Efficient techniques for modifying audio playback rates

• US 20060221788A1
• Filed: 04/01/2005
• Published: 10/05/2006
• Est. Priority Date: 04/01/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Lindahl, Aram, Williams, Joseph Mark
• Granted Patent: US 7,664,558 B2
• Time in Patent Office: Days
• US Class Current: 369/47.150
• CPC Class Codes: G10L 21/04 Time compression or expansion

Abstract

Improved techniques for modifying a playback rate of an audio item (e.g., an audio stream) are disclosed. As a result, the audio item can be played back faster or slower than normal. The improved techniques are resource efficient and well suited for audio items containing speech. The resource efficiency of the improved techniques make them well suited for use with portable media devices, such as portable media players.

Claims

1. An audio playback system, comprising:

a user interface that enables a user of said audio playback system to specify a particular playback rate that is faster or slower than a normal playback rate;

a memory for storage of at least one rate adjustment parameter, the at least one rate adjustment parameter being dependent on the particular playback rate;

a processing device operatively connected to said user interface and said memory, said processing device being operable to;

receive an input audio stream associated with a normal playback rate, determine the at least one rate adjustment parameter based on the particular playback rate provided via said user interface, store the at least one rate adjustment parameter to said memory, modify the input audio stream in accordance with the at least one rate adjustment parameter to produce an output audio stream associated with the particular playback rate; and

an audio output device for facilitating audiblization of the output audio stream.

2. An audio playback system as recited in claim 1, wherein said audio output device is a speaker or a connector for a speaker.

3. An audio playback system as recited in claim 1, wherein the at least one rate adjustment parameter includes an overlap frequency and an overlap size.

4. An audio playback system as recited in claim 1, wherein the input audio stream and the output audio stream pertain to speech.

5. An audio playback system as recited in claim 1, wherein said processing device is operable to modify the input audio stream as appropriate to produce the output audio stream in a resource efficient manner.

6. An audio playback system as recited in claim 1, wherein said processing device does not analyze the input audio stream.

7. An audio playback system as recited in claim 1, wherein said processing device operates, as appropriate, to modify the input audio stream in a low complexity manner to produce the output audio stream.

8. An audio playback system as recited in claim 1, wherein the audio playback system is part of a hand-held media player.

9. An audio playback system as recited in claim 1, wherein the audio playback system is part of a portable media device.

10. A method for altering an audio stream for playback at different rates, said method comprising:

(a) receiving a next audio block from an input audio stream having a normal playback rate;

(b) incrementing a block count;

(c) determining whether the block count equals an overlap frequency;

(d) outputting the next audio block as part of an output audio stream without alteration when the block count does not equal the overlap frequency;

(e) altering the next audio block to produce an altered audio block when the block count does equal the overlap frequency; and

(f) outputting the altered audio block as part of the output audio stream.

11. A method as recited in claim 10, wherein said altering (e) alters the next audio block in accordance with an overlap size.

12. A method as recited in claim 10, wherein said altering (e) comprises:

(e1) receiving a subsequent audio block from the input audio stream; and

(e2) overlapping the subsequent audio block with the next audio block.

13. A method as recited in claim 12, wherein said overlapping (e2) is performed with cross-fade.

14. A method as recited in claim 13, wherein said overlapping (e2) is performed in accordance with an overlap size.

15. A method as recited in claim 10, wherein said altering (e) comprises:

(e1) outputting the next audio block as part of the output audio stream without alteration; and

(e2) overlapping the next audio block with itself to yield the altered audio block.

16. A method as recited in claim 15, wherein said overlapping (e2) is performed with cross-fade.

17. A method as recited in claim 16, wherein said overlapping (e2) is performed in accordance with an overlap size.

18. A method as recited in claim 10, wherein said method further comprises:

(g) resetting the block count when the block count does equal the overlap frequency; and

(h) repeating said operations (a) through (g) for a remaining audio block of the input audio stream.

19. A method as recited in claim 10, wherein said altering (e) comprises:

(e1) determining whether the normal playback rate is to be increased or decreased;

(e2) receiving a subsequent audio block from the input audio stream and then overlapping the subsequent audio block with the next audio block when said determining (e1) determines that the normal playback rate is to be increased; and

(e3) outputting the next audio block as part of the output audio stream without alteration and overlapping the next audio block with itself to yield the altered audio block when said determining (e1) determines that the normal playback rate is to be decreased.

20. A method as recited in claim 19, wherein the overlapping is performed with cross-fade.

21. A method as recited in claim 20, wherein the overlapping is performed in accordance with an overlap size.

22. A method as recited in claim 10, wherein said method is performed on a hand-held media player.

23. A method as recited in claim 10, wherein said method further comprises:

presenting, prior to said receiving (a), a user interface to a user of the hand-held media player;

receiving, prior to said receiving (a), a playback rate indication from the user via the user interface; and

determining at least the overlap frequency based on the playback rate indication provided via said user interface.

24. A method as recited in claim 23, wherein said method further comprises:

determining an offset size based on the playback rate indication provided via said user interface.

37. A computer readable medium as recited in claim 24, wherein said method is performed on a hand-held media player.

38. A computer readable medium as recited in claim 24, wherein said method further comprises:

computer program code for presenting a user interface to a user of the hand-held media player;

computer program code for receiving a playback rate indication from the user via the user interface; and

computer program code for determining at least the overlap frequency based on the playback rate indication provided via said user interface.

39. A computer readable medium as recited in claim 38, wherein said method further comprises:

computer program code for determining an offset size based on the playback rate indication provided via said user interface.

25. A computer readable medium including at least computer program code for altering an audio stream for playback at different rates, said computer readable medium comprising:

computer program code for receiving a next audio block from an input audio stream having a normal playback rate;

computer program code for determining whether the next audio block should be altered;

computer program code for outputting the next audio block as part of an output audio stream without alteration when said computer program code for determining determines that the next audio block should not be altered;

computer program code for altering the next audio block to produce an altered audio block when said determining computer program code for determines that the next audio block should be altered; and

computer program code for outputting the altered audio block as part of the output audio stream.

26. A computer readable medium as recited in claim 25, wherein said computer program code for altering comprises computer program code for overlapping the next audio block with another audio block or itself.

27. A computer readable medium as recited in claim 25, wherein said computer program code for altering comprises computer program code for cross-faded overlapping the next audio block with another audio block or itself.

28. A computer readable medium as recited in claim 25, wherein said computer program code for altering comprises:

computer program code for receiving a subsequent audio block from the input audio stream; and

computer program code for overlapping the subsequent audio block with the next audio block.

29. A computer readable medium as recited in claim 28, wherein the overlapping by said computer program code for overlapping is performed with cross-fade.

30. A computer readable medium as recited in claim 29, wherein the overlapping by said computer program code for overlapping is performed in accordance with an overlap size.

31. A computer readable medium as recited in claim 25, wherein said computer program code for altering comprises:

computer program code for outputting the next audio block as part of the output audio stream without alteration; and

computer program code for overlapping the next audio block with itself to yield the altered audio block.

32. A computer readable medium as recited in claim 31, wherein the overlapping by said computer program code for overlapping is performed with cross-fade.

33. A computer readable medium as recited in claim 32, wherein the overlapping by said computer program code for overlapping is performed in accordance with an overlap size.

34. A computer readable medium as recited in claim 25, wherein said computer program code for altering comprises:

computer program code for determining whether the normal playback rate is to be increased or decreased;

computer program code for receiving a subsequent audio block from the input audio stream and then overlapping the subsequent audio block with the next audio block when it is determined that the normal playback rate is to be increased; and

computer program code for outputting the next audio block as part of the output audio stream without alteration and overlapping the next audio block with itself to yield the altered audio block when it is determined that the normal playback rate is to be decreased.

35. A computer readable medium as recited in claim 34, wherein the overlapping by said computer program code for overlapping is performed with cross-fade.

36. A computer readable medium as recited in claim 35, wherein the overlapping by said computer program code for overlapping is performed in accordance with an overlap size.