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WO1994014277A1 - Synchronizing the digital video and audio signals - Google Patents

Synchronizing the digital video and audio signals Download PDF

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Publication number
WO1994014277A1
WO1994014277A1 PCT/US1993/012214 US9312214W WO9414277A1 WO 1994014277 A1 WO1994014277 A1 WO 1994014277A1 US 9312214 W US9312214 W US 9312214W WO 9414277 A1 WO9414277 A1 WO 9414277A1
Authority
WO
WIPO (PCT)
Prior art keywords
video
audio
data
packets
signals
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1993/012214
Other languages
French (fr)
Inventor
Joseph Gaucher, Jr.
Fred Allen
Todd Squires
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Viacom International Inc
Original Assignee
Viacom International Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Viacom International Inc filed Critical Viacom International Inc
Priority to AU59522/94A priority Critical patent/AU5952294A/en
Publication of WO1994014277A1 publication Critical patent/WO1994014277A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/91—Television signal processing therefor
    • H04N5/92—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
    • H04N5/926—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback by pulse code modulation
    • H04N5/9265—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback by pulse code modulation with processing of the sound signal
    • H04N5/9267—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback by pulse code modulation with processing of the sound signal using time division multiplex of the PCM audio and PCM video signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/4302—Content synchronisation processes, e.g. decoder synchronisation
    • H04N21/4307—Synchronising the rendering of multiple content streams or additional data on devices, e.g. synchronisation of audio on a mobile phone with the video output on the TV screen
    • H04N21/43072—Synchronising the rendering of multiple content streams or additional data on devices, e.g. synchronisation of audio on a mobile phone with the video output on the TV screen of multiple content streams on the same device
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
    • G11B27/102—Programmed access in sequence to addressed parts of tracks of operating record carriers
    • G11B27/105—Programmed access in sequence to addressed parts of tracks of operating record carriers of operating discs
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
    • G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
    • G11B27/28—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording
    • G11B27/30—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on the same track as the main recording
    • G11B27/3027—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on the same track as the main recording used signal is digitally coded
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/41—Structure of client; Structure of client peripherals
    • H04N21/426—Internal components of the client ; Characteristics thereof
    • H04N21/42646—Internal components of the client ; Characteristics thereof for reading from or writing on a non-volatile solid state storage medium, e.g. DVD, CD-ROM
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/432—Content retrieval operation from a local storage medium, e.g. hard-disk
    • H04N21/4325—Content retrieval operation from a local storage medium, e.g. hard-disk by playing back content from the storage medium
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/433—Content storage operation, e.g. storage operation in response to a pause request, caching operations
    • H04N21/4334—Recording operations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/434—Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream
    • H04N21/4341—Demultiplexing of audio and video streams
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/20—Disc-shaped record carriers
    • G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
    • G11B2220/2537—Optical discs
    • G11B2220/2545—CDs
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/02—Editing, e.g. varying the order of information signals recorded on, or reproduced from, record carriers
    • G11B27/031—Electronic editing of digitised analogue information signals, e.g. audio or video signals
    • G11B27/034—Electronic editing of digitised analogue information signals, e.g. audio or video signals on discs

Definitions

  • the present invention relates to a method for displaying digital video signals, and more particularly to a method for synchronizing the display of digital video signals with the playback of their corresponding digital audio signals.
  • CD-ROM compact disc-read only memory
  • Prior art methods have attempted to synchronize the audio with the video on a hardware platform- specific basis. By analyzing the capabilities of a specific hardware system, prior art methods attempted to predict the relative speed of the display of video and the relative speed of the playback of corresponding audio. For example, if an audio device of a particular video game machine is capable of playing audio data at a rate of 20 Khz after a 200 millisecond buffering delay and the video processor of the video game machine is capable of displaying video data at a rate of 40 Khz after a 10 millisecond propagation delay, prior art methods would recognize that twice as much video as audio would need to be retrieved from the compact disc and that the corresponding audio must be retrieved 190 milliseconds before the video. Using the above information, prior art methods would sequentially store the audio and video on a compact disc in this manner so that as the audio and video were retrieved by the video game machine, the corresponding audio and video would be played back and displayed at approximately the same time.
  • a general object of the present invention is to provide a method for reliably and predictably synchronizing the display of digital video signals with the playback of their corresponding digital audio signals.
  • Another general object of the present invention is to provide a method for synchronizing video and audio which is independent of any hardware specific platform.
  • the present invention embodied in an improved method for synchronizing video and audio.
  • This method is different from prior methods in that the video and audio data retrieved from the compact disc is interrogated and analyzed to ensure their synchronous display and playback.
  • the audio and video data is stored on the compact disc in an interleaved fashion, thereby providing the video display device with simultaneous access to video signals and corresponding audio signals.
  • Synchronization is achieved by first storing packets of the digital video signals and packets of digital audio signals corresponding to the packets of video signals in blocks of data on the compact disc (or other suitable recording medium) . Attribute information regarding, among other things, the relative quantity of the packets of video signals and the packets of audio signals is also stored in each block of data. To display the digital video signals, the video display device (or other microprocessor driven device) retrieves the blocks of data from the compact disc and interrogates the attribute information to recover information regarding which packets of the video signals correspond to which packets of the audio signals. Then, the video display device controls the display of the video signals and the synchronous playback of the audio signals corresponding to the video signals.
  • An advantage of the present invention includes the ability to control the synchronous display of the video signals with their corresponding audio signals on a real-time basis as the video is being displayed. Unlike other techniques, the present invention allows the video display device to recognize which video signals correspond to which audio signals. As a result, the video display device can respond to and correct any synchronization errors, thereby reducing or eliminating any unwanted drift of the audio.
  • FIG. 1 is a schematic diagram showing apparatus utilized to digitize audio and video signals and— store the digital audio and video signals on a compact disc in accordance with one aspect of a preferred embodiment of the present invention.
  • FIG. 2 is a representation of the storage format used to store the digital audio and video signals on the surface of the compact disc.
  • FIG. 3 is a block diagram of a typical video display device which may be utilized to display the digital video signals while synchronously playing back their corresponding digital audio signals in accordance with one aspect of a preferred embodiment of the present invention.
  • FIG. 1 there is shown a schematic diagram showing apparatus utilized to digitize audio and video signals and store the digital audio and video signals on a compact disc in accordance with one aspect of a preferred embodiment of the present invention.
  • a video camera 10 records analog video signals which are digitized by an analog to digital converter 18.
  • a microphone 14 records analog audio signals which are digitized by an analog to digital converter 22.
  • the digitized audio and video signals are received by a computer workstation 26 which saves the digital audio and video signals along with their attribute information in blocks of data in a digital file 28 on a hard disk drive 30 of the workstation 26.
  • the data stored in the digital file 28 is then transferred onto a compact disc.
  • the size of the blocks of data is 2048 bytes. Since, the throughput rate for a typical compact disc drive 100 (shown in FIG. 3) is approximately 150K bytes/second, each block contains the data necessary to display the video and play the audio for approximately l/75th (2048/150,000) of one second. Accordingly, in the preferred embodiment shown, the video and audio is guaranteed to be synchronized to within at least l/75th of one second. Any errors in synchronization within such a margin of error are undiscernible to the human observer. Referring to FIG. 2 there is shown a representation of the storage format used to store the digital audio and video signals on the surface of the compact disc 34.
  • Blocks of data 38 and 46 are shown having headers 40 and 48, audio data packets 42 and 50, and video data packets 44 and 52, respectfully.
  • the headers 40 and 48 store the attribute information which contains, among other things, information regarding length of the audio and video data packets. Typically, the lengths of the video packets are variable depending upon the amount of compression of the video data.
  • the attribute information also contains the offset to the next block of data and the offset to the previous block of data on the compact disc.
  • the attribute information may contain additional specific information regarding the data contained in the blocks, e.g. whether the data is compressed or not.
  • FIG. 3 there is shown a schematic diagram of a typical video display device 100 which may be utilized to display the digital video signals while synchronously playing their corresponding digital audio signals.
  • the video display device 100 may be a personal computer having a microprocessor 104 and other compatible peripherals comprising a compact disc drive 108, a video graphics card 112, an audio card 116, and a display monitor 120. Communication between the microprocessor 104 and the peripherals is achieved through the communication bus 124.
  • the video display device 100 operates 5 and is used as follows.
  • the compact disc 34 containing the blocks of audio, video and attribute data, is inserted into the compact disc drive 108.
  • the compact disc drive 108 retrieves the blocks of data 0 from the compact disc 34 and sends the data to the microprocessor 104 via the communication bus 124.
  • the microprocessor 104 stores the data in a random access memory (RAM) 128 and interrogates the attribute information to determine which packets of video data 5 corresponds to which packets of audio data.
  • the RAM 128 is comprised of three (3) buffers of 8OK bytes of memory each.
  • the microprocessor 104 initially fills each of the three buffers with the blocks of data from the compact disc o 34.
  • the microprocessor 104 may also decompress the data, if necessary.
  • the microprocessor 104 sends the audio data to the 5 audio card 116.
  • the audio data is also buffered in the audio buffer 132 of the audio card 116. Therefore, the microprocessor 104 delays a predetermined amount of time to allow the audio data to propagate through the audio buffer 132. Then, the 0 microprocessor 104 sends the video data to the video graphics card 112.
  • an interrupt routine controls the flow of data to the audio card 116 and the video graphics card 112 to ensure synchronization. If any 5 of the three buffers of the RAM 128 is depleted, the microprocessor 104 retrieves additional blocks of data from the compact disc drive 108 and loads the buffer of the RAM 128 with additional data.
  • the audio card 116 converts the audio data from digital data to an analog audio signal and then sends the audio signal to the external speaker 134 for playback.
  • the video graphics card 112 converts the video data from digital data to an analog video signal and sends the video signal to the display monitor 120.
  • the microprocessor 104 ensures the synchronous display of the video data with the playback of corresponding audio data.
  • the microprocessor 104 can simply clear the audio buffer 132 and resync itself by interrogating the attribute information of a new block of data in the buffers of the RAM 128 to determine which packets of video data corresponds to which packets of audio data.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Databases & Information Systems (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)

Abstract

A method for synchronizing the display of digital video signals with playback of corresponding digital audio signals is disclosed (Fig. 3). In operation, the present invention stores audio and video data in a interleaving format (Fig. 2). Using attribute information, the present invention determines which audio data corresponds to which video data (104). The technique (Fig. 3) provides for the reliable and predictable synchronization of the display of digital video signals with the playback of their corresponding digital audio signals.

Description

SYNCHRONIZING THE DIGITAL VIDEO
AND AUDIO SIGNALS *****************
Field Of The Invention
The present invention relates to a method for displaying digital video signals, and more particularly to a method for synchronizing the display of digital video signals with the playback of their corresponding digital audio signals.
Background Of The Invention With advent of compact disc-read only memory (CD- ROM) drives came the capability to store large amounts of data in a relatively compact area. The large capacity of the CD-ROMs has made it practical to record, retrieve and display digital video signals in full motion on the screen of video display devices, such as computers, video game machines, and so-called "CD Interactive" devices. A hurdle to overcome in the displaying of the digital video signals is the synchronization of the digital video signals with the playback of the digital audio signals that correspond to the digital video signals. If the audio is not synchronized with the video, the video display may distracting to the viewer, misleading or even unintelligible.
Prior art methods have attempted to synchronize the audio with the video on a hardware platform- specific basis. By analyzing the capabilities of a specific hardware system, prior art methods attempted to predict the relative speed of the display of video and the relative speed of the playback of corresponding audio. For example, if an audio device of a particular video game machine is capable of playing audio data at a rate of 20 Khz after a 200 millisecond buffering delay and the video processor of the video game machine is capable of displaying video data at a rate of 40 Khz after a 10 millisecond propagation delay, prior art methods would recognize that twice as much video as audio would need to be retrieved from the compact disc and that the corresponding audio must be retrieved 190 milliseconds before the video. Using the above information, prior art methods would sequentially store the audio and video on a compact disc in this manner so that as the audio and video were retrieved by the video game machine, the corresponding audio and video would be played back and displayed at approximately the same time.
The above methods, while workable, have certain drawbacks and deficiencies. Specifically, while the relative speeds and capabilities of the audio and video devices have been carefully analyzed and predicted, there is no guarantee that the audio and video will actually be played back and displayed synchronously. With the above methods, any number of problems and errors could occur to disrupt the synchronization. For example, if the actual operation of the audio and video devices vary slightly from the predicted operation, synchronization will not be maintained and the audio will continuously drift further and further away from the video as time passes. In addition, if the compact disc drive has difficulty reading some data (due to a scratch on the compact disc or if the compact disc drive is bumped, etc.), synchronization will be disrupted and the display of video and the playback of audio will remain out of sync. With the above prior art method, there is no way either 1) to determine if the video and audio is actually synchronized, or 2) to correct any errors in synchronization if they occur.
Summary Of The Invention Accordingly, a general object of the present invention is to provide a method for reliably and predictably synchronizing the display of digital video signals with the playback of their corresponding digital audio signals.
Another general object of the present invention is to provide a method for synchronizing video and audio which is independent of any hardware specific platform.
The foregoing and other objects are, in the present invention, embodied in an improved method for synchronizing video and audio. This method is different from prior methods in that the video and audio data retrieved from the compact disc is interrogated and analyzed to ensure their synchronous display and playback. In accordance with one aspect of the present invention, the audio and video data is stored on the compact disc in an interleaved fashion, thereby providing the video display device with simultaneous access to video signals and corresponding audio signals.
Synchronization is achieved by first storing packets of the digital video signals and packets of digital audio signals corresponding to the packets of video signals in blocks of data on the compact disc (or other suitable recording medium) . Attribute information regarding, among other things, the relative quantity of the packets of video signals and the packets of audio signals is also stored in each block of data. To display the digital video signals, the video display device (or other microprocessor driven device) retrieves the blocks of data from the compact disc and interrogates the attribute information to recover information regarding which packets of the video signals correspond to which packets of the audio signals. Then, the video display device controls the display of the video signals and the synchronous playback of the audio signals corresponding to the video signals.
An advantage of the present invention includes the ability to control the synchronous display of the video signals with their corresponding audio signals on a real-time basis as the video is being displayed. Unlike other techniques, the present invention allows the video display device to recognize which video signals correspond to which audio signals. As a result, the video display device can respond to and correct any synchronization errors, thereby reducing or eliminating any unwanted drift of the audio.
While the invention will be described in connection with certain preferred embodiments, it is not intended that the invention be limited to those specific embodiments but rather that it be accorded a broad scope commensurate with the appended claims, consistent with the prior art.
Brief Description Of The Drawings FIG. 1 is a schematic diagram showing apparatus utilized to digitize audio and video signals and— store the digital audio and video signals on a compact disc in accordance with one aspect of a preferred embodiment of the present invention. FIG. 2 is a representation of the storage format used to store the digital audio and video signals on the surface of the compact disc.
FIG. 3 is a block diagram of a typical video display device which may be utilized to display the digital video signals while synchronously playing back their corresponding digital audio signals in accordance with one aspect of a preferred embodiment of the present invention.
Detailed Description of the Preferred Embodiment Referring to FIG. 1, there is shown a schematic diagram showing apparatus utilized to digitize audio and video signals and store the digital audio and video signals on a compact disc in accordance with one aspect of a preferred embodiment of the present invention. In the preferred embodiment, a video camera 10 records analog video signals which are digitized by an analog to digital converter 18.
Simultaneously, a microphone 14 records analog audio signals which are digitized by an analog to digital converter 22. The digitized audio and video signals are received by a computer workstation 26 which saves the digital audio and video signals along with their attribute information in blocks of data in a digital file 28 on a hard disk drive 30 of the workstation 26. By a well known process, the data stored in the digital file 28 is then transferred onto a compact disc.
In the preferred embodiment of the present invention, the size of the blocks of data is 2048 bytes. Since, the throughput rate for a typical compact disc drive 100 (shown in FIG. 3) is approximately 150K bytes/second, each block contains the data necessary to display the video and play the audio for approximately l/75th (2048/150,000) of one second. Accordingly, in the preferred embodiment shown, the video and audio is guaranteed to be synchronized to within at least l/75th of one second. Any errors in synchronization within such a margin of error are undiscernible to the human observer. Referring to FIG. 2 there is shown a representation of the storage format used to store the digital audio and video signals on the surface of the compact disc 34. Blocks of data 38 and 46 are shown having headers 40 and 48, audio data packets 42 and 50, and video data packets 44 and 52, respectfully. The headers 40 and 48 store the attribute information which contains, among other things, information regarding length of the audio and video data packets. Typically, the lengths of the video packets are variable depending upon the amount of compression of the video data. In the preferred embodiment, the attribute information also contains the offset to the next block of data and the offset to the previous block of data on the compact disc.
Alternatively, the attribute information may contain additional specific information regarding the data contained in the blocks, e.g. whether the data is compressed or not.
Referring to FIG. 3, there is shown a schematic diagram of a typical video display device 100 which may be utilized to display the digital video signals while synchronously playing their corresponding digital audio signals. The video display device 100 may be a personal computer having a microprocessor 104 and other compatible peripherals comprising a compact disc drive 108, a video graphics card 112, an audio card 116, and a display monitor 120. Communication between the microprocessor 104 and the peripherals is achieved through the communication bus 124.
Typically, the video display device 100 operates 5 and is used as follows. The compact disc 34, containing the blocks of audio, video and attribute data, is inserted into the compact disc drive 108. Under the direction of the microprocessor 104, the compact disc drive 108 retrieves the blocks of data 0 from the compact disc 34 and sends the data to the microprocessor 104 via the communication bus 124. The microprocessor 104 stores the data in a random access memory (RAM) 128 and interrogates the attribute information to determine which packets of video data 5 corresponds to which packets of audio data. In the preferred embodiment, the RAM 128 is comprised of three (3) buffers of 8OK bytes of memory each. The microprocessor 104 initially fills each of the three buffers with the blocks of data from the compact disc o 34. The microprocessor 104 may also decompress the data, if necessary.
To display the packets of video data while synchronously playing the corresponding audio data, the microprocessor 104 sends the audio data to the 5 audio card 116. Typically, the audio data is also buffered in the audio buffer 132 of the audio card 116. Therefore, the microprocessor 104 delays a predetermined amount of time to allow the audio data to propagate through the audio buffer 132. Then, the 0 microprocessor 104 sends the video data to the video graphics card 112. In the preferred embodiment of the present invention, an interrupt routine controls the flow of data to the audio card 116 and the video graphics card 112 to ensure synchronization. If any 5 of the three buffers of the RAM 128 is depleted, the microprocessor 104 retrieves additional blocks of data from the compact disc drive 108 and loads the buffer of the RAM 128 with additional data.
The audio card 116 converts the audio data from digital data to an analog audio signal and then sends the audio signal to the external speaker 134 for playback. Simultaneously, the video graphics card 112 converts the video data from digital data to an analog video signal and sends the video signal to the display monitor 120. By controlling the timing and the flow of data to the audio card 116 and the video graphics card 112, the microprocessor 104 ensures the synchronous display of the video data with the playback of corresponding audio data. If for any reason the audio playback and video display become out of sync, the microprocessor 104 can simply clear the audio buffer 132 and resync itself by interrogating the attribute information of a new block of data in the buffers of the RAM 128 to determine which packets of video data corresponds to which packets of audio data.
While the above elements used in the illustrative embodiment of the present invention have been specifically identified above, many variations and substitutions, known to those skilled in the art, can be employed without deviating from the intended scope of the present invention. Specifically, the present invention is designed for use with any microprocessor based video display device.

Claims

What is claimed is:
1. A method for synchronizing the display of digital video signals with the playback of corresponding digital audio signals comprising the following steps: storing packets of digital video signals and packets of digital audio signals corresponding to said packets of digital video signals in blocks of data on a recording medium, said blocks of data having attribute information regarding the relative quantity of said packets of video signals and said packets of audio signals in said blocks of data; retrieving said blocks of data from said recording medium and interrogating said attribute information to determine which of said packets of audio signals correspond to said packets of video signals; displaying said packets of digital video signals while synchronously playing said packets of digital audio signals corresponding to said packets of digital video signals.
PCT/US1993/012214 1992-12-15 1993-12-15 Synchronizing the digital video and audio signals Ceased WO1994014277A1 (en)

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US99070592A 1992-12-15 1992-12-15
US990,705 1992-12-15

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