Universal container for audio data

• US 8,095,375 B2
• Filed: 04/25/2008
• Issued: 01/10/2012
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Stewart, William G., McCartney, James E., Wyatt, Douglas S.
• Primary Examiner(s): SAINT CYR, LEONARD
• Application Number:
  US12/109,686
• Publication Number:
  US 20080208601A1
• Time in Patent Office: 1,355 Days
• Field of Search: 707/104.1
• US Class Current: 704/503
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: G11B 27/3027 used signal is digitally coded
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing
• CPC Class Codes: Y10S 707/99948 Application of database or data structure, e.g. distributed, multimedia, or image
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Storing audio data encoded in any of a plurality of different audio encoding formats is enabled by parametrically defining the underlying format in which the audio data is encoded, in audio format and packet table chunks. A flag can be used to manage storage of the size of the audio data portion of the file, such that premature termination of an audio recording session does not result in an unreadable corrupted file. This capability can be enabled by initially setting the flag to a value that does not correspond to a valid audio data size and that indicates that the last chunk in the file contains the audio data. State information for the audio data, to effectively denote a version of the file, and a dependency indicator for dependent metadata, may be maintained, where the dependency indicator indicates the state of the audio data on which the metadata is dependent.

Claims

1. A method for storing audio information in a particular file format, comprising:

a computing device storing, as part of a single audio file that has said particular file format, audio data that represents an audio stream that was produced as a result of an audio encoding of audio by an audio encoder in conformance with any one of a plurality of audio encoding formats that are supported by the particular file format;

wherein the plurality of audio encoding formats that are supported by the particular format include at least one constant bit rate audio encoding format, at least one constant sample frames per packet-variable bit rate audio encoding format, and at least one variable sample frames per packet-variable bit rate audio encoding format;

wherein said audio data comprises one or more packets, each packet of the one or more packets having boundaries within the audio stream that depend on which of the plurality of audio encoding formats is the actual audio encoding format for the audio data;

wherein each packet of the one or more packets comprises one or more sample frames;

wherein each sample frame comprises one sample for each of one or more channels;

wherein at least one of the one or more packets includes a plurality of samples;

wherein storing said single audio file includes;

determining which of the plurality of audio encoding formats is the actual audio encoding format for the audio data, and

based on the actual audio encoding format for the audio data, storing, in said single audio file, metadata information from which the boundaries, within the audio stream, of each packet of the one or more packets may be determined;

wherein storing said metadata information comprises;

storing, in said single audio file, a value for a first field that indicates whether the actual audio encoding format for the audio data is a constant bit rate audio encoding format or a variable bit rate audio encoding format, and

storing, in said single audio file, a value for a second field that indicates whether the actual audio encoding format for the audio data is a variable sample frames per packet audio encoding format or a constant sample frames per packet audio encoding format.

2. The method of claim 1, wherein said metadata information further includes information that indicates:

how many sample frames per second are in said stream;

how many bytes are in each packet; and

how many sample frames are in each packet.

3. The method of claim 2, wherein:

said information about how many bytes are in each packet indicates that said audio data is encoded in a format, of said plurality of formats, that has a variable packet size; and

said metadata information further includes packet size information that indicates sizes for packets in said audio stream.

4. The method of claim 3, wherein said metadata information further includes:

metadata that indicates how many sample frames that said audio stream uses for priming or processing latency; and

metadata that indicates how many sample frames, in a last packet that contains actual audio data, in said audio stream follow a last sample frame of actual audio data.

5. The method of claim 2, wherein:

said information about how many sample frames are in each packet indicates that said audio data is encoded in a format, of said plurality of formats, that has a variable number of sample frames per packet; and

said metadata information further includes frame count information that indicates how many sample frames are in packets in said audio stream.

6. The method of claim 5, wherein said metadata information further includes:

metadata that indicates how many sample frames that said audio stream uses for priming or processing latency; and

metadata that indicates how many sample frames, in a last packet that contains actual audio data, in said audio stream follow a last sample frame of actual audio data.

7. The method of claim 1, further comprising:

sampling said audio stream to generate a set of statistics corresponding to data points in said audio stream; and

wherein said metadata information includes said set of statistics.

8. The method of claim 7, wherein said set of statistics includes a minimum amplitude and a maximum amplitude for each of said data points.

9. The method of claim 7, further comprising:

after said set of statistics has been stored in said audio file, reading said set of statistics from said audio file to generate a display of statistics associated with said audio stream.

10. The method of claim 7, wherein:

said set of statistics is one of a plurality of sets of statistics that are stored within said audio file; and

each set of statistics, of said plurality of sets of statistics, contains the same type of statistics, sampled at different resolutions.

11. The method of claim 1, wherein storing the values for the first and second fields comprises:

if the actual audio encoding format for the audio data is a constant bit rate audio encoding format, then storing, in said single audio file, a value for said first field that indicates that the actual audio encoding format for the audio data is a constant bit rate audio encoding format, and storing, in said single audio file, a value for said second field that indicates that the actual audio encoding format for the audio data is a constant sample frames per packet audio encoding format,

if the actual audio encoding format for the audio data is a constant sample frames per packet-variable bit rate audio encoding format, then storing, in said single audio file, a value for said first data field that indicates that the actual audio encoding format for the audio data is a variable bit rate audio encoding format, and storing, in said single audio file, a value for said second field that indicates that the actual audio encoding format for the audio data is a constant sample frames per packet audio encoding format, and

if the actual audio encoding format for the audio data is a variable sample frames per packet-variable bit rate audio encoding format, then storing, in said single audio file, a value for said first field that indicates that the actual audio encoding format for the audio data is a variable bit rate audio encoding format, and storing, in said single audio file, a value for said second field that indicates that the actual audio encoding format for the audio data is a variable sample frames per packet audio encoding format.

12. The method of claim 1, wherein:

the first field is for indicating how many bytes are in each packet of the one or more packets; and

the second field is for indicating how many sample frames are in each packet of the one or more packets.

27. The method of claim 1, wherein storing in said single audio file metadata information from which the boundaries within the audio stream of each packet of the one or more packets may be determined includes storing, in said single audio file, metadata information that would not be stored in said single audio file for an audio encoding format of the plurality of audio encoding formats that is different from the actual audio encoding format for the audio data.

28. The method of claim 27, wherein the actual audio encoding format of the audio stream is a variable bit rate audio encoding format.

13. A computer-readable non-transitory storage medium storing one or more sequences of instructions for storing audio information in a particular file format, said instructions, when executed by one or more computing devices, causes the one or more computing devices to perform:

storing, as part of a single audio file that has said particular file format, audio data that represents an audio stream that was produced as a result of an audio encoding of audio by an audio encoder in conformance with any one of a plurality of audio encoding formats that are supported by the particular file format;

wherein the plurality of audio encoding formats that are supported by the particular format include at least one constant bit rate audio encoding format, at least one constant sample frames per packet-variable bit rate audio encoding format, and at least one variable sample frames per packet-variable bit rate audio encoding format;

wherein said audio data comprises one or more packets, each packet of the one or more packets having boundaries within the audio stream that depend on which of the plurality of audio encoding formats is the actual audio encoding format for the audio data;

wherein each packet of the one or more packets comprises one or more sample frames;

wherein each sample frame comprises one sample for each of one or more channels;

wherein at least one of the one or more packets includes a plurality of samples;

wherein storing said single audio file includes;

determining which of the plurality of audio encoding formats is the actual audio encoding format for the audio data, and

based on the actual audio encoding format for the audio data, storing, in said single audio file, metadata information from which the boundaries, within the audio stream, of each packet of the one or more packets may be determined;

wherein storing said metadata information comprises;

storing, in said single audio file, a value for a first field that indicates whether the actual audio encoding format for the audio data is a constant bit rate audio encoding format or a variable bit rate audio encoding format, and

storing, in said single audio file, a value for a second field that indicates whether the actual audio encoding format for the audio data is a variable sample frames per packet audio encoding format or a constant sample frames per packet audio encoding format.

14. The computer-readable non-transitory storage medium of claim 13, wherein said metadata information further includes information that indicates:

how many sample frames per second are in said stream;

how many bytes are in each packet; and

how many sample frames are in each packet.

15. The computer-readable non-transitory storage medium of claim 14, wherein:

said information about how many bytes are in each packet indicates that said audio data is encoded in a format, of said plurality of formats, that has a variable packet size; and

said metadata information further includes packet size information that indicates sizes for packets in said audio stream.

16. The computer-readable non-transitory storage medium of claim 15, wherein said metadata information further includes:

metadata that indicates how many sample frames that said audio stream uses for priming or processing latency; and

metadata that indicates how many sample frames, in a last packet that contains actual audio data, in said audio stream follow a last sample frame of actual audio data.

17. The computer-readable non-transitory storage medium of claim 14, wherein:

said information about how many sample frames are in each packet indicates that said audio data is encoded in a format, of said plurality of formats, that has a variable number of sample frames per packet; and

said metadata information further includes frame count information that indicates how many sample frames are in packets in said audio stream.

18. The computer-readable non-transitory storage medium of claim 17, wherein said metadata information further includes:

metadata that indicates how many sample frames that said audio stream uses for priming or processing latency; and

metadata that indicates how many sample frames, in a last packet that contains actual audio data, in said audio stream follow a last sample frame of actual audio data.

19. The computer-readable non-transitory storage medium of claim 13, wherein said one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform:

sampling said audio stream to generate a set of statistics corresponding to data points in said audio stream; and

wherein said metadata information includes said set of statistics.

20. The computer-readable non-transitory storage medium of claim 19, wherein said set of statistics includes a minimum amplitude and a maximum amplitude for each of said data points.

21. The computer-readable non-transitory storage medium of claim 19, wherein said one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform:

after said set of statistics has been stored in said audio file, reading said set of statistics from said audio file to generate a display of statistics associated with said audio stream.

22. The computer-readable non-transitory storage medium of claim 19, wherein:

said set of statistics is one of a plurality of sets of statistics that are stored within said audio file; and

each set of statistics, of said plurality of sets of statistics, contains the same type of statistics, sampled at different resolutions.

23. The computer-readable non-transitory storage medium of claim 13, wherein storing in said single audio file metadata information from which the boundaries within the audio stream of each packet of the one or more packets may be determined includes storing, in said single audio file, metadata information that would not be stored in said single audio file for an audio encoding format of the plurality of audio encoding formats that is different from the actual audio encoding format for the audio data.

24. The computer-readable non-transitory storage medium of claim 23, wherein the actual audio encoding format of the audio stream is a variable bit rate audio encoding format.

25. The computer-readable non-transitory storage medium of claim 13, wherein storing the values for the first and second fields comprises:

if the actual audio encoding format for the audio data is a constant bit rate audio encoding format, then storing, in said single audio file, a value for said first field that indicates that the actual audio encoding format for the audio data is a constant bit rate audio encoding format, and storing, in said single audio file, a value for said second field that indicates that the actual audio encoding format for the audio data is a constant sample frames per packet audio encoding format,

if the actual audio encoding format for the audio data is a constant sample frames per packet-variable bit rate audio encoding format, then storing, in said single audio file, a value for said first data field that indicates that the actual audio encoding format for the audio data is a variable bit rate audio encoding format, and storing, in said single audio file, a value for said second field that indicates that the actual audio encoding format for the audio data is a constant sample frames per packet audio encoding format, and

if the actual audio encoding format for the audio data is a variable sample frames per packet-variable bit rate audio encoding format, then storing, in said single audio file, a value for said first field that indicates that the actual audio encoding format for the audio data is a variable bit rate audio encoding format, and storing, in said single audio file, a value for said second field that indicates that the actual audio encoding format for the audio data is a variable sample frames per packet audio encoding format.

26. The computer-readable non-transitory storage medium of claim 13, wherein:

the first field is for indicating how many bytes are in each packet of the one or more packets; and

the second field is for indicating how many sample frames are in each packet of the one or more packets.