Method for compressing image data and image data compressing system

• US 10,264,267 B2
• Filed: 04/12/2017
• Issued: 04/16/2019
• Est. Priority Date: 06/04/2016
• Status: Active Grant

• Current Assignee: Xueshan Technologies Inc. (Wi-LAN Inc.)
• Original Assignee: MStar Semiconductor Incorporated (MediaTek, Inc.)
• Inventors: Huang, Yi-Chin, Tung, Yi-Shin
• Primary Examiner(s): Hon, Ming Y
• Application Number:
  US15/485,315
• Publication Number:
  US 20170353728A1
• Time in Patent Office: 734 Days
• 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 19/146 Data rate or code amount at the encoder output
• 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 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream

Abstract

A method for compressing image data is provided. The image data includes a file to be compressed, which includes N blocks to be compressed. The method includes: setting a target data increment of each of the N blocks of the file according to a 0^th accumulated target data size and an N^th accumulated target data size; before compressing an n^th block, calculating an (n−1)^th accumulated target data size of an (n−1)^th block according to the 0^th accumulated target data size and the target data increment; when a difference between an (n−1)^th accumulated compressed data size and the (n−1)^th accumulated target data size is smaller than a predetermined threshold, removing X least significant bit(s) of a plurality of sets of data in the n^th block to generate an updated n^th block; and compressing the updated n^th block to generate a compressed n^th block.

Claims

1. A method for compressing image data, comprising:

setting a target data increment of each of N blocks that need to be compressed of an image to be compressed according to a 0^th accumulated target data size and an N^th accumulated target data size;

before compressing an n^th block among the N blocks, calculating an (n−

1)^th accumulated compressed data size of an (n−

1)^th block among the N blocks;

calculating an (n−

1)^th accumulated target data size of the (n−

1)^th block according to the 0th accumulated target data size and the target data increment;

removing X least significant bit(s) of a plurality of sets of data in the n^th block when a difference between the (n−

1)^th accumulated compressed data size and the (n−

1)^th accumulated target data size is smaller than a first predetermined threshold to generate an updated n^th block; and

compressing the updated n^th block to generate a compressed n^th block;

wherein, N and X are finite positive integers, and n is a finite positive integer not greater than N.

2. The method according to claim 1, further comprising:

before an m^th block among the N blocks is compressed, calculating an (m−

1)^th accumulated compressed data size of an (m−

1)^th block among the N blocks;

calculating an (m−

1)^th accumulated target data size of the (m−

1)^th block according to the 0^th accumulated target data size and the target data increment;

removing Y least significant bit(s) of a plurality of sets of data in the m^th block when a difference between the (m−

1)^th accumulated compressed data size and the (m−

1)^th accumulated target data size is greater than the first threshold but smaller than a second threshold to generate an updated m^th block; and

compressing the updated m^th block to generate a compressed m^th block;

wherein, the second predetermined threshold is greater than the first predetermined threshold, Y is a finite positive integer smaller than X, and m is a finite positive integer not greater than N and different from n.

3. The method according to claim 2, wherein X is 2 and Y is 1.

4. The method according to claim 1, wherein 0^th accumulated target data size is greater than the first predetermined threshold.

5. The method according to claim 1, further comprising updating the 0^th accumulated target data size according to compression archives of each of the blocks that needs to be compressed.

6. The method according to claim 1, wherein the N^th accumulated target data size is a total data size divided by a target compression rate.

7. An image data compressing system, comprising:

a compressor, compressing an image to be compressed according to a predetermined compression algorithm, wherein data of the image comprises N blocks that need to be compressed; and

a compression rate control circuit, coupled to the compressing module, comprising;

a compressed data accumulator, calculating an (n−

1)^th accumulated compressed data size of an (n−

1)^th block among the N blocks before an n^th block among the N blocks is compressed according to a block compressed data size that the compressing module generates after compressing the (n−

1)^th block;

a target data accumulator, calculating an (n−

1)^th accumulated target data size of the (n−

1)^th block according to a 0^th accumulated target data size and a target data increment of each of the blocks; and

a comparator, outputting a first compression control signal to the compressing module when a difference between the (n−

1)^th accumulated compressed data size and the (n−

1)^th accumulated target data size is smaller than a first predetermined threshold;

wherein, the compressing module further removes X least significant bit(s) of a plurality of sets of data in the n^th block to generate an updated n^th block when receiving the first compression control signal, and compresses the updated n^th block to generate a compressed n^th block; and

N and X are finite positive integers, and n is a finite positive integer not greater than N.

8. The image data compressing system according to claim 7, wherein:

the compressed data accumulator further calculates an (m−

1)^th accumulated compressed data size of an (m−

1)^th block among the N blocks before an m^th block among the N blocks is compressed;

the target data accumulator further calculates an (m−

1)^th accumulated target data size of the (m−

1)^th block according to the 0^th accumulated target data size and the target data increment;

the comparator further outputs a second compression control signal to the compressing module when a difference between the (m−

1)^th accumulated compressed data size and the (m−

1)^th accumulated target data size is greater than the first threshold but smaller than a second threshold;

the compressor further removes Y least significant bit(s) of a plurality of sets of data in the m^th block when the second compression control signal is received to generate an updated m^th block, and compresses the updated m^th block to generate an compressed m^th block; and

the second predetermined threshold is greater than the first predetermined threshold, m is a finite positive integer not greater than N and different from n, and Y is a finite positive integer smaller than X.

9. The image data compressing system according to claim 8, wherein X is 2 and Y is 1.

10. The image data compressing system according to claim 7, wherein 0^th accumulated target data size is greater than the first predetermined threshold.

11. The image data compressing system according to claim 7, wherein the compression rate control circuit further updates the 0^th accumulated target data size according to compression archives of each of the blocks that needs to be compressed.

12. The image data compressing system according to claim 7, wherein the N^th accumulated target data size is a total data size divided by a target compression rate.