Digital video data compression technique

• US 5,673,370 A
• Filed: 05/09/1996
• Issued: 09/30/1997
• Est. Priority Date: 01/29/1993
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Laney, Stuart T.
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): LEGREE, TRACY MICHELLE
• Application Number:
  US08/646,714
• Time in Patent Office: 509 Days
• Field of Search: 395/109, 395/114, 395/101, 358/261.1, 358/261.2, 358/261.3, 358/261.4, 358/426, 358/466, 358/524, 358/433, 358/539, 382/166, 382/244, 382/239, 382/191, 348/396, 348/420, 348/391
• US Class Current: 358/1.9
• CPC Class Codes: G06T 9/005 Statistical coding, e.g. Huffman, run length coding

Abstract

A technique for compressing digital video data provides improved compression over conventional block compression techniques. In this technique, image data is broken down into cells and iteratively compressed. The cells are compressed using compression formats that are most appropriate for the contents of the cells. A determination is first made whether a cell is substantially identical to a succeeding cell in a previous frame. If the cell is substantially identical to the cell in the previous frame, the cell is encoded in compressed form as a duplicate of the previous cell. Moreover, solid-color compression approaches, two-color compression approaches and eight-color compression approaches may be integrated into the compression technique.

Claims

1. In a data processing system, a method of decompressing compressed color data, including a bitmap and encodings of colors, for pixels of a cell, comprising the steps of:

a) determining whether the color data for the cell is compressed as a solid-color cell;

b) if the color data for cell is compressed as a solid-color cell, decompressing the color data for the cell by assigning each pixel in the cell a color that is encoded in the compressed color data;

c) determining whether the color data for the cell is compressed as a two-color cell;

d) if the color data for the cell is compressed as a two-color cell, decompressing the color data of the cell by assigning each pixel one of two colors encoded by the encodings in the compressed color data, based on a value in the bitmap that is contained in the compressed color data;

e) determining whether the color data for the cell is compressed as an eight-color cell; and

f) if the color data for the cell is compressed as an eight-color cell, decompressing the color data for the cell by assigning each pixel in each sub-cell of the cell, one of two colors encoded for the sub-cell in the encodings in the compressed color data according to a value of at least one bit in the bitmap, that is included in the compressed color data.

2. A computer-readable storage medium for use in a computer system, holding instructions for performing a method of decompressing compressed color data, including a bitmap and encodings of colors, for pixels of a cell, said method comprising the steps of:

a) determining whether the color data for the cell is compressed as a solid-color cell;

b) if the color data for cell is compressed as a solid-color cell, decompressing the color data for the cell by assigning each pixel in the cell a color that is encoded in the compressed color data;

c) determining whether the color data for the cell is compressed as a two-color cell;

d) if the color data for the cell is compressed as a two-color cell, decompressing the color data of the cell by assigning each pixel one of two colors encoded by the encodings in the compressed color data, based on a value in the bitmap that is contained in the compressed color data;

e) determining whether the color data for the cell is compressed as an eight-color cell; and

f) if the color data for the cell is compressed as an eight-color cell, decompressing the color data for the cell by assigning each pixel in each sub-cell of the cell, one of two colors encoded for the sub-cell in the encodings in the compressed color data according to a value of at least one bit in the bitmap, that is included in the compressed color data.

3. The computer-readable storage medium of claim 2 further holding instructions for compressing the color data to produce the compressed color data.

4. In a computer system, a method comprising the computer-implemented steps of:

a) compressing color data for pixels of a first cell of a frame of color data to produce compressed color data that includes a bitmap and encodings of colors;

b) determining whether the color data for the first cell is compressed as a solid-color cell;

c) if the color data for the first cell is compressed as a solid-color cell, decompressing the color data for the cell by assigning each pixel in the first cell a color that is encoded in the compressed color data;

d) determining whether the color data for the first cell is compressed as a two-color cell;

e) if the color data for the first cell is compressed as a two-color cell, decompressing the color data of the first cell by assigning each pixel one of two colors encoded by the encodings in the compressed color data, based on a value in the bitmap that is contained in the compressed color data;

f) determining whether the color data for the first cell is compressed as an eight-color cell; and

g) if the color data for the first cell is compressed as an eight-color cell, decompressing the color data for the first cell by assigning each pixel in each sub-cell of the cell, one of two colors encoded for the sub-cell in the encodings in the compressed color data according to a value of at least one bit in the bitmap, that is included in the compressed color data.