Abstract:
A signal processor comprises: a first buffer memory for outputting an image signal after storage; a second buffer memory for outputting an audio signal after storage; and a playback control section. The play back control section variably adjusts the playback progress speed of at least one of the image signal and the audio signal by individually controlling the output timings of the image signal and the audio signal from the first and second buffer memories in response to a given command.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a signal processor and others for processing signals read from information recording media such as CDs (Compact Disks), DVDs (Digital Versatile Disks), and MDs (Mini Disks).  
         [0003]     2. Description of the Related Art  
         [0004]     There has been developed a digital playback system capable of audio effects control in real time through tempo (BPM: Beats Per Minute) change applied to playback audio of audio data read from an information recording medium such as CD. Such a digital playback system allows users&#39; real-time processing so as to playback audio through operation of dials and buttons, e.g., tempo acceleration, tempo deceleration, playback pause, and backward playback. With such processing, original audio effects can be extemporaneously produced by the user. Conventionally, with an analog record player, tempo change of playback audio has been done by varying the movement speed of a phonograph needle that traces grooves formed on an analog record for audio recording. This is done by users during playback of the analog record by forcibly rotating a turntable carrying thereon the analog record with a speed different from the normal rotation speed. Such tempo change and others conventionally done with the analog record player is now done by the above-described digital playback system using CDs and DVDs which store digital information.  
         [0005]     The conventional technology relevant to such a digital playback system is found in Patent Document 1 (Japanese Patent Kokai No. 2003-132634), for example. While, in recent years, optical disks storing video information such as movies have been commonly on the market, no system is yet available for exercising real-time control over video effects during video playback from such optical disks.  
       SUMMARY OF THE INVENTION  
       [0006]     In view of the foregoing, it is an object of the present invention to provide a signal processor capable of controlling playback effects of video and audio read from a recording media.  
         [0007]     According to the present invention, there is provided a signal processor for processing an image signal and an audio signal corresponding to the image signal. The signal processor comprises a first buffer memory for outputting the image signal after storage; a second buffer memory for outputting the audio signal after storage; and a playback control section for variably adjusting a playback progress speed of at least one of the image signal and the audio signal by individually controlling output timings of the image signal and the audio signal from the first and second buffer memories in response to a given command.  
         [0008]     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiment.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic block diagram illustrating an optical disk playback system (or signal processor) which is an embodiment of the present invention;  
         [0010]      FIG. 2  is a schematic front view illustrating an outer appearance of the optical disk playback system;  
         [0011]      FIG. 3  is a bottom view of the optical disk playback system shown in  FIG. 2 ;  
         [0012]      FIG. 4  is a schematic diagram illustrating output videos and audio data;  
         [0013]      FIG. 5  is a schematic flowchart illustrating a procedure of an asynchronous playback process of a first example;  
         [0014]      FIG. 6  is another schematic flowchart illustrating a procedure of the asynchronous playback process of the first example;  
         [0015]      FIG. 7  is a schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process;  
         [0016]      FIG. 8  is another schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process;  
         [0017]      FIG. 9  is still another schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process;  
         [0018]      FIG. 10i s a schematic flowchart illustrating the procedure of an asynchronous playback process of a second example;  
         [0019]      FIG. 11  is a schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process;  
         [0020]      FIG. 12  is another schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process; and  
         [0021]      FIG. 13  is still another schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     In the below, various examples of an embodiment of the present invention will be described.  
         [0023]     Structure of Optical Disk Playback System  
         [0024]      FIG. 1  is a schematic block diagram illustrating an optical disk playback system  1  of the embodiment,  FIG. 2  is a schematic front view illustrating an outer appearance of this optical disk playback system  1 , and  FIG. 3  is a bottom view of the optical disk playback system  1  shown in  FIG. 2 . As shown in  FIG. 1 , the optical disk playback system  1  is provided with: a disk drive  2 ; a signal processing section  3 ; a control section  22 ; an operation section  23 ; a display section  24 ; an audio output section  20 ; and a video output section  21 . The control section  22  is connected to the processing components  2 ,  3 ,  20 ,  21 ,  23 , and  24  over a bus (not shown) which transfers control signals and data signals.  
         [0025]     The control section  22  includes a CPU (Central Processing Unit), ROM (Read Only Memory) and RAM (Random Access Memory) storing various control programs, and an input/output interface. The control section  22  includes a playback control section  28 , which will be described later, as a control program to be executed by the CPU. While, in this embodiment, the playback control section  28  is implemented in computer programs, hardware may be an alternative option.  
         [0026]     The operation section  23  issues commands to the control section  22  in response to any external operation made by a user who uses the optical disk playback system  1 . In accordance with the command provided by the operation section  23 , the control section  22  generates various types of control signals for supply to the processing components  2 ,  3 ,  20 , and  21 .  FIG. 2  is a front view illustrating the front panel of the operation section  23 . This front panel includes various input buttons  42 A,  42 B,  43 A,  43 B, and others, and a jog dial (control panel)  55  which is rotatable about a center axis  55   c,  those of which will be described later.  
         [0027]     The disk drive  2  includes a loading mechanism  25  used for loading in a detachable manner an optical disk  10  such as CD or DVD. In addition thereto, the disk drive  2  also includes a spindle motor  11 , an optical head  13 , an RF amplifier  14 , a driver  12 , and a servo circuit  15 . The optical disk  10  stores signals obtained by multiplexing an image signal and its corresponding audio signal, compressing and decoding the multiplexed signal based on MPEG (Moving Picture Experts Group) format or others, and then encoding the compressed and encoded signal based on the physical format of the optical disk  10 . For information reading from the optical disk  10 , the spindle motor  11  receives a drive power from the driver  12  to spin the optical disk  10 . Herein, the driver  12  is under the control of the servo circuit  15 . At the time of information reading, the optical head  13  exposes the recording layer of the optical disk  10  to light beams so as to detect a light beam reflected on the surface of the recording layer. The optical head  13  then forwards the resulting detection signal to the RF amplifier  14 . The RF amplifier  14  amplifies the detection signal provided by the optical head  13 , and provides the amplified signal to the servo circuit  15 . From the amplified signal provided by the RF amplifier  14 , the servo circuit  15  generates a playback signal (or RF signal; Radio-Frequency signal) for output to the signal processing section  3 . The servo circuit  15  also goes through a servo process of generating a tracking error signal or a focus error signal from the signals provided by the RF amplifier  14 , and the resultant signals are provided to the optical head  13 .  
         [0028]     The signal processing section  3  is provided with a decoding section  16 , memory  17 , and buffer memory  27 . The decoding section  16  performs A/D conversion of an analog signal coming from the disk driver  2 , and decodes the resulting digital signal using the memory  17  such as RAM. The decoded digital signal is separated into image data and audio data and is outputted to the buffer memory  27 . The buffer memory  27  includes an audio memory (first buffer memory)  18  for temporarily storing the audio data, and a video memory (second buffer memory)  19  for temporarily storing the image data. As an exemplary structure, the buffer memory  27  may include two-port memory for image data storage, and another for audio data storage. The audio memory  18  and the video memory  19  latch incoming data with a predetermined timing responding to input/output control signals CTA and CTV provided by the control section  22 , and read out their own addressed storage data for output. As a result, the audio memory  18  outputs an audio signal AD to the audio output section  20 , and the video memory  19  outputs an image signal ID to the video output section  21 .  
         [0029]     To the audio signal AD received from the buffer memory  27 , the audio output section  20  subjects a filtering process and a modulation process, and forwards the result to an externally-located audio playback system (not shown). The audio output section  20  includes an interpolation circuit  20 a that goes through an interframe interpolation process and a decimation process. The video output section  21  subjects the image signal ID received from the buffer memory  27  to various types of processes, i.e., color tone process, filtering process, noise elimination process, and modulation process. As a result, a video signal is generated, and is forwarded to an externally-provided display unit (not shown). The video output section  21  includes an interpolation circuit  21   a  that performs interframe interpolation and decimation. Note here that the control section  22  individually controls the operations of the audio output section  20  and the video output section  21 .  
         [0030]     Referring to  FIG. 2 , responding to a user&#39;s action by pressing a power switch  56  of the optical disk playback system  1 , the control section  22  (see  FIG. 1 ) detects the press of the power switch  56 . Thereafter, the control section  22  reads an initial program from internally-provided ROM (not shown) for execution so that the optical disk playback system  1  is activated in system. When the user inserts the optical disk  10  from a disk insertion port  61  of  FIGS. 2 and 3 , the loading mechanism  25  (see  FIG. 1 ) guides the inserted optical disk  10  to inside so that the optical disk  10  is loaded at a predetermined position. Herein, with a press of an eject button (not shown), the loaded optical disk  10  can be ejected from the optical disk playback system  1 .  
         [0031]     In the below, operations of the optical playback system  1  of the above structure will be described in detail.  
         [0032]     Basic Operation  
         [0033]     When the user presses a playback button  45  with the loading mechanism  25  loading the optical disk  10 , the control section  22  detects the press of the playback button  45 . Then, recording data is read from the optical disk  10  to start playback of video and audio. At this time, the playback control section  28  (see  FIG. 1 ) provides control signals CTV and CTA to both the video memory  19  and the audio memory  18  to individually control the memories  19  and  18 . The playback control section  28  allows the video memory  19  and the audio memory  18  to output the image signal ID and the audio signal AD, respectively. The video output section  21  and the audio output section  20  then forward the video signal and the audio signal, respectively.  
         [0034]      FIG. 4  is a schematic diagram illustrating output videos coming from the video output section  21  for display on a frame basis, and audio signals coming from the audio output section  20 . In the drawing, along a temporal axis, displayed are image frames structuring the output videos, i.e., F 1 , F 2 , F 3 , . . . , FN and others, and audio data structuring the audio signals, i.e., D 1 , D 2 , D 3 , . . . , DN and others. Between the output videos and the audio signals, temporal synchronization is established. To show such temporal synchronization, the audio data D 1 , D 2 , D 3 , . . . , DN and others are so displayed as to be placed at the same position on the temporal axis as the image frames F 1 , F 2 , F 3 , . . . , FN and others. In the present embodiment, for convenience of description, the output videos are displayed in a sequential manner on a frame basis (progressively displayed). Here, the interlaced display may be an option which displays the output videos alternately between even fields locating on even-numbered lines and odd fields locating on odd-numbered lines.  
         [0035]     When the user presses the playback button  45  during such a synchronous playback operation, the control section  22  detects the press of the playback button  45 , and temporarily suspends the operation of the system. In detail, the playback control section  28  temporarily stops driving the optical disk  10 , and allows the buffer memory  27  to repeatedly output an image frame at the time when the playback button  45  is pressed to fix the playback video. In this manner, the display unit keeps displaying the same image frame. If the user presses the playback button  45  again during when the system is temporarily suspended, the control section  22  detects the press, and puts the system back to the synchronous playback operation. Responding to the user&#39;s action by pressing the eject button (not shown), the control section  22  ends the synchronous playback operation, and makes the loading mechanism  25  eject the optical disk  10 .  
         [0036]     The user may slide a slider (speed adjustment knob)  53  upward or downward to change the playback progress speed of video and audio. The playback control section  28  detects the position of the slider  53 , and changes the playback progress speed in accordance with the position. The lower the slider  53  slides, the faster the playback progress speed becomes, and the upper the slider  53  slides, the slower the playback progress speed becomes. Herein, the playback progress speed (hereinafter referred to as “playback speed”) denotes a temporal change rate of video information and audio information. For example, assuming that video information recorded on the optical disk  10  displays a clock telling the time, if the playback speed is doubled, the progress speed of the time displayed by the image of clock is also doubled, and the time interval for time-telling is reduced to a half.  
         [0037]     If the user presses a search button  42 B or  42 A, the playback control section  28  detects the press, and makes the playback position of video and audio skip in the forward or backward direction on a file basis. More in detail, when the search button  42 B locating on the right is pressed once, the playback position is skipped in the forward direction to the head position of the next file. When the search button  42 A on the left is pressed once, the playback position is skipped in the backward direction to the head position of the current or previous file. If the user presses a fast-forward button  43 B or a fast-backward button  43 A, the playback control section  28  detects the press, and plays back video and audio in the forward or reverse direction faster in speed than usual to fast-forward or fast-backward the video and audio for playback.  
         [0038]     Described next is the playback effects referred to as “braking”, “spinning”, and “scratching”. The playback control section  28  can individually control the audio memory  18 , the video memory  19 , the audio output section  20 , and the video output section  21 . The playback control section  28  has a speed control function of controlling, in real time, the playback speed of video and audio to be played back from the image signal ID and the audio signal AD coming from the buffer memory  27 . The “braking”, “spinning”, and “scratching” are the playback effects produced by such a speed control function. Specifically, the “braking” is an effect observed when the playback speed of video and audio is abruptly reduced. To produce such an effect, the user may press the playback button  45 . In response, the playback control section  28  abruptly reduces the playback speed of video and audio at a predetermined change rate for temporary system suspension. Thereafter, if the user presses the playback button  45  again, the playback control section  28  abruptly increases the playback speed of video and audio up to the normal speed at a predetermined change rate. Herein, a suspension adjustment knob  58 A is input means for adjusting the change rate when the playback speed of video and audio is reduced, and a start adjustment knob  58 B is input means for adjusting the change rate when the playback speed is increased. Through operation of the suspension adjustment knob  58 A and the start adjustment knob  58 B, the user can change the playback speed at any desired change rate to produce his or her desired video and audio effects.  
         [0039]     The “spinning” is an effect observed when the playback speed of video and audio is suddenly changed differently from the normal speed. To produce such an effect, the user may press a top board  55 t of the jog dial  55  or the playback button  45  for temporary system suspension, and then may spin the jog dial  55 . In response, the playback control section  28  detects the rotation speed and direction of the jog dial  55 , and even if the user releases the jog dial  55 , plays back the video and audio with the speed corresponding to the detected rotation speed and direction. When the jog dial  55  is rotated clockwise, the video and audio are played back in the forward direction, and when the jog dial  55  is rotated counterclockwise, the video and audio are played back in the reverse direction.  
         [0040]     The “scratching” is an effect observed when the playback speed of video and audio is forcibly changed. To produce such an effect, the user may rotate the jog dial  55  with the top board  55 t thereof pressed. In response, the playback control section  28  temporarily stops playing back the video and audio, and then starts playback of the video and audio with the playback speed corresponding to the rotation angle and direction of the jog dial  55 . When the jog dial  55  is rotated clockwise, the video and audio are played back in the forward direction, and when the jog dial  55  is rotated counterclockwise, the video and audio are played back in the reverse direction. Through operation of the jog dial  55 , the user can change the playback speed in real time so that his or her desired specific video and audio effects can be produced.  
         [0041]     First Example of Asynchronous Playback Process Described next is the asynchronous playback process by referring to FIGS.  5  to  9 .  FIGS. 5 and 6  are both a schematic flowchart illustrating procedures of an asynchronous playback process of a first example. In the flowcharts, flowchart connectors C 1  and C 2  indicate continuation of  FIG. 5  to  FIG. 6 . FIGS.  7  to  9  are all a schematic flowchart illustrating exemplary output videos and audio data to be generated as a result of the asynchronous playback process.  
         [0042]     Referring to  FIG. 5 , first in step S 1 , the control section  22  makes a determination whether a playback command is coming from the operation section  23 . The control section  22  is in the wait state until a playback command comes from the operation section  23 . Responding to the user&#39;s action by pressing the playback button  45 , the operation section  23  issues a playback command, and the playback control section  28  detects the command. As a result, the playback command is determined as coming, and playback is started for video and audio (step S 2 ).  
         [0043]     In the next step S 3 , the playback control section  28  makes a determination whether the system is in an asynchronous mode. Specifically, when a shift switch  41  is flipped up, the playback control section  28  goes through the synchronous playback operation described above, and when the shift switch  41  is flipped down, the playback control section  28  determines that the system is in the asynchronous mode through detection of such flip-down. Then, the playback control section  28  makes another determination whether the playback command is coming based on existence of a jog input, i.e., based on rotation of the jog dial  55  (step S 4 ). When the jog dial  55  is determined as not rotating, the procedure goes to step S 11 .  
         [0044]     On the other hand, when the jog dial  55  is determined as rotating in step S 4 , through detection of such rotation, the playback control section  28  determines that a jog input is made. Then, the procedure goes to step S 5  and onward. Specifically, determined in step S 5  is whether or not to change the playback speed of video. In the default operation, the playback control section  28  determines to change the playback speed of video, and the procedure goes to step S 6  and onward. On the other hand, if a selection button  47  (see  FIG. 2 ) is being pressed, through detection of the press, the control section  28  determines not to change the playback speed of video, i.e., to change the playback speed of audio. Thereafter, the procedure goes to step S 20  and onward (see  FIG. 6 ).  
         [0045]     In step S 6 , through detection of the rotation direction of the jog dial  55 , the playback control section  28  makes a determination whether the rotation direction is in the forward direction (FWD) or not, i.e., whether clockwise or counterclockwise. When the jog dial  55  is rotating in the forward direction (FWD), i.e., clockwise, the playback control section  28  increases the playback speed of video than the normal speed (step S 7 ). To be specific, the playback control section  28  allows the interpolation circuit  21   a  in the video output section  21  to go through a decimation process of decimating image frames while controlling the timing of outputting the audio signal AD and the image signal ID from the buffer memory  27 . In this manner, the playback speed of video can be increased to be faster than the normal speed. Referring to  FIG. 7 , until the jog dial  55  is rotated in the forward direction, the video and audio are synchronously played back, and synchronization is observed among the image frames F 1 , F 2 , F 3  and others, and the audio data D 1 , D 2 , D 3  and others. At the time point when the image frame F 6  is displayed, the jog dial  55  is started rotating in the forward direction. Thereafter, the image frames are displayed alternately, i.e., F 8 , F 10 , F 12 , F 14  and other even-numbered frames. In this way, the output videos are played back with the speed twice faster than the audio.  
         [0046]     When the jog dial  55  is determined in step S 6  as rotating in the reverse direction, i.e., counterclockwise, the playback control section  28  then makes another determination whether the rotation speed is a predetermined threshold value TV or higher (step S 8 ). If the rotation speed is determined as being smaller than the threshold value TV, the playback control section  28  decreases the playback speed of video to be slower than the normal speed (step S 9 ). To be specific, the playback control section  28  allows the interpolation circuit  21   a  in the video output section  21  to go through an interframe interpolation process of interpolating image frames while controlling the timing of outputting the audio signal AD and the image signal ID from the buffer memory  27 . In this manner, the playback speed of video can be increased to be faster than the normal speed. Referring to  FIG. 8 , until the jog dial  55  is rotated in the reverse direction, the video and audio are synchronously played back, and synchronization is observed among the image frames F 1 , F 2 , F 3  and others, and the audio data D 1 , D 2 , D 3 , and others. At the time point when the image frame F 6  is displayed, the jog dial  55  is started rotating in the reverse direction. Thereafter, the image frames F 7 , F 7 , F 8 , F 8 , F 9 , F 9 , . . . are displayed sequentially. In this way, the output video is played back with the speed twice slower than the audio.  
         [0047]     In step S 8 , when the jog dial  55  is determined as rotating in the reverse direction with the speed equal to or higher than the threshold value TV, the playback control section  28  goes through video playback in the reverse direction (step S 10 ). To be specific, the playback control section  28  addresses the audio data stored in the audio memory  18  in the forward direction in the temporal sense, and the image data stored in the video memory  19  in the reverse direction in the temporal sense. In this manner, video playback can be done in the reverse direction. Referring to  FIG. 9 , until the jog dial  55  is rotated in the reverse direction, the video and audio are synchronously played back, and synchronization is observed among the image frames F 1 , F 2 , F 3 , and others, and the audio data D 1 , D 2 , D 3  and others. At the time point when the image frame F 6  is displayed, the jog dial  55  is started rotating fast in the reverse direction. Thereafter, the image frames F 6 , F 6 , F 5 , F 5 , F 4 , F 4 , F 3 , F 3 , F 2 , F 2 , . . . are displayed sequentially. In this way, the output videos are played back with the speed twice slower than the audio in the reverse direction.  
         [0048]     After completion of the processes of steps S 7 , S 9 , and S 10 , the procedure goes to step S 11 .  
         [0049]     On the other hand, through detection of the selection button  47  pressed, when the playback control section  28  determines in step S 5  as not to change the playback speed of video, the procedure goes to step S 20  and onward of  FIG. 6 . In step S 20 , the playback control section  28  detects the rotation direction of the jog dial  55  to determine whether the rotation direction is forward or not, i.e., clockwise or counterclockwise. When determining that the jog dial  55  is rotating in the forward direction, i.e., clockwise, the playback control section  28  increases the playback speed of audio to be faster than the normal playback speed of video (step S 24 ). In this case, for example, the playback speed of audio may be increased to be twice of the playback speed of video. On the other hand, when determining in step S 20  that the jog dial  55  is rotating in the reverse direction, i.e., counterclockwise, the playback control section  28  then makes another determination whether the rotation speed is a predetermined threshold value TA or higher (step S 21 ). If the rotation speed is smaller than the threshold value TA, the playback control section  28  decreases the playback speed of audio to be slower than the normal playback speed of video (step S 22 ). In this case, for example, the playback speed of audio may be decreased to be a half of the playback speed of video. On the other hand, if the rotation speed is determined as being equal to or larger than the threshold value TA in step S 21 , the playback control section  28  reverses the playback direction of audio (step S 23 ). In this case, for example, the playback speed of audio may be decreased to be a half of the normal playback speed in the reverse direction. After completion of the processes of steps S 24 , S 22 , and S 23 , the procedure goes to step S 11 .  
         [0050]     In step S 11 , the control section  22  determines whether or not to end the playback operation. In response to the user&#39;s action by pressing an end button (not shown) or others, the control section  22  determines to end the playback operation, and the procedure is accordingly terminated.  
         [0051]     On the other hand, if the control section  22  determines not to end the playback operation in step S 11 , the procedure repeats step S 3  and onward. In this case, responding to the user&#39;s action by flipping up the shift switch  41  that has been flipped down, the playback control section  28  determines in step S 3  that the system is not in the asynchronous mode, and thus goes through synchronous playback of video and audio (step S 12 ). For example, once the shift switch  41  is flipped up, the asynchronously-played-back videos as shown in FIGS.  7  to  9  become synchronized with audio.  
         [0052]     In a case where the determination in step S 3  exists that the system is in the asynchronous mode, and the determination in step S 4  is made that no jog input is made, the playback control section  28  maintains the deviation of playback speed between video and audio. Thus, the once-produced deviation of the playback speed can be maintained without the need for any new playback command from the operation section  23 .  
         [0053]     Herein, as an exemplary asynchronous playback operation, described above are double-speed playback ( FIG. 7 ), half-speed playback ( FIG. 8 ), and half-speed reverse playback ( FIG. 9 ), no limitation thereto intended. The system may be designed so as to produce the playback speed of any arbitrary speed scale depending on the rotation speed of the jog dial  55 .  
         [0054]     Moreover, not to degrade the image and audio quality due to the change of the playback speed, or to improve the image and audio quality, the audio output section  20  and the video output section  21  include the interpolation circuits  20   a  and  21   a,  respectively. These interpolation circuits  20   a  and  21   a  each have a capability of performing interframe interpolation or decimation on sampled input signals in accordance with a control signal coming from the control section  22 . The audio output section  20  and the video output section  21  can reduce the playback speed of video and audio by performing the interframe interpolation of audio frames and image frames with a predetermined output rate retained. Also, the audio output section  20  and the video output section  21  can increase the playback speed of video and audio by performing the decimation of audio frames and image frames with a predetermined output rate retained.  
         [0055]     As described in the foregoing, according to the asynchronous playback process, in response to a playback command based on the rotation direction and speed of the jog dial  55 , the playback control section  28  individually adjusts the playback speed of the video signal ID and that of the audio signal AD to generate a speed deviation therebetween. This thus allows asynchronous playback with user&#39;s desired speed deviation between video and audio, leading to their desired original video and audio effects.  
         [0056]     Second Example of Asynchronous Playback Process  
         [0057]     Described next is the asynchronous playback operation by referring to FIGS.  10  to  13 .  FIG. 10  is a schematic flowchart illustrating the procedure of an asynchronous playback operation of a second example, and FIGS.  11  to  13  are all a schematic diagram illustrating exemplary output videos and audio data produced as a result of the asynchronous playback process. The flowchart of  FIG. 10  is the same as that of  FIG. 5  except that a process block of steps S 30  and S 31  is inserted between steps S 4  and S 11 . In the flowcharts, flowchart connectors C 1  and C 2  indicate continuation of  FIG. 10  to  FIG. 6 .  
         [0058]     Referring to  FIG. 10 , in steps S 1  to S 4 , executed are the same processes as steps S 1  to S 4  of  FIG. 6 . When the playback control section  28  determines in step S 4  that a jog input exists, the processes of steps S 5  to S 10 , or those of steps S 20  to S 24  (see  FIG. 6 ) are executed. As a result, the playback speed of video deviates from the playback speed of audio, or the playback speed of audio deviates from the playback speed of video. Referring to FIGS.  11  to  13 , until the jog dial  55  is rotated, the video and audio are synchronously played back, and synchronization is observed between the image frames F 1 , F 2 , F 3 , and others, and the audio data D 1 , D 2 , D 3 , and others. At the time point when the image frame F 6  is displayed, the jog dial  55  is started rotating. After this point in time, video and audio are asynchronously played back. In an example shown in  FIG. 11 , the video is played back with a speed twice as that of the audio, and in an example shown in  FIG. 12 , the video is played back with a speed half as that of the audio. In an example shown in  FIG. 13 , the video is played back with a speed half as that of the audio in the reverse direction.  
         [0059]     In step S 11 , when the control section  22  determines not to end the playback operation, the procedure repeats steps  3  and onward. In this case, if the playback control section  28  determines in step S 4  that no jog input exists, another determination is made whether the video or audio is asynchronously played back (step S 30 ). Here, if it is determined that no asynchronous playback is executed, the procedure goes to step S 11 . On the other hand, if it is determined in step S 30  that the asynchronous playback is executed, the playback control section  28  executes the process of putting back the playback speed of video or audio to a normal speed (step S 31 ), and thereafter, the procedure goes to step S 11 . As described, if a user wants to maintain the playback speed of video or audio different from the normal speed, he or she has to continue rotating the jog dial  55 . Once the rotation of the jog dial  55  is stopped, the playback command is stopped to go from the operation section  23  to the control section  22 . Thus, the procedure goes to step S 31  so that the playback speed of video or audio is put back to the normal speed.  
         [0060]     Referring to  FIG. 11 , the jog dial  55  is continuously rotated in the forward direction after the image frame F 6  is displayed, and the rotation of the jog dial  55  is stopped after the image frame F 14  is displayed. Thereafter, the playback speed of video is put back to the normal speed, and the image frames F 15 , F 16 , F 17 , F 18 , . . . are sequentially displayed. Referring to  FIG. 12 , the jog dial  55  is continuously rotated in the reverse direction after the image frame F 6  is displayed, and the rotation of the jogdial  55  is stopped after the image frame F 8  is displayed. Thereafter, the playback speed of video is put back to the normal speed, and the image frames F 9 , F 10 , F 11 , F 12 , . . . are sequentially displayed. Moreover, referring to  FIG. 13 , the jog dial  55  is continuously rotated fast in the reverse direction after the image frame F 6  is displayed, and the rotation of the jog dial  55  is stopped after the image frame F 4  is displayed. Thereafter, the playback speed of video is gradually put back to the normal speed, and the image frames F 3 , F 4 , F 5 , F 6 , F 7 , . . . are sequentially displayed.  
         [0061]     According to the asynchronous playback process of this example, in the period of time when no playback command comes based on the rotation direction and speed of the jog dial  55 , the playback control section  28  puts the deviated playback speed of video or audio back to the normal playback speed to adjust the playback speeds to the same speed. This allows users to easily control the deviation of the playback speed.  
         [0062]     It is understood that the foregoing description and accompanying drawings set forth the preferred embodiments of the invention at the present time. Various modifications, additions, and alternatives will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the spirit and scope of the disclosed invention. Thus, it should be appreciated that the invention is not limited to the disclosed embodiments but may be practiced within the full scope of the appended claims.  
         [0063]     This application is based on a Japanese Patent Application No. 2003-337526 which is hereby incorporated by reference.