Guaranteed data compression

Patent metadata

Field	Value
Publication number	US-11611754-B2
Application number	US-202217713307-A
Country	US
Kind code	B2
Filing date	Apr 5, 2022
Priority date	Jun 29, 2018
Publication date	Mar 21, 2023
Grant date	Mar 21, 2023

Abstract

A method of converting 10-bit pixel data (e.g. 10:10:10:2 data) into 8-bit pixel data involves converting the 10-bit values to 7-bits or 8-bits and generating error values for each of the converted values. Two of the 8-bit output channels comprise a combination of a converted 7-bit value and one of the bits from the fourth input channel. A third 8-bit output channel comprises the converted 8-bit value and the fourth 8-bit output channel comprises the error values. In various examples, the bits of the error values may be interleaved when they are packed into the fourth output channel.

First claim

What is claimed is:

1. A method of converting 10-bit format pixel data into 8-bit format data, the method comprising, for each pixel of the 10-bit format pixel data:
generating an error value for each of a plurality of 10-bit input data channels by comparing, for each of a first subset of the channels, a first number of least significant bits (LSBs) of the input data channel and a same first number of bits derived from a truncated version of the channel, and for each of a second, non-overlapping subset of channels, a second number of LSBs of the input data channel and a same second number of bits derived from a truncated version of the channel;
outputting, for each of the channels in the first subset, an 8-bit channel comprising the truncated version of the channel with a different appended bit from the further input data channel;
outputting, for each of the channels in the second subset, an 8-bit channel comprising the truncated version of the channel and outputting an 8-bit channel comprising the error values.

2. The method according to claim 1 , wherein each of truncated versions of the channels in the first subset comprise 7 bits and each of the truncated versions of the channels in the second subset comprise 8 bits.

3. The method according to claim 1 , wherein generating an error value for each of the 10-bit input data channels by comparing, for each of the first subset of channels, a first number of LSBs of the input data channel and a same first number of bits derived from the truncated version of the channel, and for each of the second subset of channels, a second number of LSBs of the input data channel and a same second number of bits derived from the truncated version of the channel comprises:
generating an error value for each of the 10-bit input data channels by combining using an XOR logic block, for each of the first subset of channels, three LSBs of the input data channel and three bits derived from the truncated version of the channel, and for each of the second subset of channels, two LSBs of the input data channel and two bits derived from the truncated version of the channel.

4. The method according to claim 1 , wherein the first number of bits derived from each of the truncated versions of the channels in the first subset comprise the three most significant bits (MSBs) of the truncated version of the channel and the second number of bits derived from each of the truncated versions of the channels in the second subset comprise the two MSBs of the truncated version of the channel.

5. The method according to claim 1 , further comprising:
prior to generating the error values, expanding, using bit replication, each of the truncated versions of the channels to 10 bits,
and wherein the first number of bits derived from each of the truncated versions of the channels in the first subset comprise the three LSBs of the expanded truncated version of the channel and the second number of bits derived from each of the truncated versions of the channels in the second subset comprise the two LSBs of the expanded truncated version of the channel.

6. The method according to claim 1 , wherein the truncated versions of the channels are encoded using Gray coding.

7. The method according to claim 1 , wherein outputting, for each of the channels in the first subset, an 8-bit channel comprising the truncated version of the channel with a different appended bit from the further input data channel comprises:
outputting, for each of the channels in the first subset, an 8-bit channel comprising the truncated version of the channel with a different bit from the further input data channel appended as an MSB.

8. The method according to claim 1 , wherein the 10-bit pixel data comprises RGBA pixel data.

9. A method of compressing 10-bit format pixel data comprising:
converting 10-bit format pixel data into 8-bit format data using the method as set forth in claim 1 ; and
compressing a block of 8-bit format data using a lossless compression method to generate a first compressed data block.

10. The method according to claim 9 , further comprising:
assessing the first compressed data block against a target compression threshold;
in response to determining that the first compressed data block satisfies the target compression threshold, outputting the first compressed data block; and
in response to determining that the first compressed data block does not satisfy the target compression threshold, discarding one or more bits from the 8-bit channel comprising the error values in the block of 8-bit format data to generate a reduced size block of data and compressing the reduced size block of data using the lossless compression method to generate a second compressed data block, wherein the second compressed data block is smaller than the first compressed data block.

11. The method according to claim 10 , further comprising:
outputting the second compressed data block.

12. The method according to claim 10 , further comprising:
assessing the second compressed data block against the target compression threshold;
in response to determining that the second compressed data block satisfies the target compression threshold, outputting the second compressed data block; and
in response to determining that the second compressed data block does not satisfy the target compression threshold, outputting, instead of the second compressed data block, a third compressed data block generated from the block of 8-bit format data, wherein the third compressed data block is generated using a lossy compression technique, and wherein the lossy compression technique is arranged to ensure that the third compressed data block satisfies the target compression threshold.

13. A non-transitory computer readable storage medium having stored thereon computer executable code that when executed causes at least one processor to perform the method as set forth in claim 1 .

14. A method of converting 8-bit format pixel data into 10-bit format data, the method comprising:
determining whether a last channel of a plurality of input data channels is an 8-bit channel and in response to determining that the last channel comprises fewer than 8-bits per pixel, converting the last channel into an 8-bit channel by adding one or more zeros to data for each pixel;
removing a most significant bit (MSB) from each of a first subset of the input data channels and combining them to form a 2-bit last output channel;
using bit replication to increase each of the input data channels except the last channel to 10-bit channels;
for each of the first subset of the channels, modifying a first number of least significant bits (LSBs) by combining them with corresponding bits from the last channel to generate corresponding 10-bit output channels and for each of a second subset of channels, modifying a second number of LSBs by combining them with corresponding bits from the last channel to generate a corresponding 10-bit output channel.

15. The method according to claim 14 , further comprising:
Gray decoding the 2-bit last output channel.

16. A non-transitory computer readable storage medium having stored thereon computer executable code that when executed causes at least one processor to perform the method as set forth in claim 14 .

17. A data decompression unit arranged to convert 8-bit format pixel data into 10-bit format data, the hardware comprising:
conversion logic arranged, for each pixel of a plurality of input data channels, to determine whether a last channel of said plurality of input data channels is an 8-bit channel and in respon

Assignees

• Imagination Tech Ltd

Inventors

• Martinelli Ilaria
• Bond Jeff
• Fenney Simon
• Lacey Peter Malcolm
• Clark Gregory

Classifications

• G06T9/00

  Image coding (bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00) · CPC title

• H04N1/60 Primary

  Colour correction or control {(H04N1/54 takes precedence)} · CPC title

• H04N19/182

  the unit being a pixel · CPC title

• H04N19/184

  the unit being bits, e.g. of the compressed video stream · CPC title

• H04N19/176

  the region being a block, e.g. a macroblock · CPC title