USING DOUBLE BUFFERING FOR SCREEN SHARING

• US 20110276900A1
• Filed: 05/04/2010
• Published: 11/10/2011
• Est. Priority Date: 05/04/2010
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Oommen, Toji T., Khan, Nayab, Lin, Meng, Singh, Jaydeep
• Granted Patent: US 9,407,724 B2
• Time in Patent Office: Days
• US Class Current: 715/753
• CPC Class Codes: G09G 2350/00 Solving problems of bandwidth in display systems
• CPC Class Codes: G09G 2370/022 Centralised management of display operation, e.g. in a server instead of locally
• CPC Class Codes: H04L 65/401 wherein the services involve a main real-time session and one or more additional parallel real-time or time sensitive sessions, e.g. white board sharing or spawning of a subconference
• CPC Class Codes: H04L 67/01 Protocols
• CPC Class Codes: H04L 67/131 Protocols for games, networked simulations or virtual reality

Abstract

Remote desktop sharing allows a user to access applications and data on a remote computer over a network. An intermediary computer can communicate with a host computer and one or more client computers to facilitate remote desktop sharing. The host can send the intermediary computer an encoded key frame and encoded updates. The intermediary computer can decode the host screen data, and apply subsequent updates to the decoded image so that the intermediary computer has a near live host screen image in a first buffer. A second buffer on the intermediary computer can store an instance of a screen encoder for each client computer that has joined the session and the most current host image that the client computer has. The encoder compares the near live screen image and the stored client computer host image to create an encoded differential screen image update to pass to the client computer.

Claims

1. A system comprising:

an intermediary computer;

the intermediary computer comprising a processor and a memory; and

a module on the intermediary computer configured to cause the processor to;

in response to receiving a communication from a host computer requesting a screen sharing session on the intermediary computer, establish the screen sharing session on the intermediary computer;

receive a communication from the host computer providing an encoded screen image comprising an encoded key frame;

decode the encoded key frame and store the decoded key frame in a first buffer on the intermediary computer;

receive a communication from the host computer providing an encoded screen image comprising a screen image update;

decode the encoded screen image update and apply the decoded screen image update to the stored key frame in the first buffer to create a near live host screen image;

receive a communication from at least one client computer of a plurality of client computers, the communication comprising a request for the at least one client computer to join the screen sharing session on the intermediary computer;

create for each client computer of the plurality of client computers sending a session join request to the intermediary computer, an instance of an encoder on the intermediary computer in a second buffer, the second buffer also comprising a latest version of a host screen image for each client computer of the plurality of client computers sending the session join request;

in response to receiving an update request from the at least one client computer, send an encoded differential screen image update to the at least one client computer, the encoded differential screen image update comprising a difference between the latest version of the host screen image for the at least one client computer and the near live host screen image in the first buffer.

2. The system of claim 1, wherein the intermediary computer is a web server and is not a proxy server and wherein communications between the host computer and the intermediary computer and between the intermediary computer and the at least one computer are sent via HTTP commands.

3. The system of claim 1, wherein the intermediary computer creates a FIFO queue for storing encoded screen image updates from the host computer and stores the encoded screen image updates received from the host computer in the FIFO queue.

4. The system of claim 3, wherein encoded screen image updates for a first group of client computers are stored in the FIFO queue and wherein encoded screen image updates for a second group of client computers are generated by comparing the near live host screen image and a latest version of a host screen image for a client computer of the second group of client computers to generate an encoded differential screen image update for the client computer.

5. The system of claim 1, wherein a constant amount of memory is used in the intermediary computer for the first buffer.

6. The system of claim 1, wherein an amount of memory that is proportional to a number of client computers joined to the screen sharing session is used for the second buffer on the intermediary computer.

7. The system of claim 3, wherein all of the plurality of client computers receive encoded screen image updates from the FIFO queue.

8. A method comprising:

in response to receiving a communication from a host computer requesting a screen sharing session on an intermediary computer, establishing the screen sharing session on the intermediary computer;

receiving a communication from the host computer providing an encoded screen image comprising a encoded key frame;

decoding the encoded key frame and storing the decoded key frame in a first buffer on the intermediary computer;

receiving a communication from the host computer providing an encoded screen image comprising a differential screen image update;

decoding the differential screen image update and applying the decoded differential screen image update to the stored key frame in the first buffer to create a near live host screen image in the first buffer;

receiving a communication from at least one client computer of a plurality of client computers, requesting to join the screen sharing session on the intermediary computer;

creating a second buffer on the intermediary computer;

for each client computer of the plurality of client computers sending a session join request, creating an instance of an encoder on the intermediary computer in a second buffer, and storing a copy of a version of a host screen image in the second buffer for each client computer of the plurality of client computers sending the session join request;

in response to receiving an update request from the at least one client computer, sending an encoded differential screen image update to the at least one client computer, the differential screen image update comprising a difference between the copy of a version of a host screen image for the at least one client computer and the near live host screen image stored in the first buffer.

9. The method of claim 8, further comprising:

receiving communications comprising the encoded key frame or the encoded differential screen image update from the host computer in an HTTP GET or POST command.

10. The method of claim 9, further comprising:

wherein the intermediary computer is a web server and is not a proxy server.

11. The method of claim 8, further comprising

wherein, on the intermediary computer, a constant amount of memory is used for the first buffer and wherein an amount of memory proportional to a number of client computers connected to the screen sharing session is used for the second buffer.

12. The method of claim 8, further comprising:

creating a FIFO queue on the intermediary computer and storing encoded screen image updates received from the host computer in the FIFO queue.

13. The method of claim 12, further comprising:

triggered by monitored conditions, switching between storing encoded screen image updates received from the host computer in the FIFO queue and storing the near live host screen image in the first buffer.

14. The method of claim 12, further comprising:

storing encoded screen image updates for a first group of client computers in the FIFO queue and wherein encoded screen image updates for a second group of client computers are generated by comparing the near live host screen image in the first buffer and the stored copy of the version of the host screen image for each client computer in the second group of client computers to generate encoded differential screen image updates for a second group of client computers.

15. A computer-readable storage medium comprising computer-executable instructions which when executed cause at least one processor to:

in response to receiving a communication from a host computer requesting a screen sharing session on the intermediary computer, establish the screen sharing session on the intermediary computer;

receive a communication from the host computer providing an encoded screen image comprising an encoded key frame;

decode the encoded screen image and store the decoded key frame in a first buffer on the intermediary computer;

receive a communication from the host computer providing an encoded screen image comprising a screen image update;

decode the encoded screen image update and apply the decoded screen image update to the stored key frame in the first buffer to create a near live host screen image stored in the first buffer;

receive a communication from at least one client computer of a plurality of client computers, the at least one computer requesting to join the screen sharing session on the intermediary computer;

create for the at least one computer, an instance of an encoder on the intermediary computer in a second buffer, the second buffer also storing a version of a host screen image for the at least one client computer;

in response to receiving an update request from the at least one client computer, send an encoded differential screen image update to the at least one client computer, the differential screen image update comprising a difference between the stored version of the host screen image and the near live host screen image in the first buffer.

16. The computer-readable storage medium of claim 15, comprising further computer-executable instructions, which when executed cause the at least one processor to:

create a FIFO queue on the intermediary computer and store encoded screen image updates received from the host computer in the FIFO queue.

17. The computer-readable storage medium of claim 15, comprising further computer-executable instructions, which when executed cause the at least one processor to:

use a fixed amount of memory on the intermediary computer for the first buffer and use an amount of memory proportional to a number of client computers joining the screen sharing session for the second buffer.

18. The computer-readable storage medium of claim 15, comprising further computer-executable instructions, which when executed cause the at least one processor to:

store encoded screen image updates for a first group of client computers in the FIFO queue and generate encoded screen image updates for a second group of client computers by comparing the near live host screen image in the first buffer and the stored version of the host screen image for the second group of client computers.

19. The computer-readable storage medium of claim 15, comprising further computer-executable instructions, which when executed cause the at least one processor to:

monitor specified conditions, and in response to the monitoring, switch between storing encoded screen image updates received from the host computer in the FIFO queue and storing the near live host screen image in the first buffer.

20. The computer-readable storage medium of claim 19, comprising further computer-executable instructions, which when executed cause the at least one processor to:

send communications to and receive communications from the host computer and the plurality of client computers via HTTP POST and GET commands.