Method of compressing stress data, encoder, display driver and display device

Patent metadata

Field	Value
Publication number	US-12293697-B2
Application number	US-202418651869-A
Country	US
Kind code	B2
Filing date	May 1, 2024
Priority date	Sep 27, 2023
Publication date	May 6, 2025
Grant date	May 6, 2025

Abstract

In a method of compressing stress data in a display device, the stress data is divided into block stress data for a pixel block, a plurality of compressed codes are generated by encoding the block stress data in a plurality of encoding modes, it is determined whether the plurality of encoding modes are available encoding modes for the block stress data based on code lengths of the plurality of compressed codes and a number of available bits for the pixel block, a final encoding mode is selected among the available encoding modes based on quantization values of the available encoding modes, and a compressed bitstream for the pixel block is generated based on a compressed code corresponding to the final encoding mode among the plurality of compressed codes.

First claim

What is claimed is:

1. A method of compressing stress data in a display device, the method comprising:
dividing the stress data into block stress data for a pixel block;
generating a plurality of compressed codes by encoding the block stress data in a plurality of encoding modes;
determining whether the plurality of encoding modes are available encoding modes for the block stress data based on code lengths of the plurality of compressed codes and a number of available bits for the pixel block;
selecting a final encoding mode among the available encoding modes based on quantization values of the available encoding modes; and
generating a compressed bitstream for the pixel block based on a compressed code corresponding to the final encoding mode among the plurality of compressed codes.

2. The method of claim 1 , wherein the plurality of encoding modes differ from each other in at least one selected from an encoding algorithm and a quantization value.

3. The method of claim 1 , wherein the generating the plurality of compressed codes by encoding the block stress data in the plurality of encoding modes includes:
generating a pulse code modulation (PCM) code, as one of the plurality of compressed codes, by performing a quantization operation on the block stress data.

4. The method of claim 3 , wherein the generating the plurality of compressed codes by encoding the block stress data in the plurality of encoding modes further includes:
generating a predictive PCM code based on reconstructed block stress data for an adjacent pixel block adjacent to the pixel block; and
generating a differential PCM (DPCM) code, as one of the plurality of compressed codes, based on the PCM code and the predictive PCM code.

5. The method of claim 4 , wherein the generating the plurality of compressed codes by encoding the block stress data in the plurality of encoding modes further includes:
generating an entropy code, as one of the plurality of compressed codes, by performing entropy coding on the DPCM code.

6. The method of claim 5 , further comprising:
determining whether a copy mode is an available encoding mode by comparing a code length of the entropy code with a number of sub-pixels included in the pixel block.

7. The method of claim 4 , wherein the DPCM code for the pixel block includes a first color DPCM code for first color sub-pixels included in the pixel block, a second color DPCM code for second color sub-pixels included in the pixel block, and a third color DPCM code for third color sub-pixels included in the pixel block, and
wherein the generating the plurality of compressed codes by encoding the block stress data in the plurality of encoding modes further includes:
generating a first difference DPCM code by subtracting the first color DPCM code from the second color DPCM code;
generating a second difference DPCM code by subtracting the first color DPCM code from the third color DPCM code; and
generating, as one of the plurality of compressed codes, a color difference DPCM code including the first color DPCM code, the first difference DPCM code and the second difference DPCM code.

8. The method of claim 1 , wherein the number of available bits for the pixel block corresponds to a sum of a number of unused bits for a previous pixel block and a number of bits allocated to the pixel block.

9. The method of claim 8 , wherein the number of bits allocated to the pixel block is determined based on a number of bits of the block stress data and a target compression rate.

10. The method of claim 1 , wherein the determining whether the plurality of encoding modes are the available encoding modes includes:
with respect to an encoding mode among the plurality of encoding modes, comparing a code length of a compressed code corresponding to the encoding mode among the plurality of compressed codes with the number of available bits;
when the code length is less than or equal to the number of available bits, determining that the encoding mode is an available encoding mode; and
when the code length is greater than the number of available bits, determining that the encoding mode is not the available encoding mode.

11. The method of claim 1 , further comprising:
determining whether the block stress data is specific pattern data.

12. The method of claim 11 , wherein the specific pattern data includes at least one selected from white pattern data having a same value for all sub-pixels included in the pixel block, and check pattern data having a same value for same color sub-pixels included in the pixel block.

13. The method of claim 1 , wherein the selecting the final encoding mode includes:
selecting an available encoding mode having a lowest quantization value among the available encoding modes as the final encoding mode.

14. The method of claim 1 , wherein the selecting the final encoding mode includes:
checking a lowest quantization value among the quantization values of the available encoding modes;
comparing a difference between a previous quantization value of a final encoding mode for a previous pixel block and the lowest quantization value with a reference quantization difference value;
when a value obtained by subtracting the lowest quantization value from the previous quantization value is less than or equal to the reference quantization difference value, selecting an available encoding mode having the lowest quantization value among the available encoding modes as the final encoding mode; and
when the value obtained by subtracting the lowest quantization value from the previous quantization value is greater than the reference quantization difference value, selecting an available encoding mode having a quantization value higher than the lowest quantization value among the available encoding modes as the final encoding mode.

15. The method of claim 1 , wherein the compressed bitstream for the pixel block includes a mode bit representing the final encoding mode.

16. The method of claim 15 , wherein, when the final encoding mode is a PCM mode, the compressed bitstream further includes:
a PCM code having one bit for each sub-pixel included in the pixel block.

17. The method of claim 15 , wherein, when the final encoding mode is a DPCM mode, the compressed bitstream further includes:
an intra prediction mode bit representing a direction in which a DPCM code is calculated; and
the DPCM code having two bits for each sub-pixel included in the pixel block.

18. The method of claim 15 , wherein, when the final encoding mode is an entropy coding mode, the compressed bitstream further includes:
an intra prediction mode bit representing a direction in which a DPCM code is calculated; and
an entropy code which is generated by performing entropy coding on the DPCM code and has variable bits for each sub-pixel included in the pixel block.

19. The method of claim 15 , wherein, when a code length of an entropy code generated by encoding the block stress data in an entropy coding mode among the plurality of encoding modes is equal to a number of sub-pixels included in the pixel block, the final encoding mode is determined as a copy mode, and
wherein, when the final encoding mode is the copy mode, the compressed bitstream includes only the mode bit and an intra prediction mode bit.

20. The method of claim 15 , wherein, when the block stress data is white pattern data having a same value with respect to all sub-pixels included in the pixel block, the final encoding mode is determined as a white mode, and
wherein, w

Assignees

• Samsung Display Co Ltd

Inventors

• Kim Hyeonmin
• Baek Yunki
• Park Jong-Woong
• Park Hye-Sang
• Lee Sooyeon
• Lee Wonbok

Classifications

• G09G2340/00

  Aspects of display data processing · CPC title

• G09G2320/043

  Preventing or counteracting the effects of ageing · CPC title

• H03M7/60

  General implementation details not specific to a particular type of compression · CPC title

• H03M7/3044

  Conversion to or from differential modulation with several bits only, i.e. the difference between successive samples being coded by more than one bit, e.g. differential pulse code modulation [DPCM] (H03M7/3004 takes precedence; voice coding G10L19/00; image coding H04N19/00) · CPC title

• G09G3/3208 Primary

  organic, e.g. using organic light-emitting diodes [OLED] · CPC title