Image compression with transform coefficient analysis

• US 7,079,697 B2
• Filed: 03/19/2002
• Issued: 07/18/2006
• Est. Priority Date: 03/19/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Zhou, Minhua
• Primary Examiner(s): Alavi, Amir
• Application Number:
  US10/102,323
• Publication Number:
  US 20020164081A1
• Time in Patent Office: 1,582 Days
• Field of Search: 382/172, 382/218, 382/232, 382/233, 382/250, 375/240.03, 375/240.18, 375/240.2, 348/395.1, 348/400.1, 348/414.1
• US Class Current: 382/250
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A method of image/video compression with intra-coding blocks analyzed for sum of absolute magnitudes of AC coefficients of DCT of block to determine whether to approximate the block with 0 AC coefficients, and with inter-coding blocks analyzed for sum of absolute differences of block and predicted block to determine whether to approximate the block with a 0 block.

Claims

1. A method of image compression, comprising:

(a) transforming a block of pixel values to a set of coefficients;

(b) comparing a measure of a subset of the set of coefficients to a threshold,

wherein said subset contains at least two coefficients, and when the measure is less than the threshold, treating the subset as zero coefficients.

2. The method of claim 1, wherein:

(a) said transforming is a DCT; and

(b) said subset of the set of coefficients is the subset of AC coefficients.

3. An image compressor, comprising:

(a) a DCT transformer;

(b) a comparator coupled to said transformer and operable to compare a measure of a subset of the set of DCT coefficients from said DCT transformer to a threshold wherein said subset contains at least two coefficients; and

(c) a compressor coupled to the output of said DCT transformer and to said comparator, and when the comparator indicates said measure is less than said threshold, the compressor is operable to treat the subset as zero coefficients.