Abstract:
A method and a system are provided for playing back sequences of segments of video media data stored on a storage media. A segment of the video media data is retrieved at a predetermined period prior to playback and stored in a temporary storage. Control information correlated with the segment of the video media data is subsequently supplied for processing the segment of the video media data. The control information specifies the processing of the segment of the video media data during playback. The segment of the video media data is then processed according to the control information to generate processed video for playback.

Description:
BACKGROUND 
     This invention relates to editing video media data on computers. 
     In pc-based video editing systems, video media data is compressed and stored on disk. (Video media data includes video data, video and graphics data, audio and video data, or combinations thereof.) The user edits the video media data to form video programs which the user may then play back on a monitor or to a video tape recording machine. During play back, the user can change attributes of the processing applied to the video media data, e.g., audio levels, audio filter, video effects. However, there is typically a latency between the time the attributes are modified and the time the effects of modification appear in the video program being played back. 
     SUMMARY OF THE INVENTION 
     In one general aspect, the invention features playing back sequences of segments of video media data stored on a storage media. A segment of the video media data is retrieved at a predetermined period prior to playback and stored in a temporary storage. Control information correlated with the segment of the video media data is subsequently supplied, for processing the segment of the video media data. The control information specifies the processing of the segment of the video media data during playback. The segment of the video media data is then processed according to the control information to generate processed video for playback. 
     Embodiments of the invention may include one or more of these features. 
     The control information for the segment of the video media data is generated or modified during or after retrieving the segment of the video media data. A graphical user interface is displayed for a user to generate or modify the control information for the segment of the video media data during or after retrieving the segment of the video media data. The control information can also be modified or generated before the video media data is retrieved. 
     The video media segment may be a frame of video, a field of a frame of video, audio data (e.g a sample, a selected number of samples, or samples associated with a video frame), or graphics data. 
     A video effects operation may be applied to the video media data, where the video effects operation is selected from among a group of video effects operations including dissolves, wipes, and digital video effects, color effects, single or multiple overlays, and filters. The video effects operation may be characterized by an attribute selected from among a group of attributes comprising border width, range, reverse effect, crop, softness, transparency, and border color. 
     Similarly, an operation is performed on the audio, where the operation includes applying an audio filter. The audio filter can be selected from among a group of audio filters including equalization filter, audio compression filter, and sound effects filter. The operation also can be changing a playback volume of the audio or includes changing the pan balance between two channels. A characteristic of the processed media video data is monitored and the results of said monitoring is then displayed. 
     The storage media can be a digital database and retrieving the segment of the video media data can include accessing the digital database across a network. The storage media can also be one of a magnetic disk and a CD-ROM drive. 
     The processed video media data is played back and a subsampled image of the processed video is displayed when playing back the processed video media data. 
     A host computer retrieves the segment of the video media data and a peripheral board connected to the computer processes the segment of the video media data. Retrieving the segment of the video media data further includes sending at the predetermined time a request, from the peripheral board to the host computer, for the host computer to retrieve the segment of the video media data. Additionally, a list of segments of the video data to be played back is maintained. It is then determined which one of the segments of the video media data is to be played back at the predetermined time and a request is sent, from the peripheral board to the host computer, for the host computer to retrieve said one of the segments of the video media data. 
     Subsequent to retrieving the segment of the video media, the segment of the video media is scheduled, at the peripheral board, for playback. A request is then sent, from the peripheral board to the host computer, for the control information. The segment of the video media data may be processed at the host computer prior to processing the segment of the video media data at the peripheral board. Scheduling the segment of the video media data is accomplished by placing a pointer identifying the segment of the video media data on a segment playback queue. 
     Embodiments of the invention include one or more of the following advantages. 
     Embodiments of the invention allow for the delivery of control information to be delayed until the time it is required for playing back a frame. In other words, the control information is delivered “just in time” for the frame to be played back. This manner of just in time delivery of control information allows the user to modify the data until the last possible time before it is needed for playing back a frame. Viewed in another way, this manner of just in time delivery of control information reduces the latency between the user modifying the control information during play back and the user viewing or hearing the effects of that change on the video that is played back. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a schematic block diagram of the structure of an example of a nonlinear video editor  10 . 
     FIGS. 2A-2C show graphic user interface (GUI) windows associated with editing a video program. 
     FIG. 3A illustrates the data structure of a frame cache link list. 
     FIGS. 3B-3F are flow charts of processes associated with the frame cache link list. 
     FIG. 4A illustrates the data structure of audio and video commit queues. 
     FIGS. 4B-4D are flow charts of processes associated with the audio and video commit queues. 
     FIG. 5 is a flow chart of the process associated with playing back a video program. 
    
    
     DESCRIPTION 
     FIG. 1 shows a schematic block diagram of the structure of an example of a nonlinear video editor  10 . Nonlinear video editor  10  allows a user to edit video media data to produce a video program assembled out of a number of audio clips (i.e., a sequence of samples of audio data) and video clips (i.e., a sequence of frames of video data). In the described embodiment, nonlinear video editor  10  supports up to two channels of video. Nonlinear video editor  10  also supports up to sixteen channels of audio. The sixteen audio channels are organized in pairs into eight audio tracks so that nonlinear video editor  10  can supports certain audio effects such as cross-fading from one audio channel to another. Nonlinear video editor  10  also supports a graphics channel for titles to be combined with the video data. In other embodiments, nonlinear video editor  10  may support greater or lesser numbers of audio, video, and graphics channels. 
     Nonlinear video editor  10  includes a host computer  12  and a peripheral board  14  connected to a bus  16  of host computer  12 , for example, by being installed in a expansion slot of host computer  12 . Host computer  12  has a central processing unit (CPU)  20 , a random access memory (RAM)  22 , a long-term data storage unit (e.g. magnetic disk drive or CD-ROM drive)  24 , and a monitor  26  connected via a graphics card  28  to bus  16 . 
     Data storage unit  24  stores compressed video media data. In other embodiments, data storage unit  24  may store noncompressed video data. Memory  22  stores a nonlinear video editing application  18  which is executed by host CPU  20  and is used by a user to edit the video media data to produce a final edited video program. Generally, nonlinear video editing application  18  produces a list of video clips, audio clips, and title files to be processed according to a set of instructions and then combined into the video program. The set of instruction may include control information for various types of processing such as video effects and audio filter. 
     In some embodiments, host computer  20  may be capable of connecting via a network to a remote digital database, searching that remote digital database for appropriate video media data, and using that video media data in producing the video program. Such a system is described in detail in the commonly assigned application of Suzanne M. Pietropaolo, Phillip T. DiBello and Anthony M. Scotto Jr., incorporated in its entirety by reference, “NONLINEAR VIDEO EDITING SYSTEM,” filed on Mar. 9, 1998, and Ser. No. 09/037,310, now U.S. Pat. No. 6,351,765 B2. 
     Peripheral board  14  includes a peripheral board central processing unit (CPU)  30  and an associated peripheral board random access memory (RAM)  32 . Peripheral board  14  also has a busmaster unit  34  which is responsible for retrieving video media data stored in memory  22  via bus  16 . For playing back video data, peripheral board  14  has a video buffer  34  which temporarily stores the frames of video retrieved by busmaster  34 . Video buffer  40  supports two video channels and may be implemented by a separate buffer for each video channel. A codec  42  decompresses the frames of video before transmitting the frames to video effects processor  44 . Codec  42  supports two video channels and may be implemented by a separate codec chip for each video channel. A title buffer  60  temporarily stores title files which are retrieved by bus master unit  34  for being combined with the video data by video effects processor  44 . Alternatively, title files may be written to title buffer  60  by host CPU  20 . Video effects processor  44  applies video effects processing to the video data and title files, according to the control information received from nonlinear video editing application  18 . 
     For playing back the associated audio, peripheral board  14  has an audio buffer  50  and an audio processor  52 . Audio buffer  50  and audio processor  52  support sixteen channels of audio and may implemented by sixteen audio buffers and audio processors, respectively. Audio buffer  50  temporarily stores the audio data downloaded by busmaster unit  34 . Audio processor  52  processes the audio data stored in audio buffer  50  according to the control information from nonlinear video editing application  18 . Audio processor  52  also provides nonlinear video editing application  18 , via peripheral CPU  30 , with information with respect to the output of audio processor  52  after processing the audio data. 
     During playback, peripheral board  14  may output the final video program, for example, to a video tape recording machine (or an external monitor) and/or to monitor  26 . In the case of playing back to a video tape recording machine or an external monitor, digital to analog convertor  48  converts the video digital data into analog video signals and digital to analog convertor  54  converts the audio digital data into analog audio signals in two stereo output audio channels. In other embodiments, more audio output channels may be supported. Additionally, in other embodiments, the digital audio and video data may also be outputted. In the case of playing back to monitor  26 , peripheral board  14  uses a subsampler  46  to subsample the video images before sending them to busmaster unit  24  to send the subsampled video images to graphics card  28  of host computer  12 . 
     Referring to FIGS. 2A-2C, I will now describe how the user of nonlinear video editor  10  uses a variety of graphical user interface (GUI) windows to change control information used by video effects processor  44  (FIG. 1) and audio processor  52  (FIG.  1 ). 
     FIG. 2A shows a video editing graphic user interface (GUI) window  200  for editing a video clip or an entire video program. Video editing window  200  includes a time line region  202  where the time line of the video clip or program is shown. Time lines  202   a  and  202   b  show the video time lines of each of the two channels of video supported by nonlinear video editor  10 . Effects time line  202   c  shows the time line of any video effects to be applied to the channels of video. If applicable, a similar time line may also be shown for a title file. Current time marker  204  indicates to the user the point in the time line of the video clip or program which is being currently played back and also shown in video program monitor region  212 . During operation, the user may select to play back a video clip or program by clicking on a play button  210   a  in the play back control region  210 . The user may also select to have a program or a clip played repeatedly by clicking on a repeat button  210   b.  (Note that, as is well known in the arts, various features of a GUI window may be “clicked on”, i.e. pointed to by a graphic pointer guided by a pointing device such as a mouse and then selected by the user pressing a button of the pointing device. The features that may be clicked on to be manipulated include pull-down menus, buttons, scroll bars, etc.) 
     The user may select a video effect to be applied to the video clip or program by clicking on one of the video effects buttons in the video effects selector region  206 . In FIG. 2A, video effects selection region  206  features three buttons corresponding to three video effects: dissolves, wipes, and digital video effects. Other video effects can, for example, include color effects, single or multiple overlays, filters, and so on. The user can use a video effect subcategory pull-down menu  207  to select a subcategory of a video effect he or she has selected. Each video effect is associated with a set of attributes which the user can modify to achieve desired results. The user may adjust the various attributes a particular selected video effect in video effects attribute adjustment region  208 . Attributes may include border width, range, reverse effect, crop, softness, transparency, border color, and so on. 
     Nonlinear video editing application  18  converts the user input into control information which host CPU  20  or video effects processor  44  use to apply video effects processing to the video data. The user can change the video effects attributes or select different video effects as video clip or program is played back in real time. Nonlinear video editor  10  applies these changes in real time to video media data as the video program or clip is played back, as will be described in detail below. 
     FIG. 2B shows an audio equalization graphical user interface (GUI) window  220  for changing or setting the parameters of an equalization filter to be applied to audio tracks associated with a video clip or program. Audio equalization window  220  includes an audio track selector pull-down menu  222 . In a preset audio filter region  224 , audio equalization window features a list of preset audio filters each having preset attribute values. The current audio clip being played back is highlighted. Audio equalization window  220  further includes three control regions for each of the low, medium, and high frequency spectrums of the selected audio track (regions  226 ,  228 ,  230 ). In each of these regions, a filter selection pull-down menu  232  allows the user to select a particular type of filter to be applied to the corresponding frequency spectrum. The types of filters include, for example, parametric, high pass, low pass, high shelf, low shelf, notch, noise, and hum filters. The types of filter may include any other kind of filter such as audio compression or sound effects type filters (e.g. reverb). Regions  226 ,  228 ,  230  also display the parameters for the corresponding filters. Regions  226 ,  228 ,  230  also include control sliders  234  which the user can click on and move to change the values of the various filter parameters. Audio equalization window  220  also features an audio equalization graph  236  which graphically demonstrates the filter that is applied during playback. In other embodiments, audio equalization window  220  may include a display of real time analysis (e.g. frequency spectrum analysis) of the audio after applying the filter. Audio processor  52  monitors and analyzes the output audio and supplies the appropriate data to video editing application  18 . 
     FIG. 2B shows an audio volume control graphical user interface (GUI) window  250  for changing or setting the volume for the audio tracks associated with a video clip or program. Audio volume control window  250  features a track/clip selector region  252  where the user can select between changing the volume for a particular video clip or for a particular audio track. Audio volume control window  250  includes a master volume region  256  and a track volume region  254 . In master volume region  256 , the user can change the volume for all of the tracks by clicking on and moving volume control slider  262 . In track volume region  254 , the user can change the volume for a particular track by clicking on and moving a volume control slider  258  associated with that track. Additionally, the user can change the balance of a track between the two output channels by clicking and moving a pan balance control slider  260 . As with video effects parameters, the user can change the parameters associated with the audio tracks in windows  220  and  250  in real time as the video clip or video program is played back. Nonlinear video editor  10  applies the changes input by the user in real time to the video media data as the video program or video clip is played back, as will be described in detail below. Audio volume control window  250  also include volume level indicators  262  for each track and for the master volume. These indicators indicate the volume of audio outputted by peripheral board  14  based on data provided by peripheral board  14  in real time. 
     Having described how the user modifies the control information associated with the video media data as the video media data is played back, I will now describe how these control information are applied to the video media data in real time. It should be noted that, in the described embodiment, a frame of a program that is played back may be a composition of up to two channels of video, up to sixteen channels of audio, and a channel of graphics (i.e. title files). In order the simplify the description below, I will use the term “a frame to be played back” to refer to a frame of the final video program, which may be a composition of many channels of audio and video. I will use the term “associated audio and video data” to refer to the data in the video, audio, and title channels which, after processing, will be formed into the frame to be played back. 
     Prior to describing the process of video media data play back in detail, I will first provide a brief overview. Generally, the peripheral board at a predetermined time (in the described embodiment, 2 seconds) before a frame of video is to be played back, sends a request to nonlinear video editor application  18 . Nonlinear video editing application in response loads the associated audio, video, and title data for the frame to be played back into host memory  22 . The loaded video data may be a frame of video. Host CPU  20  stores in memory  22  in two data packets memory addresses of the audio and video portions of the loaded data. Host CPU  20  provides the peripheral board CPU  30  with address pointers to these data packets. Peripheral board CPU  30  stores these pointers, together with a pointer to any title data, in a frame cache link list  300  (FIG. 3A) in peripheral board memory  32  as will be described below. 
     Peripheral board CPU  32  also maintains a video commit queue and an audio commit queue (FIG.  4 A). Each commit queue is implemented as a first-in-first-out (FIFO) queue. Each queue includes a predetermined number of queue elements where each queue element includes addresses to processed data packets containing memory addresses of the segments of video media data stored in memory  22  for a frame to be played back. The processed data packets also contain the control information for the stored video media data. When peripheral board  14  finishes playing back a particular frame, peripheral board CPU  30  takes the next queue elements from the commit queues and begins the process by playing back the frame. At this point, CPU  30  also takes the next element from frame cache link list  300 , places it on the commit queues, and sends a request to nonlinear video editing application  18  for the appropriate control information. Nonlinear video editing application  18  supplies the control information for the video media data for the frame associated with the frame cache element just in time before the frame&#39;s queue elements reach the head of the commit queues. As it is readily apparent, nonlinear video editor  10  in this manner allows a user to continue modifying the control information for a segment after the segment is loaded into memory  22  and until shortly before the segment is played back. Therefore, the user can view or hear the results of modifying video effects controls or the audio controls substantially simultaneously as when he or she modifies those controls. 
     I will now describe the above process in detail. Referring to FIG. 3A, frame cache link list  300  is a linked list of a number of frame cache elements  302 . Each element corresponds to a frame to be played back and contains at least five types of information. Frame number  304  is a sequential number assigned to the frame. Pointers  306  contain the memory address of the previous and subsequent frame cache elements. Pointers  308  contain the memory address of raw video packets for the frame to be played back. Generally, raw video data packets contain the address of the video data (i.e. frames of video in the two channels of video) associated with a frame to be played back. As host CPU  20  loads each frame of video from storage unit  24  into memory  22 , host CPU  20  stores the address of the location of the video frame in an appropriate raw video data packet. Pointers  310  similarly contain addresses of raw audio packets on the host memory  22 . Each raw audio data packet points to loaded audio data associated with a single frame to be played. Each raw audio data packet can contain pointers for up to sixteen channels of associated raw audio packets. Pointer  312  contains the address of any title data on host memory  22  for the frame to be played back. Alternatively, pointer  312  may contain a unique identifier for a title file. In response to a request from peripheral board CPU  30 , host CPU  20  then can use that unique identifier to identify the title file and directly load the appropriate title data into title buffer  60 . 
     FIG. 3B is a flow chart  300  of a foreground task executed by peripheral board CPU  30  to create new frame cache elements. A foreground task may be defined as a task that peripheral board CPU  30  executes repeatedly according to a scheduling policy. For example, in the described embodiment, peripheral board CPU  30  maintains a circular list of foreground tasks. Each time peripheral board CPU  30  becomes idle from a higher priority program, peripheral board CPU  30  executes the next task in the list. Therefore, in step  322 , peripheral board CPU  30  begins executing the task. Peripheral board CPU  30  then determines if the frame cache link list  300  has a sufficient number of frame cache elements for the next five seconds of video program to be played back (step  324 ). If the frame cache link list  300  has enough number of elements, peripheral board CPU  30  ends executing the task (step  328 ). If the frame cache link list  300  does not have a sufficient number of elements, peripheral board CPU creates a new frame cache element  302  and adds it to the frame cache link list  300  (step  326 ). To create a new frame cache element  302 , peripheral board CPU  30  increments a frame number counter and assigns its value as the frame number  304  of the new frame cache element. All other segments of the new frame cache element  302  are left empty. Peripheral CPU  30  also appropriately updates pointers  306  of the last frame cache element  302  and of the new frame cache element  302 . 
     FIG. 3C is a flow chart  330  of another foreground task executed by peripheral board CPU  30 . In this foreground task, peripheral processor sends a request to nonlinear video editing application for loading the video data for a frame to be played at a predetermined time in the future. After peripheral board processor  30  begins executing the foreground task (step  332 ), peripheral board processor  30  determines whether a request has been made to retrieve the video data associated with the frame to be played in two seconds (step  334 ). The period of two seconds is the outer limit of the time it takes in the described embodiment to load two video frames (one for each channel) from storage unit  24  into host memory  22 . The value of this parameter depends on a particular embodiment&#39;s specifications and therefore varies embodiment to embodiment. 
     If peripheral board CPU  30  determines that a request has been made to retrieve the video data associated with the frame to be played in two seconds, peripheral board CPU  30  ends executing the foreground task (step  338 ). If peripheral board CPU  30  determines that a request has not been made to retrieve the video media data associated with the frame to be played in two seconds, peripheral board CPU  30  sends a request to the nonlinear editing application  18  to begin loading the video data for the frame to be played back in two seconds and to send the raw video packets pointers for the loaded data. Peripheral board CPU  30  also sends the frame number of the next available frame cache element. This frame number will be used by peripheral board CPU  30  and host CPU  20  to identify the frame for which data will be loaded. 
     FIG. 3D is a flow chart  340  of a foreground task, similar to the foreground task in FIG. 3C, for requesting audio data for a frame to be played to be loaded from storage  24  to host memory  22 . Steps  342 - 344  are the same as steps  332 - 334  described in reference to FIG. 3C, except that the request to load is made regarding audio data. It should be noted that in step  344 , the period of two seconds is the outer limit of the time it takes in the described embodiment to load from storage unit  24  into host memory  22  sixteen channels of audio data for a frame to be played. The value of this parameter depends on a particular embodiment&#39;s specifications and therefore varies from embodiment to embodiment. 
     FIG. 3E is a flow chart  350  of a foreground task, similar to the foreground task in FIG. 3C, for requesting title data for a frame to be played to be loaded from storage  24  to host memory  22 . Steps  352 - 354  are the same as steps  332 - 334  described in reference to FIG. 3C, except that the request to load is made regarding title data. It should be noted that in step  354 , the period of five seconds is the outer limit of the time it takes in the described embodiment to load from storage unit  24  into host memory  22  title data for a frame to be played. The value of this parameter depends on a particular embodiment specifications and therefore varies embodiment to embodiment. 
     In response to these requests, nonlinear video editing application  18  loads the appropriate audio, video, or title data into memory  22  from storage unit  24  and creates the appropriate raw audio and video data packets. Nonlinear video editing application  18  then sends an interrupt request (IRQ) to the peripheral CPU  30  together with the appropriate frame number. Nonlinear video editing application  18  also sends the pointer to the raw audio packet, raw video packet, or memory address of the title data, as the case may be. Referring to FIG. 3F, the IRQ causes peripheral board CPU to place the received pointer in the appropriate frame cache element (steps  360 - 364 ). 
     Having described the process for loading the video media data for a frame to be played back into memory  22  and maintaining frame cache link list  300 , I will now describe the process of nonlinear video editing application  18  providing peripheral board  14  with control information for processing the loaded video media data. 
     Referring to FIG. 4A, peripheral board CPU  30  maintains a video commit queue  400  and an audio commit queue  410 . Each of these commit queues has a predetermined number of queue elements, each being associated with a frame to be played. When a queue element reaches the head of the queue, its associated frame is played back. As each frame is placed in the queue, a request is sent to nonlinear video editing application  18  to supply the appropriate control information for processing the video media data (i.e. audio, video, and graphics or title) for that frame. The time it takes for a frame to move to the head of the queue equals the time it takes to play back the number of frames in the commit queues. In the described embodiment, the time it takes is approximately the play back time for five and a half frames. Since video programs are typically played back at 30 frames per second, this time is approximately 0.2 seconds. This time is selected to equal the maximum time needed to allow peripheral board CPU  30  send a request for the control information for a frame to played back and to allow nonlinear video editing application  18 , in response to the request, process the video media data for that frame and deliver the control information “just in time” for the frame to be played back. 
     FIG. 4A shows the data structure of audio and video commit queues  400 ,  410 . In video commit queue  400 , each queue element  402  contains the frame number  404  of the frame to be played, pointers  406  to the processed video data packets in peripheral board memory  32  which will be described below, and a pointer  408  to any associated title data. In audio commit queue  410 , each queue element  412  contains the frame number  414  of the frame to be played back and pointers  416  to the processed audio data packets in peripheral memory  32  which will be described below. 
     Referring  4 B, at the end of playing back of a frame, video effects processor  44  (FIG. 1) generates an IRQ (step  422 ). In response, peripheral board CPU  30  loads the information for the next frame to be played back from the next frame cache element  302  into the audio and video commit queues  410 ,  400  (step  424 ). Peripheral board CPU  30  then sends nonlinear editing application  18  a request for the control information for the video media data for the newly added frame (step  416 ). This request includes the frame number and the pointers, stored in the associated frame cache element  302 , for the title data and the raw audio and video packets. Peripheral board  14  then proceeds to play back the next frame and its associated data, which will be described below in reference to FIG.  5 . 
     Referring to FIG. 4C, the request from peripheral board CPU  30  for control information causes an IRQ in host processor  20  (step  432 ). Nonlinear video editing application  18  uses the received pointers to the raw audio and video packets to retrieve the packets (step  434 ) and uses the address pointers in those packets to identify the appropriate data in host memory  22  (step  436 ). Nonlinear video editing application  18  then proceeds to process the video and audio data according to the control information determined based on the inputs from the user in the various GUI windows described already. (step  438 ). Nonlinear video editing application may, for example, perform video effects processing and audio equalization processing, if required by the user. The processed audio and video data are then stored in host memory  22 . Nonlinear video editing application  18  then sends the peripheral board the control information for processing to be performed by the peripheral board and the addresses for the location of the processed video and audio data stored in host memory  22  (step  440 ). 
     Referring to FIG. 4D, the information sent by nonlinear video editing application  18  causes an IRQ in peripheral board CPU  30  (step  452 ). In response, peripheral board CPU  30  places the control information and the address of the processed video and audio data in host memory  22  into processed audio and video data packets. The control information for the title is also placed in the processed video data packet (step  454 ). Peripheral board CPU  30  then updates the appropriate queue elements in the audio and video commit queues with the received control information and pointers to the processed audio and video data packets. 
     As stated above, this control information is supplied just in time for playing back the frame. Referring to FIG. 5, I will now describe the play back process. As described above, at the end of playing back a frame, peripheral board CPU  30  adds a new frame to the audio and video commits queues  410 ,  400 . Peripheral board CPU  30  then proceeds to initialize codec  42  (step  502 ), title buffer  60  (step  516 ), and audio processor  52  (step  510 ) with the respective address pointers for the processed video, title, and title data. Peripheral board CPU  30  also initializes audio processor  52  with the audio control information (step  510 ) and video effects processor  44  with the video control information and the title control information (step  504 ). 
     Codec  42 , title buffer  60 , and audio processor  52  then supply busmaster unit  34  with the addresses for the processed video, title and audio data. Codec  42 , title buffer  60 , and audio processor  52  also request busmaster unit  34  to load the processed video, audio, and title data to the appropriate one of video and audio buffers  40 ,  50 , and  60  (steps  506  and  512 , respectively). In some embodiments, the title buffer is initialized and loaded prior to the time when the frame is played back. 
     Video effects processor  44  then processes the video and title data according to the video control information (step  508 ) and the video frame is played back. Audio processor  52  at the same time processes the associated audio data according to the audio control information (step  514 ). The processed data (i.e. the frame of the video program being played back) may then be converted to the appropriate format for play back (e.g. analog video and audio signals). 
     Other embodiments are within the scope of the following claims. 
     For example, in some embodiments, the use may select to repeatedly play a frame. In that case, the commit queues are then continually loaded with the data for that frame and the processing proceeds in the same manner as described above. The user can then vary the control information associated with the audio or video portion of the frame, observe the effects of his or her action in real time, and arrive at a desired result. 
     In the above embodiment, the control information was supplied for an entire frame of data. However, in other embodiments, the control information may, for example, be supplied for a field or a line of video data at a time. Similarly, audio control information may be supplied for a predetermined number of sample, or even a single sample. In this manner, the latency between changing the controls and seeing the effects of the change may be further reduced. 
     In some embodiments, the video media data may be retrieved from storage  22  and loaded into a memory unit on peripheral board  14 , bypassing host computer memory  22 .