Methods and systems for start code emulation prevention and data stuffing

• US 7,839,895 B2
• Filed: 03/06/2009
• Issued: 11/23/2010
• Est. Priority Date: 01/22/2002
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Estrop, Stephen J., Sullivan, Gary J.
• Primary Examiner(s): Moe; Aung S
• Assistant Examiner(s): Grey; Christopher P
• Application Number:
  US12/399,818
• Publication Number:
  US 20090168805A1
• Time in Patent Office: 627 Days
• Field of Search: 370/395.64, 370/474, 370/475, 370/476, 370503-514, 375363-368
• US Class Current: 370/474
• CPC Class Codes: H04J 3/0605 Special codes used as synchronising signal
• CPC Class Codes: H04J 3/07 using pulse stuffing for systems with different or fluctuating information rates or bit rates
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding
• CPC Class Codes: H04N 21/23424 involving splicing one content stream with another content stream, e.g. for inserting or substituting an advertisement
• CPC Class Codes: H04N 21/2343 involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements video transcoding H04N19/40; media packet handling at the source H04L65/762
• CPC Class Codes: H04N 21/44016 involving splicing one content stream with another content stream, e.g. for substituting a video clip
• CPC Class Codes: H04N 21/8455 involving pointers to the content, e.g. pointers to the I-frames of the video stream

Abstract

Methods and systems provide approaches to start code emulation prevention at a granularity higher than the bit level. By operating at a level other than the bit level, processing capability requirements on both the encoder and decoder side can be reduced. In accordance with one or more embodiments, a start code emulation prevention method looks for data patterns relative to fixed-size data portions larger than single bits. When a particular pattern is found, start code emulation prevention data is inserted to prevent start code emulation. The inserted data is larger than a single bit and, in some embodiments, comprises a byte. When a decoder decodes data that has had start code emulation prevention data inserted, it can easily identify legitimate start codes and then can remove the start code emulation prevention data to provide the original data that was protected. In addition, a data stuffing method is described which allows payload data to be rounded up in size to an integer number of byte sizes, and then allows filler data to be added in a manner which is easily detectable by a decoder.

Claims

1. In a computing device that implements a media processing system, a method comprising:

with the computing device that implements the media processing system, stuffing a data payload of encoded media data in a data stream with one or more stuffing bits, including inserting the one or more stuffing bits after the data payload in the stuffed data, wherein the inserting the one or more stuffing bits includes;

inserting a 1-bit after the data payload;

inserting any of zero to seven 0-bits after the 1-bit, wherein number of inserted 0-bits varies depending on number of bits in the data payload, such that the stuffed data consists of an integer number of bytes that ends with a non-zero byte that includes the one or more stuffing bits, and such that the non-zero byte that includes the one or more stuffing bits differs from a first byte of a start code and thereby facilitates start code emulation prevention; and

with the computing device that implements the media processing system, inserting one or more bytes equal to 0x00 after the non-zero byte that ends the stuffed data and before the start code.

2. The method of claim 1 further comprising, with the computing device that implements the media processing system, inserting the start code in the data stream after the one or more bytes equal to 0x00.

3. The method of claim 1 wherein the data payload is one of plural data payloads of encoded media data, the method further comprising, for each of one or more other data payloads of the plural data payloads, repeating for the other data payload the inserting one or more stuffing bits and the inserting one or more bytes equal to 0x00, wherein the number of inserted 0-bits is different for at least two of the plural data payloads.

4. The method of claim 1 wherein the first byte of the start code is in a start code prefix.

5. The method of claim 4 wherein the start code prefix begins with a string of plural consecutive 0-bits, such that any 0-bits in the one or more stuffing bits have the same value as the bits of the first byte of the start code and such that the one or more bytes equal to 0x00 have the same value as the bits of the first byte of the start code.

6. The method of claim 5 wherein the start code prefix consists of a string of plural consecutive 0-bits followed immediately by a 1-bit.

7. The method of claim 5 wherein the start code prefix consists of two bytes each equal to 0x00 followed immediately by a byte equal to 0x01.

8. The method of claim 1 wherein the start code emulation prevention includes:

with the computing device that implements the media processing system, searching the data payload for a pattern of the start code; and

if the pattern is found, with the computing device that implements the media processing system, inserting a start code emulation prevention byte in the data payload to prevent emulation of the start code.

9. In a computing device that implements a media processing system, a method comprising:

at the computing device that implements the media processing system, receiving stuffed data comprising a data payload and one or more stuffing bits, the data payload including encoded media data; and

with the computing device that implements the media processing system, locating the data payload in the stuffed data, including;

with the computing device that implements the media processing system, detecting one or more bytes equal to 0x00 that were inserted after a non-zero byte that ends the stuffed data and before a start code that begins a next data payload; and

with the computing device that implements the media processing system, searching for the one or more stuffing bits in the stuffed data, the one or more stuffing bits consisting of;

a 1-bit that was inserted; and

any of zero to seven 0-bits that were inserted after the 1-bit to provide an integer number of bytes in the stuffed data, wherein number of inserted 0-bits varies depending on number of bits in the data payload, wherein the stuffed data consists of the integer number of bytes that ends with the non-zero byte that includes the one or more stuffing bits, and wherein the non-zero byte that includes the one or more stuffing bits differs from a first byte of the start code and thereby facilitates start code emulation prevention.

10. The method of claim 9 further comprising, with the computing device that implements the media processing system, discarding the one or more bytes equal to 0x00 and the one or more stuffing bits.

11. The method of claim 9 further comprising, at the computing device that implements the media processing system, receiving the start code after the one or more bytes equal to 0x00.

12. The method of claim 9 wherein the data payload is one of plural data payloads of encoded media data, the method further comprising, for each of one or more other data payloads of the plural data payloads, repeating for the other data payload the locating, the detecting and the searching, wherein the number of inserted 0-bits is different for at least two of the plural data payloads.

13. The method of claim 12 wherein the first byte of the start code is in a start code prefix, wherein the start code prefix begins with a string of plural consecutive 0-bits, and wherein any 0-bits in the one or more stuffing bits have the same value as the bits of the first byte of the start code and the one or more bytes equal to 0x00 have the same value as the bits of the first byte of the start code.

14. The method of claim 13 wherein the start code prefix consists of a string of plural consecutive 0-bits followed immediately by a 1-bit.

15. The method of claim 13 wherein the start code prefix consists of two bytes each equal to 0x00 followed immediately by a byte equal to 0x01.

16. The method of claim 9 further comprising:

with the computing device that implements the media processing system, searching the data payload for a start code emulation byte that prevents emulation of the start code; and

if the start code emulation byte is found, with the computing device that implements the media processing system, removing the start code emulation prevention byte from the data payload.

17. A computing device that implements a media processing system, the computing device comprising:

a processor;

memory; and

storage storing computer-executable instructions for causing the computing device to perform a method comprising;

with the computing device that implements the media processing system, stuffing a data payload in a data stream with one or more stuffing bits, including inserting the one or more stuffing bits after the data payload in the stuffed data, wherein the data payload includes encoded media data, and wherein the inserting the one or more stuffing bits includes;

inserting a 1-bit after the data payload; and

inserting any of zero to seven 0-bits after the 1-bit, wherein number of inserted 0-bits varies depending on number of bits in the data payload, such that the stuffed data consists of an integer number of bytes that ends with a non-zero byte that includes the one or more stuffing bits, and such that the non-zero byte that includes the one or more stuffing bits differs from a first byte of a start code and thereby facilitates start code emulation prevention; and

with the computing device that implements the media processing system, inserting one or more bytes equal to 0x00 after the non-zero byte that ends the stuffed data and before the start code.

18. The computing device of claim 17 wherein the storage further stores computer-executable instructions for causing the computing device that implements the media processing system to insert the start code in the data stream after the one or more bytes equal to 0x00, wherein the first byte of the start code is in a start code prefix, and wherein the start code prefix begins with a string of plural consecutive 0-bits, such that any 0-bits in the one or more stuffing bits have the same value as the bits of the first byte of the start code and such that the one or more bytes equal to 0x00 have the same value as the bits of the first byte of the start code.

19. The computing device of claim 17 wherein the start code emulation prevention includes:

with the computing device that implements the media processing system, searching the data payload for a pattern of the start code; and

if the pattern is found, with the computing device that implements the media processing system, inserting a start code emulation prevention byte in the data payload to prevent emulation of the start code.

20. The computing device of claim 17 wherein the encoded media data is video data.