Randomized playback of tracks in a multimedia player

• US 20030156503A1
• Filed: 02/21/2002
• Published: 08/21/2003
• Est. Priority Date: 02/21/2002
• Status: Active Grant

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Tanana, Jacob, Schilling,, Walter W. Jr.
• Granted Patent: US 6,707,768 B2
• Time in Patent Office: Days
• US Class Current: 369/30.3
• CPC Class Codes: G11B 2220/2545 CDs
• CPC Class Codes: G11B 2220/40 Combinations of multiple record carriers
• CPC Class Codes: G11B 27/105 of operating discs

Abstract

An audio reproduction apparatus randomizes or shuffles the playback order of tracks from a prerecorded media such as a compact disc within a multiple-disc changer. Shuffle sequences are generated using a linear congruential random number generator (LCRNG). The shuffle sequence does not have to be stored since a next track in the sequence can always be generated from the LCRNG using a particular set of parameters. The parameters are determined in response to the number of track (or discs) in a sequence and include elements obtained from a lookup table and elements that are randomly selected so that the same sequence is not always generated for a certain sequence length.

Claims

1. A method of determining a shuffle sequence for playing tracks from a prerecorded media, comprising the steps of:

determining a modulus m greater than or equal to the total number of tracks T to be randomized in said shuffle sequence, said tracks being stored on said prerecorded media in a predetermined order x_i, where i is an index;

determining a multiplier a for which (a−

1) is a multiple of every prime number less than m that is a factor of m, wherein if m is a multiple of 4 then (a−

1) is also a multiple of 4; and

determining an increment c which is relatively prime with m;

wherein said shuffle sequence is determined in response to a linear congruential random number generator.

2. The method of claim 1 wherein said linear congruential random number generator determines a next track number x_i+1 of said shuffle sequence in response to the formula:

x_i+1=(a·

x_i+c)modm.

3. The method of claim 1 wherein said increment c is randomly selected from a plurality of prime numbers.

4. The method of claim 1 wherein said modulus m and said multiplier a are obtained from a predetermined table in response to said total number of tracks T.

5. The method of claim 1 further comprising the step of:

determining a beginning track number x₀ when said shuffle sequence is initialized, wherein said beginning track number x₀ is comprised of a currently playing track when said shuffle mode is initiated.

6. The method of claim 1 wherein a beginning track number x₀ is randomly selected.

7. The method of claim 1 wherein a next track x_i+1 in said shuffle sequence is determined while a track x_i is playing, and wherein if said shuffle sequence has been previously initialized with values for m, a, and c then said determination of said next track x_i+1 re-uses said previously initialized values for m, a, and c.

8. The method of claim 1 wherein shuffle sequences are generated for a plurality of discs in a multiple-disc changer, said method further comprising the steps of:

randomly determining when to change to a different disc in said multiple-disc changer; and

when changing to said different disc, determining a next disc using a random disc sequence;

wherein said random disc sequence is determined in response to a linear congruential random number generator.

9. A method of operating a multimedia player in a shuffle mode for playing selections from a prerecorded media, comprising the steps of:

initiating a shuffle mode;

detecting a trigger event requiring determination of a next random track number;

detecting whether a shuffle sequence is initialized for said prerecorded media and if not, then;

determining a modulus m greater than or equal to the total number of tracks T to be randomized in said shuffle sequence, said tracks being stored on said prerecorded media in a predetermined order x_i, where i is an index;

determining a multiplier a for which (a−

1) is a multiple of every prime number less than m that is a factor of m, wherein if m is a multiple of 4 then (a−

1) is also a multiple of 4; and

determining an increment c which is relatively prime with m; and

determining said next random track number using said determined modulus m, said determined multiplier a, and said determined increment c in a linear congruential random number generator.

10. The method of claim 9 wherein said trigger event is comprised of a detection of an ending of a currently playing track.

11. The method of claim 10 wherein said trigger event is comprised of detection of a predetermined time interval remaining until playing of said currently playing track is completed.

12. The method of claim 9 wherein said trigger event is a manual navigation action initiated by a user.

13. The method of claim 9 wherein a next track x_i+1 in said shuffle sequence is determined while a track x_i is playing, and wherein if said shuffle sequence has been previously initialized with values for m, a, and c then said determination of said next track x_i+1 re-uses said previously initialized values for m, a, and c.

14. The method of claim 9 wherein shuffle sequences are generated for a plurality of discs in a multiple-disc changer, said method further comprising the steps of:

randomly determining when to change to a different disc in said multiple-disc changer; and

when changing to said different disc, determining a next disc using a random disc sequence;

wherein said random disc sequence is determined in response to a linear congruential random number generator.

15. Audio apparatus comprising:

an audio source generating audio signals from a prerecorded media;

a user control interface for initiating a shuffle mode; and

a controller responsive to said shuffle mode for generating a shuffle sequence in response to a linear congruential random number generator, wherein said controller;

determines a modulus m greater than or equal to the total number of tracks T to be randomized in said shuffle sequence, said tracks being stored on said prerecorded media in a predetermined order x_i, where i is an index;

determines a multiplier a for which (a−

1) is a multiple of every prime number less than m that is a factor of m, wherein if m is a multiple of 4 then (a−

1) is also a multiple of 4; and

determines an increment c which is relatively prime with m.

16. The audio apparatus of claim 15 wherein said controller detects a trigger event for indicating a need to identify a next random track in said shuffle sequence, wherein said trigger event includes detection of an ending of a currently playing track.

17. The audio apparatus of claim 15 wherein said audio source generates audio signals from a plurality of prerecorded media contained therein, and wherein said controller randomly determines when to change to a different one of said prerecorded media and determines a next one of said prerecorded media to be reproduced using a random disc sequence.

18. The audio apparatus of claim 17 wherein said audio source is comprised of a CD changer and said prerecorded media are comprised of compact discs loaded into said CD changer.

19. The audio apparatus of claim 15 further comprising a random number generator for randomly selecting a value for said increment c.

20. The audio apparatus of claim 15 further comprising a table comprising predetermined values for modulus m and multiplier a according to said total number of tracks T.