Audio video timing measurement and synchronization

1. A method of inserting synchronization information into a media program having video data describing a video signal and audio data describing an audio signal temporally associated with the video signal, comprising the steps of:

detecting a video event according to a video event discriminant in the video signal;

generating a timing signal according to an identified type of the detected video event; and

inserting the timing signal into the audio signal.

2. The method of claim 1 , wherein the video signal comprises a plurality of frames, and the video event discriminant is a change determined by a lack of correlation between a first frame and a second frame of the plurality of frames.

3. The method of claim 1 , wherein the audio signal comprises a multiple channel audio signal and wherein the step of inserting the timing signal into the audio signal comprises the step of:

inserting sub-timing signals into the channels, the phase and amplitude of the sub-timing signals selected such that the combination of the sub-timing signals is zero.

4. The method of claim 1 , wherein the audio signal comprises a left audio signal and a right audio signal, and wherein the step of inserting the timing signal into the audio signal comprises the step of:

inserting a first timing signal in the left audio signal and a second timing signal having the same amplitude and opposite phase than the first timing signal in the right audio signal.

5. The method of claim 1 , wherein the timing signal is a sinusoidal pulse.

6. The method of claim 5 , wherein the sinusoidal pulse is a differential sinusoidal pulse defined according to

cos

⁡

(

ω

⁢

⁢

t

)

ω

⁢

⁢

t

-

sin

⁡

(

ω

⁢

⁢

t

)

(

ω

⁢

⁢

t

)

2

,

wherein ω is a fundamental frequency of the pulse.

7. The method of claim 6 , wherein the sinusoidal pulse is windowed according to

ω

⁡

(

n

)

=

0.5

⁢

(

1

-

cos

⁡

(

2

⁢

π

⁢

⁢

n

N

-

1

)

)

wherein 0≦n≦N−1.

8. The method of claim 7 , wherein the audio signal has a peak and a zero crossing adjacent thereto, and wherein the pulse is added to the audio signal such that the zero crossing occurs at a defined time offset from the video event.

9. The method of claim 5 , wherein a duration of the sinusoidal pulse is between 100 milliseconds and 5 seconds.

10. The method of claim 5 , wherein the fundamental frequency of the sinusoidal pulse is between 16 and 24 Hertz.

11. The method of claim 1 , wherein the timing signal is a sinusoidal pulse, and the type of video event is determined from a fundamental frequency of the sinusoidal pulse.

12. The method of claim 1 , wherein the video event discriminant is one of a group of video event discriminants, and the inserted timing signal is one of a group of timing signals, each timing signal associated with one of the group of video event discriminants.

13. The method of claim 12 , wherein the video signal comprises a plurality of video frames, and the group of video event discriminants includes different portions of the video frames.

14. The method of claim 12 , wherein the group of timing signals includes sinusoidal pulses of different fundamental frequencies.

15. A method of synchronizing information in a media program having video data describing a video signal and audio data describing an audio signal temporally associated with the video signal, comprising the steps of:

receiving the video signal and the audio signal, the audio signal having a timing signal indicating a type of video event and a time of the video event detected according to a video event discriminant in the video signal;

detecting the timing signal in the received audio signal and determining the type of the video event from the detected timing signal;

detecting the video event in the received video signal; and

synchronizing the video signal with the audio signal using the detected timing signal and the detected video event.

16. The method of claim 15 , wherein the timing signal comprises a left audio signal and a complimentary right audio signal 180 degrees out of phase with the left audio signal.

17. The method of claim 15 , wherein the timing signal is a sinusoidal pulse.

18. The method of claim 17 , wherein the timing signal is a differential sinusoidal pulse defined according to

cos

⁡

(

ω

⁢

⁢

t

)

ω

⁢

⁢

t

-

sin

⁡

(

ω

⁢

⁢

t

)

(

ω

⁢

⁢

t

)

2

,

wherein ω is a fundamental frequency of the sinusoidal pulse.

19. The method of claim 18 , wherein the sinusoidal pulse is windowed according to

ω

⁡

(

n

)

=

0.5

⁢

(

1

-

cos

⁡

(

2

⁢

π

⁢

⁢

n

N

-

1

)

)

wherein 0≦n≦N−1.

20. The method of claim 18 , wherein the timing signal is a sinusoidal pulse having a peak and a zero crossing adjacent thereto, and wherein the step of synchronizing the video signal with the audio signal using the detected timing signal comprises the steps of:

finding the zero crossing adjacent the peak of the detected timing signal; and

presenting the video signal and the audio signal such that the video event is presented at a defined time offset from the zero crossing of the timing signal.

21. The method of claim 20 , wherein the step of presenting the video signal and the audio signal such that the video event is presented at a defined time offset from the zero crossing of the audio signal comprises the step of delaying the audio signal and/or the video signal so that the video event is presented at the defined time offset from the zero crossing of the audio signal.

22. The method of claim 15 , wherein the video signal comprises a plurality of frames and wherein the video event discriminant is a change in luminance of a portion of a first frame and the portion of a second frame.

23. The method of claim 15 , wherein the video signal comprises a plurality of frames, and the video event discriminant is a change determined by a lack of correlation between a first frame and a second frame.

24. The method of claim 15 , wherein the video signal comprises a plurality of frames, and the video event discriminant is a temporal change in color between a portion of a first frame and the portion of a second frame.

25. The method of claim 17 , wherein a duration of the sinusoidal pulse is between 100 milliseconds and 5 seconds.

26. The method of claim 17 , wherein the fundamental frequency of the sinusoidal pulse is between 16 and 24 Hertz.

27. The method of claim 15 , wherein the timing signal is a sinusoidal pulse, and the type of video event is determined from a fundamental frequency of the sinusoidal pulse.

28. The method of claim 15 , further comprising the steps of:

generating a second timing signal from the determined type of timing signal; and

subtracting the second timing signal from the audio signal to remove the timing signal.

29. The method of claim 15 , wherein the video event discriminant is one of a group of video event discriminants, and the inserted timing signal is one of a group of timing signals, each timing signal associated with one of the group of video event discriminants.

30. The method of claim 28 , wherein the video signal comprises a plurality of frames, and the group of video event discriminants includes different portions of the video frames.

31. The method of claim 28 , wherein the group of timing signals includes a sinusoidal pulses of different fundamental frequencies.

32. An apparatus for inserting synchronization information into a media program having video data describing a video signal and audio data describing an audio signal temporally associated with the video signal, comprising:

a video analysis module for detecting a video event according to an video event discriminant in the video signal;

a timing signal generator for generating a timing signal according to an identified type of the detected video event; and

a mixer for inserting the timing signal into the audio signal.

33. The apparatus of claim 32 , wherein the video signal comprises a plurality of frames, and the video event discriminant is selected from the group comprising:

a change in luminance of a portion of a first frame and the portion of a second frame;

a change determined by determining a lack of correlation between a first frame and a second frame; and

a temporal change in color between a portion of a first frame and the portion of a second frame.

34. The apparatus of claim 32 , wherein the audio signal comprises a left audio signal and a right audio signal, and wherein:

the timing signal generator generates a left timing signal and a right timing signal having the same amplitude and opposite phase than the left timing signal; and

the mixer inserts a left timing signal in the left audio signal and a right timing signal in the right audio signal.

35. The apparatus of claim 32 , wherein the timing signal comprises a sinusoidal pulse.

36. The apparatus of claim 35 , wherein the sinusoidal pulse is defined according to a differential sinusoidal pulse

cos

⁡

(

ω

⁢

⁢

t

)

ω

⁢

⁢

t

-

sin

⁡

(

ω

⁢

⁢

t

)

(

ω

⁢

⁢

t

)

2

,

wherein ω is a fundamental frequency of the pulse.

37. The apparatus of claim 35 , wherein the sinusoidal pulse is defined according to

cos

⁡

(

ω

⁢

⁢

t

)

ω

⁢

⁢

t

-

sin

⁡

(

ω

⁢

⁢

t

)

(

ω

⁢

⁢

t

)

2

,

wherein ω is a fundamental frequency of the pulse and the pulse is windowed according to

ω

⁡

(

n

)

=

0.5

⁢

(

1

-

cos

⁡

(

2

⁢

π

⁢

⁢

n

N

-

1

)

)

wherein 0≦n≦N−1.

38. The apparatus of claim 35 , wherein the audio signal has a peak and a zero crossing adjacent thereto, and wherein the mixer adds the pulse to the audio signal such that the zero crossing occurs at a defined time offset from the video event.

39. The apparatus of claim 35 , wherein a duration of the pulse is between 100 milliseconds and 5 seconds.

40. The apparatus of claim 35 , wherein the fundamental frequency of the pulse is between 16 and 24 Hertz.

41. The apparatus of claim 32 , wherein the video discriminant is one of a group of video discriminants, and the timing signal is one of a group of timing signals, each timing signal associated with one of the group of video discriminants.

42. The apparatus of claim 40 , wherein the video signal comprises a plurality of frames, and the group of video discriminants includes different portions of the video frames.

43. The apparatus of claim 40 , wherein the group of timing signals includes sinusoidal pulses of different fundamental frequencies.

44. An apparatus for synchronizing information in a media program having video data describing a video signal and audio data describing an audio signal temporally associated with the video signal, comprising the steps of:

a receiver for receiving the video signal and the audio signal, the audio signal having a timing signal indicating a type of a video event and a time of the video event detected according to a video event discriminant in the video signal;

a video event detector, for detecting a video event in the received video signal;

a synchronization detector, for detecting the timing signal and for determining the type of the video event from the detected timing signal; and

a synchronizer for synchronizing the video signal with the audio signal using the detected timing signal and the detected video event.

45. The apparatus of claim 44 , wherein the timing signal is a sinusoidal pulse.

46. The method of claim 45 , wherein the timing signal is a differential sinusoidal pulse defined according to

cos

⁡

(

ω

⁢

⁢

t

)

ω

⁢

⁢

t

-

sin

⁡

(

ω

⁢

⁢

t

)

(

ω

⁢

⁢

t

)

2

,

wherein ω is a fundamental frequency of the sinusoidal pulse.

47. The method of claim 46 , wherein the sinusoidal pulse is windowed according to

ω

⁡

(

n

)

=

0.5

⁢

(

1

-

cos

⁡

(

2

⁢

π

⁢

⁢

n

N

-

1

)

)

wherein 0≦n≦N−1.

48. The apparatus of claim 44 , wherein the timing signal is a sinusoidal pulse having a peak and a zero crossing adjacent thereto, and wherein:

the synchronization detector comprises a signal analyzer for finding the zero crossing adjacent the peak; and

the synchronizer comprises delay module for presenting the video signal and the audio signal such that the video event is presented at a defined time offset from the zero crossing of the audio signal.

49. The apparatus of claim 48 , wherein the delay module delays the audio signal so that the video event is presented at a defined time offset from the zero crossing of the audio signal.

50. The apparatus of claim 44 , wherein the timing signal comprises a left audio signal and a complimentary right audio signal 180 degrees out of phase with the left audio signal.

51. The apparatus of claim 44 , wherein the timing signal is a sinusoidal pulse, and the type of video event is determined from a fundamental frequency of the sinusoidal pulse.

52. The apparatus of claim 44 , further comprising:

a timing signal generator, for generating a second timing signal from the determined type of timing signal;

a subtractor, for removing the second timing signal from the audio signal to remove the timing signal.

53. The apparatus of claim 44 , wherein the video signal comprises a plurality of frames and wherein the video event discriminant is a change from a luminance of a first portion of a first frame to a luminance of the first portion of a second frame.

54. The apparatus of claim 44 , wherein the video signal comprises a plurality of frames, and the video event discriminant is a change determined by a lack of correlation between a first frame and a second frame.

55. The apparatus of claim 42 , wherein the video signal comprises a plurality of frames, and the video event discriminant is a temporal change in color between a portion of a first frame and the portion of a second frame.

56. A method of synchronizing information in a media program having video data describing a video signal and audio data describing an audio signal temporally associated with the video signal, comprising the steps of:

receiving the video signal and the audio signal, the audio signal having a timing signal indicating a time of a video event;

detecting the timing signal;

detecting the video event;

synchronizing the video signal with the audio signal using the detected timing signal and the detected video event; and

generating a second timing signal from the detected timing signal; and

subtracting the second timing signal from the audio signal to remove the timing signal.