JP2001078151A - Digital decoding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow only a decoder to realize seamless reproduction of scenes of a moving picture without intervention of an encoder. SOLUTION: A read rate of data from a data storage medium 12 is controlled in response to a date residual amount in a buffer 15 at each joint point so that a data quantity in the buffer 15 is a specified quantity or over at a decode start point of time of a first frame of each scene. That is, a read rate of a current scene from a data storage medium is controlled so that the data quantity in the buffer is a specified quantity or over at a decode start point of time of the first frame of a succeeding scene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital decoding method for sequentially decoding an encoded bit stream of each scene so that a plurality of scenes of a moving image can be seamlessly reproduced.

[0002]

2. Description of the Related Art MPEG (Moving Picture Experts Group) is a typical example of a moving picture compression coding technique. JP-A-9-331524 discloses that each MP
A digital encoding method for seamlessly combining a plurality of bit streams (a plurality of scenes) encoded according to the EG standard is disclosed. According to this method,
Near the end of the first bitstream and near the beginning of the second bitstream to seamlessly combine the second scene after the first so as to avoid decoder buffer corruption (overflow and underflow) And the encoding bit rate (compression rate) of each is limited.

[0003]

In the above prior art, the encoder side prepares for seamless reproduction of a plurality of scenes. Therefore, there is a problem that a scene to be combined is specified. There is also a problem that image quality varies in each scene.

An object of the present invention is to realize seamless reproduction of a plurality of scenes only on the decoder side without the intervention of an encoder.

[0005]

According to a first method of the present invention, a coded bit stream of a moving image read from a data storage medium is supplied to a decoder via a buffer. A digital decoding method for sequentially decoding a bit stream of each scene so that a plurality of scenes are seamlessly reproduced in a digital reproduction device configured as described above, wherein a decoding start time of a first frame of a next scene is determined. The reading rate of the current scene from the data storage medium is controlled so that the amount of data in the buffer in (1) becomes equal to or greater than a specified amount.

A second method according to the present invention is directed to a digital reproducing apparatus configured to supply an encoded bit stream of a moving image to a decoder via a buffer.
A digital decoding method for sequentially decoding a bit stream of each scene so that a plurality of scenes are seamlessly reproduced, and predicting an amount of data in the buffer at the time of starting decoding of a first frame of each scene,
If the predicted data amount at the start of decoding a certain scene is less than the specified amount, the data of the first scene is stored in the buffer by an amount obtained by adding the insufficient data amount to the specified amount. After that, the decoding of the first frame of the first scene is started.

[0007] A third method according to the present invention is directed to a digital reproducing apparatus configured to supply an encoded bit stream of a moving image to a decoder via a buffer.
A digital decoding method for sequentially decoding a bit stream of each scene so that a plurality of scenes are reproduced seamlessly, wherein the input rate of each scene to the buffer is controlled under a certain limit, and The amount of data in the buffer at the start of decoding the first frame is predicted, and if the predicted data amount at the start of decoding a certain scene is less than the specified amount, the insufficient data amount is added to the specified amount. Waiting for the data of the first scene to be stored in the buffer by the amount obtained in
The decoding of the first frame of the first scene is started.

[0008]

FIG. 1 is a block diagram of a first recording / playback apparatus using a digital decoding method according to the present invention. In FIG. 1, 11 is an encoding unit (encoder), 12 is a data storage medium, 13 is a data read control unit, 14 is a data input control unit, 15 is a bit stream storage unit (buffer), 16 is a data output control unit, 1
7 is a decoding unit (decoder), 18 is a transfer rate control unit,
BS1 to BS6 are coded bit streams.

The apparatus shown in FIG. 1 is a so-called codec having an encoder 11 and a decoder 17. The encoder 11 generates a bit stream BS1 by compression coding of a moving image signal. The generated bit stream BS1 is recorded on the data storage medium 12. The data storage medium 12 is a recording medium such as a magneto-optical disk, a magnetic tape, and a semiconductor memory. The data read control unit 13 can read the bit stream BS2 from the data storage medium 12 at a variable rate. The data input control unit 14 includes the data read control unit 13
Receives the bit stream BS3 and the synchronization control signal from the buffer 15 and writes the bit stream BS4 to the buffer 15 in synchronization with the reading of the bit stream BS2. The buffer 15 is a memory for temporarily storing the bit stream BS4 supplied from the data input control unit 14.
The data output control unit 16 reads the bit stream BS5 from the buffer 15. The decoder 17 decodes the bit stream BS6 supplied from the data output control unit 16, and outputs a reproduction moving image signal obtained as a result.
The transfer rate control unit 18 stores a buffer based on data input information (write address information of the buffer 15) obtained from the data input control unit 14 and data output information (read address information of the buffer 15) obtained from the data output control unit 16. 15 is calculated, and the data storage medium 1 is calculated based on the information on the remaining data obtained by the calculation and the image compression information such as the number of frames and the compression rate of each scene.
2 is determined, and information on this rate is given to the data read control unit 13 as transfer rate information.

Here, the bit rate (buffer input rate) of the bit stream BS4 input to the buffer 15 is equal to the read rate of the data storage medium 12, and is variable. The bit rate (decoding rate) related to decoding by the decoder 17 matches the encoding bit rate (compression rate) for each scene. Note that a part of the memory resources shared by the encoder 11, the decoder 17, and other circuit blocks is allocated to the buffer 15.

FIG. 2 shows a decoding buffer 1 shown in FIG.
5 shows a temporal change of the data amount. DI1,
DI2 and DI3 are the first to buffer 15, respectively.
This is the input period of the bit stream of the second and third scenes. The input period DI2 of the second scene starts from time t20, and the input period DI3 of the third scene starts from time t30. Each scene is, for example, one GOP
(Group Of Picture). The broken line drawn by a dashed line in FIG. 2 indicates the locus of the data amount in the buffer 15 when the buffer input rate of each scene is set to the same value Ri, and the broken line drawn by a solid line in FIG. The trajectories of the amount of data in the buffer 15 when the buffer input rates of the first, second and third scenes are set to Ri (1), Ri (2) and Ri (3), respectively. The slope of the polygonal line “upward line segment” indicates the buffer input rate, and the length of the polygonal line “vertical line segment” indicates the amount of picture data per frame. Here, it is assumed that the extraction of each picture data from the buffer 15 is completed instantaneously.

Sv in FIG. 2 is the size of a virtual buffer used for controlling the amount of code generation in the encoder 11,
That is, VBV (Video Bufferin) defined by MPEG
g Verifier) Indicates the buffer size. That is, for each scene, data of the specified amount Sv or more is stored in the buffer 1
At this point, decoding of the first frame can begin. This specified data amount Sv is also the maximum data amount extracted from the buffer 15 at one time.

T in FIG. 2 represents one frame period. NTSC (National Television System Committe
e) For the video rate (30 frames / s), T =
33.3 ms.

According to FIG. 2, at time t11 when one frame period T has elapsed from time t10, the buffer 15
Reaches the specified amount Sv.
Therefore, decoding of the first scene can be started from time t11. The buffer 15 at the decoding start time t21 of the first frame of the second scene
Is greater than or equal to the specified amount Sv in both the dashed-dotted line and the solid line locus, so that the second scene can be seamlessly joined to the first scene without underflow in the buffer 15. Can be. Furthermore, the third
Since the amount of data in the buffer 15 at the decoding start time t31 of the first frame of the scene is the specified amount Sv in both the dashed line and the solid line, the buffer 1
5, the third scene can be seamlessly combined with the second scene without underflow.

The trajectory of the dashed line in FIG. 2 will be described in detail. At time t20, data of the specified amount Sv of the last frame of the first scene is extracted from the buffer 15 and output to the decoder 17. In the subsequent one frame period T, the data amount in the buffer 15 is restored to the specified amount Sv by the data input (buffer input rate Ri) of the second scene. Then, at time t21, the data of the specified amount Sv of the first frame of the second scene is stored in the buffer 1
As a result, the data amount in the buffer 15 becomes 0 as a result of being extracted from 5 and output to the decoder 17. That is, the time t
The data amount in the buffer 15 before data extraction at 20 is 2 × Sv−Ri × T. Therefore, even in the worst case where the data of the specified amount Sv is continuously extracted from the buffer 15 twice, when the total capacity of the buffer 15 is Sb, Sb = 2 × Sv−Ri × T (1) As long as the total buffer capacity Sb satisfies the condition, the second scene can be seamlessly combined with the first scene without causing the buffer 15 to fail (overflow and underflow). The total buffer capacity Sb may be larger than 2 × Sv−Ri × T.

Furthermore, according to the locus of the dashed line in FIG.
Assuming that the number of frames of the second scene is N (2) and the encoding bit rate (compression rate) of the scene is Re (2), for the seamless combination of the third scene with the second scene, In order to secure the specified data amount Sv at time t31, the data amount in the buffer 15 is set to 0 during the time T × N (2) from time t21 to time t31.
From this, it is understood that it is necessary to increase by the specified amount Sv at the rate of Ri-Re (2). That is, the buffer input rate Ri may be set so as to satisfy Ri = Sv / (T × N (2)) + Re (2) (2)

Specifically, Sv = 1.835 Mbit,
T = 33.3 ms, N (2) = 15, Re (2) = 8 Mbps
Then, Ri = 111.67 Mbps from equation (2), and Sb = 3.281 Mbit from equation (1). That is, the total buffer capacity Sb is set to 3.281 Mbit.
The buffer input rate (data storage medium 12
) Is set to 11.67 Mbps, so that the bit stream of each scene is sequentially decoded so that three scenes can be seamlessly reproduced without causing the buffer 15 to fail (overflow and underflow). be able to.

In the locus indicated by the solid line in FIG. 2, at time t20, a smaller amount of data than the specified amount Sv of the last frame of the first scene is extracted from the buffer 15 in which the total capacity Sb is filled with data. It is to be output to the decoder 17. In the subsequent one frame period T, the data amount in the buffer 15 recovers beyond the specified amount Sv due to the data input of the second scene. Therefore, at time t21, when data of the specified amount Sv of the first frame of the second scene is extracted from the buffer 15 and output to the decoder 17, α (>
Only data 0) remains. In accordance with the remaining data amount α, the transfer rate control unit 18 sets the buffer 1 at the decoding start time t31 of the first frame of the third scene.
5 so that the data amount in 5 becomes the specified amount Sv, Ri (2) = (Sv−α) / (T × N (2)) + Re (2) (3) The rate (the read rate of the data storage medium 12) Ri (2) is controlled. Even in this case, the data of the specified amount Sv is secured in the buffer 15 at the decoding start time t31, so that the buffer 15 does not underflow.
The third scene can be seamlessly combined with the second scene. In addition, under the same conditions as in the case of the dashed-dotted line, for example, when α = 0.5 Mbit, Ri (2) = 10.67 Mbps from equation (3).
The power consumption in the input period DI2 of the second scene can be reduced.

As described above, according to the configuration of FIG. 1, by controlling the reading rate of the data storage medium 12 in accordance with the remaining amount of data in the buffer 15 for each scene connection point, a plurality Can be seamlessly reproduced.

In FIG. 2, for example, the data remaining amount β at time t20, that is, the data of the last frame of the first scene is extracted from the buffer 15 and
The buffer input rate of the second scene (the reading rate of the data storage medium 12) Ri (2) may be controlled in accordance with the amount of data in the buffer 15 at the time when the data is output to the buffer 15.

FIG. 3 is a block diagram of a second recording / reproducing apparatus using the digital decoding method according to the present invention.
3, reference numeral 11 denotes an encoding unit (encoder); 12, a data storage medium; 13, a data read control unit;
Denotes a data input control unit, 15 denotes a bit stream storage unit (buffer), 16 denotes a data output control unit, 17 denotes a decoding unit (decoder), 19 denotes a decoding control unit, and BS1 to BS6.
Is an encoded bit stream.

The apparatus shown in FIG. 3 is a so-called codec having an encoder 11 and a decoder 17. The encoder 11 generates a bit stream BS1 by compression coding of a moving image signal. The generated bit stream BS1 is recorded on the data storage medium 12. The data storage medium 12 is a recording medium such as a magneto-optical disk, a magnetic tape, and a semiconductor memory. The data read control unit 13 reads the bit stream BS2 from the data storage medium 12 at a fixed rate. The data input control unit 14 receives the bit stream BS3 from the data read control unit 13. The buffer 15 is a variable capacity memory for temporarily storing the bit stream BS4 supplied from the data input control unit 14. A part of the memory resources shared by the encoder 11, the decoder 17, and other circuit blocks is allocated to the buffer 15. The data output control unit 16 controls the buffer 1
5, the bit stream BS5 is read. Decoder 1
7 decodes the bit stream BS6 supplied from the data output control unit 16, and outputs a reproduction moving image signal obtained as a result. The decoding control unit 19 determines whether or not the first frame of each scene is to be decoded based on the image compression information such as the number of frames and the compression rate of each scene and the reproduction information such as the reproduction order of the scenes. When the data amount is predicted and the predicted data amount at the start of decoding of a certain scene is less than the specified amount (VBV buffer size) Sv, the buffer 15 defined assuming that the data amount will not be insufficient is determined. The buffer size information is provided to the data input control unit 14 and the data output control unit 16 so as to increase the capacity Sb (see equation (1)) by the insufficient data amount γ, and then the insufficient data amount γ is added to the specified amount Sv. The first scene data is buffer 1
The decoding start information is given to the data output control unit 16 so that the decoding of the first frame of the first scene is started after waiting for the data to be stored in the memory 5. Further, the decoding control unit 19 includes the data input information (write address information of the buffer 15) obtained from the data input control unit 14, the data output information (read address information of the buffer 15) obtained from the data output control unit 16, From the buffer 15 can be grasped.

FIG. 4 shows a temporal change in the amount of data in the buffer 15 in FIG. Here, buffer 15
The input bit rate (buffer input rate) Ri is constant regardless of the scene. The broken line drawn by the one-dot chain line in FIG. 4 indicates that the data in the buffer 15 indicates that when decoding of the first frame of the first scene starts at time t11, an underflow occurs in the buffer 15 at time t31 ′. It is a locus of quantity. In this case, the input periods of the bit streams of the first, second, and third scenes to the buffer 15 are DI1 ', DI2', and DI3 '. The input period DI2 ′ of the second scene is at time t20 ′.
Therefore, the input period DI3 ′ of the third scene is at time t30 ′.
Starts with The broken line drawn by a solid line in FIG. 4 indicates that the buffer 15 does not underflow when the decoding of the first frame of the first scene is delayed until time t12. It is a trajectory. In this case, the input period of the bit stream of the first, second, and third scenes to the buffer 15 is DI
1, DI2 and DI3. The input period DI2 of the second scene is changed from the time t20 to the input period DI of the third scene.
3 starts from time t30.

According to FIG. 4, at time t11 when one frame period T has elapsed from time t10, the buffer 15
Reaches the specified amount Sv.
In the trajectory of the dashed line, decoding of the first frame of the first scene starts at this time t11. In this case as well, at time t21 ', which is one frame period T elapsed from time t20', data of the specified amount Sv is secured in the buffer 15, so that decoding of the first frame of the second scene is immediately started. be able to. However,
Time t after a lapse of one frame period T from time t30 '
In 31 ′, since the data amount shortage γ occurs with respect to the specified amount Sv in the buffer 15, the decoding of the first frame of the third scene cannot be started immediately, and the specified amount Sv of the specified amount is stored in the buffer 15. One has to wait until time t32 'when the data is stored. That is, at time t31 '
A so-called VBV delay (startup delay) occurs between the time t and the time t32 ', and the third scene cannot be seamlessly combined with the second scene. For example, when the encoding bit rate of the second scene is considerably high, seamless reproduction may not be realized without taking measures such as increasing the buffer input rate of the second scene (Equation (2)). 3)).

The insufficient data amount γ is obtained by setting the number of frames of the first and second scenes to N (1) and N (2), respectively, and setting the encoding bit rate (compression rate) of both scenes to R
When e (1) and Re (2), It can be estimated as follows. That is, the insufficient data amount γ is the difference Re (2) −Re (1) between the compression rates of two consecutive scenes.
And the ratio N (2) / N (1) of the number of frames in both scenes.

According to the locus of the solid line in FIG.
To the time t12 when the period DT has elapsed, that is, until the time t12 when the data of the first scene is stored in the buffer 15 by the amount obtained by adding the shortage γ predicted by the equation (4) to the specified amount Sv. Wait and start decoding the first frame of the first scene. Thereby, the decoding start time t21 of the first frame of the second scene
In addition, the buffer 15 does not underflow even at the decoding start time t31 of the first frame of the third scene. That is, for the first scene, the second scene
Can be seamlessly combined with the third scene with respect to the second scene. However, to prevent the buffer 15 from overflowing,
It is necessary to increase the total capacity of the buffer 15 to Sb + γ.

As described above, according to the configuration of FIG. 3, by delaying the start of the decoding of the first scene in accordance with the expected insufficient data amount γ, seamless reproduction of a plurality of scenes is realized only on the decoder side. be able to.

In the example of FIG. 3, the data storage medium 1
2 is fixed, so that the input bit rate of the buffer 15 (buffer input rate) is constant regardless of the scene. However, when the reading rate of the data storage medium 12 can be changed to a certain upper limit rate, the input rate of each scene to the buffer 15 is controlled to some extent according to the method described with reference to FIGS. 3 and 4 may be employed. According to this, the capacity increment γ of the buffer 15 in FIG. 4 can be reduced.

Also, taking into account the number of scenes to be combined, the encoding bit rate of each scene, and the number of frames in each scene, the capacity of the buffer 15 is ensured to be slightly larger than the number of scenes. Is also possible.

In the first and second recording / reproducing apparatuses, it is assumed that the next scene to be seamlessly combined with the current scene is known. However, a scene combination request may be suddenly given while a certain scene is being reproduced. The recording / playback apparatus described below can cope with such a situation.

FIG. 5 is a block diagram of a third recording / reproducing apparatus using the digital decoding method according to the present invention.
The transfer rate control unit 18a in FIG. 5 differs from the transfer rate control unit 18 in FIG. 1 in that it is configured to receive a scene combination request. Other configurations in FIG. 5 are the same as those in FIG.

The transfer rate control unit 18a shown in FIG. 5 responds to a scene combination request given during the reproduction of the current scene, and starts the decoding of the first frame of the next scene to be combined. Predict the amount of data,
If the predicted data amount is less than the specified amount Sv, the data storage medium 12 is adjusted to compensate for the insufficient data amount γ.
To control the rate of reading out the remaining frames of the current scene from.

FIG. 6 shows the decoding buffer 1 in FIG.
5 shows an example of a temporal change of the data amount in FIG. D
I1, DI2, and DI3 are input periods of the bit stream of the first, second, and third scenes to the buffer 15, respectively. The input period DI2 of the second scene is at time t2
From 0, the input period DI3 of the third scene starts from time t30. Here, it is assumed that a request for combining the third scene is given during the reproduction of the second scene. The trajectory drawn by the dashed line in FIG. 6 indicates that if the buffer input rates Ri (1), Ri (2) and Ri (3) of each scene are maintained at the same value Ri, the buffer 15 at time t31 This indicates that underflow occurs.
The trajectory drawn by the solid line in FIG. 6 indicates that the buffer input rate Ri (2) of the second scene is Te in response to the scene combination request.
Indicates that the buffer 15 does not underflow when the maximum read rate Rimax of the data storage medium 12 is increased for a short period of time.

According to the locus of the alternate long and short dash line in FIG.
At time t31 after a lapse of one frame period T from 30, a shortage of data amount γ occurs with respect to the specified amount Sv in the buffer 15, so that decoding of the first frame of the third scene cannot be started immediately, Buffer 1
5 must wait until time t32 when the data of the specified amount Sv is stored. That is, from time t31 to time t3
Up to two, a startup delay occurs,
The third scene cannot be seamlessly combined with the second scene. Here, the insufficient data amount γ can be estimated by the above equation (4).

According to the trajectory indicated by the solid line in FIG. 6, the buffer of the second scene during the period Te required for replenishment of the insufficient data amount γ in one frame period T starting from time t22 immediately after the application of the scene combination request. The input rate (readout rate of the data storage medium 12) Ri (2) is the maximum rate Rimax
To be increased. That is, the buffer input rate Ri (2) is increased during a period Te satisfying γ = (Rimax−Ri) × Te (5). Then, after the replenishment of the insufficient data amount γ is completed, the rate Ri is returned to the original rate Ri. Therefore, simple control after receiving the scene combination request allows the buffer 15
Thus, the third scene can be seamlessly combined with the second scene without causing underflow.

FIG. 7 shows the decoding buffer 1 shown in FIG.
5 shows another example of the temporal change of the data amount in 5.
When a request to combine the third scene is given during the reproduction of the second scene, as in the case of FIG. 6, the trajectory drawn by the solid line in FIG. This shows that underflow does not occur in the buffer 15 when the buffer input rate (read rate of the data storage medium 12) Ri (2) of the remaining frames of the scene is increased to a certain rate Rie on average.

According to the trajectory indicated by the solid line in FIG. 7, the buffer input rate Ri (2) of the second scene is reduced to the insufficient data amount γ over a plurality of frame periods starting from time t22 immediately after receiving the scene combination request. Is increased to the rate Rie required for replenishment. That is, assuming that the number of remaining frames of the current scene (second scene) at the time when the scene combination request is given is Nr (2), the remaining time available for reading the current scene from the data storage medium 12 is T × Nr (2)
In view of this, the rate Rie that satisfies Rie = Ri + γ / (T × Nr (2)) (6) is adopted as the reading rate of the remaining frame. Therefore, as in the case of FIG.
Without underflow in the buffer 15, the second
The third scene can be seamlessly combined with the third scene.

As described above, according to the configuration of FIG. 5, the rate of reading the remaining frames of the current scene from the data storage medium 12 in accordance with the insufficient data amount γ expected at the time when the scene combination request is given. By performing the control, seamless reproduction of a plurality of scenes can be realized only on the decoder side.

In the example of FIG. 6, since Te <T, the readout rate of only one of the remaining frames in the second scene is controlled. For example, T <Te <2T
Then, the reading rate of two frames may be controlled.

[0040]

As described above, according to the present invention, seamless reproduction of a plurality of scenes can be realized only on the decoder side without the intervention of an encoder.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first recording / playback apparatus using a digital decoding method according to the present invention.

FIG. 2 is a bit stream storage unit (buffer) in FIG. 1;
FIG. 4 is a time chart showing a temporal change of a data amount in the table.

FIG. 3 is a block diagram of a second recording / playback apparatus using a digital decoding method according to the present invention.

FIG. 4 is a bit stream storage unit (buffer) in FIG. 3;
FIG. 4 is a time chart showing a temporal change of a data amount in the table.

FIG. 5 is a block diagram of a third recording / playback apparatus using a digital decoding method according to the present invention.

FIG. 6 shows a bit stream storage unit (buffer) in FIG.
FIG. 7 is a time chart diagram showing an example of a temporal change of the data amount in FIG.

FIG. 7 is a bit stream storage unit (buffer) in FIG. 5;
FIG. 9 is a time chart diagram illustrating another example of a temporal change in the data amount in FIG.

[Explanation of symbols]

 Reference Signs List 11 encoding unit (encoder) 12 data storage medium 13 data read control unit 14 data input control unit 15 bit stream storage unit (buffer) 16 data output control unit 17 decoding unit (decoder) 18, 18a transfer rate control unit 19 decoding Control section BS1 to BS6 bit stream

Claims (14)

[Claims] 1. A digital reproduction apparatus configured to supply an encoded bit stream of a moving image read from a data storage medium to a decoder via a buffer so that a plurality of scenes can be reproduced seamlessly. A digital decoding method for sequentially decoding a bit stream of each scene, wherein a data amount in the buffer at a decoding start time of a first frame of a next scene is equal to or more than a specified amount. A digital decoding method characterized by controlling a reading rate of the current scene. 2. The digital decoding method according to claim 1, wherein the data storage medium is responsive to an amount of data in the buffer at the time when data of a first frame of a current scene is output from the buffer to the decoder. A digital decoding method characterized by controlling a reading rate of a current scene from a digital camera. 3. The digital decoding method according to claim 1, wherein the data of the last frame of the scene immediately before the current scene is output from the buffer to the decoder, according to the amount of data in the buffer. And controlling a reading rate of a current scene from the data storage medium. 4. The digital decoding method according to claim 1, wherein the buffer at the start of decoding of the first frame of the next scene to be combined in response to a scene combination request given during reproduction of the current scene. If the predicted data amount at the start of decoding the next scene is less than the prescribed amount, the data amount of the current scene from the data storage medium is compensated so as to compensate for the insufficient data amount. A digital decoding method comprising controlling a reading rate of remaining frames. 5. The digital decoding method according to claim 4, wherein a reading rate from said data storage medium is maximized until said insufficient amount of data is compensated. 6. The digital decoding method according to claim 4, wherein an increase in a read rate is obtained by dividing the insufficient data amount by a remaining time available for reading a current scene from the data storage medium. A digital decoding method characterized by increasing a reading rate of a remaining frame of a current scene from a storage medium by the increment. 7. A digital playback device configured to supply a coded bit stream of a moving image to a decoder via a buffer, wherein a bit stream of each scene is sequentially converted so that a plurality of scenes are seamlessly played back. A digital decoding method for decoding, wherein the amount of data in the buffer at the start of decoding of the first frame of each scene is predicted, and when the amount of predicted data at the start of decoding of a certain scene is less than the prescribed amount, Waiting for data of the first scene to be stored in the buffer by an amount obtained by adding the insufficient data amount to the prescribed amount, and starting decoding of the first frame of the first scene. A digital decoding method characterized by the following. 8. The digital decoding method according to claim 7, wherein a capacity of the buffer, which is determined on the assumption that the shortage of the data amount does not occur, is increased by the shortage data amount. Digital decoding method. 9. The digital decoding method according to claim 8, wherein an increase in the capacity of the buffer is determined according to a difference between a compression rate of two consecutive scenes and a ratio of the number of frames. . 10. In a digital playback device configured to supply a coded bit stream of a moving image to a decoder via a buffer, a bit stream of each scene is sequentially converted so that a plurality of scenes are played back seamlessly. A digital decoding method for decoding, comprising controlling the input rate of each scene to the buffer under a certain limit, and predicting the amount of data in the buffer at the start of decoding of the first frame of each scene, If the predicted data amount at the start of decoding a certain scene is less than the specified amount, the data of the first scene is stored in the buffer by an amount obtained by adding the insufficient data amount to the specified amount. And starting decoding of the first frame of the first scene. 11. The digital decoding method according to claim 10, wherein data of a first frame of each scene is output to said buffer in accordance with a predicted data amount in said buffer at a time when said data is output from said buffer to said decoder. A digital decoding method characterized by controlling an input rate of each scene. 12. The digital decoding method according to claim 10, wherein the data of the last frame of the previous scene is output from the buffer to the decoder at a time when the predicted data amount in the buffer is determined. A digital decoding method, wherein an input rate of each scene to the buffer is controlled. 13. The digital decoding method according to claim 10, wherein a capacity of said buffer determined assuming that the shortage of the data amount does not occur is increased by the shortage data amount. Digital decoding method. 14. The digital decoding method according to claim 13, wherein an increase in the capacity of the buffer is determined according to a difference between a compression rate of two consecutive scenes and a ratio of the number of frames. .