Method for reducing framebuffer memory accesses

• US 8,358,314 B2
• Filed: 02/08/2008
• Issued: 01/22/2013
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Dyke, Kenneth C.
• Primary Examiner(s): WASHBURN, DANIEL C
• Application Number:
  US12/028,450
• Publication Number:
  US 20090201306A1
• Time in Patent Office: 1,810 Days
• Field of Search: 345/531, 345/545, 345/592, 345/629
• US Class Current: 345/545
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence

Abstract

A method and electronic device employing a method of reducing memory accesses during the readout of a scanline of a frame buffer is provided, which includes reading out a series of bits on the scanline corresponding to a series of regions of pixels of the scanline, entering a default pixel value for each pixel of a region if a corresponding bit is set, and entering a pixel value obtained from accessing the scanline for each pixel of the region if the corresponding bit is not set.

Claims

1. A method of reading a scanline of a framebuffer, comprising:

reading a series of bits from a framebuffer, each bit of the series of bits corresponding to a respective one of a plurality of regions of pixels in a scanline of the framebuffer;

obtaining a stored pixel value for each pixel of a respective region of the scanline by accessing the respective region if a bit corresponding to the respective region is not set; and

obtaining a predetermined pixel value for all pixels of the respective region without accessing the respective region if the bit corresponding to the respective region is set.

2. The method of claim 1, wherein the region of pixels has a size of one read burst length.

3. The method of claim 1, wherein the framebuffer is configured to hold pixel data for a frame of one of a plurality of layers.

4. The method of claim 1, wherein the predetermined pixel value is transparent.

5. The method of claim 1, wherein the series of bits is stored at the end of the scanline.

6. The method of claim 1, wherein obtaining the stored pixel value for each pixel of the particular region of the scanline further comprises setting the bit corresponding to the particular region if all pixel values for the pixels of the particular region are of the predetermined pixel value.

7. An electronic device, comprising:

a display;

memory circuitry comprising a framebuffer with a plurality of scanlines, each scanline encoding a row of pixels in a frame, wherein associated with each of the plurality of scanlines is a series of additional bits located within the framebuffer, each bit corresponding to a region in a plurality of regions of pixels in a scanline; and

display control circuitry coupled to the memory circuitry and the display, the display control circuitry being configured to prepare pixels for display on the display by setting pixels associated with a region of a scanline to a value obtained from accessing the region if a bit corresponding to the region is not set and setting pixels associated with the region to a preset value without accessing the region if the bit corresponding to the region is set.

8. The electronic device of claim 7, wherein each region of the scanline has a size of one read burst length.

9. The electronic device of claim 7, wherein setting pixels comprises entering pixel data into display control circuitry that is configured to set the bit corresponding to the region if all values obtained from accessing the region are of the preset value.

10. The electronic device of claim 7, wherein the series of additional bits is stored within the scanline with which the series of additional bits is associated.

11. The electronic device of claim 7, wherein the framebuffer is associated with one of a plurality of layers of pixel data.

12. The electronic device of claim 11, wherein the framebuffer is associated with a topmost layer of pixel data.

13. The electronic device of claim 7, wherein the preset value comprises a value representative of a transparent pixel.

14. The electronic device of claim 7, wherein the electronic device comprises at least one of a media player, a portable phone, or a personal data organizer, or any combination thereof.

15. A method of controlling an electronic display, comprising:

fetching from a framebuffer a plurality of bits corresponding to a plurality of regions of pixels in a scanline of the framebuffer; and

entering a preset pixel value for all pixels in a region of the plurality of regions of the scanline if a bit of the plurality of bits corresponding to the region is set.

16. The method of claim 15, wherein entering the preset pixel value for all pixels in the region comprises writing the preset pixel value to a buffer.

17. The method of claim 15, comprising fetching and entering a pixel value for each pixel in the region of the scanline if the bit corresponding to the region is not set.

18. The method of claim 17, comprising setting the bit corresponding to the region of the scanline if the pixel value for each pixel in the region is the preset pixel value.

19. The method of claim 17, comprising writing the plurality of bits back to memory.

20. The method of claim 15, wherein the preset pixel value comprises a transparent alpha value for the pixel.

21. A method of displaying a frame of pixels stored in a framebuffer, comprising:

reading from a framebuffer a series of bits, wherein each bit of the series of bits is associated with a respective region of pixels within a series of regions of pixels in a scanline of the framebuffer; and

writing pixel data stored in the framebuffer to a first-in-first-out (FIFO) buffer one region at a time, wherein writing pixel data to the FIFO buffer comprises entering a preset pixel value for all pixels in a region of the scanline if a bit corresponding to the region is set and accessing the region to obtain a stored value for each pixel in the region and entering the stored pixel value for each pixel if the bit corresponding to the region is not set.

22. The method of claim 21, wherein the series of regions of pixels in the scanline of the framebuffer is a series of regions of data, each region having a size of one read burst length.

23. The method of claim 22, wherein writing pixel data stored in the framebuffer to the FIFO buffer further comprises setting the bit corresponding to the region if the stored pixel value for each pixel in the region is transparent.

24. The method of claim 21, wherein writing pixel data stored in the framebuffer to the FIFO buffer further comprises setting the bit corresponding to the region if the stored pixel value for each pixel in the region is the same.

25. A method of obtaining data stored in a framebuffer comprising the acts of:

(a) fetching from a framebuffer a plurality of bits corresponding to a plurality of regions of pixels in a scanline of a framebuffer;

(b) entering a preset pixel value for all pixels in a region of the plurality of regions of the scanline if a bit of the plurality of bits corresponding to the region is set;

(c) fetching from memory all pixels in the region of the plurality of regions of the scanline if the bit of the plurality of bits corresponding to the region is not set, and setting the bit of the plurality of bits corresponding to the region if all pixels fetched from the region are of the preset pixel value;

(d) repeating acts (b) and (c) for each region of the plurality of regions until all pixel data from the scanline of the framebuffer has been obtained;

(e) entering the plurality of bits back into memory when all pixel data from the scanline of the framebuffer has been obtained; and

(f) repeating acts (a) through (e) until all pixel data from the framebuffer has been obtained.

26. The method of claim 25, comprising the act of (g) resetting all bits of the plurality of bits if the framebuffer is subsequently modified such that each bit of the plurality of bits is not set.

27. The method of claim 25, wherein the preset pixel value indicates that the pixel is transparent.