System and method for multimedia delivery in a wireless environment

• US 7,421,048 B2
• Filed: 01/20/2005
• Issued: 09/02/2008
• Est. Priority Date: 01/20/2005
• Status: Expired due to Fees

• Current Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Original Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Inventors: Doyle, James, Ducharme, Paul, Chiu, Adeline, Girardeau, James Jr.
• Primary Examiner(s): liu; Shuwang
• Assistant Examiner(s): PATEL, DHAVAL V
• Application Number:
  US11/038,856
• Publication Number:
  US 20060161675A1
• Time in Patent Office: 1,321 Days
• Field of Search: 375/354, 709/231, 370/509
• US Class Current: 375/354
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/235 Processing of additional data, e.g. scrambling of additional data or processing content descriptors
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/435 Processing of additional data, e.g. decrypting of additional data, reconstructing software from modules extracted from the transport stream
• CPC Class Codes: H04N 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer
• CPC Class Codes: H04N 21/6332 directed to client
• CPC Class Codes: H04N 21/8547 involving timestamps for synchronizing content

Abstract

A multimedia processing system and method thereof are provided. The system and method provide for synchronizing a first clock of a multimedia decoder of a first multimedia processing device to a second clock of a multimedia encoder of a second multimedia processing device, synchronizing a first timing reference of the multimedia decoder to a second timing reference of the multimedia encoder, receiving, at a network interface of the first multimedia processing device, an encoded multimedia data stream from a network interface of the second multimedia processing device, wherein the encoded multimedia data stream is encoded by the multimedia encoder based on the second clock and the second timing reference, and decoding the encoded multimedia data stream at the multimedia decoder based on the first clock and the first timing reference.

Claims

1. A method comprising:

receiving, at a first multimedia processing device, a first offset value representative of a frequency offset between a first clock signal of a first clock source and a second clock signal of a second clock source of a second multimedia processing device, the first clock signal driving a multimedia encoder of the second multimedia processing device and the second clock signal driving a network interface of the second multimedia processing device;

determining, at the first multimedia processing device, a second offset value representative of a frequency offset between the second clock signal and a third clock signal of a third clock source, the third clock signal driving a network interface of the first multimedia processing device;

adjusting a fourth clock signal of a fourth clock source of the first multimedia processing device based on the first offset value and the second offset value to generate an adjusted fourth clock signal, the adjusted fourth clock signal driving a multimedia decoder of the first multimedia processing device;

receiving, at the network interface of the first multimedia processing device, an encoded multimedia data stream from the network interface of the second multimedia processing device, wherein the encoded multimedia data stream is encoded based on the first clock signal; and

decoding the encoded multimedia data stream at the multimedia decoder based on the adjusted fourth clock signal.

2. The method of claim 1, wherein adjusting the fourth clock signal further comprises adjusting the fourth clock signal based on an error value determined from a fullness of an input buffer to store the encoded multimedia data stream at the first multimedia processing device.

3. The method of claim 1, wherein the network interfaces comprise wireless transceivers.

4. The method of claim 3, wherein the wireless transceivers are compatible with IEEE 802.11.

5. The method of claim 1, wherein the network interfaces include PHY-based interfaces.

6. The method of claim 1, wherein the first offset value represents a difference between clock ticks of the first clock signal and clock ticks of the second clock signal over a predetermined time period.

7. The method of claim 1, further comprising:

receiving, at the first multimedia processing device, a multimedia stream having a first plurality of timing references, the first plurality of timing references representing absolute timing references converted to relative timing references based on the first clock signal;

converting, at the first multimedia device, the first plurality of timing references from the relative timing references to absolute timing references based on the adjusted fourth clock signal to generate a second plurality of timing references; and

synchronizing a numerically controlled oscillator (NCO) of the multimedia decoder based on at least a subset of the second plurality of timing references.

8. The method of claim 7, further comprising filtering an output of the NCO using a phase-locked loop (PLL).

9. The method of claim 7, wherein the multimedia stream includes an MPEG stream.

10. The method of claim 9, wherein the first plurality of timing references include primary reference clock (PRC) values or system reference clock (SRC) clock values.

11. The method of claim 1, wherein the encoded multimedia data stream comprises an MPEG stream.

12. The method of claim 1, wherein the multimedia encoder is an MPEG encoder and the multimedia decoder is an MPEG decoder.

13. A method comprising:

determining, at a first multimedia processing device, a first frequency offset between a first clock source used to drive a multimedia encoder of the first multimedia processing device and a second clock source used to drive a network interface of the first multimedia processing device;

encapsulating a value representative of the first frequency offset in at least one packet;

providing the at least one packet to a second multimedia processing device via the network interface of the first multimedia processing device;

determining a second frequency offset between the second clock source and a third clock source used to drive a network interface of the second multimedia processing device; and

adjusting a fourth clock source used to drive a multimedia decoder of the second multimedia processing device based on the first frequency offset and the second frequency offset.

14. The method of claim 13, wherein determining the first frequency offset includes comparing a number of clock cycles of the first clock source over a predetermined period with a number of clock cycles of the second clock source over the predetermined period.

15. The method of claim 13, wherein the network interface comprises a wireless interface.

16. The method of claim 13, wherein the wireless interface is compatible with IEEE 802.11.

17. The method of claim 13, wherein the first frequency offset represents a difference between clock ticks of the first clock source and clock ticks of the second clock source over a predetermined time period.

18. The method of claim 13, wherein the multimedia encoder comprises an MPEG encoder. pg,6

19. A system comprising:

a first multimedia processing device including;

a first clock source having an output to provide a first clock signal;

a second clock source having an output to provide a second clock signal;

a multimedia encoder having a first input operable coupled to the output of the first clock source, a second input to receive multimedia data, and an output to provide the encoded multimedia stream based on the first clock signal;

a first network interface having a first input operable coupled to the output of the multimedia encoder, a second input operable coupled to the second clock source, and an output to provide the encoded multimedia stream; and

a second multimedia processing device including;

a third clock source having an output to provide a third clock signal;

a fourth clock source having an output to provide a fourth clock signal;

a second network interface having a first input operably coupled to the output of the first network interface, a second input operably coupled to the output of the third clock source, and an output to provide the encoded multimedia stream;

a multimedia decoder having a first input operably coupled to the output of the fourth clock source, a second input operably coupled to the output of the second network interface and an output to provide a decoded multimedia stream, and

a first synchronization module having a input operably coupled to the output of the fourth clock source and an output operably coupled to the multimedia decoder, the first synchronization module operable to adjust the fourth clock signal based on a first offset value and a second offset value, the first offset value representative of a frequency offset between the first clock signal and the second clock signal and the second offset value representative of a frequency offset between the second clock signal and the third clock signal.

20. The system of claim 19, wherein the first multimedia processing device further comprises:

a second synchronization module having a first input to receive the first clock signal and a second input to receive the second clock signal and an output to provide the first offset value based on the first clock signal and the second clock signal; and

wherein the network interface is operable to provide a packetized representation of the first offset value for transmission.

21. The system of claim 20, wherein the first synchronization module is further operable to determine the second offset value.

22. The system of claim 19, wherein the second multimedia processing device further comprises an input buffer having an input operably coupled to the output of the second network interface, and wherein the first synchronization module further is operably to adjust the fourth clock signal based on an error value determined from a fullness of the input buffer.

23. The system of claim 19, wherein the first and the second network interfaces comprise wireless interfaces.

24. The system of claim 23, wherein the wireless interfaces are compatible with IEEE 802.11.

25. A multimedia processing device comprising:

a first clock source having an output to provide a first clock signal;

a second clock source having an output to provide a second clock signal;

a network interface having a first input to receive a signal representative of an encoded multimedia data stream from a network and a second input operable coupled to the output of the first clock source, the encoded multimedia data stream having a plurality of relative timing reference values;

a multimedia decoder having a first input operable coupled to the output of the second clock source and a second input operable coupled to the network interface, the multimedia decoder to decode at least a portion of the encoded multimedia data stream; and

a synchronization module having a first input operably coupled the output of the first clock source, a second input operable coupled to the output of the second clock source and a third input operably coupled to the network interface, the synchronization module operable to;

receive, from a second multimedia processing device, a first offset value representative of a frequency offset between a third clock source and fourth clock source of the second multimedia processing device the third clock source driving a multimedia encoder of the second multimedia processing device and the fourth clock source driving a network interface of the second multimedia processing device;

determine a second offset value representative of a frequency offset between

the first clock source and the fourth clock source;

adjust the second clock source based on the first offset value and the second offset value; and

convert the relative timing reference values to absolute timing reference values based on the second clock source.

26. The device of claim 25, further comprising an input buffer having an input operably coupled to the network interface and an output operably coupled to the second input of the multimedia decoder, and wherein the synchronization module is further adapted to adjust the second clock source based on an error value determined from a fullness of the input buffer.

27. The device of claim 25, wherein the first offset value represents a difference between clock ticks of the third clock source and clock ticks of the fourth clock source over a predetermined time period and the second offset value represents a difference between clock ticks of the first clock source and clock ticks of the second clock source over a predetermined time period.

28. The device of claim 25, wherein the multimedia data stream includes an MPEG stream.

29. The device of claim 25, wherein the network interface includes a wireless interface.

30. The device of claim 29, wherein the wireless interface is compliant with IEEE 802.11.