Method and apparatus for simplifying the decoding of data

• US 20080177769A1
• Filed: 01/07/2007
• Published: 07/24/2008
• Est. Priority Date: 01/07/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Gies, Sean, Albert, Eric J., Begeman, Nathaniel
• Granted Patent: US 7,716,166 B2
• Time in Patent Office: Days
• US Class Current: 707/101
• CPC Class Codes: H04N 1/41 Bandwidth or redundancy reduction by scanning H04N1/17 ; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00

Abstract

The various methods and devices described herein relate to devices which, in at least certain embodiments, may include a method of decoding data or a data stream in a file, which may include checking for a first data portion of a plurality of data portions in the file, the first data portion having a first data value, reading in data from another data portion of the plurality of data portions, decoding or decompressing the data, performing a checksum operation on the decoded data if the first data portion having the first data value is not detected, and skipping a checksum operation on the decoded data if the first data portion having the first data value is detected. In the embodiment, a checksum operation on encoded data may also be skipped. In an embodiment, the first data value may include information or instructions about how a decoder may decode the data and may also include a tag or identifier.

Claims

1. A method of converting data in a file, comprising:

checking for a first data portion of a plurality of data portions in the file, the first data portion having a first data value;

reading in data from a second data portion of the plurality of data portions;

decoding the data in the second data portion of the plurality of data portions;

performing a checksum operation on the decoded data from the second data portion if the first data portion having the first data value is not detected; and

skipping the checksum operation on the decoded data from the second data portion if the first data portion having a first data value is detected.

2. The method of claim 1 wherein checking for the first data portion includes checking for a critical data chunk in an image file.

3. The method of claim 2 wherein checking for a critical data chunk in an image file includes checking for a critical data chunk in a Portable Network Graphics (PNG) file.

4. The method of claim 1 wherein reading in data from a second data portion includes reading in compressed data from an image data chunk.

5. The method of claim 1 further comprising skipping a multiplication of a color value with a transparency value if the first data portion having the first data value is detected.

6. The method of claim 5 wherein skipping the multiplication of the color value with the transparency value includes skipping a multiplication of a red, green and blue (RGB) value with an alpha value.

7. The method of claim 1 wherein checking for the first data portion having the first data value includes checking for the first data portion having an identifier that identifies the first data portion as a critical chunk that instructs a decoder to inflate data without a header.

8. A machine-readable medium storing executable program instructions which when executed cause the machine to perform a method comprising:

checking for a first data portion of a plurality of data portions in the file, the first data portion having a first data value;

reading in data from a second data portion of the plurality of data portions;

decoding the data in the second data portion of the plurality of data portions;

performing a checksum operation on the decoded data from the second data portion if the first data portion having the first data value is not detected; and

skipping the checksum operation on the decoded data from the second data portion if the first data portion having the first data value is detected.

9. The machine-readable medium of claim 8 wherein checking for the first data portion includes checking for a critical data chunk in an image file.

10. The machine-readable medium of claim 8 wherein the method further comprises skipping a checksum operation on data that is not decoded if the first data portion having the first data value is detected.

11. The machine-readable medium of claim 8 wherein reading in data from a second data portion includes reading in deflated data from an image data chunk.

12. The machine-readable medium of claim 8 wherein performing the method further comprises skipping a multiplication of a color value with a transparency value if the first data portion having the first data value is detected.

13. The machine-readable medium of claim 12 wherein the second data portion includes a premultiplied red, green and blue (RGB) value with an alpha value.

14. The machine-readable medium of claim 8 wherein decoding the data in the second data portion includes inflating data with little-endian format.

15. The machine-readable medium of claim 8 wherein decoding the data in the second data portion includes decoding data for an opaque image encoded with a four-channel RGBA format.

16. An apparatus, comprising:

means for checking for a first data portion of a plurality of data portions in the file, the first data portion having a first data value;

means for reading in data from a second data portion of the plurality of data portions;

means for decoding the data in the second data portion of the plurality of data portions;

means for performing a checksum operation on the decoded data from the second data portion if the first data portion having the first data value is not detected; and

means for skipping the checksum operation on the decoded data from the second data portion if the first data portion having a first data value is detected.

17. A digital storage medium having stored thereon data representing an image capable of being read and displayed by a data processing system, wherein the data representing the image includes a data file, comprising:

a first data section of a plurality of data sections in the data file, the first data section having a first data value or a second data value; and

a second data section of the plurality of data sections in the data file, the second data section to skip a data check if the first data section includes the first data value, the second data section to include a data check if the first data section includes the second data value.

18. The digital storage medium of claim 17 wherein the first data section of the plurality of data sections includes a critical chunk in a Portable Network Graphics (PNG) file.

19. The digital storage medium of claim 17 wherein the first data value includes a function call that does not include a checksum and the second data value includes a function call that does include a checksum.

20. The digital storage medium of claim 17 wherein the data processing system is a handheld portable device.

21. The digital storage medium of claim 17 wherein the data processing system is a handheld cellular telephone.

22. The digital storage medium of claim 17 wherein the second data section includes data including a grayscale value that has been premultiplied with an alpha value.

23. The digital storage medium of claim 17 wherein the second data section includes data in a data chunk that is not preceded by a header.

24. The digital storage medium of claim 23 wherein the first data section includes a critical chunk that identifies the decoded data from an image data chunk as having little-endian format

25. The digital storage medium of claim 17 wherein the first data section includes a first data value including instructions to decode data without a header.

26. The digital storage medium of claim 17 wherein the first data section including instructions for decoding data having an arbitrary pixel ordering.

27. The digital storage medium of claim 26 wherein the arbitrary pixel ordering is B-G-R-A.

28. The digital storage medium of claim 18 wherein the first data section includes an indication to a decoder that each scan line of an image has been filtered with a same filter.

29. An apparatus, comprising:

a processor; and

a memory coupled to said processor, said memory having stored thereon instructions which, when executed by a decoder cause the decoder to perform a method, the method comprising;

checking for a first data portion of a plurality of data portions in a file, the first data portion having a first data value;

reading in data from a second data portion of the plurality of data portions;

decoding the data in the second data portion of the plurality of data portions;

performing a checksum operation on the data from the second data portion if the first data portion having the first data value is not detected; and

skipping the checksum operation on the data from the second data portion if the first data portion having a first data value is detected.

30. The apparatus of claim 29 wherein checking for the first data portion includes checking for a critical data chunk in an image file.

31. The apparatus of claim 29 wherein reading in data from a second data portion includes reading in image data from a portable networks graphics (PNG) file.

32. The apparatus of claim 29 wherein the memory has further stored thereon instructions to decode data for an opaque image encoded with a 4-channel RGBA format.

33. The apparatus of claim 30 wherein the memory has further stored thereon instructions for decoding data including an arbitrary ordering of components for a pixel.

34. The apparatus of claim 33 wherein the arbitrary ordering of components for a pixel comprises B-G-R-A.

35. The apparatus of claim 29 wherein checking for a first data portion having a first data value includes checking for a data portion that indicates to a decoder that each scan line of an image was filtered with a same filter type.

36. The apparatus of claim 29 wherein checking for a first data portion having a first data value includes checking for a first data portion that indicates to a decoder that each scan line of an image was filtered with a same filter method.

37. A portable network graphics (PNG) data file, comprising:

an image data chunk, included in a plurality of data chunks in the file; and

a critical data chunk, included in the plurality of data chunks in the file, the critical data chunk to convey information to a decoder about skipping a verification operation during a decoding of data in the image data chunk.

38. The data file of claim 37 wherein the information about skipping the verification operation includes information about skipping a computation of a checksum.

39. The data file of claim 38 wherein the information about skipping the verification operation further includes information about skipping the reading of a header in the image data chunk.

40. The data file of claim 39 wherein the image data chunk includes image data that is not preceded by a header.

41. The data file of claim 37 wherein the image data chunk includes data including a premultiplied alpha channel.

42. A modified portable network graphics (PNG) data file, comprising:

an image data chunk, included in a plurality of data chunks in the file, the image data chunk to include data encoded without a data check; and

a critical data chunk, included in the plurality of data chunks in the file, the critical data chunk to indicate to a decoder that the image data chunk includes data encoded without the data check.

43. The PNG data file of claim 42 wherein the image data chunk includes data encoded without a cyclic redundancy check.

44. The PNG data file of claim 42 wherein at least some of the data in the image data chunk includes data representing an opaque image that is encoded with a four-channel RGBA format.

45. A digital storage medium having stored thereon a data file representing an image, wherein the data file includes data stored in a portable network graphics (PNG) file format, the PNG file format modified to include:

an image data chunk, included in a plurality of data chunks in the file;

a critical data chunk, included in the plurality of data chunks in the file, the critical data chunk to convey to a decoder information about simplifying the decoding of the image data chunk.

46. The digital storage medium of claim 45 wherein the information about simplifying the decoding of the image data chunk includes information about skipping a data check.

47. A method, comprising:

encoding data into a first data section of a plurality of data sections in a file, the first data section including a first data value of a first type or a second type; and

encoding data into a second data section of the plurality of data sections in the file, the second data section to include information to allow a decoder to perform a data check on the data of the second data section if the first data section includes the first data value of the first type, the second data section to include information to allow the decoder to skip the data check on the data of the second data section if the first data section includes a first data value of the second type.

48. The method of claim 47 wherein encoding data into the first data section including the first data value of the first type includes encoding information into a critical data chunk in a PNG file that indicates to a decoder that a computation of a checksum will be performed.

49. The method of claim 48 wherein encoding data into the second data section includes encoding a data check value appended to the data in the second data section.

50. The method of claim 47 wherein encoding data into the first data section including a first data value of the second type includes encoding information into a critical data chunk in a PNG file that indicates to a decoder that a computation of a checksum will not be performed.

51. The method of claim 50 wherein encoding data into the second data section includes encoding data without a data check value appended to the data in the second data section.

52. The method of claim 47 wherein encoding data into the first data section includes encoding an indication to a decoder that a scan line of an image represented by the file has been filtered with a same filter as another scan line of the image represented by the file.

53. An apparatus, comprising:

means for encoding data into a first data section of a plurality of data sections in a file, the first data section including a first data value of a first type or a second type; and

means for encoding data into a second data section of the plurality of data sections in the file, the second data section to include information to allow a decoder to perform a data check on the data in the second data section if the first data section includes the first data value of the first type, the second data section to include information to allow the decoder to skip the data check on the data of the second data section if the first data section includes a first data value of the second type.

54. A machine-readable medium storing executable program instructions which when executed cause the machine to perform a method comprising:

encoding data into a first data section of a plurality of data sections in a file, the first data section including a first data value of a first type or a second type; and

encoding data into a second data section of the plurality of data sections in the file, the second data section including information to allow a decoder to perform a data check on the data in the second data section if the first data section includes the first data value of the first type, the second data section including information to allow the decoder to skip the data check on the data of the second data section if the first data section includes a first data value of the second type.

55. The machine-readable medium of claim 54 wherein said encoding of data into the first data section including the first data value of the first type comprises encoding information into a critical data chunk in a PNG file that indicates to a decoder that a computation of a checksum will be performed.

56. The machine-readable medium of claim 55 wherein said encoding of data into the second data section includes encoding a data check value into an image data (IDAT) chunk.

57. The machine-readable medium of claim 54 wherein said encoding of data into the first data section including a first data value of the second type comprises encoding information into a critical data chunk in a PNG file that indicates to a decoder that a computation of a checksum will not be performed.

58. The machine-readable medium of claim 57 wherein said encoding of data into the second data section comprises encoding data without a data check value into an image data chunk (IDAT).

59. The machine-readable medium of claim 54 wherein said encoding of data into the first data section includes encoding information to inform a decoder that each scan line of an image represented by the file has been filtered by a same filter.

60. The machine-readable medium of claim 54 wherein said encoding of data into the first data portion includes encoding information to inform a decoder that an image has been encoded with an arbitrary ordering of components for a pixel.

61. The machine-readable medium of claim 60 wherein said encoding of data into the second data section includes encoding data representing an image with an arbitrary ordering of components for a pixel.

62. The machine-readable medium of claim 54 wherein said encoding of data into the second data section includes encoding a premultiplied alpha channel into the second data section.

63. A method, comprising:

encoding data into a first data section of a plurality of data sections in a file, the first data section including a first data value of a first type or a second type; and

encoding data into a second data section of the plurality of data sections in the file, the second data section to include information specifying a data check to be performed on the data of the second data section if the first data section includes the first data value of the first type, the second data section to include information specifying to skip the data check on the data of the second data section if the first data section includes a first data value of the second type.

64. A machine-readable medium storing executable program instructions which when executed cause the machine to perform a method comprising:

encoding data into a first data section of a plurality of data sections in a file, the first data section including a first data value of a first type or a second type; and

encoding data into a second data section of the plurality of data sections in the file, the second data section to include information specifying a data check to be performed on the data of the second data section if the first data section includes the first data value of the first type, the second data section to include information specifying to skip the data check on the data of the second data section if the first data section includes a first data value of the second type.