at least some higher spatial frequency bands;

(ii) means for scanning frequency component values from said plurality of spatial frequency bands with a repeating scan pattern to form a scanned data stream, said scan pattern being such that a number of frequency component values are read from corresponding spatial positions within each given spatial frequency band, said number being proportional to how many frequency component values are in said given spatial frequency band; and

(iii) means for entropy encoding said scanned data stream to form compressed image data, said means for entropy encoding including means for generating end of block codes indicating that all further frequency component values within a scan pattern from a current position are zeros.