Video frame self-refresh in a sink device

• US 8,704,839 B2
• Filed: 05/24/2011
• Issued: 04/22/2014
• Est. Priority Date: 05/26/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Kobayashi, Osamu
• Primary Examiner(s): Crawford, Jacinta M
• Application Number:
  US13/114,971
• Publication Number:
  US 20110292059A1
• Time in Patent Office: 1,064 Days
• Field of Search: 345/545, 345/530, 345/531
• US Class Current: 345/545
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 2370/045 using multiple communication channels, e.g. parallel and serial
• CPC Class Codes: G09G 2370/10 Use of a protocol of communication by packets in interfaces along the display data pipeline
• CPC Class Codes: G09G 5/003 Details of a display terminal, the details relating to the control arrangement of the display terminal and to the interfaces thereto specific for a CRT G09G1/165; for a flat panel G09G3/2092
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: G09G 5/363 Graphics controllers

Abstract

A sink device having a display panel capable of performing a video frame self-refresh as directed by a source device is described. A source determines that a video frame will persist (i.e., remain the same). In this situation, the frame data does not need to be repeatedly transmitted over a main link between the source and sink devices. The main link can be turned off and transmission can cease for a certain time thereby reducing power usage by the devices or system as a whole. The source ensures that the last frame transmitted to the sink is correct by performing CRC checks and then instructs the sink, via certain bit settings in a video status indication symbol, to store the last transmitted frame in the sink'"'"'s local buffer and use that frame to refresh the panel. The source can then disable the self-refresh when the frame changes.

Claims

1. A method of enabling self-refreshing of video frame data on a sink device, the method comprising:

determining that a video frame will persist;

setting a first bit of a primary video status indication symbol to 1;

calculating a source-derived cyclic redundancy check (CRC) value;

receiving a sink-derived CRC value from the sink device;

determining whether the source-derived CRC value and the sink-derived CRC value are equal;

completing transmission of the video frame to the sink device where the video frame is stored in a sink buffer; and

terminating transmission of subsequent video frame data to the sink device, wherein the sink device reads the stored video frame in the sink buffer for display on a panel in the sink device.

2. A method as recited in claim 1 wherein determining that a video frame will persist further comprises:

examining graphics rendering commands; and

determining whether said commands have been executed.

3. A method as recited in claim 1 wherein determining whether the source-derived CRC value and the sink-derived CRC value are equal further comprises:

comparing the source-derived CRC value and the sink-derived CRC value in a graphics controller of the source device.

4. A method as recited in claim 1 further comprising:

setting a second bit in the primary video status indication symbol to 1 upon determining the source-derived CRC value and the sink-derived CRC value are equal, wherein the second bit indicates whether a video stream is being transmitted.

5. A method as recited in claim 4 further comprising:

switching to an idle pattern after setting the second bit to 1.

6. A method as recited in claim 4 further comprising:

turning off a main link between the source device and the sink device after the second bit in the primary video status indication symbol is 1 for a predetermined number of lines.

7. A method as recited in claim 1 further comprising:

disabling a self-refresh mode of the sink device based on an active video line total.

8. A method as recited in claim 7 further comprising:

disabling a self-refresh mode of the sink device based on a total line count.

9. A method as recited in claim 8 further comprising:

disabling a self-refresh mode of the sink device based on a line period.

10. A method as recited in claim 9 wherein the line period is a self-refresh video frame line period.

11. A method as recited in claim 9 further comprising:

receiving the active video line total, the total line count, and the line period in a single auxiliary burst read.

12. A method as recited in claim 1 wherein the first bit is set to 0 to disable self-refresh on the sink device.

13. A method as recited in claim 1 further comprising:

adjusting the timing of resuming transmission of video frame data to coincide with a vertical blanking interval of a self-refresh video frame.

14. A method as recited in claim 1 wherein the sink device determines to enter a self-refresh mode if it does not receive video data from the source device for a predetermined amount of time.

15. A source device comprising:

a source frame buffer for storing video frame data;

a network interface for interfacing with a main link and an auxiliary channel; and

a graphics controller having a transmitter for sourcing video data over the main link and a cyclic redundancy check (CRC) value comparison logic module, a frame persistence module, and a primary video status indication symbol modification module,

wherein the frame persistence module is configured to determine whether a video frame will persist, the symbol modification module is configured to set a value of a primary video status indication symbol based on a determination that a video frame will persist, and the transmitter is configured to terminate sourcing video data based on an output of the CRC value comparison logic module.

16. A source device as recited in claim 15 wherein the graphics controller reads video frame data from the source frame buffer and writes video frame data to the source frame buffer.

17. A source device as recited in claim 15 wherein the CRC value comparison logic module compares a source CRC value and a sink CRC value.

18. A source device as recited in claim 15 wherein the symbol modification module switches one or more values of one or more bits in a primary video status indication symbol, wherein said switches in values depend on video frame properties.

19. A source device as recited in claim 18 wherein the video frame properties include frame persistence and a video frame CRC check.

20. A source device as recited in claim 15 wherein the frame persistence module determines whether a video frame will persist by examining graphics rendering commands.

21. A source device as recited in claim 15 further comprising:

a source CRC calculation module.

22. A graphics controller comprising:

a transmitter;

a network interface for interfacing with one or more data communication channels;

a cyclic redundancy check (CRC) checking module for performing CRC checks;

a video frame persistence module for determining whether a video frame will persist; and

a primary video status indication symbol modification module for changing bits in a status indication symbol based on a determination that a video frame will persist,

wherein the transmitter is configured to terminate transmission of video frame data based on an output of the CRC checking module.

23. A graphics controller as recited in claim 22 wherein the CRC checking module compares a source CRC value and a sink CRC value.

24. A graphics controller as recited in claim 23 wherein the CRC checking module calculates the source CRC value.

25. A graphics controller as recited in claim 22 wherein the symbol modification module changes bits in a status indication symbol depending on frame persistence and a video frame CRC check.

26. A graphics controller as recited in claim 22 wherein the frame persistence module determines whether a video frame will persist by examining graphics rendering commands.