Per-image forward error correction

• US 8,621,320 B2
• Filed: 04/07/2011
• Issued: 12/31/2013
• Est. Priority Date: 04/07/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yang, Yan, Jeong, Hyeonkuk, Abuan, Joe S., Zhou, Xiaosong
• Primary Examiner(s): Rizk, Sam
• Application Number:
  US13/082,381
• Publication Number:
  US 20120260145A1
• Time in Patent Office: 999 Days
• Field of Search: 714/752, 714/755, 714/758
• US Class Current: 714/758
• CPC Class Codes: H03M 13/1102 Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes
• CPC Class Codes: H03M 13/1505 Golay Codes
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/152 Bose-Chaudhuri-Hocquenghem [BCH] codes
• CPC Class Codes: H03M 13/19 Single error correction without using particular properties of the cyclic codes, e.g. Hamming codes, extended or generalised Hamming codes
• CPC Class Codes: H03M 13/356 Unequal error protection [UEP]
• CPC Class Codes: H03M 13/6312 Error control coding in combination with data compression
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35

Abstract

Some embodiments provide a method for encoding digital video. The method receives a digital video image. The method encodes the digital video image. The method generates error correction information for the encoded digital video image using only data from the encoded digital video image. The method transmits the generated error correction information with the encoded digital video image. In some embodiments, the method determines a level of error protection for the encoded digital video image based on an image type of the encoded digital video image.

Claims

1. A non-transitory computer readable medium storing a computer program which when executed by at least one processor encodes digital video, the computer program comprising sets of instructions for:

receiving a video stream comprising a plurality of digital video images;

encoding an image of the plurality of digital video images to generate an encoded digital video frame;

generating error correction information for the encoded digital video frame, wherein more error correction information is generated for an I-frame than for a non I-frame, wherein the generating error correction information comprises;

dividing the encoded digital video frame into a plurality of data packets to transmit over a network;

determining a number of packets required to generate error correction information for the encoded digital video frame;

when the required number of packets is not greater than a number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame; and

when the required number of packets is greater than the number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame and additional pseudo-packets, wherein the additional pseudo-packets comprise predetermined data that is not obtained from the video stream, wherein the required number of packets is not greater than the sum of the number of data packets in the plurality of data packets the number of additional pseudo-packets; and

transmitting the generated error correction information with the encoded digital video frame.

2. The computer readable medium of claim 1, wherein the set of instructions for generating error correction information comprises sets of instructions for:

generating error correction information for the encoded digital video frame using information from each of the data packets.

3. The computer readable medium of claim 1, wherein the generated error correction information depends on statistics of a network over which the encoded digital video frame and error correction information are transmitted.

4. The computer readable medium of claim 1, wherein the set of instructions for transmitting comprises a set of instructions for transmitting only a portion of the generated error correction information, the portion dependent on a frame type of the encoded digital video frame and statistics of a network over which the encoded digital video frame and error correction information are transmitted.

5. The computer readable medium of claim 1, wherein the digital video frame is a frame for a video-conference.

6. A non-transitory computer readable medium storing a computer program which when executed by at least one processor encodes a digital video image, the computer program comprising sets of instructions for:

identifying a frame type for an encoded digital video frame;

determining a level of error protection for the encoded digital video frame based on the identified frame type, wherein the level of error protection is greater for an I-frame than for a P-frame or a B-frame;

generating error correction information for the encoded digital video frame according to the level of error protection, wherein the generating error correction information comprises;

dividing the encoded digital video frame into a plurality of data packets to transmit over a network;

determining a number of packets required to generate error correction information for the encoded digital video frame;

when the required number of packets is not greater than a number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame; and

when the required number of packets is greater than the number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame and additional pseudo-packets, wherein the additional pseudo-packets comprise predetermined data that is not obtained from the encoded digital video frame, wherein the number of packets comprised in the plurality of data packets and the additional pseudo-packets is at least the required number of packets;

transmitting the generated error correction information with the encoded digital video frame.

7. The computer readable medium of claim 6, wherein the frame type is an I-frame that is encoded without reference to other digital video frames.

8. The computer readable medium of claim 6, wherein the frame type is one of a P-frame and a B-frame that is encoded by reference to at least one other digital video frame.

9. The computer readable medium of claim 6, wherein the error correction information comprises parity bits.

10. The computer readable medium of claim 9, wherein the error correction information includes additional parity bits when the digital video image is encoded without reference to other digital video images.

11. The computer readable medium of claim 6, wherein the encoded digital video frame is transmitted via a network, the computer program further comprising a set of instructions for determining statistics of the network over which the encoded digital video frame is transmitted.

12. The computer readable medium of claim 11, wherein the set of instructions for determining the level of error protection accounts for the statistics of the network.

13. The computer readable medium of claim 12, wherein the set of instructions for determining the level of error protection comprises sets of instructions for:

increasing an amount of error correction information when a packet loss rate of the network increases; and

decreasing the amount of error correction information when the packet loss rate of the network decreases.

14. The computer readable medium of claim 12, wherein the set of instructions for determining the level of error protection comprises sets of instructions for:

increasing an amount of error correction information when a delay time of the network decreases; and

decreasing the amount of error correction information when the delay time of the network increases.

15. A non-transitory computer readable medium storing a computer program which when executed by at least one processor encodes a digital video image, the computer program comprising sets of instructions for:

determining a packet size for transmitting an encoded video frame over a network;

dividing the encoded video frame into a plurality of data packets to transmit over the network based on the packet size;

determining a number of packets required to generate error correction information for the encoded video frame;

when the required number of packets is greater than a number of data packets into which the video frame is divided, creating additional pseudo-packets, wherein the additional pseudo-packets comprise predetermined data that is not obtained from the encoded video frame;

generating error correction information for the encoded video frame using the plurality of data packets and the created pseudo-packets; and

transmitting the plurality of data packets over the network with at least one error correction information packet.

16. The computer readable medium of claim 15, wherein the packet size is based on a maximum transmission unit of the network.

17. The computer readable medium of claim 15, wherein the encoded video frame is divided into a minimum number of packets possible given the packet size.

18. The computer readable medium of claim 15, wherein the number of packets required to generate error correction information is based on a code length of an error correction algorithm used to generate the error correction information.

19. The computer readable medium of claim 18, wherein the number of packets is the largest whole number divisor of the code length.

20. The computer readable medium of claim 15, wherein the pseudo-packets comprise all zero bits.

21. A method of encoding digital video, comprising:

receiving a video stream comprising a plurality of digital video images;

encoding an image of the plurality of digital video images to generate an encoded digital video frame;

generating error correction information for the encoded digital video frame, wherein more error correction information is generated for an I-frame than for a non I-frame, wherein the generating error correction information comprises;

dividing the encoded digital video frame into a plurality of data packets to transmit over a network;

determining a number of packets required to generate error correction information for the encoded digital video frame;

when the required number of packets is not greater than a number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame; and

when the required number of packets is greater than the number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame and additional pseudo-packets, wherein the additional pseudo-packets comprise predetermined data that is not obtained from the video stream, wherein the required number of packets is not greater than the sum of the number of data packets in the plurality of data packets the number of additional pseudo-packets; and

transmitting the generated error correction information with the encoded digital video frame.

22. A method of encoding digital video image, comprising:

identifying a frame type for an encoded digital video frame;

determining a level of error protection for the encoded digital video frame based on the identified frame type, wherein the level of error protection is greater for an I-frame than for a P-frame or a B-frame;

generating error correction information for the encoded digital video frame according to the level of error protection, wherein the generating error correction information comprises;

dividing the encoded digital video frame into a plurality of data packets to transmit over a network;

determining a number of packets required to generate error correction information for the encoded digital video frame;

when the required number of packets is not greater than a number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame; and

when the required number of packets is greater than the number of data packets in the plurality of data packets, generating error correction information using data only from the encoded digital video frame and additional pseudo-packets, wherein the additional pseudo-packets comprise predetermined data that is not obtained from the encoded digital video frame, wherein the number of packets comprised in the plurality of data packets and the additional pseudo-packets is at least the required number of packets;

transmitting the generated error correction information with the encoded digital video frame.

23. A method of encoding digital video image, comprising:

determining a packet size for transmitting an encoded video frame over a network;

dividing the encoded video frame into a plurality of data packets to transmit over the network based on the packet size;

determining a number of packets required to generate error correction information for the encoded video frame;

when the required number of packets is greater than a number of data packets into which the video frame is divided, creating additional pseudo-packets, wherein the additional pseudo- packets comprise predetermined data that is not obtained from the encoded video frame;

generating error correction information for the encoded video frame using the plurality of data packets and the created pseudo-packets; and

transmitting the plurality of data packets over the network with at least one error correction information packet.