JP2001054066A - Decoding device, image display system, and image display method - Google Patents

Abstract

(57) [Problem] To realize smooth fast-forward reproduction and lean reproduction without waste in a device such as a personal computer that does not need to reproduce at a fixed frame rate. An MPEG2 decoder 152 decodes and outputs moving image data read from a DVD medium at a frame rate of 30 frames / second in a standard playback mode, but decodes the video data in a fast-forward playback mode or a slow playback mode. Change the processing speed. For example, 1 /
In the case of performing the flow reproduction at the speed of 2, 15 frames /
The decoding processing speed of the MPEG2 decoder 152 is set to の of that in the standard reproduction mode so that the VRAM 17 is rewritten at a frame rate of seconds, and 60 frames / sec. The decoding processing speed of the MPEG2 decoder 152 is set to twice that in the standard reproduction mode so that the VRAM 17 is rewritten at the frame rate of.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a decoding device, an image display system, and an image display method, and more particularly to a decoding device, an image display system, and an image display method for reproducing encoded image data.

[0002]

2. Description of the Related Art In recent years, with the development of computers and multimedia technology, various personal computers compatible with multimedia have been developed. This type of personal computer is provided with a function for reproducing moving image data recorded on a DVD medium or the like, in addition to reproducing text data and graphics data.

[0003] The moving image data recorded on the DVD is MPE.
G2. When reproducing this moving image data on a personal computer, first, D
The encoded stream of the moving image data is read from the VD drive device into the main memory of the personal computer, and is transferred to the MPEG2 decoder. In the MPEG2 decoder, decoding processing for expanding the encoded stream is performed. The decoded moving image data is sent to a display controller (VGA controller) that controls a display monitor of a personal computer. This V
The moving image data sent to the GA controller is once written in an image memory and then displayed on a display monitor or a TV, like ordinary graphics data provided by an OS or an application program.

[0004] The moving picture data stored on the DVD is created based on a TV picture signal of the same NTSC system as a home TV, and the frame rate of the moving picture data decoded by the MPEG2 decoder is 30 frames / sec. It is. Therefore, the decoding process by the MPEG2 decoder is performed in accordance with the frame rate of 30 frames / second, and the image signal obtained by the decoding is always transferred from the MPEG2 decoder to the VGA controller at a fixed frame rate of 30 frames / second. The same applies to trick playback such as fast forward playback and slow playback.
Image signals are transferred at a fixed frame rate of 30 frames / sec.

[0005] As described above, reproduction at a fixed frame rate of 30 frames / second is always required because of the conventional MP.
This is because the EG2 decoder is premised on outputting an image signal obtained by decoding to a TV, and unless the image signal is finally output to the TV at a fixed frame rate of 30 frames / sec, an image is normally output. This is because it cannot be displayed.

Therefore, conventionally, when performing trick playback such as fast-forward playback or slow playback, a playback frame is thinned out or the same frame is played back a plurality of times, so that a fixed frame rate of 30 frames / second is finally obtained. I was playing. In addition, when a pause is made to stop reproduction on a specific screen, a process of outputting the same frame to the TV while decoding the same frame over and over so as to keep the same screen displayed on the screen. This is because if the supply of the image signal to the TV is interrupted, nothing is displayed on the TV screen.

[0007]

However, in the case of using the conventional fast-forward playback method in which playback frames are thinned out and played back at a fixed frame rate, in practice, decoding is performed without referring to the previous or next frame. It is necessary to perform a process of extracting and decoding and reproducing only I pictures capable of performing the decoding, and thinning out P pictures and B pictures without decoding and reproducing. For this reason, discrete images are displayed, and smooth reproduction cannot be performed.

Further, at the time of slow reproduction or pause, the same frame is repeatedly decoded, so that useless processing is performed accordingly.

However, unlike a TV, a device such as a personal computer does not always need to reproduce at a fixed frame rate. Once the image data obtained by decoding is once drawn in the image memory, the VGA controller performs the screen display while sequentially reading the image data from the image memory at a predetermined refresh rate determined by the screen resolution or the like. is there.
That is, even if the image signal is not transferred from the MPEG2 decoder to the VGA controller at a fixed frame rate of 30 frames / second, there is no problem in display.

Therefore, the conventional trick reproduction method on the assumption of decoding and reproduction at a fixed frame rate is not suitable for devices such as personal computers in that smooth reproduction is impaired and unnecessary decoding processing is performed. It was an inefficient method.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is intended for processing such as smooth fast-forward reproduction, efficient slow reproduction, and pause in a device such as a personal computer that does not need to reproduce at a fixed frame rate. It is an object of the present invention to provide a decoding device, an image display system, and an image display method capable of performing the above.

[0012]

According to the present invention, there is provided a decoding apparatus for decoding coded image data, comprising the steps of: Decoding means for decoding and outputting according to the following, and according to a reproduction mode of the image data,
And a frame rate control means for changing a frame rate of the decoding means.

In this decoding device, the frame rate of the decoding means is changed in accordance with the reproduction mode, and the image data of the variable frame rate is finally output from the decoding device. Therefore, for example, during fast forward playback, image data is decoded and output at a frame rate higher than the standard playback frame rate, and at slow playback, image data is decoded and output at a lower frame rate than the standard playback frame rate. It can be carried out. Therefore, by applying the decoding device to a device such as a personal computer, transferring the image data of the variable frame rate output from the decoding device to the display control device and rewriting the image memory, the reproduced frame can be reproduced. Smooth fast-forward reproduction and lean reproduction without waste can be easily realized without performing processing such as thinning out or reproducing the same frame a plurality of times.

In a pause for stopping reproduction on a specific screen, image data necessary for reproduction of a specific screen is decoded and then written once into an image memory. Thereafter, new writing is not performed during pause. Since the same screen can be continuously displayed, it is preferable to control the decoding processing of the image data necessary for reproducing the specific screen to be performed only once and then stopped. As a result, useless decoding processing, transfer of image signals, and rewriting of the image memory can be prevented, and power saving can be achieved.

The frame rate of the decoding means can be variably set by changing the processing speed of the decoding processing of the decoding means. In particular, when the decoding process is performed by software, the processing speed of the decoding process may be changed by, for example, changing the processing speed of a processor that executes the software or providing a processing speed control function in the software itself. It can be easily realized by such as.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of a computer system according to an embodiment of the present invention. This computer system is a notebook personal computer in which a flat panel display such as an LCD is attached to a computer main body so as to be openable and closable. As shown, a CPU 11, a main memory 12, a DVD drive 1
3, satellite tuner 14, DVD decoder 15, V
GA controller 16, Video RAM (VRAM) 17
It has. These are respectively connected to the PCI bus.

The CPU 11 controls the operation of the entire system, and executes an operating system loaded into the main memory 12, an application program to be executed, and the like. The reproduction of the moving image data on the DVD medium driven by the DVD drive 13 is as follows.
This is performed by causing the CPU 11 to execute various driver programs for hardware control and an application program for reproduction.

The DVD drive 13 has 1
Moving image data stored on a DVD medium having a storage capacity of about 0 GB is read at a maximum transfer rate of 10.8 Mbps. For example, a DVD title such as a movie can be recorded on the DVD medium. The movie information can include main video (video), sub-video (sub-picture) up to 16 channels, and audio (audio) up to 32 channels. In this case, these video, sub-picture, and audio are digitally compression-encoded and recorded according to the MPEG2 standard. According to the MPEG2 standard, other encoded data can be included in data encoded by MPEG2, and the encoded data is treated as one MPEG2 program stream.

MPEG2 is used for video encoding.
Run-length encoding and DOLBY AC3 are used for encoding the sub-picture and the audio, respectively. Even in this case, the encoded video, sub-picture, and audio are treated as one MPEG2 program stream.

The satellite tuner 14 receives video data transmitted from digital satellite broadcasting and transfers the video data to the main memory 12. When the video data by digital satellite broadcasting is composed of an MPEG2 stream, the DVD read from the DVD drive 13
The decoding process is performed by the MPEG2 decoder of the DVD decoder 15 in the same manner as the video MPEG2 stream.

The DVD decoder 15 is a DVD drive 1
3 and the MPEG2 program stream received by the satellite tuner 14.
The program stream is received via the main memory 12, and the received stream is subjected to a descrambling process and a decoding process for decompression. This DVD decoder 15
Is composed of a PCI interface 151 and an MPEG2 decoder 152 as shown.

The PCI interface 151 is a PCI interface.
An interface between the bus 10 and the MPEG2 decoder 152, and an MP received via the PCI bus 10
The EG2 stream is sent to the MPEG2 decoder 152.
The PCI interface 151 includes a reproduction control register 153, a frame rate control unit 154, and a video port control unit 155, as shown in the figure.

The reproduction control register 153 stores the DV
This is a register for designating the playback mode of the moving image data stored in the D medium, in which information indicating the playback mode designated by the playback application program is set. The reproduction mode includes modes such as a slow reproduction mode, a fast forward reproduction mode, and a pause in addition to the standard reproduction mode.

The frame rate control unit 154 controls the frame rate of the MPEG2 decoder 152, that is, the decoding speed of moving image data, and the speed of the video data from the DVD decoder 15 to the VGA controller 16 in accordance with the playback mode set in the playback control register 153. The transfer rate of the image signal is variably set. The variable setting of the frame rate of the MPEG2 decoder 152 is based on the MPEG2 decoder 15.
2 is realized by changing the processing speed.

That is, the MPEG2 decoder 152
In the standard playback mode, the moving image data read from the DVD medium is decoded and output at a frame rate of 30 frames / sec. In the fast-forward playback mode and the slow playback mode, the image data rewriting speed for the VRAM 17 is eventually reduced. The decoding processing speed is changed so that the decoding is performed at a higher or lower speed than in the standard reproduction mode.

For example, when performing flow reproduction at 1/2 speed, the VR is reproduced at a frame rate of 15 frames / sec.
The decoding processing speed of the MPEG2 decoder 152 is set to 1 / the speed of the standard reproduction mode so that the AM17 is rewritten.
2 and fast forward playback at 2 × speed, the VRAM 17 has a frame rate of 60 frames / sec.
MPEG2 decoder 152 so that
Is set twice as fast as in the standard reproduction mode. As a result, without performing control such as thinning out the reproduction frame or switching back and reproducing the same frame,
Fast forward playback and slow playback can be realized.

The playback speed of moving image data is MPEG2
Since it is determined by the decoding processing speed of the decoder 152, for example, 28 frames / second, 29 frames / second
Seconds, 30 frames / second, 31 frames / second, 32 frames / second, 33 frames / second,..., Or 29.8 frames / second, 29.9 frames / second,
The playback speed can be changed in units of 30 frames / second, 30.1 frames / second, 30.2 frames / second, 30.3 frames / second,....

The video port control unit 155 is an MPEG2
The digital YUV format image signal output from the decoder 152 is transmitted to a video input port of the VGA controller 16 via a video bus including a ZV port and the like.

The VGA controller 16 is provided with an LC provided as a dedicated display monitor on the computer body.
It controls a D display and an external CRT display, and supports not only graphics display of VGA / SVGA specifications but also moving image display. Video data is P
The video signal is input to the video port not via the CI bus 10 but via the video bus. The moving image data input to the video port is sequentially written to the VRAM 17. In this case, the rewriting speed of the moving image data in the VRAM 17 basically depends on the DVD decoder 15 and the VGA controller 1.
6, which corresponds to the frame transfer rate of moving image data.

Next, referring to FIG. 2, the reproduction mode, D
The relationship with the transfer speed of the moving image data from the VD decoder 15 to the VGA controller 16 will be described.

(Standard Playback Mode) FIG. 2A shows the operation in the standard playback mode. In this case, the moving picture data is transmitted from the DVD decoder 15 to the VGA controller 16 at a frame rate of 30 frames / sec. Transferred and VR
It is written to AM17. The VGA controller 16
The data is read out from the VRAM 17 at the screen resolution of the display monitor (18 or 19) or at a predetermined refresh rate set by the user, and displayed on the display monitor (18 or 19).

(Fast-forward playback mode) FIG. 2B shows the operation in the double-speed fast-forward playback mode. in this case,
When the MPEG2 decoder 152 executes the decoding process at twice the speed of the standard reproduction, the DVD decoder 1
5 to the VGA controller 16 at a frame rate of 60 frames / sec.
Written to M17. The rewriting speed of the VRAM 17 is twice that in the standard reproduction mode. Therefore, even if the screen display is controlled at the same refresh rate as in the standard reproduction mode, double-speed fast-forward reproduction can be realized. MPE
The G2 decoder 152 does not perform processing such as frame thinning, and decodes all frames.
Therefore, compared to the normal fast-forward playback mode in which moving image data is finally played back at a frame rate of 30 frames / sec by performing frame thinning, the image quality of a playback image can be improved.

(Slow Playback Mode) FIG.
The operation in the slow playback mode at the speed of FIG. In this case, the MPEG2 decoder 152 executes the decoding process at half the speed of the standard reproduction, so that the moving image data is transferred from the DVD decoder 15 to the VGA controller 16 at a frame rate of 15 frames / sec.
It is written to AM17. As a result, the rewriting speed of the VRAM 17 is half that in the standard reproduction mode.
The refresh rate for screen display is the same as in the standard playback mode. Also, since the processing speed of the MPEG2 decoder 152 has been reduced to half, the same frame is repeatedly output while decoding, thereby finally reproducing moving image data at a frame rate of 30 frames / sec. There is no need to perform useless processing such as in the flow reproduction mode, and power saving can be realized.

(Moving Picture Reproduction Control Method) Next, FIGS.
With reference to the flowchart of FIG. 5, the moving image reproduction control method of the present embodiment will be described. The system of the present embodiment can use the following six trick modes in addition to the standard playback mode.

"Fast-forward playback mode" 1) Normal FF mode: Fast-forward playback of moving image data at a frame rate of 30 frames / sec by performing frame thinning-out 2) High-quality FF mode: Faster frame rate itself To perform fast-forward playback of moving image data without performing frame skipping. “Slow playback mode” 1) Normal slow mode: A frame rate of 30 frames / second is finally obtained by decoding and playing the same frame a plurality of times. 2) Power saving slow mode: Slow playback of video data without decoding the same frame multiple times by slowing down the frame rate itself. "Pause" 1) Normal pause: Specific VGA while decoding the screen repeatedly 2) Power saving pause: decoding of a specific screen and transfer to the VGA controller are performed only once (fast forward playback) First, referring to the flowchart of FIG. 3, fast forward playback mode (Normal FF mode / high The image quality FF mode will be described.

When the user instructs to switch the playback mode at the start of playback or during playback, the playback application program determines the current playback mode specified by the user (step S101). If the playback mode is other than the “fast-forward playback mode”, the playback application program performs a setting process for that (step S102). In the case of the "fast forward playback mode", the playback application program is Norma
It is determined which of the 1FF mode and the high image quality FF mode has been selected by the user (step S103).

When the NormalFF mode is selected, the reproduction application program uses the frame rate control unit 154 to execute the MPEG2 decoder 1
After setting 52 to the normal frame rate of 30 frames / second (step S104), only the frame corresponding to the I picture is read from the encoded data transferred from the DVD medium to the main memory 12, and the MPEG2 decoder is read. 152 (step S105). Then, a decoding process is performed by the MPEG2 decoder 152 (step S106), and the decoded image signal is transferred to the VGA controller 16 at a frame rate of 30 frames / second and written into the VRAM 17 (step S107). In this manner, in the Normal FF mode, decoding and transfer are performed at the same frame rate of 30 frames / sec as in the standard reproduction mode while thinning out frames.

On the other hand, when the high image quality FF mode is selected, the reproduction application program uses the frame rate control unit 154 to execute the MPEG2 decoder 1
After setting 52 to a high-speed frame rate such as 60 frames / second (step S108), data of all frames transferred from the DVD medium to the main memory 12 is sequentially read from the main memory 12, and MPEG2
The data is transferred to the decoder 152 (step S109). The decoding process by the MPEG2 decoder 152 is 6
It is executed at a high processing speed corresponding to 0 frames / sec (step S110), and the decoded image signal
The data is transferred to the VGA controller 16 at a high frame rate of frames / second and written to the VRAM 17 (step S111). In this manner, in the high image quality FF mode, decoding of all frames is performed at high speed.

(Slow Playback) Next, the slow playback mode (Normal slow / power saving slow) will be described with reference to the flowchart of FIG.

When the user instructs to switch the playback mode at the start of playback or during playback, the playback application program determines the current playback mode specified by the user (step S201). If it is the "slow playback mode", the playback application program determines which of the normal slow mode and the power saving slow mode has been selected by the user (step S203).

If the normal slow mode is selected, the reproduction application program sets the MPEG2 decoder 152 to the normal frame rate of 30 frames / second using the frame rate control unit 154 (step S204). The data of all the frames transferred from the DVD medium to the main memory 12 are sequentially read from the main memory 12 and transferred to the MPEG2 decoder 152 (step S205). And MP
The decoding process by the EG2 decoder 152 is performed twice for the same frame (step S206), and the decoded image signal is transferred to the VGA controller 16 at a frame rate of 30 frames / sec.
(Step S201). Thus, in the normal slow mode, the image signal corresponding to the same frame is transferred to the VGA controller 16 while being repeated twice each.

On the other hand, when the power saving slow mode is selected, the reproduction application program sets the MPEG2 decoder 152 to a low frame rate such as 15 frames / sec by using the frame rate control unit 154. (Step S208), the data of all the frames transferred from the DVD medium to the main memory 12 are sequentially read from the main memory 12 and are read out from the
The data is transferred to the second decoder 152 (step S209). Then, the decoding process by the MPEG2 decoder 152 is executed at a low processing speed corresponding to 15 frames / second (step S210), and the decoded image signal is
The data is transferred to the VGA controller 16 at a low frame rate of 5 frames / second and written to the VRAM 17 (step S211). Thus, in the power saving slow mode, redundant decoding and transfer processing are not performed.

(Pause) Next, the pause (Normal pause / power saving pause) will be described with reference to the flowchart of FIG.

When a pause is instructed by the user during reproduction (YES in step S301), the reproduction application program determines whether the pause specified by the user is a normal pause or a power-saving pause. (Step S303).

If the pause is normal, the reproduction application program reads data for displaying a pause screen from the main memory 12 and stores the data in the MPEG2 format.
The data is transferred to the decoder 152 (step S304). Then, decoding processing is performed by the MPEG2 decoder 152 (step S305), and the decoded image signal is transferred to the VGA controller 16 at the currently set frame rate and written into the VRAM 17 (step S306). Step S305 and step S3
Step 06 is repeatedly executed during the pause period.

On the other hand, in the case of the power saving pause, the reproduction application program reads data for displaying the pause screen from the main memory 12 and stores the data in the MPEG2
The data is transferred to the decoder 152 (step S307). Then, a decoding process is performed by the MPEG2 decoder 152 (step S308), and the decoded image signal is transferred to the VGA controller 16 at the currently set frame rate and written into the VRAM 17 (step S309). The processes in steps S307 to S309 are performed only once, and when the data reading for displaying the pause screen is completed, the decoding process and the transfer process are stopped during the remaining pause period.

(Software Decoding) Next, with reference to FIG. 6, an example in which decoding processing is performed by software will be described.

In this case, the application program for reproduction includes the reproduction control module 21 and the MPEG
And two decoder modules 22. The playback control module 21 receives a playback instruction from the user via the GUI, and variably controls the decoding processing speed (frame rate) of the MPEG2 decoder module 22 according to the playback mode instructed by the user. The procedure of this control is basically the same as that described in the flowcharts of FIGS.

That is, in the high image quality FF mode,
After setting the MPEG2 decoder module 22 to a high frame rate such as 60 frames / sec, the reproduction control module 21 transfers the moving image data from the DVD drive 13 to the main memory 12 through the OS 23 and the file system 24. Then, the frame data is sequentially read from the main memory 12 and passed to the MPEG2 decoder module 22. Thereafter, the decoding process by the MPEG2 decoder module 22 is performed at 60 frames / frame.
The decoded image signal is executed at a high processing speed corresponding to seconds, transferred to the VGA controller 16 through the OS 23 and the display driver 25 at a high frame rate of 60 frames / second, and written into the VRAM 17.

In the power saving slow mode, the reproduction control module 21 sets the MPEG2 decoder module 22 to a low frame rate such as 15 frames / sec. As a result, the decoding process by the MPEG2 decoder module 22 is executed at a low processing speed corresponding to 15 frames / second, and the decoded image signal is output at a low frame rate of 15 frames / second.
The data is transferred to the VGA controller 16 through the OS 23 and the display driver 25 and is written in the VRAM 17.

As described above, even when a software decoder is used, smooth fast-forward reproduction and lean reproduction without waste can be realized by variably setting the data processing speed of the software decoder. Note that the decoding processing speed of the MPEG2 decoder module 22 can be dynamically changed by changing the processing speed itself of the CPU 11 by, for example, changing the operation clock frequency of the CPU 11.

Further, even in the pause mode, the data corresponding to the pause screen is decoded only once by the MPEG2 decoder module 22, and the writing of the pause screen to the VRAM 17 is performed only once, thereby reducing the load. be able to.

Playback control module 21 and M
If the PEG2 decoder module 22 is recorded on a computer-readable recording medium, the reproduction control module 21 and the MPEG2 decoder module 22 are simply introduced into a normal computer through the recording medium, and the same effects as in the present embodiment can be obtained. Can be obtained.

(TV output) The LCD 18 and the CRT 1
9, the moving image data is displayed on the display monitor of the computer, but as shown in FIG.
TV encoder 16 that converts image data on RAM 17 into a video signal for television such as NTSC or PAL and outputs it
If 1 is provided in the VGA controller 16 or the like, trick reproduction by variable frame rate control can be realized even when moving image data is reproduced on a TV. In the case of a TV capable of displaying a variable frame rate,
The display signal of the variable frame rate can be directly supplied to the TV and displayed. Therefore, in this case, as shown in the figure, the TV encoder 156 that converts the image signal of the variable frame rate from the MPEG2 decoder 152 into a video signal for television and outputs it is used as the DVD decoder 1.
5, it is also possible to directly output a video signal for a television having a variable frame rate output from the TV encoder 156 to the TV.

The moving picture reproducing method according to the present embodiment is not limited to a personal computer, but can be applied to a reproducing apparatus for consumers such as a DVD player and a set-top box. FIG. 8 shows a configuration example in this case.

As shown in FIG. 8, the reproducing apparatus 10
0 includes a compressed image data storage unit 101, a reproduction control unit 102, and a compressed image data decoding unit 103. The compressed image data storage unit 101 is an MPEG
2 is a storage device for storing moving image data that has been compression-encoded by, for example,
It consists of media and a hard disk device for recording digital satellite broadcast programs received by satellite tuners. The reproduction control unit 102 variably sets the decoding processing speed of the compressed image data decoding unit 103 according to the reproduction mode specified by the user. When the compressed image data decoding unit 103 is realized by a RISC processor or the like, the RIS
What is necessary is just to change the processing speed of the C processor according to the reproduction mode.

The image signal of the variable frame rate output from the compressed image data decoding unit 103 is directly output to a TV capable of displaying the variable frame rate, or is fixed after being written in the VRAM. Output to a normal TV at a rate.

[0059]

As described above, according to the present invention,
Slow playback is realized by lowering the frame rate, and fast-forward playback is realized by increasing the frame rate.Thus, in slow playback, there is no need to perform useless decoding and data transfer, and the processing amount can be reduced. During fast-forward playback, smooth display can be performed. Further, since the playback speed can be changed depending on the frame rate to be set, it is possible to set the playback speed in smaller units than in the past.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a computer system according to an embodiment of the present invention.

FIG. 2 is an exemplary view for explaining a relationship between a moving image playback mode and a frame rate used in the computer system of the embodiment.

FIG. 3 is an exemplary flowchart showing a processing procedure for fast-forward playback (Normal FF mode / high image quality FF mode) executed by the computer system of the embodiment.

FIG. 4 is an exemplary flowchart showing a processing procedure for a slow playback mode (Normal throw / power saving throw) executed by the computer system of the embodiment.

FIG. 5 is an exemplary flowchart illustrating a processing procedure for a pause (Normal pause / power saving pause) executed in the computer system of the embodiment.

FIG. 6 is an exemplary view showing the functional configuration of software when decoding processing is performed by software in the computer system of the embodiment.

FIG. 7 is an exemplary block diagram showing another configuration example of the computer system of the embodiment;

FIG. 8 is an exemplary block diagram showing a configuration example of a playback device to which the moving image playback control method according to the embodiment is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... CPU 12 ... Main memory 13 ... DVD drive 14 ... Satellite tuner 15 ... DVD decoder 16 ... VGA controller 17 ... VRAM 151 ... PCI interface 152 ... MPEG2 decoder 153 ... Reproduction control register 154 ... Frame rate control part 155 ... Video port control Department

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Claims (6)

[Claims] 1. A decoding device for decoding encoded image data, comprising: decoding means for decoding the encoded image data in accordance with a specified frame rate and outputting the decoded image data; And a frame rate control means for changing a frame rate of the decoding means in accordance with the reproduction mode. 2. The frame rate control means sets a frame rate of the decoding means to a value higher than a frame rate at the time of normal reproduction when performing fast-forward reproduction. Decoding device. 3. The frame rate control means, when performing slow reproduction, sets a frame rate of the decoding means to a value lower than a frame rate at the time of standard reproduction. Decoding device. 4. A decoding means for decoding encoded image data in accordance with a designated frame rate and outputting the decoded image data; an image memory in which the image data decoded by the decoding means is written; Display control means for reading out image data from the image memory at a refresh rate and displaying the image data on a display device; and changing the frame rate of the decoding means for performing fast forward or slow trick reproduction. An image display system comprising: a reproduction control unit that variably sets a rewriting speed of image data. 5. The reproduction control means according to claim 1, wherein in a pause for stopping reproduction on a specific screen, decoding processing of image data necessary for reproduction of said specific screen is executed once and then the decoding processing is stopped. 5. The image display system according to claim 4, wherein said decoding means is controlled. 6. An image display method for displaying encoded image data, comprising: decoding encoded image data in accordance with a specified frame rate and writing the decoded image data to an image memory. Executing, at a predetermined refresh rate, reading out image data from the image memory and displaying it on a display device, and performing a fast-forward or slow trick reproduction by changing a frame rate of the decoding process. An image display method characterized by variably setting a rewriting speed of image data for the image data.