KR100947043B1 - Device and method for managing the access to a storage medium, video decoding device and television receiver - Google Patents

Abstract

The present invention relates to a method and a device for managing access to a recording medium comprising a digital broadcast data set, said set comprising broadcast information and navigation information. The device comprises: a cache memory for temporarily storing a data structure comprising broadcast information read from the recording medium and at least data contained in the navigation information associated with the broadcast information; Broadcast information residing in the cache memory for erasing broadcast information and its associated data structure, and for reading digital broadcast data from the recording medium to write corresponding broadcast information and its associated data structure to the cache memory. It is made to include means for managing.

Description

TECHNICAL DEVICE AND METHOD FOR MANAGING THE ACCESS TO A STORAGE MEDIUM, VIDEO DECODING DEVICE AND TELEVISION RECEIVER}

The present invention relates to a device and a method for managing access to a recording medium comprising a digital broadcast data set, and a system comprising such a device.

More specifically, the present invention is in a multimedia environment.

Digital broadcast data sets recorded on direct access recording media (CDs, DVDs, hard disks) generally contain navigation information that allows to obtain at least one position from the recorded broadcast information in addition to the broadcast information. . Such navigation information makes it possible to identify at least some of the access units forming the broadcast stream and to individually access each group of access units or groups of access units on the storage unit for reading. Such navigation data may be transmitted in a broadcast stream or may be generated locally in the system by analyzing the broadcast stream.

The digital broadcast data set consisting of the broadcast stream and the navigation information may be a data structure that groups the access units together, allowing random access to each access unit or groups of access units. This structure is called Enriched Multimedia Structure in the case of the present application.

"Broadcast information" is understood to be any information that is intended to be distributed during the time from a recording medium to a broadcast device (TV set, audio system, etc.) or transmission channel. The broadcast information is related to, for example, but not limited to video and / or audio signals, but may also be related to signals of other characteristics. In a general manner, an "object" represents one element or group of elements making up a broadcast stream. "Direct-access recording medium" refers to any information medium that allows for direct positioning into a read mode, perhaps a write mode, at any location or specific access location of the medium.

In fact, in the case of an audiovisual stream compressed according to the Motion Picture Expert Group (MPEG) standard such as MPEG-2, for example, a hard disk, or hard disk drive (HDD), is used. Packetized elementary streams (PES) packets, or packets of a base-stream type known as transport stream, ie, packets of TS type, are recorded on the packet. In this case, the object may represent an MPEG image, or a group of MPEG images, or a PES packet or MPEG audio frame, or a set of multiplexed TS packets.

Before a broadcast stream is read from the MPEG decoder and transmitted to the MPEG decoder, for example in a system stored in a storage device, which is probably a hard disk in a digital video decoder, the user may have the possibility of using a special presentation mode. want. The special presentation mode (or “trick mode”) may in particular consist of a fast forward or fast rewind, slow motion or pause replay mode for the image.

Conversely, the representation of video sequences encoded in the MPEG format is a difficult problem. The reason is that according to the MPEG format, the access unit constituting the MPEG video stream is coded with reference to the previously transmitted object. In fact, the access unit is transmitted in that decoding order for display at the end in a different order.

The enhanced multimedia architecture allows for the analysis and processing of broadcast multimedia content, in particular describing to implement a special presentation mode.

In accordance with known systems, the proper processing of an EMS (Enriched Multimedia Structure) containing video allows the content to be circulated at an accelerated or slowed rate or appropriately provided round or backwards. Thus, all display modes conventionally available on a video recorder are implemented.

A study of this type of processing shows that access to broadcast data within this trick mode can have the following characteristics:

The access unit is read discontinuously:

     The access unit is not all read

     The access unit is not read in the correct order.

A particular access unit is read several times in a limited period of time, and at the moment the interval is densely located.                 

Conventional methods for accessing and forwarding streams utilize a system for pseudo-continuous reading of storage media, using cyclically managed buffer memory. This method is proved to be inappropriately adapted to the trick mode described above, because:

Successive readings cause more objects to be read than just those needed

The reading direction of the stream is probably not constant, so there is a difficult discontinuity related to the circularity and discontinuous filling of the buffer,

If you want to keep one access unit in the circular buffer longer than the other, it is not possible to leave an access unit which is not used from the buffer but is loaded later.

Therefore, the present invention proposes a device which, while avoiding memory consumption, makes it possible to solve the above-mentioned drawback by accessing a stream per image to optimize access to the recording medium.

To this end, the present invention proposes a device for managing access to a recording medium comprising a digital broadcast data set comprising broadcast information and navigation information,

A cache memory for temporarily storing a data structure comprising broadcast information read from a recording medium and at least data contained in navigation information associated with such broadcast information;                 

Means (20) for managing broadcast information stored in cache memory (6) capable of erasing said broadcast information and its associated data structure according to information contained in different data structures stored in cache memory. do.

This device is called the image cache.

The image cache must help the client by making available to the client the objects it needs in memory. Therefore, the image cache is responsible for managing the cache memory dedicated to the image cache for loading new objects from the recording medium into cache memory and deleting unused objects from the cache memory.

Cache memory is a memory area that is substantially smaller in size than the size of the recording medium, but is faster than the recording medium at this moment through the access mode and number of times that symbolize the memory.

The cache memory of the image cache is a memory area in which broadcast information is temporarily stored. This memory area may simply be a partition of the system's shared memory. The broadcast information is preferably digital data coming from a recording medium and intended for a broadcast device or transmission channel. Typically such broadcast data is coded according to a standard such as MPEG-2 and represents an access unit or group of access units.

The management means may simply be software available to the system and operating a shared computing unit. The management means can also be implemented as hardware by an ASIC cell (Application Specific Integrated Circuit). This management means determines the reading of a new object from the recording medium and the deletion of an existing object already existing in the cache memory to ensure that the object requested from the recording medium exists in the cache memory.

The data structure used for management of the image cache describes at least an identifier of broadcast information stored in the memory, and parameters specific to the storage (eg, address and size). This data structure makes it possible to know which broadcast data is in the cache and to access these data to read the data.

According to one particular characteristic, a data structure related to broadcast information includes at least data taken among types, time-based criteria and indexes of broadcast information. Therefore, the data structure contains data that allows the image cache to manage the containing image in an effective manner.

This parameter allows advantageous management of broadcast data present in the cache. The reason is that, when a new object is needed for decoding, the management means of the cache memory must replace the broadcast data with data read from the recording medium corresponding to the object requested by the decoder.

In one preferred embodiment, the broadcast information is preferably audio and / or video, intended for trick mode.

The present invention is particularly advantageous in this case by comparison with known techniques, especially when the use of the circular buffer reads in the rewind play mode, which does not allow the access units to be extracted in a different order than the input order. Moreover, the data structure associated with the broadcast information makes it possible to load the desired image.

According to another feature, upon receiving the broadcast information request request, the management means erases the broadcast information present in the cache memory and the data structure associated with it, and based on the navigation mode or the information and trick mode present in the associated data structure, Read digital broadcast data from a recording medium.

Thus, when a new object is needed for decoding, the management means of the cache memory replaces the broadcast data with data read from the recording medium corresponding to the object requested by the decoder.

According to a first embodiment, the management means comprises broadcast data weighting means, which weights the broadcast information based on information in a data structure and / or trick mode associated with the broadcast information to be weighted.

The weighting means uses weighting rules in which broadcast data with little or no deletion and subsequent reloading is erased faster than others.

Thus, management means can selectively determine obsolescence of objects present in cache memory to delete the objects and free up memory space to receive new objects requested by the client, while minimizing It can be guaranteed to be loaded from the storage unit.

For example, in the case of an MPEG-2 video stream, the object is an image and the image to be deleted from the cache will be determined based on the index of the requested image and the direction of the representation. In the forward play mode, the image with the lowest index will be deleted from the cache. In reverse play mode, the image with the largest index will be deleted.

However, due to fragmentation of cache memory, it will occur that the deletion of a single object is not sufficient to free enough space in the cache for a new object to be loaded.

At that time, it would be advantageous to continuously delete broadcast data stored at an address adjacent to previously erased broadcast data from the cache memory. The second iteration of emptying this memory makes it possible to ensure that new deletion of such objects actually increases the size of the free monolithic memory area. Then, it can be evaluated that the smallest object is deleted from the cache to free the required memory space.

This presentation mode is in fact used in many video systems today.

Accordingly, the present invention relates to a method of accessing a recording medium comprising a digital broadcast data set, said set comprising broadcast information and navigation information, preferably audio and / or video, said broadcast data probably being various tricks. Intended for the mode.

According to the invention, the method is

Temporarily storing broadcast information read from the recording medium (8), and a data structure (50) associated with the broadcast information in a cache memory (6);

-Erasing the broadcast information and its associated data structure according to the information contained in the different data structures 50 stored in the cache memory 6.

The invention also relates to a video-decoding device comprising a device for managing access to a recording medium described above.

The invention also relates to a television receiver comprising a device for managing access to a recording medium described above.

The advantages previously mentioned for the device apply equally to the method, the video-decoding device and the television receiver according to the invention.

The invention will be better understood, and other features and advantages will become apparent from reading the description of the following illustrative examples, given by way of example and not by way of limitation, with reference to the accompanying drawings, in which: FIG.

1 shows a television decoder.

FIG. 2 illustrates a software model that is part of the device of FIG. 1 and is implemented for trick mode. FIG.

3 illustrates an example of an enhanced multimedia structure according to the present illustrative example.

4 illustrates a data structure associated with broadcast information stored in a cache memory.

5 is a flow chart illustrating loading of a new image into cache memory, implemented by management means.

The digital television-receiver decoder of FIG. 1 includes an error corrector circuit 2 supplied by a tuner and an analog / digital converter (not shown). The corrected digital signal is sent to the transmit-stream demultiplexer filter 4. This demultiplexer filter 4 is connected to the central communication bus 3 of the receiver 1. Its role is to select transport-stream packets from incoming new data streams and send them to various applications at the receiver. For this reason, the filter comprises a filter programmed by the microprocessor 11.

To record the MPEG stream, the receiver comprises a hard disk 8 linked to the bus 3 via an interface 7, for example an EIDE interface. The integrated memory 6 is shared by all processes of the receiver. Such memory includes especially the memory area allocated to the image cache.

To decode the stream, the receiver 1 also comprises an audio and video decoder 12 and 13 connected to the central bus 3 respectively. The second transmit-demultiplexer filter 9 may filter the audio and video components of the recorded transport stream coming from the EIDE interface and may transmit the components to the memory 6 or to the decoders 12 and 13. Depending on the recording mode, the layer of the transport stream may or may not have been previously taken off.

For this description, the navigation information includes the image type (I, P or B), the time-based criterion, the location of the present image, for each video access unit stored on the disc, and in recording order. Includes links to groups of, and details.

An example of a navigation information structure is a method and device for decoding a digital video stream in a digital video system using "dummy header insertion" of European Patent Application No. (00400941.1), filed by Thomson Multimedia on April 5, 2000. ".

2 is a diagram of a software model of the receiver 1. This includes the next element, the expression supervisor 14.

This software module serves as a general control of the decoding method. Depending on the representation method (rewind / rewind, slow / fast), this module specifies which image should be sent, decoded or displayed.

For example, if the presentation mode is fast rewind playback at normal speed multiplied by X, the module determines which image should be displayed, i.e. the type of image (I, B, P), In case, it determines the other image to be decoded in advance. This method is performed repeatedly.

The presentation supervisor accesses navigation information by the navigation-information access manager.

Based on the iterative decoding algorithm, the representation supervisor schedules the image cache to supply the image cache with the memory 6 address of the video access unit that it wishes to transmit to the MPEG video decoder 13.

Navigation-information access manager 19.

The presentation supervisor needs navigation information on the recorded stream. This information is stored in the hard disk 8. The navigation-information access manager collects information from the hard disk 8 and serves to supply the information to the expression supervisor when the expression manager requests the information.

Image-Cache Manager 20.

Each image to be decoded (in order not to be displayed or later displayed) must be temporarily loaded into the memory 6 and then sent to the MPEG video decoder 13. All the information needed to access the compressed content is supplied to the navigational information. Moreover, the image cache serves to transmit the data of the image identified by the expression supervisor from the hard disk to the memory 6 as necessary. For each image to be decoded, the expression supervisor asks the image cache to supply the parameters necessary for transmitting the image from the memory 6 to the decoder 13, and in particular the address and size of the image in the memory.

Image cache manager 20 implements the flowchart of FIG. 5. When the image cache manager 20 needs to erase data from the cache memory 6 in order to free memory space for storing a new image, it takes into account the parameters of the associated data structure as well as the current special presentation mode requested and is to be deleted. These various parameters are weighted to determine the image.

Video decoding supervisor (15)

The video decoder notifies the video decoding supervisor when to receive and identify a new video access unit. The video decoding supervisor has previously received complete instructions for scheduling and specifying the decoding and / or display of such precise images by a queue from the presentation supervisor. Based on this command, the video decoding supervisor programs the decoding of this new image detected and, when the image is displayed, tells the video display manager how this image should be displayed and how it should be done (the order of the interlaced frames). Inform.

The MPEG Video Decoding Application Programmable Interface (API) 16 allows certain types of inspection and operation related to the decoding and arbitrary display of individual images. In particular, the API may receive a command to decode an individual image and subsequently display the image for a certain number of image intervals at a given time, or to not display the image.

The presentation manager requests the delivery of a new image when needed, and waits until this delivery ends before sending another request. Transmission completion is signaled to the presentation manager by the manager of the image cache.

3 illustrates an enhanced multimedia structure. The enhanced multimedia structure consists of a digital broadcast stream 60 and navigational information associated with the various access units 61, 62, 63, 64 constituting the broadcast stream 60.

The digital broadcast stream 60 consists of access units 61, 62, 63, 64. Navigational information is associated with each access unit. Navigational information 71 and 81, 72 and 82, 73 and 83, 74 and 84 are associated with access units 61, 62, 63 and 64, respectively. Among such navigation information, there are the size of the access unit, the address of the access unit and other parameters. Items of navigational information from one access unit to another are also related to each other. In fact, it is desirable for certain types of streams, for example MPEG 2, to know what the previous or next image is. This information is stored in relationship tables 81, 82, 83, 84 associated with the access units 61, 62, 63, 64, respectively, and forming part of each enhanced multimedia structure.

4 shows a data structure 50 associated with broadcast information stored in cache memory 6.

Each data structure 50 includes two types of information, on the one hand, information 52 about characteristics specific to its image, and information 51 about the address and size of the image in cache memory. , Address and size are information needed to manage any cache memory.

The information present in field 52 allows advantageous management of cache memory. This information is for example the type of image, the time-based criterion of the image and the index of the image.                 

In FIG. 5, the representation supervisor in step E1 requests for a new image. The image cache then passes through N rows of the cache at step E2. During the test of step E3, if the required image is in the cache, go to step E10, otherwise proceed to step E4.

In step E4, it is determined whether the image from the cache should be deleted in order to place the new image required in the cache. The selection of the image to be deleted takes into account the navigation information associated with the image, the trick mode and the data structure associated with the image. This criterion is weighted to define the image to be erased.

In step E5, when the image to be deleted is determined, the memory area corresponding to this image is deallocated.

In step E6, the navigation information of the required image is copied to the data structure of the cache instead of the navigation information of the deleted image. In particular, this information provides the required image size.

In step E7 a test is made to see if the space deallocated during step E5 is sufficient to store the required image. If the size of the deallocated space is smaller than the size of the required image, then at step E8, the additional image is deleted, which is preferably stored in the memory of the area adjacent to the previously deleted image.

Otherwise, if the deallocated memory space is sufficient to store the required image, go to step E9, during which the required image is loaded from the hard disk into the image cache.

Next, proceed to step E10, where the details of the coordinates of the image in the memory 6 are provided to the representation supervisor so that the representation supervisor can send the details of the coordinates to the video decoder. It is possible.

An example of routing of data in the television decoder of FIG. 1 will now be described, in which case the reverse play mode is taken as a special presentation mode.

Assume that the size of the cache is fixed at 4, and the cache contains four images:

Row A, image with index value 1234, internal image 0,

Row B, image with index value 1235, predictive image 3,

Row C, image with index value 1238, predictive image 6,

Row D, image with index value 1240, predictive bidirectional image 5.

Image index 1240 is the final image used and requested by the supervisor of trick mode 14.

The supervisor now requests the image B4 (predictive bidirectional image 4) before the bidirectional image 5. This request from the supervisor consists in sending a reference in memory to a descriptor of the desired image to the image cache. This image cache may find the index of the desired image, which is 1239 in the descriptor of the image, and compare this index with the indices of the image already present in the cache, which are stored in memory in the data structure. Therefore, scanning of the data structure provides the result that the image 1239 is not in the cache. Therefore, it is necessary to load the image 1239 into the cache, but it needs to free some space to do this.

As an example, suppose a weighting means uses an index of an image to perform weighting. In reverse play mode, the image with the largest index must be deleted, i.e., the image with index 1240 is deleted here.

The data associated with the image in row D in the data structure is index 1240, type, bidirectional, number of images (time-based reference) in the GOP (5), image size (11356) and compressed data of the image. It is a memory address. Therefore, first, the memory area used for the image with index 1240 is deallocated, providing the address of this area to the memory manager.

The data associated with cache row D is then updated based on the descriptor of the new image in the navigation information. This data is an index 1239, type (B), time-based criterion (4), size (11356 bytes), and a meaningless address, for example 0x00000, which is filled when the data is written to the cache. .

The memory area must be reserved in order to be able to store the compressed data of this image. The memory manager is then asked to allocate 11536 bytes. If this assignment is successful, the administrator returns, for example, to the address 0xAF000800 of the allocated area. This address is then written to the data structure to replace the initial meaningless address.                 

If the memory space emptied by the deletion of the image from cache row D with index 1240 was not sufficient, it would be necessary to delete additional images from the cache to free more memory. Then, it will be possible to search for a cache row or rows using a memory area adjacent to the area that has just been deallocated, delete this row, and retry the allocation.

The compressed data of the image is then loaded from the hard disk (recording medium) into the cache memory in the previously allocated area. To access the image in the digital file during reading, the location of the first byte of this image in the file is used, which is supplied by the navigation information. This location, the size of the image, and the address to be loaded are sent to a file manager that sends data from the hard disk to the memory. Once this transmission is complete, the digital data can be retransmitted from the cache memory to the MPEG video decoder.

The image cache then prepares to process the new request. This request is a request for a logically predictive image 3, i.e., an image having an index 1235 present in cache row B. Since such an image already exists in the cache, the cache sends the image directly to the MPEG video decoder and does not need to read the data on the hard disk.

Images are loaded into the cache only once, which improves performance. Operation in the video decoding device is parallel. For example, when the cache reads broadcast information from the disc, the previous image is transmitted to the MPEG video decoder, for example by using a DMA type of transmission driven by the processor 11. In the meantime, the decoder decodes the previous image, and the display also displays other previous images.

As mentioned above, the present invention is used in devices and methods for managing access to recording media including digital broadcast data sets, and systems including such devices.

Claims (12)

delete delete delete A device for managing access to a recording medium (8) comprising a set of digital broadcast data (60) comprising broadcast information and navigation information, comprising: A cache memory (6) for temporarily storing a data structure (50) comprising at least broadcast information read from said recording medium (8) and data contained in said navigation information associated with said broadcast information; Means (20) for managing broadcast information residing in the cache memory (6) capable of erasing the broadcast information and its associated data structure according to information contained in different data structures stored in the cache memory. Including, The management means, upon receiving a broadcast information request request, erases (E5) broadcast information and its associated data structure 50 present in the cache memory, and associates it with the associated navigation information or associated data structure 50. And read digital broadcast data from said recording medium based on information and a trick mode. A device for managing access to a recording medium (8) comprising a set of digital broadcast data (60) comprising broadcast information and navigation information, comprising: A cache memory (6) for temporarily storing a data structure (50) comprising at least broadcast information read from said recording medium (8) and data contained in said navigation information associated with said broadcast information; Means (20) for managing broadcast information residing in the cache memory (6) capable of erasing the broadcast information and its associated data structure according to information contained in different data structures stored in the cache memory. Including, The management means comprises weighting means for broadcasting data, wherein the weighting means weights the broadcast information based on information on a data structure associated with the broadcast information to be weighted or based on a trick mode, Device for managing access to recording media. A device for managing access to a recording medium (8) comprising a set of digital broadcast data (60) comprising broadcast information and navigation information, comprising: A cache memory (6) for temporarily storing a data structure (50) comprising at least broadcast information read from said recording medium (8) and data contained in said navigation information associated with said broadcast information; Means (20) for managing broadcast information residing in the cache memory (6) capable of erasing the broadcast information and its associated data structure according to information contained in different data structures stored in the cache memory. Including, The management means manages access to a recording medium, characterized in that it can repeatedly erase (E7, E8) broadcast information stored in a memory in an adjacent area of the cache memory whenever there is not enough free space. Device for delete A method of accessing a recording medium comprising a digital broadcast data set, wherein the set includes broadcast information and navigation information, and the broadcast data is probably intended for various trick modes. Temporarily storing the broadcast information read from the recording medium (8) and a data structure (50) associated with the broadcast information in a cache memory (6); Erasing the broadcast information and its associated data structure according to information contained in different data structures 50 stored in the cache memory 6. Including, The broadcast information present in the cache memory 6 and its associated data structure are erased (E5), and the digital broadcast data is recorded based on the associated navigation information or information or trick mode present in the associated data structure 50. A method of accessing a recording medium, characterized in that it is read from the medium (8). 9. A method according to claim 8, characterized in that the broadcast information is weighted based on information on the data structure (50) associated with the broadcast information to be weighted or based on the trick mode. A device for managing access to a recording medium (8) comprising a set of digital broadcast data (60) comprising broadcast information and navigation information, comprising: A cache memory (6) for temporarily storing a data structure (50) comprising at least broadcast information read from said recording medium (8) and data contained in said navigation information associated with said broadcast information; Means (20) for managing broadcast information residing in the cache memory (6) capable of erasing the broadcast information and its associated data structure according to information contained in different data structures stored in the cache memory. Including, The management means comprises weighting means for broadcasting data, wherein the weighting means weights the broadcast information based on information on a data structure associated with the broadcast information to be weighted and based on a trick mode. Device for managing access to the recording medium. A method of accessing a recording medium comprising a digital broadcast data set, wherein the set includes broadcast information and navigation information, and the broadcast data is probably intended for various trick modes. Temporarily storing the broadcast information read from the recording medium (8) and a data structure (50) associated with the broadcast information in a cache memory (6); Erasing the broadcast information and its associated data structure according to information contained in different data structures 50 stored in the cache memory 6. Including, The broadcast information present in the cache memory 6 and its associated data structure is erased (E5), and the digital broadcast data is based on associated navigation information or information present in the associated data structure 50 and based on a trick mode. Characterized in that it is read from the recording medium (8). 9. A method according to claim 8, characterized in that the broadcast information is weighted based on the information on the data structure (50) associated with the broadcast information to be weighted and based on the trick mode.

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