Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F12/00—Accessing, addressing or allocating within memory systems or architectures
  • G06F12/02—Addressing or allocation; Relocation
  • G06F12/08—Addressing or allocation; Relocation in hierarchically structured memory systems, e.g. virtual memory systems
  • G06F12/0802—Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
  • G06F12/0875—Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches with dedicated cache, e.g. instruction or stack
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F12/00—Accessing, addressing or allocating within memory systems or architectures
  • G06F12/02—Addressing or allocation; Relocation
  • G06F12/08—Addressing or allocation; Relocation in hierarchically structured memory systems, e.g. virtual memory systems
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F12/00—Accessing, addressing or allocating within memory systems or architectures
  • G06F12/02—Addressing or allocation; Relocation
  • G06F12/08—Addressing or allocation; Relocation in hierarchically structured memory systems, e.g. virtual memory systems
  • G06F12/12—Replacement control
  • G06F12/121—Replacement control using replacement algorithms
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
  • G11B27/005—Reproducing at a different information rate from the information rate of recording
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
  • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
  • G11B27/102—Programmed access in sequence to addressed parts of tracks of operating record carriers
  • G11B27/105—Programmed access in sequence to addressed parts of tracks of operating record carriers of operating discs
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
  • H04N21/432—Content retrieval operation from a local storage medium, e.g. hard-disk
  • H04N21/4325—Content retrieval operation from a local storage medium, e.g. hard-disk by playing back content from the storage medium
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
  • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
  • H04N21/845—Structuring of content, e.g. decomposing content into time segments
  • H04N21/8455—Structuring of content, e.g. decomposing content into time segments involving pointers to the content, e.g. pointers to the I-frames of the video stream
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B2220/00—Record carriers by type
  • G11B2220/20—Disc-shaped record carriers

Definitions

• the present invention relates to a device and a method for managing access to a recording medium including a set of digital broadcast data as well as to a system including such a device.
• the invention lies within the context of multimedia.
• a set of digital broadcast data recorded on a direct-access recording medium generally comprises, in addition to the broadcast information, navigation information, making it possible to obtain at least one position from the broadcast information recorded.
• This navigation information makes it possible to identify at least some of the access units forming the broadcast stream and makes it possible to have access individually to each group of access units or to groups of access units on the storage unit in order to read them off.
• These navigation data may be transmitted with the broadcast streams or may have been produced locally in the system by analyzing the broadcast stream.
• the set of digital broadcast data consisting of the broadcast stream and of the navigation information may be a data structure grouping together access units, and allows random access to each access unit or to groups of access units. This structure is called Enriched Multimedia Structure in the case of the present application.
• broadcast information is understood any information intended to be distributed in the course of time from a recording medium, ei- ther directly to a bradcast apparatus (television set, audio system, etc.) or to a transmission channel.
• the broadcast information relates, for example but not exclusively, to video and/or audio signals, but may also relate to signals of another nature.
• object designates an element or a group of elements constituting the broadcast stream.
• Direct-access recording medium designates any information medium allowing direct positioning in read mode, and possibly in write mode, either at any position of the medium or at certain access positions.
• an object could designate an MPEG image, or a group of MPEG images, or a PES packet or an MPEG audio frame, or a set of multiplexed TS packets
• the user wishes to have the possibility of using special presentation modes
• the special pres- entation modes may consist particularly of replay modes in fast forward or fast reverse, slow-motion or pause on images
• the presentation, in the reverse order, of a video sequence encoded to the MPEG format is a difficult problem This is because, according to the MPEG format, the access units constituting the MPEG video stream are coded by reference to the previously transmitted object In fact, the access units are transmitted in the order of their decoding in order to be displayed finally in a different order
• the Enriched Multimedia Structure allows analysis of the broadcast multimedia content which it describes and its processing especially in order to implement special presentation modes
• the access units are read non-continuously - they are not all read
• the present invention therefore proposes a device making it possible to overcome the drawbacks mentioned above, by accessing the stream image by image in order to avoid wasting memory, while optimizing accesses to the recording medium
• the present invention proposes a device for managing access to a recording medium including a set of digital broadcast data, the said set comprising broadcast information and navigation information, characterized in that it includes
• a cache memory for temporarily storing broadcast information read from the recording medium and a data structure including at least data included in the navigation information associated with this broadcast information
• the device is called an Images Cache
• the Images Cache has to serve its clients by making available to them, in memory, the objects which they require
• the Images Cache is therefore responsible for managing the cache memory which is dedicated to it for loading new objects into it from the recording medium and for deleting the obsolete objects from it
• the cache memory is a memory area substantially smaller in size than the size of the recording medium but with an access mode and times which are typical of the memory, in this instance faster than the recording medium.
• the cache memory of the Images Cache is a memory area in which the broadcast information is temporarily stored. This memory area may simply be a partition of the shared memory of the system.
• the broadcast information is preferably digital data coming from a recording medium and intended for a broadcast apparatus or a transmission channel. These broadcast data are generally coded according to a standard such as MPEG-2 and represent access units or groups of access units.
• the management means may simply be software run on the computing unit available in the system and shared. It could also be implemented as hardware by an ASIC cell (an acronym for "Application Specific Integrated Circuit”). This management means decides on the reading of new objects from the recording medium and on the deletion of old objects already present in the memory of the cache, so as to ensure that the objects which are requested from it are present in cache memory.
• the data structure serving for the management of the Image Cache lists at least the identifiers of the broadcast information stored in memory and the parameters specific to its storage (address and size, for example). It makes it possible to know which are the broadcast data present in the cache and to have access to these data in order to read them.
• the data structure re- lating to the broadcast information includes at least data taken from among the type, the time-based reference and the index of the broadcast information.
• the data structure therefore contains data allowing the image cache to manage the images which it contains in an effective way.
• the broadcast information is pref- erably audio and/or video and is intended for trick modes.
• the invention is particularly advantageous in this case by comparison with the known techniques, especially in the case of reading in reverse play mode where the use of circular buffers does not make it possible to extract the access units in a different order from that in which they were input Moreover, the data structure associated with the broadcast information makes it possible to load the desired image
• the management means when it receives a broadcast information demand request, erases broadcast information and its associated data structure, which are present in the cache memory, and reads digital broadcast data from the recording medium on the basis of the associated navigation information or of information present in the associated data structure and of trick modes
• the management means of the cache memory replaces broadcast data by data read from the recording medium corresponding to the object requested by the decoder
• the management means includes a means of weighting broadcast data, the said weighting means weighting the broadcast information on the basis of the information on the data structure associated with the broadcast information to be weighted and/or on the basis of the trick modes
• the weighting means uses a weighting rule such that the broadcast data for which the deletion and the subsequent reloading are only slightly or not at all are erased more rapidly than the others
• the management means can thus optimally determine the obsolescence of the objects present in the cache memory so as to delete them and free the memory spaces which will be able to receive the new objects requested by the client, while guaranteeing that a minimum number of objects will be loaded from the storage unit
• the objects are images
• the image to be deleted from the cache will be determined on the basis of the index of the image requested and of the direction of the presentation In forward play mode, it is the image which has the lowest index which will be deleted from the cache In reverse play mode, it is the im- age which has the largest index which will be deleted
• the deletion of a single object is not sufficient to free enough space in the cache for the new object to be loaded.
• the invention relates to a method of access to a recording medium including a set of digital broadcast data, the said set comprising broadcast information and navigation information, preferably audio and/or video, the said broadcast data possibly being intended for various trick modes.
• - broadcast information present in the cache memory is managed on the basis of the predetermined special presentation mode by erasing broadcast information present in the cache memory, and by reading digital broadcast data from the recording medium so as to write the corresponding broadcast information and its associated data structure into the said cache memory
• the invention also relates to a video-decoding device including a device for management of access to a recording medium as described above
• the invention also relates to a television receiver including a device for managing access to a recording medium as described above
• FIG. 2 represents a diagram of the software model of a part of the device of Figure 1 and implemented for the trick modes
• - Figure 3 represents an example of enriched multimedia structure according to the present embodiment example
• - Figure 4 represents the data structure associated with the broadcast information stored in the cache memory
• FIG. 5 represents a flow chart for loading of a new image into the cache memory, implemented by the management means
• the digital television-receiver decoder of Figure 1 comprises an error-corrector circuit 2 fed by a tuner and an analog/digital converter (which are not represented)
• the corrected digital signal is sent to a transport-stream demultiplexer filter 4
• This demultiplexer filter 4 is connected to a central communications bus 3 of the receiver 1 Its role is to select the transport-stream packets in the incoming new data stream and to send them to the various applications of the receiver To that end, it comprises filters programmed by a microprocessor 11
• the receiver comprises a hard disk 8 linked to the bus 3 by an interface 7, for example an EIDE interface
• a unified memory 6 is shared by all the processes of the receiver This memory comprises, in particular, a memory area allocated to the images cache
• the receiver 1 also comprises audio and video decoders 12 and 13 respectively, connected to a central bus 3
• a second transport-demultiplexer filter 9 is capable of filtering the audio and video components of a recorded transport stream originating from the EIDE interface and of transferring them 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 previously have been taken off
• the navigation information comprises, for each video access unit stored on the disk, and in the order of recording, the image type (I, P or B), its time-based reference, the location of the image in question, and also links and details on the groups of images.
• a navigation information structure example is described in the
• Figure 2 is a diagram of the software model of the receiver 1. It comprises the following elements: - the presentation supervisor (14).
• This software module has the role of the general control of the decoding method. Depending on the method of presentation (forward/reverse, slow/fast), this module specifies which image should be forwarded, decoded or displayed. For example, if the presentation mode is fast reverse reproduction with a normal speed multiplied by X, this module determines which image is to be displayed, the type of image (I, B, P) and, in the case of a P- or B-type image, the other images which should be decoded beforehand. This method is executed recursively. The presentation supervisor accesses the navigation information by way of the navigation-information access manager.
• the presentation supervisor schedules the images cache to supply it with the memory addresses 6 of the video-access units which it wishes to transfer to the MPEG video decoder 13.
• the presentation supervisor needs navigation information on the recorded streams. This information is stored on the hard disk 8.
• the navigation-information Access Manager has the role of collecting the information from the hard disk 8 and of supplying it to the presentation supervisor as and when the latter requests it.
• Each image which is to be decoded (either in order to be displayed or not displayed later on) has to be forwarded to the MPEG video decoder 13 after having been temporarily loaded into memory 6. All the in- formation necessary for accessing the compressed content is supplied in the navigation information.
• the image cache has the role, moreover, of transferring the data of the image identified by the presentation supervisor from the hard disk into the memory 6 if necessary. For each image having to be decoded, the images cache is called on by the presentation supervisor to supply the parameters necessary for transfer of the image from the memory 6 to the decoder 13, and especially the address of the image in memory and its size
• the manager of the image cache 20 implements the flow chart of Figure 5. When it has 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 weights these various parameters in order to determine the image to be deleted. -
• the video decoding supervisor (15)
• the video decoder informs the video decoding supervisor when it receives and identifies a new video access unit.
• the video decoding supervisor has previously received, by way of a queue originating from the presentation supervisor, a complete command scheduling and specifying the decoding and/or the display of this precise image. Based on this command, the video decoding supervisor programs the decoding of this new image detected and, if the image is to be displayed, announces to the video display manager that this image has to be displayed and how this should be done (order of the interlaced frames).
• the MPEG video decoding API Application Programmable Interface
• (16) allows certain types of checks and operations relating to the decoding and any displaying of individual images. In particular, the API can receive the order to decode an individual image and to display it subsequently at a given time and for a certain number of image intervals, or not to display it at all.
• FIG. 3 represents the enriched multimedia structure
• the enriched multimedia structure consists of the digital broadcast stream 60 and of navigation information associated with the various access units 61 , 62, 63, 64 making up this broadcast stream 60
• the digital broadcast stream 60 consists of access units 61 , 62,
• Navigation information is associated with each access unit
• the navigation information 71 and 81 , 72 and 82, 73 and 83, 74 and 84 is associated respectively with the access units 61 , 62, 63, 64 Among this navigation information there is the size of the access unit, the address of the ac- cess unit and other parameters
• the items of navigation information from one access unit to another are also related to each other In fact, it is desirable for certain types of streams, such as MPEG 2 for example, to know what the preceding or following image is
• This information is stored in relationship tables 81 , 82, 83, 84 associated respectively with the access units 61 , 62, 63 and 64 and forming part of their respective enriched multimedia structures
• Figure 4 represents the data structure (50) associated with the broadcast information stored in the cache memory (6)
• Each data structure 50 includes two types of information, on the one hand information 52 on the characteristics specific to the image itself and information 51 on the address of the image in the cache memory and its size, the address and the size being information which is necessary for managing any cache memory
• the information present in the field 52 allows advantageous management of the cache memory
• This information is, for example, the type of the image, the time-based reference of the image and the index of the image
• stage E1 the presentation supervisor makes a request for a new image
• stage E2 runs through its N rows of cache During the test of stage E3, if the required image is in the cache, stage E10 is entered, otherwise stage E4 is entered
• the memory area corresponding to this image is deallocated
• the navigation information of the image required is copied into the data structure of the cache in place of the navigation information of the deleted image This information especially gives the size of the required image
• stage E7 a test is done to discover whether the space deallo- cated in the course of stage 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 stage E8, an additional image is deleted, this image preferably being stored in memory in an area contiguous with the previously deleted image Otherwise, if the deallocated memory space is sufficient to store the required image, stage E9 is entered during which the required image is loaded from the hard disk to the image cache
• stage E10 is entered, in which it is then possible to give the presentation supervisor the details of the coordinates of the image in mem- ory 6 so that it can transfer it to the video decoder
• the supervisor now requests the image B4 (predictive bidirectional image 4) which precedes the bidirectional image 5
• This request from the supervisor consists in forwarding, to the image cache, a reference in memory to the descriptor of the image which it wants.
• the image cache finds, in the descriptor of the image, the index of the desired image which is 1239, and it will be able to compare this index with the indices of the images which are already in the cache, the indices being stored in memory in the data structure.
• the scanning of the data structure therefore gives the result that the image 1239 is not present in the cache. It will therefore be necessary to load the image 1239 into the cache, but in order to do that it is necessary to free some space.
• the weighting means uses the index of the image in order to perform the weighting.
• the image which has the largest index has to be deleted, i.e. here the image with index 1240.
• the data associated with the image of row D in the data structure are the index 1240, the type, bidirectional, the number 5 of the image (the time-based reference) in the GOP, the size of the image (1 1356) and the memory address of the compressed data of the image. Firstly, therefore, the memory area which was used for the image with index 1240 is deallocated, giving the memory manager the address of this area.
• the data associated with cache row D are then updated on the basis of the descriptor of the new image in the navigation information. These data are the index, 1239, the type, B, the time-based reference, 4, the size 1 1356 bytes and a non-meaningful address, for example 0x00000, this address being filled in when the data are written into the cache.
• a memory area has to be reserved in order to be able to store the compressed data of this image in it.
• the memory manager is then called on to allocate 1 1536 bytes. If this allocation is successful, the manager returns the address of the allocated region OxAFOOO ⁇ OO, for example. This address is then written into the data structure to replace the initial, non-meaningful address. If the memory space freed by the deletion of the image from the cache row D, with index 1240, had not been sufficient, it would have been necessary to delete an additional image from the cache in order to free more memory. It would then have been possible to search for the cache row or rows which use memory areas adjacent to the area which has just been deallocated and to delete this row then reattempt an allocation.
• the compressed data of the image are then loaded from the hard disk (recording medium) into the cache memory, in the previously allocated area.
• the position of the first bite of this image in the file is used, which is supplied by the navigation information.
• This position, the size of the image and the address where it is to be loaded are forwarded to the file manager which transfers the data from the hard disk into the memory.
• the files manager which transfers the data from the hard disk into the memory.
• the cache forwards it directly to the MPEG video decoder, and no reading of data on the hard disk is necessary.
• the images are loaded only once into the cache, and performance is therefore enhanced.
• the operations within the video decoding device are paralleled. For example, when the cache is reading broadcast information from the disk, the preceding image is transferred to the MPEG video decoder by using, for example, a transfer of DMA type driven by the processor 11. During this time, the decoder decodes the preceding image and the display displays yet another preceding image.

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• Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Databases & Information Systems (AREA)
• Signal Processing For Digital Recording And Reproducing (AREA)
• Television Signal Processing For Recording (AREA)
• Management Or Editing Of Information On Record Carriers (AREA)

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• 2001
  • 2001-02-12 FR FR0101969A patent/FR2820846B1/fr not_active Expired - Fee Related
• 2002
  • 2002-02-04 KR KR1020037010331A patent/KR100947043B1/ko active IP Right Grant
  • 2002-02-04 MX MXPA03007179A patent/MXPA03007179A/es active IP Right Grant
  • 2002-02-04 JP JP2002564746A patent/JP4325194B2/ja not_active Expired - Fee Related
  • 2002-02-04 EP EP02718104A patent/EP1362290A1/de not_active Withdrawn
  • 2002-02-04 WO PCT/EP2002/001252 patent/WO2002065299A1/en active Application Filing
  • 2002-02-04 CN CN028048865A patent/CN1491387B/zh not_active Expired - Fee Related

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