Apparatus for synchronized playback of audio-video signals

• US 6,163,647 A
• Filed: 12/02/1997
• Issued: 12/19/2000
• Est. Priority Date: 12/02/1996
• Status: Expired due to Term

• Current Assignee: NEC Personal Computers, Ltd. (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Samejima, Takashi, Sawada, Hideki, Terashima, Masaru, Tanaka, Mitsumasa
• Primary Examiner(s): NGUYEN, HUY THANH
• Application Number:
  US08/982,977
• Time in Patent Office: 1,113 Days
• Field of Search: 386/46, 386/98, 386/104, 386/105, 386/106, 386/96, 386/95, 386/111, 386/112, 386/125, 386/75
• US Class Current: 386/201
• CPC Class Codes: H04N 21/43072 of multiple content streams on the same device
• CPC Class Codes: H04N 21/4341 Demultiplexing of audio and video streams
• CPC Class Codes: H04N 9/8042 involving data reduction
• CPC Class Codes: H04N 9/8063 using time division multiplex of the PCM audio and PCM video signals

Abstract

An apparatus for producing synchronized playback of compressed digital data of audio-video signals from a desired portion of the digital data. The apparatus can be used in a system having comparatively low data processing ability, and work independent of the resolution of a software timer of the system. The apparatus comprises a frame counter for obtaining a reference time indicating reproduction time passage of the audio signal component from a reproduced data amount of the audio signal component. A delay detector detects progress of the video signal component in reference to the reference time.

Claims

1. An apparatus for synchronized playback of system signals having an audio signal component and a video signal component, said apparatus comprising:

a clock generator which calculates a reference time indicating reproduction time passage of said audio signal component from an amount of reproduced data of said audio signal component added with a compensation amount, and by referring to a sampling rate of the audio signal component and a frame rate of the video signal component;

a delay detector coupled to said clock generator, said delay detector detects a progress of said video signal component by comparing a real frame number added with a compensation number of said video signal component to an ideal frame number, said real frame number indicating a number of processed picture frames of said video frame component, said ideal frame number being the product of said reference time and said frame rate of said video signal component;

an audio data counter compensator coupled to said clock generator, said audio data counter compensator calculates said compensation amount from a playback point of said system signal where synchronized playback is requested; and

a video frame counter compensator coupled to said delay detector, said video frame counter compensator calculates said compensation number from said playback point of said system signal where synchronized playback is requested.

2. The apparatus for synchronized playback of system signals as claimed in claim 1, wherein said apparatus further comprises:

a video frame counter which counts and maintains said real frame number by accumulating a number of picture frames actually decompressed and a number of picture frames omitted to be decompressed; and

wherein said delay detector includes

a calculator which calculates said ideal frame number of said video signal component to be displayed from said reference time and said frame rate of said video signal components, and detects said progress of the video signal component by comparing said real frame number added with said compensation number to said ideal frame number.

3. The apparatus for synchronized playback of system signals as claimed in claim 1, further comprising a frame omission controller coupled to said delay detector, said frame omission controller compensates for a difference in display timing between said video signal component and said reference time by performing one of frame omission and decompression waiting of said video signal component according to said progress of the video signal component.

4. The apparatus for synchronized playback of system signals as claimed in claim 3, wherein said frame omission is performed according to an order of priority attributed to frames of said video signal component subject to said frame omission based upon kinds of said frames.

5. The apparatus for synchronized playback of system signals as claimed in claim 3, wherein said decompression waiting is performed by controlling decompression of compressed data of a frame of said video signal component to wait until said difference of display timing of said frame from said reference time is within a threshold value.

6. The apparatus for synchronized playback of system signals as claimed in claim 1, wherein said audio data counter compensator and video frame counter compensator further refers to a time difference between a first time stamp found in compressed data of said video signal component to be reproduced, indicating presentation timing of data which follows said first time stamp, and a second time stamp found in compressed data of said audio signal component to be reproduced, indicating presentation timing of data following said second time stamp.

7. The apparatus as claimed in claim 1, wherein said clock generator, said audio data counter compensator, and said video frame counter compensator refer to header information disposed in said system signals.

8. The apparatus as claimed in claim 3, further comprising:

an audio reproduction controller; and

wherein said audio signal component is processed by said audio reproduction controller without significant interruption.

9. A method for synchronizing playback of system signals having an audio signal component and a video signal component, said method comprising:

calculating a reference time indicating reproduction time passage of said audio signal component from an amount of reproduced data of said audio signal component added with a compensation amount, and by referring to a sampling rate of the audio signal component and a frame rate of the video signal component;

detecting a progress of said video signal component by comparing a real frame number added with a compensation number of said video signal component to an ideal frame number, said real frame number indicating a number of processed picture frames of said video frame component, said ideal frame number being the product of said reference time and said frame rate of said video signal component;

calculating said compensation amount from a playback point of said system signal where synchronized playback is requested; and

calculating said compensation number from a playback point of said system signal where synchronized playback is requested.

10. The method for synchronizing playback of system signals as claimed in claim 9, wherein said detecting comprises:

maintaining said real frame number by accumulating a number of picture frames actually decompressed and a number of picture frames omitted to be decompressed;

calculating an ideal frame number of said video signal component to be displayed from said reference time and said frame rate of said video signal components, and

detecting said progress of the video signal component by comparing said real frame number added with said compensation number to said ideal frame number.

11. The method for synchronizing playback of system signals as claimed in claim 9, further comprising compensating for a difference in display timing between said video signal component and said reference time by performing one of frame omission and decompression waiting of said video signal component according to said progress of the video signal component.

12. The method for synchronizing playback of system signals as claimed in claim 11, wherein said frame omission is performed according to an order of priority attributed to frames of said video signal component subject to said frame omission based upon kinds of said frames.

13. The method for synchronizing playback of system signals, as claimed in claim 11, wherein said decompression waiting is performed by controlling decompression of compressed data of a frame of said video signal component to wait until said difference of display timing of said frame from said reference time is within a threshold value.

14. The method for synchronizing playback of system signals, as claimed in claim 9, wherein said calculating of said compensation amount and said compensation number further comprises referring to a time difference between a first time stamp found in compressed data of said video signal component to be reproduced, indicating presentation timing of data which follows said first time stamp, and a second time stamp found in compressed data of said audio signal component to be reproduced, indicating presentation timing of data following said second time stamp.

15. The method of synchronizing playback of system signals as claimed in claim 9, wherein all of said calculating further includes referring to a header of said system signal.

16. The method of synchronizing playback of system signals, as claimed in claim 9, further comprising processing said audio signal component.