Assembling forward error correction frames

• US 7,779,336 B2
• Filed: 10/05/2005
• Issued: 08/17/2010
• Est. Priority Date: 10/06/2004
• Status: Expired due to Fees

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Hannuksela, Miska, Wenger, Stephan
• Primary Examiner(s): Baderman, Scott
• Assistant Examiner(s): RIZK, SAMIR WADIE
• Application Number:
  US11/244,858
• Publication Number:
  US 20060107189A1
• Time in Patent Office: 1,777 Days
• Field of Search: 714/776, 714/752, 714/755
• US Class Current: 714/776
• CPC Class Codes: H03M 13/15 Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] codes H03M13/17 takes precedence
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/47 Error detection, forward error correction or error protection, not provided for in groups H03M13/01 - H03M13/37
• CPC Class Codes: H03M 13/635 Error control coding in combination with rate matching
• CPC Class Codes: H03M 13/6356 by repetition or insertion of dummy data, i.e. rate reduction
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control

Abstract

The invention relates to a method for assembling FEC frames for a sequence of groups of coded media packets. In order to reduce a buffer delay at a decoding end (15), it is proposed that the FEC frame is aligned with the groups of media packets. To this end, a number of next subsequent groups are determined, which fit completely into a FEC frame. All coded media packets associated to this determined group or groups, if any, are selected for the FEC frame (step 202,402). Then, the selected coded media packets are encoded to obtain at least one FEC packet for the FEC frame (step 206,406). For fixed FEC frame structures, moreover the introduction of padding packets as additional media packets, if required, is proposed.

Claims

1. A method for assembling forward error correction frames with coded media packets and at least one forward error correction packet, said method comprising

selecting coded media packets for a forward error correction frame, each coded media packet including at least one header;

in case the number of said selected coded media packets is lower than a predetermined number, adding packets comprising padding values as media data in a payload to obtain said predetermined number of coded media packets for said forward error correction frame;

encoding said coded media packets to obtain said at least one forward error correction packet; and

replacing said packets comprising padding values for a transmission of said forward error correction frame by virtual padding packets having a payload length of zero bytes and indicating a size of said media data including said padding values in a payload header.

2. The method according to claim 1, wherein selecting coded media packets for a forward error correction frame comprises:

determining for a sequence of groups of coded media packets a number of next subsequent groups of coded media packets which fit completely into a forward error correction frame and selecting all coded media packets associated to said determined group or groups of coded media packets, if any, for said forward error correction frame.

3. Method according to claim 2, wherein each group of packets comprises in a first packet non-predictively coded media data and in any subsequent packet predictively coded media data.

4. The method according to claim 2, wherein selecting coded media packets for a forward error correction frame further comprises for a case where remaining coded media packets of a group of coded media packets partly included in a preceding forward error correction frame still have to be included in a forward error correction frame, wherein all of said remaining coded media packets fits into a single forward error correction frame:

determining a number of next subsequent groups of coded media packets which fit, in addition to said remaining coded media packets, completely into a forward error correction frame and selecting said remaining coded media packets and said coded media packets associated to said determined group or groups of coded media packets, if any, for said forward error correction frame.

5. The method according to claim 2, wherein selecting coded media packets for a forward error correction frame further comprises for a case where a next group of coded media data does not fit completely into a forward error correction frame or that all remaining coded media packets of a group of coded media data partly included in a preceding forward error correction do not fit into a single forward error correction frame:

determining a maximum number of next subsequent coded media packets which fit completely into a forward error correction frame and selecting said determined coded media packets for said forward error correction frame.

6. The method according to claim 1, wherein for said encoding, all selected coded media packets are supplemented to be of a same size as a largest one of said selected coded media packets by adding predetermined data to media data included in said selected coded media packets, and wherein each of said obtained at least one forward error correction packet has said size of said largest one of said selected coded media packets.

7. The method according to claim 6, wherein for a transmission of said forward error correction frame, all selected coded media packets are transmitted with an original size of included media data, each coded media packets including an indication of a size of included media data.

8. An apparatus for assembling forward error correction frames with coded media packets and at least one forward error correction packet, said apparatus comprising

a processing component configured to select coded media packets for a forward error correction frame, each coded media packet including at least one header;

a processing component configured to add packets comprising padding values as media data in a payload, in case the number of said selected coded media packets is lower than a predetermined number, to obtain said predetermined number of coded media packets for said forward error correction frame;

a processing component configured to encode said coded media packets to obtain at least one forward error correction packet for said forward error correction frame; and

a processing component configured to replace said packets comprising padding values for a transmission of said forward error correction frame by virtual padding packets having a payload length of zero bytes and to indicate a size of said media data including said padding values in payload header.

9. The apparatus according to claim 8, wherein the apparatus is one of a forward error correction frame generator and a server.

10. A communication system comprising at least one apparatus according to claim 8 and at least one forward error correction decoder.

11. The apparatus according to claim 8, wherein the processing component configured to select coded media packets for a forward error correction frame is configured to determine for a sequence of groups of coded media packets a number of next subsequent groups of coded media packets which fit completely into a forward error correction frame and to select all coded media packets associated to said determined group or groups of coded media packets, if any, for said forward error correction frame.

12. The apparatus according to claim 11, wherein the processing component configured to select coded media packets for a forward error correction frame is further configured for a case that remaining coded media packets of a group of coded media packets partly included in a preceding forward error correction frame still have to be included in a forward error correction frame, wherein all of said remaining coded media packets fits into a single forward error correction frame:

to determine a number of next subsequent groups of coded media packets which fit in addition to said remaining coded media packets completely into a forward error correction frame and to select said remaining coded media packets and said coded media packets associated to said determined group or groups of coded media packets, if any, for said forward error correction frame.

13. The apparatus according to claim 11, wherein the processing component configured to select coded media packets for a forward error correction frame is further configured for a case that a next group of coded media data does not fit completely into a forward error correction frame or that all remaining coded media packets of a group of coded media data partly included in a preceding forward error correction do not fit into a single forward error correction frame:

to determine a maximum number of next subsequent coded media packets which fit completely into a forward error correction frame and to select said determined coded media packets for said forward error correction frame.

14. The apparatus according to claim 11, wherein each group of packets comprises in a first packet non-predictively coded media data and in any subsequent packet predictively coded media data.

15. The apparatus according to claim 8, comprising a processing component configured to supplement for said encoding all selected coded media packets to be of a same size as a largest one of said selected coded media packets by adding predetermined data to media data included in said selected coded media packets, wherein each of said obtained at least one forward error correction packet has said size of said largest one of said selected coded media packets.

16. The apparatus according to claim 15, comprising a processing component configured to transmit said forward error correction frame such that all selected coded media packets are transmitted with an original size of included media data, each coded media packets including an indication of a size of included media data.

17. A computer program product in which a software code for assembling forward error correction frames with coded media packets and at least one forward error correction packet is stored, said software code realizing the following when running in a processing module:

selecting coded media packets for a forward error correction frame, each coded media packet including at least one header;

in case the number of said coded media packets is lower than a predetermined number, adding packets comprising padding values as media data in a payload to obtain said predetermined number of coded media packets for said forward error correction frame;

encoding said coded media packets to obtain said at least one forward error correction packet; and

replacing said packets comprising padding values for a transmission of said forward error correction frame by virtual padding packets having a payload length of zero bytes and to indicating a size of said media data including said padding values in a payload header.

18. An apparatus for assembling forward error correction frames with coded media packets and at least one forward error correction packet, said apparatus comprising

means for selecting coded media packets for a forward error correction frame, each coded media packet including at least one header;

means for adding packets comprising padding values as media data in a payload to obtain a predetermined number of coded media packets for said forward error correction frame in case the number of said coded media packets is lower than said predetermined number;

means for encoding said coded media packets to obtain said at least one forward error correction packet; and

means for replacing said packets comprising padding values for a transmission of said forward error correction frame by virtual padding packets having a payload length of zero bytes and to indicate a size of said media data including said padding values in payload header.