JP2001326581A - Digital data broadcast reception method and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cache management method that reduces a data reception wait time of a receiver in a data broadcast system adopting a data carousel transmission system. SOLUTION: A cache data management section 2 deletes a module whose transmission time is just around the corner from a cache 3 with priority in comparison with a transmission state of modules having been investigated and stored in advance. That is, the transmission state of modules in carousels is grasped and modules whose acquisition takes much time are left in the cache 3 with priority to reduce the module acquisition time in average.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and apparatus for receiving digital data broadcasting, and more particularly to a method and apparatus for receiving data broadcasting using data carousel transmission in digital television.

[0002]

2. Description of the Related Art In data broadcasting in digital television broadcasting, ISO / IEC 13818-6 DSM is used.
−CC (Digital Storage Media-Command and Control)
Data is transmitted from a sender (such as a broadcasting station) to a receiver according to the standard of data carousel transmission defined in l).

In data carousel transmission, data is transmitted in information transmission units called modules. Then, the data is repeatedly transmitted in units called a data carousel in which several modules are collected. It is called a carousel (carousel) because of its transmission method. Module is MP
It is divided into EG2 private section format and multiplexed in the transport stream. At the receiver, the module can be obtained by demultiplexing the transport stream, extracting the necessary private sections, and combining them.

FIG. 2 is a schematic diagram of data carousel transmission. As a data carousel transmission method, for example, a module w is transmitted as shown in FIG.
, And so on. After all the modules have been sent, the process returns to the first module and starts sending. Since the data broadcast is transmitted many times, necessary data can be obtained even if the user starts viewing the data broadcast program from the middle.

[0005] Generally, the contents of a built-in memory of a receiver are limited, and it is impractical to hold all transmitted data. In such a case, it is common practice to reduce the apparent waiting time by using a technique such as caching of a module obtained once or prefetching data to a cache. At this time, if the cache capacity becomes insufficient, the LRU (Least Recently
The data to be erased is selected from the cache by an algorithm such as sed), and after the data is erased, new data is inserted.

The invention described in Japanese Patent Application Laid-Open No. 2000-36946 proposes a method for reducing the reception waiting time in such data carousel transmission. In the present invention, the transmitting side sets the priority for each of the data to be transmitted, and the receiver obtains the data in an order based on the priority, thereby shortening the data obtaining time. Since data is acquired in the cache in an order based on the priority, the possibility that the data is cached when the next data is requested increases.

[0007]

However, the data carousel transmission method is different from the data communication via a normal network in that the transmission position of the module in the current carousel (in which order and which module is transmitted) ) Has the characteristic that the time to complete module acquisition is affected. So a simple LRU
If data in the cache is managed by an algorithm, a module that takes a long time to obtain may be discarded from the cache.

For example, assume that the module x is currently transmitting in FIG. At this time, for example, the module y transmitted next to x and the module w transmitted immediately before x differ in the time required for acquisition by one round of the carousel transmission cycle. Typically, this time is from a few seconds to possibly more than a few tens of seconds, so the user of the receiver has to wait all the time without doing anything.

In the invention described in Japanese Patent Application Laid-Open No. 2000-36946, data to be stored is determined simply by using only the priority of data. Attempts to receive may result in a very long reception waiting time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in a digital data broadcast receiving method and apparatus in a data broadcasting system using a data carousel transmission method, a cache for reducing the data reception waiting time of a receiving apparatus. Its purpose is to provide a management method and a data prefetching method.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a module for sending data is grasped by grasping a sending status of a module in a carousel, and preferentially storing a module which takes a longer time to obtain a module at the present time in a cache. Reduce waiting time.

According to the present invention, in a data carousel transmission receiving apparatus for digital data broadcasting, the transmission status of a module in a carousel is grasped, and when a module is discarded from a cache, a module which takes a long time to acquire is prioritized. It is characterized by being left in the cache.

The present invention further provides a multiplexing server on the sending side that determines the position of a module in a carousel in a certain order according to the module ID of the data carousel, thereby reducing the time required to obtain the module at the present time. It is characterized by being preferentially left in the cache.

The present invention is characterized in that in a prefetching device in a receiving device for data carousel transmission in digital data broadcasting, a predicted reception time of a module is used when performing prefetching.

Further, the present invention is characterized in that a module is always received and a module after a certain period of time is discarded from the cache.

The present invention is constituted by the following technical means. According to a first technical means of the present invention, in a digital data broadcast receiving method in which one or more modules receive transmission data cyclically transmitted by a data carousel transmission method, a part or all of the one or more modules is provided. Is stored in the cache, and when a new module is received exceeding the cache capacity, the sending status of each module in the carousel is grasped,
At this time, the module which does not take much time to be acquired in the cache is preferentially discarded from the cache,
The newly received module is stored in the cache.

According to a second technical means of the present invention, in the first technical means, the transmission status is grasped in accordance with information indicating the transmission order of each module of the data carousel included in the transmitted transmission data. It is characterized by the following.

The third technical means of the present invention is the first or second technical means.
In the above technical means, the transmission status is grasped by determining the position of the module in the data carousel from the identification numbers in the transmission order for each module.

According to a fourth technical means of the present invention, in a digital data broadcast receiving method in which one or more modules receive cyclically transmitted transmission data by a data carousel transmission method, the transmission data is included in the transmitted transmission data. According to the information indicating the transmission order of each module of the data carousel, the modules are stored in the buffer in order from the module having the closest predicted reception time to the module in the carousel.

According to a fifth technical means of the present invention, in the fourth technical means, when a new module exceeding the buffer capacity is received, the transmission status of each module in the carousel is determined according to the information indicating the transmission order and the like. It is characterized in that a module that does not require a long time to be obtained in the buffer at this time is prioritized and discarded from the buffer, and the newly received module is stored in the buffer.

According to a sixth technical means of the present invention, in a digital data broadcast receiving method in which one or more modules receive transmission data transmitted cyclically by a data carousel transmission method, the modules are always received and received. Modules are accumulated in a buffer, and are discarded from the buffer in order from a module after a certain period that does not exceed the buffer capacity.

According to a seventh aspect of the present invention, there are provided the first to third aspects.
In any one of the technical means, the module stored in the buffer according to any one of the fourth to sixth technical means is stored in the cache.

According to an eighth aspect of the present invention, there are provided the first to seventh aspects.
Means (device) for realizing any one of the technical means
It is characterized by having.

According to a ninth technical means of the present invention, in a digital data broadcast transmission method for transmitting transmission data for cyclically transmitting one or more modules by a data carousel transmission method, a position of each module in the data carousel is determined. In order to accomplish this, the module is characterized in that the module includes an identification number in the order of transmission for each module and transmits the module.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram for explaining a digital data broadcast receiving device having a cache device according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram of data carousel transmission. For example, it is assumed that the carousel is in a transmission state as shown in FIG. 2 as in the example described in the related art. Currently, module x is being transmitted. DS
When the reception of the module x is completed in the M-CC receiving unit 1, one (or more) modules must be deleted from the cache 3 in order to newly add the module x to the cache 3. When this happens, the cache data management unit 2 compares the transmission status of the module, which has been investigated, accumulated, and grasped in advance, and deletes the module with the closest transmission time from the cache 3 with priority. For example, when two modules w and y are included in the cache, the scheduled sending time tw of the module w is compared with the scheduled sending time ty of the module y, and the module y whose sending (estimated) time is closer to the current time is determined. Erase from cache.

Consider a case where a data acquisition request is made to module w after the above operation. At this time, since the module w exists in the cache, the receiver can immediately continue processing using the data. When a data acquisition request is issued to the module y, data is acquired from the carousel because the data does not exist in the cache. The time taken at this time is module y
Is the time until is sent.

In the conventional LRU method, in the above situation, whether the module w or the module y is deleted is determined based on the past module reference history. The operation when the module y is erased from the cache is the same as that of the present invention. However, if the module w is erased from the cache, a case where a data acquisition request is similarly issued to the module w is considered.

At this time, since the data does not exist in the cache, the data is obtained from the carousel. The time required at this time is the time required until the module w is transmitted.
When a data acquisition request is issued to module y, since module y exists in the cache,
The receiver can immediately continue processing such as display using the data.

However, there is a great difference between the time until the module w is transmitted and the time until the module y is transmitted. For example, assuming that the time required for transmitting each module is 2 seconds and the number of modules constituting the carousel is 5 for simplicity, one transmission cycle of the carousel is 10 seconds. At this time, the time required to acquire the module in the above example is as shown in the table below.

[0030]

[Table 1]

In the prior art, which took 0 or 10 seconds, the present invention can be performed in about 0 or 2 seconds. As described above, in the present embodiment, it is possible to finally reduce the average waiting time of the user. The present embodiment can reduce the average waiting time for a carousel having a longer transmission cycle.

(Second Embodiment) The digital data broadcast receiving apparatus according to the first embodiment does not know the time required to acquire a module unless the sending state of the module in the carousel is known in advance. Can't determine what to do. Therefore, in the digital data broadcast receiving apparatus according to the second embodiment of the present invention, the transmission status is grasped from information indicating the transmission order of each module of the data carousel included in the transmitted transmission data. For example, the position of the module in the data carousel may be determined from an identification number (ID) in the transmission data for each module in the transmission order.

(Third Embodiment) To realize the above data broadcast receiving apparatus, a transmitting side (data broadcast transmitting apparatus)
The position of the module in the carousel is determined in a certain order according to the module ID of the data carousel. In other words, the IDs of the modules to be transmitted in the transmission order are included in the modules and transmitted. This allows the data broadcast receiving apparatus to perform cache management for a carousel whose data transmission status is unknown or without grasping the data transmission status of the carousel.

(Fourth Embodiment) In the digital data broadcast receiving apparatuses of the first and second embodiments, the cache is controlled simply by the time necessary for acquiring the module. The digital data broadcast receiving apparatus according to the fourth embodiment of the present invention is configured such that, when the receiving apparatus determines the order of discarding the data in the cache by another means (such as a user's selection history or preference prediction), , The cache management method of the present invention (first and second embodiments) can be applied, and further reduction in waiting time can be expected.

(Fifth Embodiment) As a method of reducing the reception waiting time more aggressively than the data caching described in the first, second, and fourth embodiments, data that will be required in advance is received. There is data prefetching that is acquired when there is room in the processing of the machine (for example, when waiting for user input). Conventional read-ahead devices for networks use a method such as acquiring all links from the current page.To apply this method directly to data carousel transmission, a module that takes a long time to acquire is required. There is a problem trying to get.

FIG. 3 is a block diagram for explaining a digital data broadcast receiving apparatus having a buffer device according to a fifth embodiment of the present invention. In the present embodiment, a buffer 5 is provided in a stage preceding the cache 3 in the data broadcast receiving apparatus described with reference to FIG. 1, and caching is performed on the module that has performed the buffer processing.
Like the cache data management unit 2 in the cache 3, the capacity of the buffer 5 is managed by the buffer data management unit 4. The buffer device as the prefetch device according to the present embodiment, when deciding a module to be prefetched, performs prefetch from a module whose transmission time is close. As a result, the time spent for prefetching can be reduced.

(Sixth Embodiment) As a sixth embodiment of the present invention, the operation of a buffer device suitable for data carousel transmission will be described below with reference to the drawings. FIG. 4 is a diagram for explaining the operation of the buffer system of the digital data broadcast receiving device according to the sixth embodiment of the present invention. The basic configuration of the receiving device of the present embodiment is the same as that of the fifth embodiment. The currently transmitted module is always received, or received by the method according to the fifth embodiment, and the received module is stored in the prefetch buffer 5. Next, when the buffer 5 becomes full, the module with the earliest transmission time is deleted from the buffer 5 so that caching cannot be performed. For example, consider a state in which the reception of the module x is completed as shown in FIG. 4 and the module x is taken into the prefetch buffer. The module with the earliest transmission time (in this case, module v) is erased from the prefetch buffer, and a module x is newly fetched into the prefetch buffer. As a result, a module that requires a certain amount of time for reception always exists in the prefetch buffer, and the reception wait time in the worst case can be reduced.

(Seventh Embodiment) As another example of the fifth embodiment, a currently transmitted module is always received, and the received module is stored in a prefetch buffer.
The buffer data management unit 4 manages the buffer 5 so that the modules are discarded sequentially from the buffer 5 after a certain period (after reception) that does not exceed the buffer capacity.

[0039]

According to the present invention, the transmission status of a module in a carousel is grasped, and the longer the time required to obtain a module at the present time is preferentially left in the cache, the longer the waiting time for data acquisition. Time can be reduced.

According to the present invention, when a module to be prefetched is determined, prefetching is performed starting from the module having the closest sending time, so that the time spent for prefetching can be reduced.

According to the present invention, a module which requires a certain amount of time for reception always exists in the prefetch buffer, and the reception waiting time in the worst case can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a digital data broadcast receiving device having a cache device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of data carousel transmission.

FIG. 3 is a block diagram for explaining a digital data broadcast receiving device having a buffer according to a fifth embodiment of the present invention.

FIG. 4 is a diagram for explaining an operation of a buffer system of a digital data broadcast receiving device having a buffer according to a sixth embodiment of the present invention.

[Description of Signs] 1 ... DSM-CC receiving unit, 2 ... cache data management unit, 3 ... cache, 4 ... buffer data management unit, 5 ...
buffer.

Claims (9)

[Claims] 1. A digital data broadcast receiving method in which one or more modules receive cyclically transmitted transmission data according to a data carousel transmission method, wherein some or all of the one or more modules are cached. When a new module is received exceeding the cache capacity, the sending status of each module in the carousel is grasped, and the module which does not take much time to obtain in the cache at the present time is given priority in the cache. And storing the newly received module in the cache. 2. The digital data broadcast receiving method according to claim 1, wherein the transmission status is grasped in accordance with information indicating a transmission order of each module of a data carousel included in transmitted transmission data. Characteristic digital data broadcast receiving method. 3. The digital data broadcast receiving method according to claim 1, wherein the transmission status is determined by determining a position of the module in the data carousel from an identification number in a transmission order for each module. And a digital data broadcast receiving method. 4. In a digital data broadcast receiving method in which one or more modules receive cyclically transmitted transmission data according to a data carousel transmission method, a transmission order of each module of the data carousel included in the transmitted transmission data. A digital data broadcast receiving method characterized in that modules are stored in a buffer in order from a module having a closest predicted reception time of a module in a carousel in accordance with information indicating the like. 5. The digital data broadcast receiving method according to claim 4, wherein when a new module is received exceeding the buffer capacity, the transmission status of each module in the carousel is grasped according to the information indicating the transmission order and the like. ,
A digital data broadcast receiving method, wherein a module that does not take a long time to be acquired in a buffer at the present time is preferentially discarded from the buffer, and the newly received module is stored in the buffer. 6. A digital data broadcast receiving method in which one or more modules receive transmission data transmitted cyclically by a data carousel transmission method, always receiving modules, storing the received modules in a buffer, A digital data broadcast receiving method, wherein the modules are discarded from the buffer in order from a module for which a certain period has elapsed such that the buffer capacity is not exceeded. 7. The digital data broadcast receiving method according to claim 1, wherein the module stored in the buffer according to any one of claims 4 to 6 is stored in the cache. Digital data broadcast receiving method. 8. A digital data broadcast receiving apparatus comprising means for realizing the digital data broadcast receiving method according to claim 1. Description: 9. A digital data broadcast transmission method for transmitting transmission data for cyclically transmitting one or more modules according to a data carousel transmission method, wherein transmission to each module is performed to determine a position of each module in the data carousel. A digital data broadcast transmission method, characterized in that an identification number in the order is included in the module and transmitted.