JP2983851B2 - Digital video and digital audio playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital moving picture and a digital moving picture for reproducing a recording medium in which digital moving picture data is encoded at a variable bit rate and digital audio data is encoded at a fixed bit rate. The present invention relates to an audio reproducing device.

[0002]

2. Description of the Related Art Various methods have been conventionally provided for efficiently compressing and coding digital moving image data. In particular, a compression method called MPEG standardized by ISO and CCITT Recommendation H.264. In recent years, a compression coding method for digital video using a combination of intra-image compression and inter-image compression called H.261 has been actively studied,
A relatively high image quality is obtained with a high compression ratio. But,
Since the basic bit rate of these compressed data is a constant bit rate, there are parts within one digital moving image sequence where image quality must be sacrificed and parts where a given code amount is extra. There was a balance problem.

[0003] Also, various methods have been devised as techniques for efficiently compressing and encoding digital audio data. For example, in MPEG, a compression / decoding algorithm for performing synchronous reproduction with output of a digital moving image is standardized. In this standard, the bit rate is fixed, and even in other digital audio data compression methods, the encoding standard is a fixed bit rate.

[0004] In a compression coding method for a digital moving image using a mixture of intra-image compression and inter-image compression typified by MPEG, first, all image data is divided into small areas called macroblocks. The compression process is performed for each area. Here, the intra-image compression is a compression mode in which decoding can be performed using only the compressed data, and the inter-image compression uses a correlation with other image data, and uses the motion and difference to perform compression. The encoding is performed, and the compression decoding is performed using other image data at the time of decoding.

In intra-picture compression, all macroblocks in the picture are directly subjected to two-dimensional discrete cosine transform (DCT) to obtain spatial frequency components, which are subjected to matrix division called quantization. . That is, this is to divide the frequency component by a matrix with a given value,
By multiplying this matrix and the quantized data by the decoder,
It becomes possible to obtain a frequency component. Then, it becomes possible to reduce the precision below the matrix value. Then, more codes are assigned to the low frequency side than to the high frequency side. Also,
In compression between image units, for each macroblock,
A motion vector from the referenced image is obtained, and an area closest to the macro block is detected. Then, a two-dimensional discrete cosine transform (DCT) is performed on the difference between the region and the corresponding macroblock data, and quantization and compression encoding are performed, and the difference data and the motion vector are encoded. .

[0006] In the compression encoding method for digital moving images represented by MPEG, which is processed as described above, the number of generated bits differs depending on the complexity of the image, the magnitude of the motion, and the like.

For this reason, in order to perform a constant bit rate output, it is allowed to change a multiplier for a quantization matrix called a quantization width at the time of quantization. In a real digital moving picture digital audio decoding device, a process of observing a generated code amount and increasing the quantization width when the generated code amount is larger than a schedule, and decreasing the quantization width when the generated code amount is smaller than a schedule is performed. Is being done. However, naturally, when the quantization width is increased, the quantization is performed coarsely, and the encoding accuracy is reduced, and the image quality is reduced. Conversely, when the quantization is performed with an extremely small quantization width, an unnecessary code amount is assigned, and the image of the scene becomes image data of higher image quality than the average.

In recent years, however, the limitation of a constant bit rate has been eliminated due to the improvement of the technology of a reading device for a recording medium. That is, this is because by providing a buffer memory on the reading device side, it is possible to perform control without any problem even in the case of a variable bit rate. In addition, Japanese Unexamined Patent Application Publication No.
In the "recording / reproducing apparatus" described in JP-A-326687, the MPEG digital moving image compressed data is encoded at a variable bit rate, and the maximum bit rate is limited due to the limitation of the decoding apparatus and the reading apparatus. The technique of performing is disclosed.

Here, when digital moving picture encoded data at a variable bit rate and audio encoded data at a fixed bit rate are recorded on the same recording medium, control of the buffer memory in each decoding device is a major problem. Becomes

For example, when digital moving picture encoded data and digital sound encoded data are recorded on the same recording medium, the appearance frequency of the digital sound encoded data is adjusted in accordance with the bit rate of the digital moving picture to obtain synchronization. Will be adjusted. Then, it is necessary to use a buffer memory for each decoding unit to recover from a change in bit rate in a very short period of time or a failure in reading, and to relax digital video data because it has a variable bit rate. . Furthermore, each of them controls so that the data in the memory does not become empty and does not exceed it, but at a variable bit rate, the change is diversified and is not constant, so very complicated processing is required. And the circuit configuration becomes complicated. Next, this will be described with reference to FIG.

FIG. 4 is a block diagram showing an example of a conventional digital moving picture digital audio decoding apparatus.

Referring to FIG. 4, reference numeral 401 denotes a recording medium on which compressed moving image data and compressed digital audio data are recorded. Reference numeral 402 denotes reading means for reading data from the optical disk. A switching unit 405 switches between digital moving image data and digital audio data and outputs the data. Reference numeral 406 denotes a buffer memory for temporarily storing compressed digital moving image data. A buffer memory 407 temporarily stores the compressed digital audio data. Reference numeral 408 denotes a digital video decoder for decoding the video compressed data. Reference numeral 409 denotes a digital audio decoder for decoding digital audio compressed data.

Next, the operation of the conventional digital moving picture digital audio decoding apparatus will be described.

Data is read from the recording medium 401 by the reading means 402. Here, it is assumed that the reading means can intermittently read data from a predetermined point in response to a request from the buffer memories 406 and 407. This data is divided and recorded in recording units of an optical disk, usually called a sector, and information for determining whether the data is compressed digital moving image data or compressed digital audio data is recorded for each header. By using this data, the switching unit 405 can separate the compressed digital moving image data and the compressed digital audio data. The digital moving image and digital audio are temporarily stored in the buffer memory 406 and the buffer memory 407, respectively, and are temporarily decoded by the digital moving image and digital audio moving image decoder 408 and the audio decoder 409, respectively. The data is played.

[0015]

In the conventional digital moving picture digital audio decoding apparatus, if there is no regularity and compensation in each buffer memory 406 and buffer memory 407, each buffer memory 406 and buffer memory 407 does not exist. Under-control and over-state control must be performed, especially in the case of a variable bit rate.
Prediction of the required data amount becomes impossible at all. When either one of the digital audio and the digital moving image is in a data shortage state, a state in which the data on the opposite side is full may occur. At this time, it becomes difficult to synchronize and reproduce a normal image and digital audio.

When realizing synchronous reproduction of such normal images and digital audio, the difference in characteristics between digital audio data and digital moving image data becomes important. For example, in the case of digital moving image data, the buffer memory 4 is originally used because of the discrete nature of a collection of still images.
If the data in 06 and 407 is insufficient for decoding, a relatively natural image can be given to the viewer even by taking measures such as thinning out images. However, in the case of digital audio data, since the original property has continuity,
It is difficult to avoid errors such as thinning. For this reason, it is desirable that the synchronous reproduction is configured based on the decoding of the digital audio data.

However, in such a method, in a reproducing apparatus that encodes a digital video at a variable bit rate and decodes digital audio data encoded at a fixed bit rate, the regularity and compensation of the buffer memory are not sufficient. Since they are not prepared, the readout control becomes difficult, and there is a possibility that a synchronized reproduction of a normal image and digital audio becomes difficult.

Therefore, according to the present invention, when reproducing a recording medium on which compressed digital moving image data of a variable bit rate and digital audio data of a fixed bit rate are recorded, normal synchronous reproduction of a digital moving image and digital audio can be realized. It is an object of the present invention to provide a digital moving image and digital audio reproducing apparatus.

[0019]

A digital moving picture and digital sound reproducing apparatus according to claim 1 records digital moving picture data encoded at a variable bit rate and digital audio data encoded at a fixed bit rate. Mounting means for mounting the recorded recording medium, reading means for reading data at a predetermined fixed bit rate from the recording medium mounted on the mounting means, and digital moving picture data and digital audio data for reading the data read from the reading means. Switching means for separating and outputting digital moving image data output from the switching means, a digital moving image data buffer memory for temporarily storing and outputting the digital moving image data output, and a digital moving image output from the digital moving image data buffer memory. Digital moving image data decoding means for decoding image data; and digital audio data of the switching means. Digital audio data buffer memory for temporarily storing the output and outputting it, digital audio data decoding means for decoding the digital audio data output from the digital audio data buffer memory, and the digital moving image data buffer memory Control means for requesting data transfer in accordance with the data amount stored in the buffer memory and the data amount stored in the digital audio data buffer memory, and performing data read control for the reading means in accordance with the data transfer request; Wherein the ratio between the memory capacity of the digital video data buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is the maximum bit rate value of the digital video data and the digital audio data. It is set to be equal to or larger than the ratio of the fixed bit rate value of the data.

The control means of the digital moving picture and digital sound reproducing apparatus according to claim 2, wherein the data amount stored in the digital moving picture data buffer memory and the data stored in the digital sound data buffer memory are stored. Decoding control means for requesting data transfer in accordance with the amount; and read control means for performing data read control on the reading means in accordance with the data transfer request from the decoding control means.

According to a third aspect of the present invention, there is provided a digital moving image and digital audio reproducing apparatus for mounting a recording medium on which digital moving image data encoded at a variable bit rate and digital audio data encoded at a fixed bit rate are recorded. Means, reading means for reading data from a recording medium attached to the attaching means at a predetermined fixed bit rate, read buffer memory for temporarily storing data read from the reading means, and outputting the data, Reading control means for controlling the reading of data by the reading means in accordance with the amount of data stored in the reading buffer memory, and switching for separating and reading out the data read from the reading means into digital moving image data and digital audio data Means for temporarily storing the digital moving image data output of the switching means, and outputting the digital moving image data output from the switching means. An image data buffer memory, a digital moving image data decoding unit for decoding digital moving image data output from the digital moving image data buffer memory, and a digital audio data output of the switching unit, which are temporarily stored and output. A digital audio data buffer memory, a digital audio data decoding means for decoding digital audio data output from the digital audio data buffer memory, and a data amount stored inside the digital moving image data buffer memory. Decoding control means for requesting data transfer in accordance with the amount of data stored inside the digital audio data buffer memory, and controlling data transfer from the read buffer memory to the switching means in accordance with the data transfer request. A buffer for the digital video data The ratio between the memory capacity of the memory and the limit value for requesting the digital audio data buffer memory to stop reading is equal to or greater than the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the audio data. It was done.

According to a fourth aspect of the present invention, the decoding control means of the digital moving picture and digital audio reproducing apparatus requests data transfer in accordance with only the data amount of the digital audio data buffer memory.

According to a fifth aspect of the present invention, in the digital moving picture and digital audio reproducing apparatus, the decoding control means may be configured to execute when the amount of data stored in the digital moving picture data buffer memory becomes smaller than a predetermined first reference value. Requesting the data transfer of the reading means, and performing the data transfer stop control of the reading means when the amount of data stored in the digital audio data buffer memory exceeds a predetermined second reference value. It is.

According to a sixth aspect of the present invention, in the digital moving picture and digital sound reproducing apparatus, the decoding control means may be configured such that a data amount stored in the digital moving picture data buffer memory is smaller than a predetermined first reference value; When the amount of data stored in the digital audio data buffer memory becomes larger than a predetermined second reference value, the data transfer control of the reading means is performed.

According to a seventh aspect of the present invention, there is provided a digital moving image and digital audio reproducing apparatus for temporarily storing digital moving image data and temporarily storing digital audio data and a memory capacity of a digital moving image data buffer memory. The value of the ratio between the limit value for requesting the reading stop of the buffer memory for digital audio data to be output and the limit value of the maximum bit rate value of the digital moving image data and the fixed bit rate value of the digital audio data should be equal to or greater than the value. is there.

[0026]

According to a first aspect of the present invention, in a digital moving image and digital sound reproducing apparatus for reproducing a recording medium on which variable bit rate digital moving image data and fixed bit rate digital sound data are recorded, a digital moving image data The value of the ratio between the memory capacity of the buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is greater than or equal to the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. The reading and transfer are controlled according to the storage data amounts of the digital moving image data buffer memory and the digital audio data buffer memory.

According to a second aspect of the present invention, the control for requesting data transfer according to the amount of data stored in the digital audio data buffer memory and performing the data reading to the reading means in accordance with the data transfer request is controlled by A decoding control unit for requesting data transfer according to the data amount stored in the digital moving image data buffer memory, the data amount stored in the digital audio data buffer memory, and a data transfer request from the decoding control unit. This is read control means for performing data read control on the read means.

According to a third aspect of the present invention, there is provided a digital moving image and digital sound reproducing apparatus for reproducing a recording medium on which variable bit rate digital moving image data and fixed bit rate digital sound data are recorded. The value of the ratio between the memory capacity of the buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is greater than or equal to the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. The reading and transfer are controlled according to the storage data amounts of the digital moving image data buffer memory and the digital audio data buffer memory.

According to a fourth aspect of the present invention, there is provided a digital moving image and digital sound reproducing apparatus for reproducing a recording medium on which variable bit rate digital moving image data and fixed bit rate digital sound data are recorded. The value of the ratio between the memory capacity of the buffer memory and the limit value for requesting to stop reading of the digital audio data buffer memory is equal to or greater than the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. The read and transfer are controlled only by the digital audio data buffer memory.

According to a fifth aspect of the present invention, there is provided a digital moving image and digital sound reproducing apparatus for reproducing a recording medium on which variable bit rate digital moving image data and fixed bit rate digital sound data are recorded. The value of the ratio between the memory capacity of the buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is greater than or equal to the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. Data read and transfer are controlled depending on whether the digital audio data buffer memory is full and the digital moving image data buffer memory is insufficient.

According to a sixth aspect of the present invention, in a digital moving image and digital sound reproducing apparatus for reproducing a recording medium on which variable bit rate digital moving image data and fixed bit rate digital sound data are recorded, the digital moving image data The value of the ratio between the memory capacity of the buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is greater than or equal to the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. Data read and transfer are controlled by the full state of the digital audio data buffer memory and the shortage of the digital moving image data buffer memory, and the full state of the digital audio data buffer memory and the digital Shortage of buffer memory for video data occurred at the same time It can, read data, is controlled so that the transfer is not performed is performed.

In the present invention, the digital moving image data is temporarily stored, and the ratio of the memory capacity of the digital moving image data buffer memory to the limit value for requesting the digital audio data buffer memory to stop reading is: To be equal to or greater than the ratio of the maximum bit rate value of digital video data to the fixed bit rate value of digital audio data,
Reading and transferring are controlled in accordance with the amount of data stored in the digital moving image data buffer memory and the digital audio data buffer memory.

[0033]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a digital moving picture and digital audio reproducing apparatus according to the present invention.

In the description of the present embodiment, each data is simply described as digital moving image data and digital audio data. However, when the present invention is implemented, data that has been compression-encoded or simply Encoded and available in those whose digital data is reversible.

[First Embodiment] FIG. 1 is a block diagram of a digital moving picture and digital audio reproducing apparatus according to a first embodiment of the present invention.

In FIG. 1, reference numeral 101 denotes a recording medium on which digital moving image data having a variable bit rate and digital audio data having a fixed bit rate are recorded. This recording medium 10
Reference numeral 1 denotes a disk in this embodiment, but any recording medium capable of intermittently reproducing data, such as an optical disk, a magnetic disk, a magneto-optical disk,
Various recording media such as a magnetic tape can be used.
Reference numeral 102 denotes an attachment unit corresponding to the type of each recording medium 101. Reference numeral 103 denotes reading means corresponding to the type of each recording medium 101. 105 is a reading means 103
Is switching means for separating the data read out from the data into moving image data and digital audio data and outputting the separated data. Reference numeral 106 denotes a digital moving image data buffer memory that temporarily stores digital moving image data and outputs the data. Reference numeral 107 denotes a digital audio data buffer memory that temporarily stores digital audio data and outputs the digital audio data. Reference numeral 108 denotes a moving image decoder serving as digital moving image data decoding means for decoding digital moving image data. An audio decoder 109 is a digital audio data decoding means for decoding digital audio data. Reference numeral 110 denotes control means for detecting the amount of data in the buffer memories 106 and 107, determining data reading by the reading means 103 in accordance with the data amount, and switching the switching means 105 according to the read digital moving image data and digital audio data. A and B in the figure are signals for detecting the states of the buffer memories 106 and 107.

Next, the operation of the digital moving picture and digital audio reproducing apparatus of this embodiment will be described.

The data read from the recording medium 101 by the reading means 103 is separated by the switching means 105 into digital moving image data having a variable bit rate and digital audio data having a fixed bit rate, and stored in respective buffer memories 106 and 107. Is entered. Here, the reading means 103 controls reading according to the amount of data stored in the buffer memories 106 and 107.

Then, the data output from the buffer memories 106 and 107 is decoded by the digital video decoder 108 or the digital audio decoder 109, and the output of digital video and digital audio is obtained.
In this case, each data is temporarily stored in the buffer memories 106 and 107 in order to cope with a minute or macro bit rate change of the macro block.

However, it is impossible to predict at what bit rate the digital moving image data having a variable bit rate will appear. Therefore, the buffer memory 1
When storing the 06 digital moving image data, it is necessary to determine the capacity assuming that data of the maximum bit rate always comes. FIG. 2 shows an example of the recording format of the variable bit rate data.

FIG. 2 shows an example of a data sequence in which digital moving image data is encoded at a variable bit rate and digital audio data is encoded at a fixed bit rate in the digital moving image and digital audio reproducing apparatus of this embodiment. FIG.

In the embodiment shown in FIG. 2, digital moving picture data is encoded at a variable bit rate, and digital audio data is encoded at a fixed bit rate. Data indicated by hatching indicates digital audio data, and other data indicates digital moving image data.
For simplicity, system information and other data used for media have been omitted.

In the figure, the data sequence 21 shows a case where the bit rate of moving image data is three times the bit rate of digital audio data, and the data sequence 22 shows a case where the bit rate is seven times.
For synchronous reproduction of digital moving images and digital audio, data separation is performed in consideration of the decoding timing and the arrival timing at the buffer memory. As the division unit, for example, in an optical disk such as a CD-ROM and a CD, a data unit called a sector is used.
Then, as shown in the figure, the appearance frequency is the bit rate ratio (211: 212 (when the digital video bit rate is three times the digital audio bit rate)), 221: 222.
(When the digital video bit rate is seven times the digital audio bit rate)). Thus, the ratio between digital audio data and digital video data is always the bit rate ratio, and the most frequent occurrence of digital video data is
This is when the digital moving image data has the maximum bit rate.

To facilitate such data read control, the digital moving image data buffer memory 106 is used.
And the value of the ratio of the capacity of the digital audio data buffer memory 107 is equal to or greater than the value of the ratio of the maximum bit rate that can appear in the variable bit rate of digital moving image data to the fixed bit rate of digital audio data. However, in this case, in the data read from the recording medium 101,
It is assumed that the appearance frequency of digital audio data depends on the bit rate ratio between digital moving image data and digital audio data.

In this case, the appearance frequency is represented by [bit rate of digital video data] ÷ [bit rate of digital audio data]. Therefore, the largest amount of data is stored in the digital video buffer memory 106 when the digital audio data buffer memory 107 is full and the bit rate of the video data is the maximum value. It is.

In this case, the amount of moving image data stored in the buffer memory 106 is: [the amount of data stored in the buffer memory 106] ≧ [the amount of data in the buffer memory indicating a full state with digital audio data].
÷ [Fixed bit rate of digital audio data] x [Maximum bit rate of digital video data]. Therefore, if a buffer memory capacity larger than the storage data amount of the buffer memory 106 is prepared for digital moving image data, the full state of the buffer of the digital moving image data can be obtained at any bit rate of digital moving image data. The shortage state does not appear, and stable synchronous reproduction of digital moving images and digital audio can be realized.

Here, the full state of the buffer memory 106 indicates that the amount of stored data has exceeded a predetermined value. Normally, the next read unit (such as a CD-ROM sector) and the next read unit When data read in a cycle is read, this state is entered when the data exceeds the capacity of the buffer memory 106. Therefore, this reference value is determined by the read / transfer speed of the data on the read side and the transfer side, the amount of data to be transferred, and the capacity of the buffer memory 106. Also,
The shortage state indicates that the amount of stored data has become equal to or less than a predetermined value. Normally, data is being read from the buffer memory 106 by decoding / reproduction or the like. This shows a state in which the data in the buffer memory 106 runs out after the instruction is issued and before the data transfer is actually performed. For this reason, this reference value depends on the reading / transfer speed of the data on the read side / transfer side for supplying data to the buffer memory 106, and the decoding / reproduction speed from the buffer memory 106.

Although the buffer memory control is performed by the digital audio data buffer memory 107, the buffer memory control may be performed by the digital moving image data buffer memory 106.

That is, when the reading control is performed mainly by the digital moving image data buffer memory 106, when the digital moving image data buffer memory 106 is full, the digital audio data buffer memory 107 never becomes full. What should be done is not to.

In this situation, the amount of data stored in the digital audio data buffer memory 107 is calculated as follows:
[Digital video data buffer memory] ÷ [Digital video data bit rate] × [Digital audio fixed bit rate]. This indicates the maximum value when the digital moving image data indicates the lowest bit rate. Therefore, the digital audio data buffer memory 107 has the following condition: [digital audio data buffer memory] ≧ [full state of digital moving image data] Data amount of buffer memory indicating the above] ÷ [Minimum bit rate of digital video data] ×
[Fixed bit rate of digital audio data] is required.

The purpose of the variable bit rate of digital moving image data is to make the ratio of the generated code amount to the entropy at the time of encoding constant and to make the overall image quality uniform. Therefore, in order to effectively achieve this object, the minimum bit rate of the digital moving image data should not be determined. That is, an image that is almost still and has no motion or image data that has almost no brightness has a very small data amount, and depending on the image, it may be almost only a header-only data. It becomes possible. For this reason, the [minimum bit rate of digital moving image data] of the necessary buffer memory amount of the digital audio data is an extremely small value. As a result, the capacity required for the digital audio data buffer memory 107 becomes very large,
This is an unrealistic configuration. However, usually, the maximum bit rate has to be determined by the technical limit of the reading means 103 of the recording medium 101 or the decoding device. The method of determining the amount is effective.

When realizing synchronous reproduction, a difference in characteristics between digital audio data and digital moving image data becomes important. For example, in the case of digital moving image data, if the data in the buffer memories 106 and 107 is insufficient for decoding because the original property is a discrete collection of still images, it is relatively natural to take measures such as thinning out images. Video can be given to the viewer. In the case of digital audio data, since the original nature has continuity, it is difficult to avoid errors such as thinning. For this reason, it is desirable that the synchronous reproduction is configured based on the decoding of the digital audio data. From this point of view, the control led by the digital audio data buffer memory described in the present embodiment is effective.

Then, the control means 110 determines the state (A, B) of the buffer memory of the decoding buffer memories 106 and 107.
Is detected, and data reading is requested to the reading means. In this case, the digital moving image buffer memory is set as described above, and if the digital moving image data and the digital audio data are correctly arranged at the bit rate ratio in the data recorded on the recording medium, the digital moving image buffer is set. The full state of the buffer memory cannot occur.

The reading means 103 is connected to the recording medium 101.
To read data at a predetermined bit rate. This is due to the difficulty of controlling the bit rate.
For example, in an optical disk data reading device, data is read by performing PLL control so that the reading bit rate is constant. For this reason, in order to respond to the variable bit rate as needed, the operating frequency of the device must be changed as needed, resulting in a very complicated configuration.
Not realistic. For this reason, when reading an optical disk on which data of a variable bit rate is normally recorded, reading is performed at a bit rate higher than the maximum bit rate appearing in the disk, and FIG. 1
As described above, the buffer memories 106 and 107 reduce the rate. Then, the amount of data stored in the buffer memories 106 and 107 is monitored, and when the amount of data is equal to or less than a predetermined reference value, data is read. And reading the variable bit rate is controlled by storing the position. This operation is performed by the control unit 110.
Will do.

In the digital moving picture and digital sound reproducing apparatus of this embodiment, recording is performed by attaching a recording medium 101 on which digital moving picture data encoded at a variable bit rate and digital audio data encoded at a fixed bit rate are recorded. Medium attaching means 102; reading means 103 for reading data at a predetermined fixed bit rate from a recording medium 101 attached to the attaching means 102; and data read from the reading means 103 as moving image data and digital audio data. A switching unit 105 that separates and outputs the data according to the determination of the data; a digital moving image data buffer memory 106 that stores and outputs the digital moving image data output of the switching unit 105;
Decoding means comprising a moving image decoder 108 for digital moving image data for decoding digital moving image data output from the digital moving image data buffer memory 106, and digital sound data for storing and outputting the digital sound data output of the switching means 105 Buffer memory 107, decoding means including an audio decoder 109 for decoding audio data output from the digital audio data buffer memory 107, a data amount stored in the digital moving image data buffer memory 106, Control means 110 for requesting data transfer in accordance with the amount of data stored in the audio data buffer memory 107, and performing read control of the data to the read means 103 in accordance with the data transfer request; This is an embodiment of claim 1. Door can be.

In particular, in this embodiment, the ratio of the memory capacity of the digital moving image data buffer memory 106 to the limit value for requesting the digital audio data buffer memory 107 to stop reading is determined by the digital moving image data Is greater than or equal to the ratio of the maximum bit rate value to the fixed bit rate value of the digital audio data.

When the present invention is implemented, the control means 110 of this embodiment controls the amount of data stored in the digital moving image data buffer memory 106 and the amount of data stored in the digital audio data buffer memory 107. A decoding control means for requesting data transfer in accordance with a data amount, and a read control means for performing reading control of data to the reading means 103 in accordance with a data transfer request from the decoding control means. Of the present invention. These can be incorporated into an independent circuit or the reading means 103 and the switching means 105, so that the degree of freedom in design is increased.

[Second Embodiment] FIG. 3 is a block diagram of a digital moving picture and digital audio reproducing apparatus according to a second embodiment of the present invention.

In the drawing, reference numeral 301 denotes a recording medium on which digital moving image data of a variable bit rate and digital audio data of a fixed bit rate are recorded. Although the recording medium 301 of the present embodiment is an example of a disk, any recording medium capable of intermittently reproducing data may be used, such as an optical disk, a magnetic disk, a magneto-optical disk, and a magnetic tape. Recording medium can be used. Reference numeral 302 denotes an attachment unit corresponding to the type of each recording medium 301. Reference numeral 303 denotes a reading unit 302 corresponding to the type of each recording medium 301. A read buffer memory 312 temporarily stores and outputs the read data. A switching unit 305 separates the data output from the read buffer memory 312 into digital moving image data and digital audio data and outputs the separated data. Reference numeral 306 denotes a digital moving image data buffer memory that stores and outputs digital moving image data. A digital audio data buffer memory 307 stores and outputs digital audio data. Reference numeral 308 denotes a digital video decoder as a digital video data decoding unit for decoding digital video data. A digital audio decoder 309 decodes digital audio data as digital audio data decoding means. 310 is a buffer memory 30
The decoding control means observes 6,307 data amounts, determines data transfer from the read buffer memory 312 to the switching means 305 in accordance with the data amount, and outputs a switching signal for digital audio data and digital moving image data. 311
Detects the amount of data stored in the read buffer memory 312,
It is a reading control means for determining the reading of data by the reading means 303 according to the data amount. In the figure, A and B are signals for detecting the states of the buffer memories 306 and 307.

The configuration of this embodiment is different from that of the first embodiment in that the buffer memories 306 and 307 operate in the same manner as the read buffer memory 312 for reducing the reading speed, the digital moving image data buffer memory 306, and the digital audio data buffer. The operation of the memory 307 corresponds to a function obtained by dividing the function.

Next, the operation of the digital moving picture and digital audio reproducing apparatus of this embodiment will be described.

Data read from the recording medium 301 by the reading means 303 is temporarily stored in the read buffer memory 312. Then, the read buffer memory 312
Is transferred to the switching means 305, and the respective data is temporarily stored in the buffer memories 306 and 307.
The output data is decoded by the respective video decoder 308 or audio decoder 309. Again, in this case,
As in the first embodiment, the decoding control means 310 instructs the transfer while detecting the amount of data stored in the buffer memories 306 and 307. In this configuration, data transfer between the read buffer memory 312 and the buffer memories 306 and 307 becomes important.

However, since the data recorded in the read buffer memory 312 is the same as the data recording order on the recording medium 301, the read buffer memory 312
The change of the accumulation amount of No. 12 is the same. However, unlike the case where data is read directly from the recording medium 301 as in the first embodiment, a large decoding buffer memory (buffer memories 306 and 307) is prepared so that there is no delay in reading the recording medium 301. Eliminates the need.

Therefore, also in this case, similarly to the first embodiment, the digital audio data buffer memory 30 is used.
The capacity of 7 is [digital audio data buffer memory] ≧ [data amount in buffer memory indicating full state of digital moving image data] デ ジ タ ル [minimum bit rate of digital moving image data] ×
[Constant bit rate of digital audio data] is required.

The capacity of the buffer memory for digital moving image data is as follows: [buffer memory for digital moving image data] ≧ [data amount in buffer memory indicating full state of digital moving image data] ÷ [fixed bits of digital moving image data] Rate] ×
If the digital moving image data buffer memory 306 of [maximum bit rate of digital audio data] is prepared, a full state or a shortage state of the digital moving image data buffer appears at any digital moving image data bit rate. As a result, stable synchronous reproduction of digital moving images and digital audio can be realized.

In this case, the buffer memories 306 and 3
Since the configuration after 07 is highly independent, a configuration in which the recording medium attaching means 302, the read buffer 312, and the read control means 311 are separated as separate reading devices is also possible. In this case, the reading means 303 of the recording medium 301 and a configuration for connecting to the reading means 303 are provided.

As described above, the digital moving picture and digital sound reproducing apparatus according to the present embodiment is a recording medium that records digital moving picture data encoded at a variable bit rate and digital sound data encoded at a fixed bit rate. Attachment means 302 for attaching 301, read means 303 for constantly reading data from recording medium 301 attached to said attachment means 302 at the maximum possible speed, and read buffer for storing and outputting data read from said read means 303 Memory 31
2, a read control means 311 for controlling the reading of data by the read means 303 in accordance with the amount of data stored in the read buffer memory 312;
Switching means 305 for separating the data read from the digital video data and digital audio data and outputting the separated data;
Digital moving image data buffer memory 306 for storing and outputting the digital moving image data output of the switching means 305
And the digital moving image data buffer memory 306.
And a digital audio data buffer memory 307 for storing and outputting the digital audio data output of the switching means 305.
And an audio decoder 3 for decoding digital audio data output from the digital audio data buffer memory 307.
09, the digital audio data decoding means, the data amount stored in the digital moving image data buffer memory 306, and the data transfer according to the data amount stored in the digital audio data buffer memory 307. And the read buffer memory 3
A decoding buffer memory control means 310 as a data transfer means for controlling the transfer of data from the digital video data 12 to the switching means 305; the capacity of the digital moving image data and the buffer memory 306; The value of the ratio to the limit value for requesting the stop of reading is set to be equal to or larger than the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. It can be an example.

[Third Embodiment] As described in the first and second embodiments, the digital moving image data buffer memory 106 and the digital moving image data buffer memory 306 satisfy the above-described conditions as capacities. If they do, it is unlikely that a shortage state or a full state will occur during reading. Therefore, the digital audio data buffer memories 107 and 3
It is also possible to observe only the data amount state B of 07 and control the data transfer. This is an embodiment corresponding to claim 4.

In other words, in the case of this embodiment, the setting of the shortage state of the digital audio data buffer memories 107 and 307 must be determined on the assumption that the moving image data has the maximum bit rate. This is because, when the bit rate of the moving image data is high, the frequency at which the digital audio data appears in the stream decreases, and the reading speed of the recording medium 301 is constant. This is because the transfer speed of the audio data is reduced.

[Fourth Embodiment] As described in the first and second embodiments, if the capacity of the digital video data buffer memories 106 and 306 satisfies the above-described condition, the digital video data buffer memories 106 and 306 will be in an insufficient state during reading. Although the full state cannot occur, the shortage state of the digital moving image data buffer memories 106 and 306 always occurs earlier than the shortage state of the digital audio data assuming the maximum bit rate. That is, the condition for determining the shortage state is determined by the digital audio data buffer memories 107 and 30.
7, the bit rate may be constant because of the fixed bit rate. However, in the digital moving image data buffer memories 106 and 306, the bit rate of the data in the buffer memories 106 and 306 always takes into consideration the possibility of the maximum bit rate. This is because the shortage state must be detected. Therefore, the detection of the shortage state is performed by the digital moving image data buffer memory (A (empty)), and the detection of the full state is performed by the digital audio data buffer memory (B (f (f)).
(ull)). In order to prevent shortage or excess of the buffer memory, safer control becomes possible. This corresponds to the embodiment according to claim 5.

[Fifth Embodiment] In the fourth embodiment, the shortage of the digital moving image data buffer memory 306 and the full state of the digital audio data buffer memory 307 may occur simultaneously. This is a case where the digital moving image is almost in a still image state and almost no code is generated. For example, assuming that one second of digital audio data can be stored, image data may be smaller than digital audio data in this one second. In this case, as described above, the digital moving image buffer memory 306 indicates the shortage state in consideration of the fact that the bit rate is always the maximum bit rate, and this is usually the shortage state. But,
When reading is performed in this state, the digital audio data buffer memory 307 immediately becomes full. In this case, the digital audio data has a fixed bit rate,
It is natural that the digital moving image data does not disappear from the buffer memory 307 while the data is completely processed. Conversely, it is necessary to prevent excess digital audio data. For this purpose, priority is given to the full state of the digital audio data buffer memory 307, and in such a case, no data reading instruction (first embodiment) or transfer (second embodiment) is performed. This can be the embodiment of claim 6.

In the first to fifth embodiments, the usable digital video and digital audio compression methods are those in which the digital video can be encoded at a variable bit rate, and the digital audio is a fixed bit rate. Any combination is possible as long as the combination allows rate coding. In a valid example, for example, MPEG (ISO / IEC
11172 (MPEG1) or ISO / IEC 13818 (MPEG2)). In MPEG, the bit rate of digital moving image data is allowed to be variable with a minimum period from compressed data in an image unit called I Picture to the next I Picture. Also, digital audio data is normally encoded at a fixed bit rate, and as in this embodiment,
The digital moving image data meets the condition of a variable bit rate, and the digital audio data meets the condition of a fixed bit rate.

In addition, an encoding method (H.26) for mixing and compressing other intra-image unit compression and inter-image unit compression is used.
1) can be used as compressed data of a digital moving image. Although not originally a moving picture standard, there is a method of decoding still images by compressing all the still images using a still image compression standard called JPEG (ISO / IEC 10918). In this case, the generated digital moving image data has a variable bit rate.

Further, in each of the embodiments described above, the case where digital audio data and digital moving image data are recorded for each data recording unit such as a sector, such as a CD-ROM, is described. In this case, the present invention is not limited to this. For example, in a case where both digital audio data and digital moving image data are recorded in one sector or when these are recorded alternately and irregularly on a tape. Can also be applied. In particular, the conditions necessary for the recording medium when implementing the present invention are that the appearance frequency according to the bit rate at any time within a predetermined time (the bit rate of the digital moving image data at that time: the fixed bit rate of the compressed digital audio data) Is that the data is recorded.

In each of the above embodiments, the switching means 105 and 305 obtain the switching signal between digital moving image data and digital audio data by the control means 110 or the decoding control means 310. However, when implementing the present invention, switching may be performed in the switching units 105 and 305 according to the type of data written in the header of digital moving image data and digital audio data.

The digital moving image and digital audio reproducing apparatus of each of the above embodiments temporarily stores digital moving image data and stores the digital moving image data buffer memories 106 and 3.
06 and the limit value for requesting the digital audio data buffer memories 107 and 307 to stop reading is the ratio between the maximum bit rate value of the digital moving image data and the fixed bit rate value of the digital audio data. The data is read out and transferred in accordance with the amount of data stored in the digital moving image data buffer memories 106 and 306 and the digital audio data buffer memories 107 and 307. It can be an example. Therefore, by defining the relationship between the memory capacities of the digital video data buffer memories 106 and 306 and the digital audio data buffer memories 107 and 307, the shortage of the variable bit rate digital video data buffer memories 106 and 306 is achieved. No full state occurs, so that simple readout control and synchronous reproduction of digital moving images and digital audio can be realized.

[0077]

As described above, in the digital moving picture and digital sound reproducing apparatus according to the first aspect of the present invention, the limit for requesting reading and stopping of the memory capacity of the digital moving picture data buffer memory and the digital sound data buffer memory. Since the value of the ratio to the value is equal to or greater than the value of the ratio between the maximum bit rate value of the digital moving image data and the fixed bit rate value of the digital audio data, by defining the relationship between the buffer memory capacities, Insufficient or full state of the buffer memory for digital moving image data of variable bit rate does not occur, so that simple readout control and synchronous reproduction of digital moving image and digital audio can be realized.

In the digital moving picture and digital audio reproducing apparatus according to the second aspect, the control means can be divided into the decoding control means and the reading control means, and the degree of freedom in designing the structure is increased.

According to a third aspect of the present invention, a digital moving picture and digital sound reproducing apparatus defines a relationship between the memory capacity of the digital moving picture data buffer memory and the capacity of the digital sound data buffer memory, thereby providing a digital video with a variable bit rate. Since the moving image data buffer memory does not become short or full, simple data transfer control and synchronous reproduction of digital moving images and digital audio can be realized.

The digital moving picture and digital sound reproducing apparatus according to the fourth to sixth aspects can be modified by defining the relationship between the memory capacity of the digital moving picture data buffer memory and the capacity of the digital sound data buffer memory. The shortage or full state of the bit rate digital video data buffer memory does not occur, so that simple reading and transfer control and synchronous reproduction of digital video and digital audio can be realized.

The digital moving picture and digital sound reproducing apparatus according to claim 7 temporarily stores digital moving picture data, and requests the memory capacity of the digital moving picture data buffer memory and the stop of reading of the digital sound data buffer memory. The value of the ratio to the limit value is set to be equal to or greater than the ratio of the maximum bit rate value of the digital moving image data to the fixed bit rate value of the digital audio data. The read and transfer are controlled in accordance with the amount of data stored in the buffer memory for digital video data. Therefore, by defining the relationship of the capacity of the buffer memory, the buffer memory for digital moving image data with a variable bit rate may become insufficient or full. There will be no simple readout control and synchronous playback of digital video and digital audio It can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a digital moving image and digital audio reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating data in which digital moving image data is encoded at a variable bit rate and digital audio data is encoded at a fixed bit rate in a digital moving image and digital audio reproducing apparatus according to a first embodiment of the present invention; It is explanatory drawing which showed the column.

FIG. 3 is a block diagram showing a digital moving image and digital audio reproducing apparatus according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing an example of a conventional digital moving picture digital audio decoding device.

[Brief description of reference numerals]

102 recording medium attaching means 103, 303 reading means 105, 305 switching means 106, 306 digital moving image data buffer memory 107, 307 digital sound data buffer memory 108, 308 moving image decoder 109, 309 sound decoder 310 decoding control means 302 Recording medium attaching means 311 Reading control means 312 Reading buffer memory

Claims (7)

(57) [Claims] 1. A mounting means for mounting a recording medium on which digital moving image data encoded at a variable bit rate and digital audio data encoded at a fixed bit rate are provided. Reading means for reading data at a fixed bit rate, switching means for separating the data read from the reading means into digital moving image data and digital audio data, and outputting the digital moving image data. A digital moving image data buffer memory for temporarily storing and outputting the digital moving image data; a digital moving image data decoding unit for decoding digital moving image data output from the digital moving image data buffer memory; and a digital audio of the switching unit. Once memorize the data output,
A digital audio data buffer memory for outputting the same; a digital audio data decoding means for decoding the digital audio data output from the digital audio data buffer memory; and a data amount stored in the digital moving image data buffer memory. Control means for requesting data transfer in accordance with the amount of data stored in the digital audio data buffer memory, and performing data read control for the reading means in accordance with the data transfer request. The value of the ratio between the memory capacity of the video data buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is the maximum bit rate value of the digital video data and the fixed bit rate value of the digital audio data. Digital moving image characterized by having a ratio of not less than Digital audio playback device. 2. The decoding control means for requesting data transfer in accordance with an amount of data stored in the digital moving image data buffer memory and an amount of data stored in the digital audio data buffer memory. 2. A digital moving picture reproducing apparatus according to claim 1, further comprising read control means for performing read control of data to said read means in accordance with a data transfer request from said decode control means. 3. A mounting means for mounting a recording medium on which digital moving image data encoded at a variable bit rate and digital audio data encoded at a fixed bit rate are attached, and a predetermined recording medium attached to the attaching means. Reading means for reading data at a fixed bit rate, a reading buffer memory for temporarily storing data read from the reading means, and outputting the data, and a reading means for reading data in accordance with an amount of data stored in the reading buffer memory. Reading control means for controlling the reading of the data, switching means for separating the data read from the reading means into digital moving picture data and digital audio data, and outputting the digital moving picture data output from the switching means. A digital moving image data buffer memory for storing and outputting the digital moving image data; Digital moving image data decoding means for decoding digital moving image data output from the buffer memory for, temporarily storing the digital audio data output of the switching means,
A digital audio data buffer memory for outputting the same; a digital audio data decoding means for decoding the digital audio data output from the digital audio data buffer memory; and a digital moving image data buffer memory. Decoding control for requesting data transfer according to the data amount and the data amount stored inside the digital audio data buffer memory, and controlling the transfer of data from the read buffer memory to the switching means according to the data transfer request Means, the value of the ratio between the memory capacity of the digital video data buffer memory and the limit value for requesting the digital audio data buffer memory to stop reading is the maximum bit rate value of the digital video data. The ratio of the fixed bit rate value of the audio data must be greater than Reproducing apparatus for digital motion picture and digital audio, wherein. Wherein said decoding control means, according to claim 2 or claims, characterized in that makes a request for data transfer in accordance with only the amount of data in the buffer memory for the digital audio data
Item 4. A digital moving image reproducing apparatus according to item 3 . 5. The decoding control means requests a data transfer of the reading means when a storage data amount of the digital moving image data buffer memory becomes smaller than a predetermined first reference value. The data transfer stop control of the reading means is performed when the amount of data stored in the digital audio data buffer memory exceeds a predetermined second reference value. Or 1
A digital moving picture and digital audio reproducing apparatus according to any one of the first to third aspects. 6. The decoding control means according to claim 1, wherein the storage data amount of the digital moving image data buffer memory is smaller than a predetermined first reference value, and the storage data amount of the digital audio data buffer memory is reduced. The digital moving image according to any one of claims 2 to 4, wherein when the value of the digital moving image becomes larger than a predetermined second reference value, the data transfer stop control of the reading unit is performed. Digital audio playback device. 7. A digital moving picture and digital sound reproducing apparatus for reproducing digital moving picture data and digital audio data, wherein a digital moving picture data buffer memory for temporarily storing and outputting digital moving picture data; The value of the ratio of the digital audio data buffer memory for temporarily storing and outputting the digital audio data to the limit value for requesting to stop reading is the maximum bit rate value of the digital moving image data and the fixed bit rate value of the digital audio data. A digital moving picture and digital sound reproducing apparatus characterized in that the ratio is set to a value or more.