JP3173950B2 - Disc 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 disk reproducing apparatus and, more particularly, to a disk reproducing apparatus for reproducing encoded data encoded under a variable compression ratio.

[0002]

2. Description of the Related Art A typical example of a system for recording and reproducing digital data using a disk is disclosed in Japanese Patent Application Laid-Open No. 1-20.
As described in JP 0793, there is a CD-ROM in which data is recorded so as to be optically readable. C
The D-ROM has data recorded on the same optical disk as an audio CD. The data has a recording track and is spirally recorded on the disk. As described in the above publication, the data recording format constitutes a minimum unit called a frame, and each frame is composed of synchronization data, a subcode, digital data of main information, and an error correction code. . further,
Recording on the disk is continuous with a sector structure in which the digital data of 98 frames (2352 bytes) is defined as one sector, and each sector is 12 bytes of synchronous data, and 4 bytes of header data indicating an address and a mode. , 2048 bytes of digital data and 288 bytes of error detection / correction code. However, the 2340 bytes excluding the synchronization data are recorded after being subjected to scramble processing in order to average the power spectrum of the signal.

Here, in the case of obtaining encoded data by encoding a moving image signal or the like with high efficiency, changing the compression ratio means that the amount of data that can be transmitted per unit time changes. Is equivalent to changing the coding rate of. However, basically, data is read from the disk at a constant linear velocity, and the transmission rate is fixed. Therefore, encoded data to be recorded must be encoded at a compression rate that matches the average encoding rate to the fixed transmission rate of the disk. On the other hand, moving picture signals do not have the same characteristics at all times.For example, a scene with fast movement has a lower compression ratio, and a scene with less movement has a higher compression ratio so that the deterioration becomes less noticeable as a whole, and the recording time is shorter. May be reduced.

As an example of a method of reproducing encoded data having a variable encoding rate by using the CD-ROM, as described in the above-mentioned publication, the rotation of a motor is controlled in accordance with the encoding rate information. There is a method in which control is performed to change the transmission rate from the disk. Also, when the disc has a fixed transmission rate, as described in the above-mentioned publication, there is a technique in which the transmission of encoded data is skipped or paused for a certain period,
Thereby, a transmission rate lower than the maximum transmission rate has been equivalently realized.

[0005]

In THE INVENTION to be solved INVENTION The above prior art, the buffer memory by changing the data transmission rate according to the variation of the amount of coded data in encoding when data from the disk is read at a fixed transmission rate In particular, no consideration has been given to handling encoded data compressed at an encoding rate that fluctuates in each period. Also, no consideration has been given to variable-speed reproduction of encoded data compressed at such a transmission rate that varies every period.

Accordingly, a first object of the present invention is to read out data from a disk at a fixed transmission rate and convert encoded data encoded at a compression rate that varies every period according to each compression rate. It is an object of the present invention to provide a disk reproducing apparatus capable of reproducing at a transmission rate.

A second object of the present invention is to control the buffer memory so as not to cause overflow or underflow when the encoded data is reproduced at an encoding rate corresponding to a fluctuating compression rate. Another object of the present invention is to provide a disk reproducing apparatus capable of determining an optimum buffer memory capacity.

Further, a third object of the present invention is to provide a method for reproducing encoded data at a variable speed by searching for decodable encoded data from data read from a disc and decoding the data. An object of the present invention is to provide a reproducible disc reproducing apparatus.

A fourth object of the present invention is to provide a disk reproducing apparatus operable with a minimum number of memories including some memories necessary for decoding the encoded data. It is in.

[0010]

In order to achieve the first object SUMMARY OF THE INVENTION In the present invention, by a request from the decoding means of the encoded data, encoded record corresponding to the compression rate of encoded data <br Read data from the buffer memory in the
For this purpose, a write control unit and a read control unit for the buffer memory are provided.

In order to achieve the second object, the present invention provides a storage amount detecting means for detecting the data storage amount of the buffer memory, and when the storage amount exceeds a predetermined amount in the buffer memory. suspends writing to the buffer memory, at the same time, the control means to move the at least one track inside the pickup is provided, after returning to a position immediately before the pickups is moved, so as to resume the writing to the buffer memory To In addition, the buffer memory is configured so that the pickup selects one outermost track on the disk.
It is assumed that the disk has a capacity equal to or greater than the amount of data read at the transmission rate of data from the disk during the time required for the rotation.

In order to achieve the third object, according to the present invention, a control means for moving a pickup to a predetermined position in response to a request for variable speed reproduction, and a code read from a disk after the movement. Search means for searching the encoded data for desired encoded data and outputting the encoded data to the decoding means.

Further, in order to achieve the third object,
In the present invention, control means for moving the pickup to a predetermined position in response to a request for variable speed playback, and search means for searching for desired encoded data from encoded data read from the disk after the movement, A variable-speed reproduction buffer memory for temporarily storing the retrieved encoded data, and control means for reading the encoded data from the variable-speed reproduction buffer memory and outputting the encoded data to the decoding means according to the request speed of the variable-speed reproduction. Is provided.

In order to achieve the fourth object, according to the present invention, a receiving buffer memory, a frame memory and the like associated with a decoding means for coded data are used as the buffer memory and the variable speed reproduction buffer memory. Configuration.

[0015]

The writing control means writes the coded data into the buffer memory at the transmission rate from the disk, and the decoding means extracts the coding rate information contained in the coded data . According to rate information
The encoded data can be read from the buffer memory at the encoding rate.

The storage amount detecting means detects the storage amount in the buffer memory, and the writing control means interrupts the writing when the storage amount exceeds a predetermined amount in the buffer memory, and moves the pickup to at least one position. Since writing is restarted after moving to the inside of the track and waiting for the time for the disk to make one round, overflow of the buffer memory can be avoided. Furthermore, the time required for the disk to make one revolution is
If the pickup is on the outermost track of the disk, the length will be the longest.If a buffer memory with a capacity corresponding to the amount of data read at this time at the transmission rate from the disk is prepared, the buffer memory underflow will occur. Can be avoided.

Further, the pickup moving means moves the pickup to the head position of the sector in response to a request for variable speed reproduction, and the search means searches within the sector, and encodes data required for variable speed reproduction, for example, By using coded data that can be decoded only from the coded data or a signal that has already been decoded, the presence of coded data that can be decoded is checked. If such encoded data exists,
The data is output to the decoding means at the transmission rate from the disk, and when the data does not exist, the processing of moving the pickup to the predetermined sector head position by the pickup moving means is repeated. As described above, the encoded data required for variable speed reproduction can be searched and output to the decoding means, so that variable speed reproduction of encoded data compressed at a transmission rate that varies every period becomes possible. .

Further, by using a receiving buffer memory and a frame memory associated with the decoding means as the buffer memory, the number of memories in the entire apparatus can be reduced.

Further, by using a reception buffer memory and a frame memory associated with the decoding means as the buffer memory and the variable speed reproduction buffer memory, the number of memories in the entire apparatus can be reduced.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a disk reproducing apparatus according to the present invention which reproduces a moving image signal from a CD-ROM. 1 is a CD on which encoded data of a moving image signal is recorded. A disk as a ROM, 2 a motor for rotating the disk 1 at a constant linear velocity, and 3 a fixed transmission rate rp [bps] (bits)
per second), 4 is a preamplifier circuit for amplifying and waveform shaping the signal read by the pickup 3, 5 is a pickup servo circuit for controlling the pickup 3, 6 is error correction of digital data from the preamplifier circuit 4 A digital signal processing circuit for processing in accordance with the recording format of the disk 1, such as a motor servo circuit for rotating the motor 2 at a constant linear velocity;
Reference numeral 8 denotes a descrambling circuit for detecting a synchronization signal and descrambling from the data processed by the digital signal processing circuit 6 and outputting it as encoded data. Reference numeral 9 denotes a write / read circuit by the write control circuit 13 and the read control circuit. Capacitance M [b in which data input / output is controlled by a read address
Its] buffer memory 10, a decoding circuit for extracting coding rate information from the coded data read at a variable coding rate rb [bps] from the buffer memory 9, and decoding moving picture data, and 11 a decoding circuit. Circuit 1
0, a frame memory 12; a D / A (digital / analog) conversion circuit 12 for converting decoded moving image data into an analog video signal; 13 a write address; A write control circuit 14 controls a write address in accordance with the coding rate information from the decoding circuit 10, and a read control circuit controls data reading from the buffer memory 9 to the decoding circuit 10. An accumulation amount detection circuit detects the amount of data accumulation by monitoring the difference between the write address and the read address of the memory 9, 16 is a microcomputer for controlling the system, and 17 is an output terminal.

First, referring to FIG. 2, the encoded data recorded on the disk 1 will be described with reference to FIG.
However, FIG. 2 is a diagram showing how the average coding rate changes when a moving image signal is coded at an appropriate compression rate for each period. In the period t1 to t2, the average coding rate r1 is used.
Data A compressed at [bps], data B compressed at an average coding rate r2 [bps] during periods t2 to t3,
The period t3 to t4 indicates the data C compressed at the average coding rate r3 [bps]. Note that r2>r1> r3, and these data A to C are continuously recorded on the disc 1 including transmission rate information.

The transmission rate rp [bp] from the disk 1
s] is set under the condition of rp ≧ r2 and is fixed. For example, if rp = r2, the time required to read data B from the disk 1 is (t
3-t2) [sec], but to read data A, (t2-t1) × r1 / r2 [sec], and to read data C, (t4-t1) × r3 / r2 [sec]. In addition, the time is shorter than the actual playback time. In order to absorb such a difference between the read time from the disk 1 and the actual reproduction time, the transmission rate rb [bps] for reading data from the buffer memory 9 is variable.

The read operation will be described in detail with reference to FIG. FIG. 3 is a block diagram showing a specific configuration of the decoding circuit 10 in FIG. 1 and its peripheral parts.
Are given the same reference numerals.

By the way, as a current moving picture signal coding method, a method in which orthogonal transformation, quantization and variable length coding are combined with inter-frame prediction is generally used, and the MPEG method of ISO (International Organization for Standardization) is also used. The method is based on this. FIG. 3 shows a case where a decoder corresponding to the MPEG system is used as the decoding circuit 10, and 101 is a reception buffer memory for absorbing fluctuations in the amount of coded data necessary for each image frame within a unit time. , 102 is a variable length decoding circuit, 103 is an inverse quantization (IQ) circuit, 10
4 is an inverse discrete cosine transform (IDCT) circuit, 105 is an adder, and 106 is a motion compensation (MC) circuit.

The coded data coded according to the MPEG system has a structure including coding rate information at the head thereof. As in this embodiment, the coded data is coded every certain period. When the data rate changes, the coding rate information is included at each change. When such coded data is supplied from the buffer memory 9 to the variable length decoding circuit 102 via the receiving buffer memory 101, the coding rate information is decoded and output to the read control circuit 14. The read control circuit 14 generates a read address according to the coding rate information, and always reads data from the buffer memory 9 to the decoding circuit 10 at an appropriate transmission rate. With this process, even if encoded data having different compression rates is read out continuously from the disk 1, it is possible to reproduce the encoded data at the corresponding encoding rate.

On the other hand, the other main data decoded by the variable length decoding circuit 102 includes an IQ circuit 103 and an IDCT circuit 1
In 04, IQ processing and IDCT processing are performed, respectively,
At 05, it is added to the reference frame image data after the MC processing, and then output as final image data. The frame memory 11 is necessary for the MC circuit 106 to perform the MC processing, and has a capacity of at least two frames of image data.

Next, the operation related to the capacity of the buffer memory 9 in FIG. 1 will be described with reference to FIGS.

FIG. 4 shows the state of the tracks on the disk 1, where (m-1), m, (m + 1),.
(M + n), (m + n + 1) [where m and n are natural numbers]
Represents a sector, and P1 to P3 represent reading positions of the pickup 3.

FIG. 5 shows a state of data transmission. FIG. 5A shows an arrangement of data read from the disk 1 by the pickup 3, and FIG. FIG. 3C shows the state of detection of the accumulated amount of the buffer memory 9, and FIG. 4C shows the state of data writing from the descramble circuit 8 to the buffer memory 9 by the write control circuit 13. D1)
d3 schematically represents the storage amount of the buffer memory 9.

In FIG. 4, since the tracks on the disk 1 are read from the inside to the outside, the position of the pickup 3 changes in the order of P1-P2-P3. As shown in FIG. 5 (a), it is sequentially continuous from m to (m + n). In this case, the operation is performed in a state where the accumulated amount of the buffer memory 9 has a margin equal to or less than the capacity as indicated by d1 in FIG. However, the data transmission rate rb [bps] from the buffer memory 9 is higher than the data transmission rate rp [bps] from the disk 1.
s] is a low value (rp> rb), a certain time point (t
In 5), the buffer memory 9 is in a state in which the data accumulation amount is full (full) as shown by d2 in FIG. 5D, reading cannot be completed in time, and further writing cannot be performed. , Overflow).

The storage amount detection circuit 15 includes a write control circuit 13
The amount of data stored in the buffer memory 9 is detected by monitoring the difference between the write address from the read address and the read address from the read control circuit 14. When the storage amount detection circuit 15 detects the full state of the buffer memory 9 at time t5 as shown in FIG. 5B, the microcomputer 16 stops generating the write address by the write control circuit 13 and As shown in c), the writing of data to the buffer memory 9 is temporarily stopped. Furthermore, at the same time,
The microcomputer 16 moves the pickup 3 one track inward by the pickup servo circuit 5, so that the read position of the pickup 3 moves again in the order of P1-P2-P3. Until time t6 when the position address of the pickup 3 on the disk 1 returns to the position before the movement, m to (m +
Although the data of n) is read twice, FIG.
As shown in FIG.
Since the writing is restarted only at time t6 without writing the data to the buffer memory 9, the arrangement of the data written in the buffer memory 9 is as follows:..., (M + n), (m + n + 1),
... and so on.

Further, during the period from time t5 to time t6, data reading from the buffer memory 9 to the decoding circuit 10 is performed at the transmission rate rb [bps]. As shown by d3 in FIG. 5D, rb × (t6−t5) is changed from the full state.
The state returns to the state in which the space has been created by [bits].

Here, considering the capacity of the buffer memory 9, if the buffer memory 9 becomes completely empty between times t5 and t6,
Data cannot be read any more (this is called underflow). The transmission rate is rp ≧ rb, and (t6−t5) [sec] is the longest when the reading position of the pickup 3 is at the outermost circumference of the disk 1. Therefore, the time required for the disk 1 to make one rotation at that time. Is (t6−t5) = T [sec], the capacity M of the buffer memory 9 is at least M ≧ (rp × T) [bit
s], underflow can be avoided.

For example, data is read from the disk 1 at a transmission rate rp = 9 [Mbps] and a linear velocity v =
Assuming that 3.6 [m / sec], since the outermost peripheral length of the CD-ROM is l = 0.364 [m], M = rp × l
/V=9×0.364/3.6=0.91 [Mbit
s].

As described above, in this embodiment, overflow of the buffer memory can be avoided by controlling the reading of data from the disk by monitoring the storage amount of the buffer memory, and this control is performed. Therefore, by ensuring a sufficient capacity, underflow of the buffer memory can be avoided.

FIG. 6 is a block diagram showing a main part of a second embodiment of the disk reproducing apparatus according to the present invention. Reference numeral 18 denotes a memory, and parts corresponding to those in FIG. Description is omitted.

A new configuration in this embodiment is a memory 18, which is a combination of the buffer memory 9 and the reception buffer memory 101 with one memory 18.
In this case, the read control circuit 14 directly controls the data read from the memory 18 to the variable length coding circuit 102, and the capacity of the reception buffer memory 101 is usually set smaller than the capacity of the buffer memory 9. Therefore, the capacity of the memory 18 depends on the method of determining the capacity of the buffer memory 9.

As described above, in this embodiment, the number of memories in the entire apparatus can be reduced by using two memories.

FIG. 7 is a block diagram showing a main part of a third embodiment of the disk reproducing apparatus according to the present invention. Reference numeral 19 denotes a memory, and parts corresponding to those in FIG. Description is omitted.

In this embodiment, a new configuration is a memory 19, which is composed of a buffer memory 9, a reception buffer memory 101, and a frame memory 11 as one memory 19.
It is also used as This embodiment differs from the second embodiment shown in FIG. 6 in that the data to be stored in the memory 18 and the frame memory 11 are different, such as coded data and image data. Then, it must be able to be used as both memories at the same time. However, since the frame memory 11 has a capacity of two frames of image data, for example, if a capacity of 2.4 [Mbits] is required, a memory of 4 [Mbits] is used as a general-purpose memory. Become. Therefore, by using the remaining 1.6 [Mbits] as the buffer memory 9 and the reception buffer memory 101, the buffer memory 9 and the reception buffer memory 101 can be shared.

As described above, according to this embodiment, the number of memories in the entire apparatus can be further reduced by using three memories.

FIG. 8 is a block diagram showing a fourth embodiment of the disk reproducing apparatus according to the present invention. In FIG. 8, reference numeral 20 denotes a search circuit, and parts corresponding to those in FIG. Omitted.

The search circuit 20 has a new configuration in this embodiment. In the case of normal reproduction, the first reproduction shown in FIG.
The same processing as in the embodiment is performed.

Hereinafter, a specific example of the processing operation of this embodiment in the case of variable speed reproduction will be described with reference to FIG.

First, the microcomputer 16 having received the request for variable speed reproduction invalidates the coding rate information output from the decoding circuit 10 and searches the data stored in the buffer memory 9 for the search circuit. Read control circuit 1
4 is controlled. The search circuit 20 searches the buffer memory 9 for a flag indicating the mode in which the data was coded, for example, a coding type (step 9).
00). If the found encoding type is a type indicating that intra-frame encoding has been performed, that is, if it is an I picture (step 901), the subsequent data is decoded by the decoding circuit 1.
0, decrypted and displayed (step 90).
2). Then, after the decoding of the picture is completed, or if the search result of the encoding type is not an I picture (step 901), it is determined whether or not all the data in the buffer memory 9 has been transmitted (step 903). If not, the above process is repeated . If it has been transmitted (step 903), the microcomputer 16 causes the pickup 3 to jump by N sectors (where N is a natural number) (step 90).
4) Send a control signal to the pickup servo circuit 5 to move to the predetermined sector start position. The data reproduced from the disk 1 is amplified and waveform-shaped by a preamplifier circuit 4, subjected to error correction and the like by a digital signal processing circuit 6, and then subjected to detection of a synchronization signal and descrambling by a descrambling circuit 8. Output to the search circuit 20. As shown in FIG. 10, the search circuit 20 searches for a coding type in the user data area in the sector (step 905). If the searched coding type is an I picture (step 906),
The subsequent data is output to the decoding circuit 10, and is decoded and displayed (Step 907).

Then, after the decoding of the picture is completed (step 907), or when the searched encoding type is a data encoded using bidirectional prediction, such as a B picture instead of an I picture. If it is (step 906), the microcomputer 16 sets the pickup 3 again to N
A sector jump is performed (step 904), and the above processing is repeated.

Next, another specific example of the processing operation of this embodiment in the case of variable speed reproduction will be described with reference to FIG.

First, the microcomputer 16 having received the request for the variable speed reproduction invalidates the coding rate information output from the decoding circuit 10 and searches the data stored in the buffer memory 9 for the search circuit. Read control circuit 1
4 is controlled. In the search circuit 20, data encoded using only the data itself from the buffer memory 9,
Other header data indicating a group composed of a plurality of encoded data, for example, a GOP (Group of Pictur)
e) Retrieve the header (step 1100). And
If the GOP header is searched (step 1101), the coding type is searched from the subsequent user data area (step 1102). If the retrieved encoding type indicates that intra-frame encoding has been performed, that is, if the picture is an I-picture (step 1103), the subsequent data is sent to the decoding circuit 10 to be decoded and displayed. (Step 1104). Then, after decoding of the picture is completed, or when the GOP header cannot be searched (step 1101), or when the search result of the coding type is not an I picture (step 110)
3) It is determined whether all the data in the buffer memory 9 has been transmitted (step 1105). If not, the above processing from step 1100 is repeated.

If it has been transmitted (step 1105), the microcomputer 16 makes the pickup 3 jump by N sectors (step 1106), and sends a control signal to the pickup servo circuit 5 to move it to a predetermined sector head position. The data reproduced from the disk 1 is amplified and waveform-shaped by a preamplifier circuit 4, subjected to error correction and the like by a digital signal processing circuit 6, and then subjected to detection of a synchronization signal and descrambling by a descrambling circuit 8. Output to the search circuit 20. Search circuit 20
Then, as shown in FIG. 12, it is searched whether or not the GOP header exists in the user data area in the sector (step 110).
7) If the GOP header is searched (step 110)
8), and search for an encoding type existing thereafter (step 1109). If the searched encoding type is an I picture (step 1110), the subsequent data is output to the decoding circuit 10 and decoded and displayed (step 1111).

After the decoding of the picture is completed (step 1111), or when the GOP header cannot be searched (step 1108), or when the searched coding type is not an I picture (step 1111)
0), the pickup 3 is again jumped by N sectors by the microcomputer 16 (step 1106), and the above processing is repeated.

In this specific example, the coding type of the I picture is searched after searching the GOP header. However, in the above-described MPEG, since the I picture data is coded after the GOP header, the GOP header is searched. After that, the subsequent data can be output to the decoding circuit 10.

The value N for the sector jump can be determined by the processing capability of the digital signal processing circuit and the decoding circuit.

As described above, in this embodiment, in response to a request for variable-speed playback, the coded data of the I picture required for variable-speed playback is searched, and the data is output to the decoding means. Also, video can be displayed in variable speed reproduction.

FIG. 13 is a block diagram showing a fifth embodiment of the disk reproducing apparatus according to the present invention, in which 21 is a search circuit, 22 is a variable speed reproduction buffer memory, and a portion corresponding to FIG. The same reference numerals are given and detailed description is omitted.

What is different from the first embodiment shown in FIG. 1 in this embodiment is a search circuit 21 and a variable speed reproduction buffer memory 22. In the case of the normal reproduction, the same processing as in the first embodiment is performed, and the description thereof is omitted.

Hereinafter, a specific example of the variable speed reproduction operation of this embodiment will be described with reference to FIG.

First, the microcomputer 16 having received the request for the variable speed reproduction invalidates the coding rate information output from the decoding circuit 10 and searches the data stored in the buffer memory 9 for the search circuit. Read control circuit 1
4 is controlled. The search circuit 21 searches the buffer memory 9 for a flag indicating the mode in which the data was coded, for example, a coding type (step 1400). A type indicating that the searched encoding type has performed intra-frame encoding (ie, an I picture);
Alternatively, a type indicating that predictive encoding has been performed using one piece of data that has already been decoded (ie, a P picture)
If so (step 1401), the picture data is temporarily written into the variable speed playback buffer memory 22 (step 1402). Then, the read control circuit 14 generates a read address in accordance with the variable speed reproduction request speed (M times speed) from the microcomputer 16 and reads data from the variable speed reproduction buffer memory 22 to the decoding circuit 10.
The decoding circuit 10 decodes this and displays it (step 1403). After decoding of the picture is completed, or when the search result of the encoding type is an I picture or P picture
If it is not a picture (step 1401), it is determined whether all the data in the buffer memory 9 has been transmitted (step 1404). If not, the above processing from step 1400 is repeated.

If all the data in the buffer memory 9 has been transmitted (step 1404), the microcomputer 16 causes the pickup 3 to jump by N sectors (step 140).
5) Output a control signal to the pickup servo circuit 5 to move to a predetermined sector head position. The data reproduced from the disk 1 is amplified and waveform-shaped by a preamplifier circuit 4, subjected to error correction and the like by a digital signal processing circuit 6, and then subjected to a descrambling circuit 8 to detect a synchronization signal and to cancel descrambling. Is output to the search circuit 21. The search circuit 21 searches for a coding type in the user data area in the sector (step 1406). If the searched coding type is an I picture or a P picture (step 1407), the picture data is searched. Variable speed playback buffer memory 22
(Step 1408). Then, the read control circuit 14 generates a read address in accordance with the request speed of variable speed reproduction (M times speed) from the microcomputer 16, reads data from the variable speed reproduction buffer memory 22 to the decoding circuit 10, and decodes the data. The decoding circuit 10 performs decoding and displays the decoded data (step 1409).

After the decoding of the picture is completed (step 1409), or if the searched encoding type is not coded data of an I picture or a P picture (step 1409), the microcomputer 16 picks up the image again. 3 is jumped by N sectors (step 140).
9) Repeat the above process.

FIG. 15 shows a specific example of the above-mentioned variable speed reproduction data. FIG. 15A shows a video sequence, I indicates an I picture (intra-frame encoding),
P is a P picture (unidirectional predictive coding from a past I or P picture), and B is a B picture (a past or future I picture).
Or bidirectional prediction encoding from a P picture). The encoded data of the video sequence encoded as described above is recorded on the disk 1 as CD-ROM recording data shown in FIG. The encoded data of the I or P picture searched by the search circuit 21 is shown in FIG.
As shown in (c), the data is stored in the variable speed reproduction buffer memory 22. Then, the data is read from the variable speed reproduction buffer memory 22 according to the request speed of the variable speed reproduction, and is decoded. For example, in the case of triple speed, as shown in FIG. 15D, I1, P2, P3, P4, P
5, I6, P7, and P8 are decoded in the search order,
It can be realized by displaying. In the case of 6 times speed,
As shown in FIG. 15E, this can be realized by decoding and displaying in the order of I1, P3, P5, and P7. However, in this case, I6 only performs decoding.

As described above, in the fifth embodiment, in response to a request for variable speed playback, the coded data of the I picture and P picture required for variable speed playback are retrieved and output to the decoding means. Thus, the video can be displayed even in the variable speed reproduction.

The value N for the sector jump can be determined by the processing capability of the digital signal processing circuit and the decoding circuit.

In the fifth embodiment, similarly to the fourth embodiment shown in FIG. 8, in response to a request for variable-speed reproduction, encoding of I-pictures and P-pictures required for variable-speed reproduction is performed. By retrieving the data and outputting the data to the decoding means, it is possible to display a video even in variable speed reproduction. Further, in the fourth embodiment, since the I picture is searched and only the picture is displayed, the speed of the variable speed reproduction is determined by the interval of the I picture. For example,
Variable speed playback that can be realized when the interval between I pictures is 15 is 15 × speed playback. However, in the fifth embodiment, the speed of the variable speed reproduction can be determined by the interval between the I picture and the P picture. For example, the variable speed reproduction that can be realized when the interval between the I picture and the P picture is 3 is 3,6,9,.

In the fifth embodiment, the buffer memory 9 and the variable speed reproduction buffer memory 22 can be shared by one memory, and the reception buffer memory 101 and the variable speed reproduction buffer memory 22 can be combined into one memory. And the buffer memory 9 and the reception buffer memory 101.
And the variable-speed playback buffer memory 22 can be shared by one memory, or the buffer memory 9, the reception buffer memory 101, the frame memory 11, and the variable-speed playback buffer memory 22 can be shared by one memory. .
In this way, by using a memory, the number of memories in the entire apparatus can be reduced.

Further, in the fourth and fifth embodiments, the description has been made such that the buffer memory 9 is searched first at the time of variable speed reproduction, but the present invention is not limited to this. For example, the variable speed reproduction can be performed ignoring the buffer memory 9.

Further, in each of the above embodiments, the case of a CD-ROM in which data is recorded on a spiral track has been described. However, the present invention is not limited to this. For example, a plurality of concentric circular data may be used. The present invention can be applied to the case of a hard disk or the like recorded on a track.

In each of the above embodiments, the case where only moving picture data is handled as coded data has been described. However, the present invention is also applicable to the case of handling coded data in which moving picture data and audio data are multiplexed. The invention can be applied without problems.

Further, in each of the above embodiments, the case where the compression ratio of the encoded data recorded on the disk fluctuates in three stages is described, but the present invention is not limited to the three stages.

Further, in each of the above embodiments, the MPEG system has been described as an example of the video signal encoding system, but the present invention is not limited to this.

[0070]

As described above, according to the present invention,
Since data can be read from the buffer memory at a coding rate corresponding to the compression rate of the coded data according to a request from the decoding means, the coded data coded at the fluctuating compression rate can be continuously read. Can be played.

Further, by detecting the amount of data stored in the buffer memory and controlling the position of the pickup to perform the idle reading, the overflow of the buffer memory can be avoided.

Further, from the transmission rate of data from the disk and the time required to read one round of the outermost circumference of the disk, it is possible to determine a sufficient capacity of the buffer memory to avoid an underflow of the buffer memory. .

Furthermore, in the case of variable speed reproduction, encoded data to be displayed at the time of variable speed reproduction is directly searched from the data reproduced from the disc and decoded. Variable speed reproduction can be performed without considering the transmission rate of the encoded data.

Further, by using some memories associated with the decoding means as a buffer memory and a buffer memory for variable speed reproduction, the number of required memories can be reduced, and the size and cost of the apparatus can be reduced. Down can be planned.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a disk reproducing apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of a change in an average transmission rate of encoded data recorded on a disc.

FIG. 3 is a block diagram showing a specific example of a decoding circuit in FIG. 1;

FIG. 4 is a diagram showing an example of a track on a CD-ROM disc.

FIG. 5 is a diagram for explaining a state of reading data from a disk and inputting / outputting data of a buffer memory.

FIG. 6 is a block diagram showing a main part of a second embodiment of the disk reproducing apparatus according to the present invention.

FIG. 7 is a block diagram showing a main part of a third embodiment of the disk reproducing apparatus according to the present invention.

FIG. 8 is a block diagram showing a fourth embodiment of the disc reproducing apparatus according to the present invention.

FIG. 9 is a flowchart showing a specific example of a processing operation at the time of variable speed reproduction according to the fourth embodiment shown in FIG. 8;

FIG. 10 is a diagram for explaining a specific example of a variable speed reproduction process according to the fourth embodiment shown in FIG. 8;

FIG. 11 is a flowchart showing another specific example of the processing operation at the time of variable speed reproduction of the fourth embodiment shown in FIG.

FIG. 12 is a diagram for explaining another specific example of the variable speed reproduction process according to the fourth embodiment shown in FIG. 8;

FIG. 13 is a block diagram showing a fifth embodiment of the disk reproducing apparatus according to the present invention.

FIG. 14 is a flowchart showing a specific example of a processing operation at the time of variable speed reproduction according to the fifth embodiment shown in FIG.

FIG. 15 is a diagram showing a state of data of variable speed reproduction according to the fifth embodiment shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 disk 2 motor 3 pickup 4 preamplifier circuit 5 pickup servo circuit 6 digital signal processing circuit 9 buffer memory 10 decoding circuit 13 write control circuit 14 read control circuit 15 storage amount detection circuit 16 microcomputer 18, 19 memory 101 reception buffer memory 102 variable Long decoding circuit 20, 21 Search circuit 22 Variable speed playback buffer memory

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshifumi Takeuchi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Media Research Laboratory, Hitachi, Ltd. (56) References JP-A-1-200793 (JP, A) JP-A-5-36194 (JP, A) JP-A-5-344494 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/76-5/956 G11B 20/10- 20/12

Claims (14)

(57) [Claims] 1. A disc reproducing apparatus for reproducing digital data encoded on a spiral or concentric recording track at different compression rates for each period from a disk, wherein the digital data is read from the disk. storage means for temporarily storing the digital data issued, and a write control means for controlling the writing of said digital data to said memory means, during normal reproduction, the different compression from the digital data
Decoding means capable of taking out a coding rate information corresponding to the rate, the code該復Goka means from said storage means
And a read control means for controlling to read out the digital data at a data rate based on the coding rate information, daisy that at the time of variable-speed playback, read out from the disk
Search for desired digital data from the
A disc reproducing apparatus comprising a search means for outputting to a decoding means . 2. A disk reproducing apparatus having data reading means for reading data from a disk in which digital data encoded at a different compression ratio for each period is recorded on a spiral or concentric recording track, wherein: Bei storage means for temporarily storing the digital data read out, and a write control means for controlling the writing of said digital data to said memory means
During normal playback, the different compression
Can extract coding rate information corresponding to the rate
Decoding means, wherein the decoding means performs the encoding from the storage means.
The digital data at an encoding rate based on the rate information.
Read control means for controlling the data to be read.
For example, setting the accumulation amount detecting means for detecting a storage amount of the storage means
In addition, the storage amount detecting means determines the data storage amount in the storage means.
If it is detected that the
Control means for storing the digital data in the storage means.
Stop writing, and at the same time,
The disk at least one track of the disk
Stop reading digital data and read the data.
After the position of the transfer means returns to the position before the movement, the data
Reading the digital data by data reading means
And writing the digital data to the storage means.
And the data reading means is moved to a predetermined position during variable speed playback.
Control means for controlling movement to
The digital data read from the disk by
Searching desired digital data from data and decoding
And a search means for outputting the data to the conversion means . 3. The storage device according to claim 2, wherein a capacity M of the storage means is determined by a transmission rate rp for reading the digital data from the disk and the data reading rate.
By the time T required for one round when the removing means is on the recording track on the outermost circumference of the disk, M ≧ rp
A disc reproducing apparatus characterized by being determined under the condition of × T. 4. The apparatus according to claim 2, wherein said search means is configured to read the digital data read from said disk.
Digital data that can be decoded by itself.
A disk reproducing apparatus for searching for data. 5. The digital still camera according to claim 2 , wherein said search means is configured to read the digital data read from said disk.
Digital data that can be decoded by itself.
Data and at least one other digital data
Search for a set of digital data composed of
Disk reproducing apparatus, characterized in that that. 6. Data encoded at a different compression ratio for each period.
Spiral or concentric recording tracks of digital data
To read data from the disc recorded on the
In a disk reproducing apparatus having reading means, digital data read from the disk is temporarily stored.
First storage means for temporarily storing, and
Write control for controlling writing of the digital data
Means for compressing said different data from said digital data during normal reproduction.
Can extract coding rate information corresponding to the rate
Decoding means, and the decoding means is provided from the first storage means.
The digitization is performed at a coding rate based on the coding rate information.
Read control means for controlling readout of data
With the door, the accumulated amount detecting means for detecting a storage amount of the first storage unit
Is provided, and the storage amount detecting means stores the data in the first storage means.
Data is detected to be greater than or equal to a predetermined amount.
The writing control means stores the first storage means
Stop writing digital data and at the same time
Position of the data reading means at least one
Return the rack and stop reading the digital data
And the data reading means returns to the position before the movement.
Later, the digital data is read by the data reading means.
Data reading is resumed, and the data is read back to the first storage means.
Digital data writing is resumed, and during variable speed reproduction, the data reading means is moved to a predetermined position.
Control means for controlling movement, and reading of the data
Digital data read from the disk by
Retrieval means for retrieving desired digital data from data
And the digital data retrieved by the retrieval means.
A second storage means for temporally storing the data;
Digital data from the second storage means upon request.
A disk reproducing apparatus comprising: a control unit that controls reading . 7. The disk drive according to claim 6, wherein the capacity M of the first storage means is determined from the disk.
A transmission rate rp for reading digital data;
Means for reading the data from the outermost periphery of the disk.
Due to the time T required for one round when on the rack, M ≧
A disc reproducing apparatus characterized by being determined under the condition of rp × T. 8. The apparatus according to claim 6, wherein said search means is configured to read the digital data read from said disk.
Digital data that can be decoded by itself.
Data and one signal that has already been decoded
A disc reproducing apparatus for retrieving digital data . 9. Data encoded at a different compression ratio for each period.
Spiral or concentric recording tracks of digital data
Digital data from the disc recorded in
In a disc reproducing apparatus for reproducing, digital data read from the disc is temporarily stored.
To the first memorize means for storing, in the first storage means
Write control for controlling writing of the digital data
Means for decoding, including a second storage means for decoding,
Correspond to the different compression ratios from the digital data.
Decoding means capable of extracting encoded rate information
A third storage unit associated with the decoding unit;
The encoding means stores the encoding rate information from the first storage means.
The digital data at a data rate based on the
Read-out control means for controlling to output the data read out from the disk during variable-speed playback.
Search method for searching desired digital data from digital data
And digital data retrieved by the retrieval means.
Fourth storage means for temporarily storing, and the decoding means
In response to a request for variable speed playback, the fourth storage means
Control means for reading digital data.
Disk reproducing apparatus, characterized in that digit. 10. The disk reproducing apparatus according to claim 9 , wherein said first storage means is also used as said second storage means . 11. The method according to claim 9 , wherein said first storage means and said second storage means are stored in said third storage means.
A disc reproducing apparatus characterized in that the disc reproducing apparatus is also used as the storage means . 12. The disk reproducing apparatus according to claim 9, wherein said fourth storage means is also used as said first storage means . 13. The disk reproducing apparatus according to claim 9 , wherein said fourth storage means is also used as said second storage means . 14. The method according to claim 9 , wherein the first storage means, the second storage means, and the fourth
A disk reproducing apparatus , wherein said storage means is also used as said third storage means .