JPH04282985A - Reproduction device for multi-medium data - Google Patents

Abstract

PURPOSE:To realize sure operation of a video reproduction system in the reproduction device for a multi-medium data recorded in a way that hybrid coding being combination of discrete cosine transformation, quantization and variable length coding is applied to a video data of frame structure while synchronizing with an audio data through the addition of a frame number. CONSTITUTION:The device is provided with frame memory pairs A, B switched alternately between a write side and a display read side of a reproduction video data, registers a, b switched synchronously with the memories and holding a frame number during reproduction and a control circuit 8 collating the frame number held in the registers with a frame number of a display object and switching the frame memory pair on the condition of the end of write to the write side when the collation is coincident.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing multimedia data for games, education, and the like.

0002

[Prior Art] Currently, video data with a frame structure for use in games or education, and audio data synchronized with the video data are encoded to compress the amount of data and edited for combination. A multimedia data recording/playback system is currently under development.

Conventionally, the sector interleaving method is known as a method for recording video data and audio data on a CD-ROM while synchronizing them. This sector interleaving method has a problem in that various constraints arise, such as the number of channels of audio data and the relationship between the compression rate of video data and the compression rate of audio data, if the efficiency of sector use is to be improved.

According to a patent application filed by the present applicant entitled ``Method for editing multimedia data,'' video data having a frame structure is encoded for compression while adding a time code, and is stored in a memory to create audio data. The data is decoded for compression while adding a recording start time code only to the beginning of the data, stored in memory, and added to one frame of video data based on the audio data bit rate and video data frame rate. A new method that calculates the amount of bits of audio data that should be used, divides the audio data from the beginning using the calculated amount of bits, and combines video and audio data frame by frame based on the time code included in the header of the video data of each frame. A synchronized recording method is disclosed.

[0005]

[Problems to be Solved by the Invention] The technical problem to be solved by the present invention is to provide a novel reproduction method for reproducing multimedia data recorded according to the above-mentioned novel synchronized recording method while maintaining its synchronization. The goal is to provide equipment.

[0006]

[Means for Solving the Problems] A multimedia data reproducing device according to the present invention performs hybrid encoding that combines discrete cosine transformation, quantization, and variable length encoding on video data having a frame structure, and also performs frame number A playback device comprising a video decoder and an audio decoder for playing back recorded multimedia data while synchronizing with audio data by addition, wherein the video decoder is connected to a writing side of playback video data and a playback side. A frame memory pair that is alternately switched between the video data display readout side, a frame number holding register that is switched in synchronization with this frame memory pair and holds the frame number of the frame that is being played back; Switching control that compares the held frame number with the frame number of the frame to be displayed and, if they match, switches the pair of frame memories on the condition that writing of playback video data to the writing side frame memory is completed. It is equipped with a circuit.

[0007]

Embodiment FIG. 1 is a block diagram showing the configuration of a multimedia data reproducing apparatus according to an embodiment of the present invention, where IN is an input terminal for multimedia data to be reproduced;
1 is a demultiplexing unit, 2 is a video buffer, 3 is a variable length code decoding unit (VLD), 4 is an inverse quantization unit (Q-1), 5 is an inverse discrete cosine transform unit (DCT-1), 6, 7 1 is a selector, A and B are frame buffers with a 2-bank structure, 8 video sequencers, 9 is a memory clear section, and VO is a playback video output terminal. Furthermore, 10 is an audio buffer, 11
is an audio decoder, 12 is a frame pulse (FP)
In the generating section, A0 is a playback audio output terminal, and SYN is a frame pulse output terminal.

[0008] Multimedia data read out from the CD-ROM at a constant speed and supplied to the input terminal IN is composed of frames of video data as a unit, as shown in FIG. This is a 2-byte start code added to the beginning. "DT" is 1-byte information that specifies the data type.
(video/still image/audio), channel number, and a link bit indicating whether or not subsequent data exists within the frame. "DL" is the data length and indicates the total number of bytes of data, and "DATA" is compressed variable length video data or audio data. "

Video data A fixed length header added to the beginning of a video is
The time code (TC), the video type (T) that indicates whether the video data is a moving image or a still image, and the frame size (DX, DY) that indicates the number of horizontal and vertical pixels of the frame (Y signal). , a quantization table (QY, QC) that records quantization tables applied to each of the Y signal and the C signal in block scan order. When performing quantization in hybrid encoding, a quantization table that can be changed on a block-by-block basis is applied. At the time of decoding, a dequantization table is generated for each block from the quantization table, and dequantization corresponding to the quantization applied at the time of encoding is performed. Time code (TC) is time data that indicates the elapsed time from the reference point at the start of recording in hours, minutes, and seconds, and a serial number (hereinafter referred to as "frame number") that is consecutively assigned to the frames to be compressed. Contains.

[0010] Multimedia data to be reproduced supplied to the input terminal IN is separated into video data and audio data by a demultiplexer 1, and written into a video buffer 2 and an audio buffer 10, respectively. The video data written to video buffer 2 to be played back is
It is converted into a fixed length code by a variable length code decoding (VLD) section 3, dequantized by an inverse quantization (Q-1) section 4, and converted into display data by an inverse discrete cosine transform (DCT-1) section 5. 2, which is selected as the write side by selector 6.
The data is written to one of the bank-configured frame memories A and B.

The video sequencer 8 receives notification of the frame number of the frame currently being played from the VLD section 3, and notification of the end of writing the playback data from the DCT-1 to the frame memory (end of playback of one frame worth of video data). Upon receiving the notification, frame pulse FP from the frame pulse generator 12, etc., it controls switching between the selectors 6 and 7, and generates a synchronization signal Z for reproduction to be supplied to the audio decoder 11. The audio data written in the audio buffer 10 to be played back is played back by the audio decoder 11 which operates according to the synchronization signal Z, and is supplied to the output section from the output terminal AO.

As shown in the block diagram of FIG. 3, the above video sequencer 8 includes a control memory 21, a state register 22, a decoder 23, selectors 24 and 25, frame number registers a and b, a frame counter 26, and a comparison circuit 27 It consists of

Frame number registers a and b in FIG.
The frame memories A and B shown in FIG. Selected for retention. The frame number register selected for writing and holding is reset by reset pulses RA, R almost immediately after being selected.
After the reset is performed by B, the frame number of the frame being reproduced that is decoded by the variable length code decoding section 3 of FIG. 1 is written. The written frame number is supplied to one input terminal of a frame counter 26 and a comparison circuit 27 via a selector 25.

The frame counter 26 is connected to the selector 2
The frame number output from 5 is stored in frame memories A and B.
The load value is loaded in synchronization with the load pulse L that appears at the time of switching, and this load value is incremented in synchronization with the frame pulse FP. The comparison circuit 27 compares the frame number (α) of the frame being written or has been written outputted from the selector 25 with the frame number (β) outputted from the frame counter 26, and outputs only when β≧α. Raise X high. Prior to the rise of this output X,
Or during normal operation in which writing to the frame memory is completed by the time the next frame pulse FP appears, memory switching is output from the decoder 23 in synchronization with the frame pulse that appears immediately after the rise of the output X. The signal S0 is inverted, and the frame memories A and B on the read side (display side) and the write side are switched, the associated frame number registers a and b are switched, and the frame number is loaded into the frame counter 26, etc. will be held.

That is, the frame number (β
) is the frame number (α) output from the selector 25
It shows the display point of the frame, and the frame number (α
) to which the video data has already been written is β≧
Read (display) in synchronization with the display disclosure time specified by α
By switching to the side, the display is synchronized.

As shown in FIG. 4, the control states managed by the control memory 21 include four states S0 to S3 belonging to the steady state and four states S belonging to the initial state.
It is divided into 4 to S7. The four states S0, S2, S4, and S6 to which even numbers are added are the states in which the frame memory A is selected as the reading side, and conversely, the four states S1, S6 to which odd numbers are added are the states in which the frame memory A is selected as the reading side. S3,
In S5 and S7, frame memory B is being selected as the reading side. When both frame memories A and B are selected as the write side, whether playback data is being written or not.
Either it is stopped after this writing is completed.

The eight states S0 to S7 shown in FIG.
As shown in the state transition diagram of Figure 5, the occurrence event (event)
Transition between them according to ``a'' and ``ta.'' Occurrence events “a” to “ka” that cause state transitions in a steady state
The elements are: (A) Completion of writing of playback data to the writing side frame memory (B) β≧α (X is high) (C) Appearance of frame pulse (FP), and the combination of these elements The correspondence between this and the occurring event is as follows. “A” and “E”: (A) Katsu (B) Katsu (C) “I” and “O”: (A) “U” and “Ka”: (B) Katsu (C)

On the other hand, the occurrence events that cause the state transition in the initial state are "ki", "ku", "ke", "sa", "shi", and "su": occurrence of the system reset pulse. ”, “se”: Frame memory clearing completed “so”: (A) “ta”: (C).

[0019] When recording multimedia data to be reproduced, data compression by frame thinning is also used for moving image data having a frame structure to be compressed. This frame thinning is performed every other frame, every 2 frames, and every 3 frames.
In addition to frame dropping that is performed according to predetermined rules such as every other frame, irregular thinning is performed in which if the amount of compressed data per frame exceeds a predetermined value, that frame is subject to frame dropping. is also used together. Therefore, on the playback device side, it is necessary to play back while accurately understanding what kind of frame thinning was performed during recording based on the frame number included in the time code.

FIG. 6 is a time chart for explaining the reproduction of compressed data in which the regular frame thinning and irregular frame thinning are combined. In this example, in addition to regular thinning in which even-numbered frames are dropped, frame #9 is thinned out irregularly because its compressed data amount exceeds a predetermined value, so the frame to be played back is #1, #3, #5, #7, #
It is 11.

FIG. 7 shows, similarly to FIG. 6, when the frames to be played are #1, #3, #5, #7, and #11, a momentary interruption of the transferred data occurs during the playback of frame 5. Therefore, even if the end of the reproduction of frame 5 (the end of writing of the reproduction data to the frame memory A) is delayed by about three frames, the subsequent operation continues normally.

[0022]

Effects of the Invention Since the multimedia data reproducing apparatus according to the present invention is configured to reproduce video data using the time code added at the time of recording as described above, it can perform irregular thinning in addition to regular thinning. This has the effect that video data, which is often thinned out, can be faithfully reproduced and displayed even when there is a momentary interruption in data transfer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a multimedia data reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a data format diagram illustrating the structure of multimedia data to be reproduced.

FIG. 3 is a block diagram showing an example of the configuration of the video sequencer 8 in FIG. 1.

4 is a conceptual diagram illustrating types of control states by the video sequencer 8 of FIGS. 1 and 3. FIG.

FIG. 5 is a state transition diagram illustrating how control states change by the video sequencer of FIGS. 1 and 3;

6 is a timing chart illustrating the state of control by the video sequencer of FIGS. 1 and 3; FIG.

7 is a timing chart illustrating the state of control by the video sequencer of FIGS. 1 and 3; FIG.

[Explanation of symbols]

IN Input terminal for multimedia data to be played 1 Demultiplexer 3 Variable length code decoder (VLD) 4
Inverse quantization section (Q-1) 5
Inverse discrete cosine transform unit (DCT-1) A, B frame buffer pair 8 Video sequencer VO Playback video output terminal 11 Audio decoder

Claims (1)

[Claims] Claim 1: Multimedia recorded by subjecting frame-structured video data to hybrid encoding that combines discrete cosine transformation, quantization, and variable length coding, and synchronizing it with audio data by adding frame numbers. A playback device including a video decoder and an audio decoder for playing back data, the video decoder having a frame that is alternately switched between a write side of playback video data and a readout side for display of playback video data. A memory pair, a frame number holding register that is switched in synchronization with this frame memory pair and holds the frame number of the frame being played back, and the frame number held in this frame number holding register and the frame number of the frame to be displayed. and a switching control circuit that switches between the pair of frame memories on the condition that the writing of the playback video data to the write-side frame memory is completed when there is a match between the pair of frame memories. playback device.