Video and audio data presentation interface

Abstract

Presentation of digital video and audio data in a computer system. Am application program may call upon a driver program to manipulate streams of video and audio data, including commands to present the video or audio to an operator, retrieve status information about the presentation, simultaneously present graphics with video data, halt or pause presentations, allocate or release resources for presentation, and group multiple streams for synchrony. The driver program may operate upon the grouped streams in synchrony in response to unified commands from the application program. An interface to the driver program may comprise a interrupt instruction invoked with a designated interrupt and a designated set of commands: initialization; open and close; play, pause, stop, seek, and step; group; set and get; installation; and termination. The driver program may be called upon using a standardized interface for such functions, in which the application program may indicate a designated set of parameters for each function call.

Claims

We claim:

1. A computer system for presenting video or audio data, comprising

a processor;

memory coupled to said processor;

means for presenting video and audio data coupled to said memory;

an application program having an execution point in said memory;

means for signaling an interrupt from said application program;

a driver program in said memory, coupled to said means for signaling an interrupt and to said means for presenting video and audio data;

a first and a second data stream, said first and second data streams each comprising video or audio data, and said first and second data streams each coupled to said processor;

said driver program comprising a plurality of functions each callable from said application program with a common calling sequence, whereby said means for signaling an interrupt directs said interrupt to said driver program;

said plurality of functions comprising a function for designating said first and second data streams as a group, a function for causing a plurality of data streams in a group to change status in synchrony into a PLAY mode, a PAUSE mode, a STOP mode, a SEEK mode, or a STEP mode, a function for designating a callback function independently for said group or for said first data stream, a function for designating a signal independently for said group or for said first data stream, a function for designating a buffer in said memory as a location for data associated with said first data stream.

2. A computer system as in claim 1, wherein said application program generates video or audio, or both, in response to data said application program retrieves from a file in said computer system, or from a source device coupled to said computer system.

3. A computer system as in claim 2, wherein said source device comprises a video camera, an MPEG capture device, or a communication device.

4. Apparatus for presenting data in a computer system, comprising

means for presenting video and audio data;

means for signaling an interrupt from an application program;

a driver program coupled to said means for signaling an interrupt and to said means for presenting video and audio data;

a first and a second data stream, said first and second data streams each comprising video or audio data;

said driver program comprising a plurality of functions each callable from said application program with a common calling sequence, whereby said means for signaling an interrupt directs said interrupt to said driver program;

said plurality of functions comprising a function for designating said first and second data streams as a group, a function for causing a plurality of data streams in a group to change status in synchrony into a PLAY mode, a PAUSE mode, a STOP mode, a SEEK mode, or a STEP mode, a function for designating a callback function independently for said group or for said first data stream, and a function for designating a signal independently for said group or for said first data stream.

5. Apparatus as in claim 4, wherein said common calling sequence comprises:

a set of registers providing both input and output transfer, said set of registers having

a first register defining a high and low register space, wherein during said input transfer said high register space is reserved for an indicator of one of said plurality of functions to be called, and said low register space is reserved for an indicator for a data stream to be manipulated:

a second register reserved for a set of data flags; and

a third register and a fourth register in combination reserved for a modifiable data value or data pointer.

6. Apparatus as in claim 4, wherein said driver program comprises means for calling said callback function in response to a plurality of predetermined conditions, said plurality of predetermined conditions including a plurality of different predetermined error conditions, a condition indicative of said designated signal, a condition indicative of a completed operation for said first data stream, a condition indicative of a canceled command to said driver program, a condition indicative of allocation or deallocation of a buffer comprising video or audio data for presentation from said first data stream, and a plurality of different conditions indicative of progress of presentation of video or audio data from said buffer.

7. Apparatus as in claim 4, wherein said plurality of functions comprises a first function for presenting a stream of video or audio data, and a second function for cancelling said command, wherein when said first function is issued for a first data stream and said first function is issued for a second data stream before said first data stream is completed, said first function for said first data stream is cancelled according to said second function.

8. Apparatus as in claim 4, wherein said plurality of functions comprises a first function for presenting a first stream of video or audio data, and a second function for simultaneously cancelling said first function and issuing said first function for a second stream of video or audio data, whereby a presentation is transitioned smoothly from said first stream to said second stream without significant time in between.

9. Apparatus as in claim 4, wherein said plurality of functions comprises a function for adding or removing a data stream from said group and a function for selecting or deselecting a data stream within said group without altering the membership of said group.

10. Apparatus as in claim 4, wherein said plurality of functions comprises a function for causing said first data stream to change status into a first mode, said first mode comprising a PLAY mode, a PAUSE mode, a STOP mode, a SEEK mode, or a STEP mode, said function comprising means for designating a second mode for said first data stream to change status into after a completion of said function, said second mode comprising a PLAY mode, a PAUSE mode, a STOP mode, a SEEK mode, or a STEP mode.

11. Apparatus as in claim 4, wherein said plurality of functions comprises a function for initializing said driver program, a function for opening or closing said first data stream, a function for causing said first data stream to change status into a PLAY mode, a PAUSE mode, a STOP mode, a SEEK mode, or a STEP mode, a function for getting or setting parameters of said driver program or said first data stream, and a function for terminating said driver program.

12. Apparatus as in claim 4, wherein said plurality of functions comprises

means for determining whether said first data stream is in a ready mode; and

means responsive to said means for determining and responsive to a function for changing a status of said second data stream, for signaling a condition indicative of a canceled command to said driver program.

13. Apparatus as in claim 4, wherein said plurality of functions comprises

means for receiving a flag indicative of a test call for a function; and

means responsive to said means for receiving for disabling operations of said driver program other than indicating whether said function is supported by said driver program.

14. Apparatus as in claim 4, wherein said signal comprises a condition where said means for presenting reaches an arbitrary point in said first data stream, said arbitrary point having been designated by said application program and being other than a start or end point for said first data stream.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a video and audio data presentation interface.

2. Description of Related Art

Known computer systems, particularly personal computer systems known as "PC"s, often have coupled peripheral devices that are able to perform some special function. For example, a peripheral device may be coupled to a computer system for presenting video or audio to an operator, such as by displaying pictures or producing sounds for the operator to view and hear. It is generally desirable to place these peripheral devices under the control of a central processing unit (CPU). Particularly, it is generally desirable to control the operation of these peripheral devices from an application program executing on the CPU.

One known method for controlling a peripheral device from an application program is use of a "driver" program. A driver program may be installed with an operating system for the CPU (it may be installed with installation of the operating system, or it may be added later), and may be responsive to a designated interrupt. The application program may execute the designated interrupt to cause the driver program to operate, and may pass arguments, such as control signals or data, to the driver program for its use. The driver program may then control the peripheral device directly.

While this method achieves the purpose of controlling the peripheral device, it has the drawback that two or more driver programs may attempt to use the same designated interrupt. This problem has sometimes been addressed by "chaining", in which the operating system may first assign the interrupt to the driver program that was most recently installed. If this driver program does not recognize the function which the application calls on it to perform, it may cause the operating system to select the driver program that was next-most-recently installed. Chaining may be repeated until some driver program responds to the interrupt, or until an error is returned to the application program.

Chaining is subject to drawbacks. First, if the chain of driver programs that must be selected in turn is too long, response to the application program will be slow. This can be a particularly serious problem in the case of presentation of video and audio data. Slow response may cause the presentation to vary significantly from a realistic presentation.

Second, a chain of driver programs, each attempting to respond to the same designated interrupt, has been found to be prone to error. A relatively innocuous programming error in the operating system, or a relatively minor ambiguity in the arguments used to call upon the driver program, can cause the wrong driver program to be selected. When the wrong driver program is selected, results for the application program are generally unpredictable at best, and catastrophic at worst.

Accordingly, it would be desirable to use a limited number of designated interrupts while avoiding the drawbacks of chaining.

Another drawback of the prior art is related to presentation of video and audio data. Generally, a first peripheral device may be used for video display, while a second peripheral device may be used for audio presentation. Accordingly, different driver programs may be used to control the different devices. However, commonly an application program seeks to present video and audio in synchrony, and must thus attempt to coordinate its commands to different driver programs to achieve that result.

Although some known drivers provide commands for synchronizing data streams, the application program is still generally required to call upon the driver program for each data stream separately. This can increase the complexity of the application program, particularly where there are a multitude of commands to be issued to the driver program. For example, in presentation of video and audio data, there may be commands for "FAST FORWARD", "PLAY", "PAUSE", "REWIND", and "STOP". It would be advantageous if a group of data streams that are to be synchronized could be treated by the application program as a single data stream, so that only a single command to the driver program would be required to manipulate the entire group.

Another drawback of the prior art is that application programs (or at least their programmers) are generally required to comprehend the nature of the peripheral device to make full use of the driver program's commands. For example, if the application program seeks to display both video data and graphics on a single display, it must generally comprise a fair amount of knowledge about how the peripheral device will respond to commands to do so. It would be advantageous if the driver program would handle this for the application program. This would simplify application programs and allow the driver program to use information about the nature of the video and audio peripheral devices, which would otherwise be easy for the application program to mistake.

Another drawback of the prior art is that application programs may desire to provide video or audio data for presentation, but this is not well supported by prior art. For example, the application program may generate the video or audio data itself, may generate the video or audio data in response to data it retrieves from a file, or may retrieve video or audio data from another device (such as a video camera, an MPEG capture device, or a communication device, such as one coupled to a modem or to a T1 communication line). Known interfaces for presentation of video and audio data do not provide operations to make such operation convenient.

Accordingly, it is an object of this invention to provide an improved method for presentation of video and audio data.

SUMMARY OF THE INVENTION

The invention provides an improved method for presentation of digital video and audio data in a computer system, in which the video or audio data may be generated by an application program or may be retrieved from a recorded medium. In a preferred embodiment, an application program may call upon a driver program to manipulate streams of video and audio data, including commands to (1) present the video or audio to an operator, (2) retrieve status information about the presentation, (3) simultaneously present graphics with video data, (4) halt or pause presentations, (5) allocate or release resources for presentation, and (6) group multiple streams for synchrony. The driver program may operate upon the grouped streams in synchrony in response to unified commands from the application program.

In a preferred embodiment, an interface to the driver program may comprise a interrupt instruction invoked with a designated interrupt and one or more of the following commands:

(1) an initialization command--to initialize the driver program;

(2) open and close commands--to open and close a data stream, respectively;

(3) play, pause, stop, seek, and step commands--to present a data stream, pause a presentation, stop a presentation, relocate to a designated position in a data stream, and step increment a data stream, respectively;

(4) a group command--to designate multiple streams as a group to be synchronized;

(5) set and get commands--to set and get parameters (of the driver or a data stream), respectively;

(6) installation commands, including a callback command and a signal command--to install a callback function or a signal for a data stream, respectively; and

(7) a termination command--to terminate and release resources for the driver program.

In a preferred embodiment, the driver program may be called upon using a standardized interface for such functions, in which video and audio data for presentation may be treated uniformly whether the data is generated by an application program or retrieved from a recorded medium. In the standard interface, the application program may indicate the following set of parameters for each function call: an identifier of which command is called upon, an indicator for which data stream is to be manipulated, a set of data flags, a data value or data pointer (which may be modified to comprise a returned data value or data pointer), and a register reserved for a returned error code.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a computer system including a video data presentation device.

FIGS. 2A, 2B, 2C, and 2D (collectively called "FIG. 2") show a flow diagram of an interface between an application program and a device for presenting video and audio data.

FIG. 3 shows a flow diagram of a responsive procedure for a device for presenting video and audio data.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Those skilled in the art would readily understand, after perusal of this application, that methods and techniques described for operation on a processor or computer system would be readily implemented on digital computer systems such as those described herein without undue experimentation. Accordingly, detailed description of computer programing techniques or methods of implementation are not set forth herein, except where such techniques or methods are specific to the invention.

Information in this application may be supplemented by a technical appendix, appearing at the end of this text. The technical appendix is an integral part of the disclosure of this application, and moreover is hereby incorporated by reference as if fully set forth herein.

SYSTEM INCLUDING PRESENTATION DEVICE

FIG. 1 shows a block diagram of a computer system including a video data presentation device.

A computer system 101 may comprise a processor 102, memory 103, and mass storage 104, all coupled to a system bus 105. For example, in a preferred embodiment, the computer system 101 may comprise an IBM compatible PC, having an Intel 386 processor operating at 25 MHz or better, with at least 2 MB of RAM and at least 2 MB of space free on a magnetic disk drive mass storage unit, and having an ISA or EISA bus. Such systems are known in the art.

The computer system 101 may also comprise a video and audio presentation device 106. In a preferred embodiment, the presentation device 106 may comprise a VGA display controller that supports a VESA feature connector, and a peripheral device such as the "Reel Magic" product (available from Sigma Designs Corporation, of Fremont, Calif.). The memory 103 may comprise an operating system 107, such as MS-DOS 6.2 or a variant thereof, and a driver program 108 as disclosed herein. The driver program 108 may sometimes be referred to herein as the "FMP DOS" driver.

In a preferred embodiment, the presentation device 106 may be coupled to the system bus 105 using a known methods for coupling an add-in board to the system bus 105, such as the ISA or EISA specification for a device to bus coupling. The processor 102 may communicate with the presentation device 106 by means of the bus 105, or by means of reading from and writing to the memory 103; communication techniques therefor are known in the art.

In a preferred embodiment, a data stream 109 comprising video or audio data for presentation, may be held in memory 103, in mass storage 104, or may be received by the computer system 101 from another peripheral device, such as a video camera or audio microphone, or from a communication medium, such as a network or telephone connection. Such other devices and communication media are known in the art. Such other devices may be coupled to the computer system 101 by means of the system bus 105, by means of a direct connection to memory 103, or by other known means.

In a preferred embodiment, the FMP DOS driver program 108 may have the following commands:

    ______________________________________
    FMP.sub.-- INIT
                initialize the driver program 108
    FMP.sub.-- OPEN
                open a data stream 109
    FMP.sub.-- CLOSE
                close a data stream 109
    FMP.sub.-- PLAY
                present ("play") a data stream 109
    FMP.sub.-- PAUSE
                pause a data stream 109
    FMP.sub.-- STOP
                stop a data stream 109
    FMP.sub.-- SEEK
                locate ("seek") a designated position in a
                data stream 109
    FMP.sub.-- STEP
                increment the position of a data stream 109
                by one video frame
    FMP.sub.-- GROUP
                designate data streams 109 as a group
    FMP.sub.-- SET
                set a parameter of the driver program 108
                or a data stream 109
    FMP.sub.-- GET
                get a parameter of the driver program 108
                or a data stream 109
    FMP.sub.-- CALLBACK
                install a callback function for a data stream
                109
    FMP.sub.-- SIGNAL
                install a signal for a data stream 109
    FMP.sub.-- UNLOAD
                terminate the driver program 108 and
                unload it from memory
    ______________________________________

    __________________________________________________________________________
    FMPM.sub.-- ERROR
                 An error occurred while executing a command
                 given by the application program. The value
                 may comprise an error code, which may com-
                 prise one of the following error codes:
     FMPE.sub.-- DOS
                 A DOS error occurred while reading the data
                 stream 109. Register AL may comprise the
                 DOS error code.
     FMPE.sub.-- HARDWARE
                 A hardware error occurred with the presenta-
                 tion device 106. Register AL may comprise
                 information about the error.
     FMPE.sub.-- STREAM
                 The data stream 109 comprises invalid data.
     FMPE.sub.-- DATA
                 The data stream 109 has no available data.
    FMPM.sub.-- SIGNAL
                 This message is issued when the data stream
                 109 reaches a position specified with the
                 FMP.sub.-- SIGNAL command, or when a period has
                 completed. The value may comprise the cur-
                 rent position of the data stream 109.
    FMPM.sub.-- COMPLETE
                 This message is issued when a command issued
                 by the application program has been com-
                 pleted, for example when a "play" command has
                 ended. The data stream 109 will be in a
                 ready mode, i.e., paused or stopped. The
                 value may comprise the command identifier for
                 the completed command.
    FMPM.sub.-- CANCEL
                 This message is issued when a new command has
                 been sent by the application program before
                 the previous command was completed. The
                 value may comprise the command identifier for
                 the canceled command.
    FMPF.sub.-- BUF.sub.-- CREATE
                 This message is sent when a buffered data
                 stream 109 is opened. The application pro-
                 gram may allocate and initialize buffers upon
                 receiving this message. The value may com-
                 prise the value passed by the application
                 program to the FMP.sub.-- OPEN command, and a zero
                 value may be returned on success.
    FMPF.sub.-- BUF.sub.-- CLOSE
                 This message is sent when a buffered data
                 stream 109 is to be closed. The application
                 program may release any memory allocated for
                 the buffer when this message is received.
    FMPF.sub.-- BUF.sub.-- SEEK
                 This message is sent to the application pro-
                 gram to seek to a given position in bytes.
                 The value may comprise the position to reach,
                 in bytes.
    FMPM.sub.-- BUF.sub.-- EMPTY
                 This message is sent to the application pro-
                 gram when the buffer for a buffered data
                 stream 109 is empty and more data is needed
                 to complete the command issued by the appli-
                 cation program. The application program may
                 specify an address for a new buffer with the
                 FMP.sub.-- SET -- FMPI.sub.-- BUF.sub.-- ADDR command.
                 Alterna-
                 tively, the application may set FMPI.sub.-- BUF.sub.-- LOOP
                 to cause the driver program to scan the same
                 buffer again. Otherwise, the data stream 109
                 will be stopped.
    FMPM.sub.-- BUF.sub.-- POS
                 This message is sent to the application pro-
                 gram when the buffer for a buffered data
                 stream 109 reaches a position indicated when
                 the data stream 109 was initiated (using the
                 FMPI.sub.-- BUF.sub.-- POS parameter). When the data
                 stream 109 is played, the application program
                 will generally receive this message before it
                 receives FMPM.sub.-- BUF.sub.-- EMPTY, so it does not have
                 to prepare the first buffer before opening
                 the data stream 109.
    __________________________________________________________________________

    ______________________________________
    STOP mode  The data stream 109 is stopped. There is no
               video picture and no audio sound.
    PAUSE mode The data stream 109 is paused. For an audio
               data stream 109, this is the same as STOP
               mode. For a video data stream 109, the last
               (most recent) video frame is held frozen in a
               presentation frame window.
    PLAY mode  The data stream 109 is playing, i.e., being
               presented by the presentation device 106.
               This mode is valid for both video and audio.
    SEEK mode  The data stream 109 is moving to a designated
               location. This mode is valid for both video
               and audio.
    STEP mode  The data stream 109 is moving forward one
               frame. This mode is valid for video data
               streams 109 only.
    ______________________________________

• Inventors
  Harscoet, Philippe; Chiang, Chen-Huei;
• Assignee
  Sigma Designs, Inc. (Fremont, CA)
• Published
  Mar-25-1997
• Current US Classes:
  709/231
  715/500.1
  719/322
• Application #
  221164
• International Classes
  G06F 013/24; G06F 015/00
• Field of Search
  395/650 395/700 395/154
• Examiner
  Kriess; Kevin A.
• Agent
  D'Alessandro & Ritchie
• US Patent References:
  5111292
  5111409
  5122875
  5157716
  5168356
  5191410
  5208745
  5231492
  5289276
  5339413
  5375068
  5392239
  5397853
  5416749
  5426756
  5428730
  5434913
  5450544
  5471576
  5487167