JP2005044218A - Image display memory management device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image displaying memory management device capable securing a maximum allocatable memory by a request from an application, returning only a necessary requirement to the application from a memory block, and dividing and managing the rest as an available space. <P>SOLUTION: When a memory request is made from the application 103, a requirement space is allocated from the available space 301, while a memory area management structure 402 associated with the allocated area (an area 401 in use) is newly created and managed as a list structure connecting the memory area management structure 404 of the available space 403 to an address sequence. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display memory management device that efficiently uses a memory on a device (OS / driver) that is restricted in terms of a unit of capacity to be secured even if there is a mechanism for securing a dynamic memory. The present invention relates to an image display memory management device used for decompressing and displaying a compressed image in software for displaying a data broadcast in a digital television broadcast.

  FIG. 2 is a block diagram showing a configuration of a general digital television receiver. Television broadcast waves enter from the antenna 201, are tuned by the tuner 202, and demodulated by the demodulator 203. The demodulated signal is divided into video / audio data and other data by the TS decoder 204, and the video / audio data is sent to the video decoder 206 and the audio decoder 205, respectively, and processed.

  As data other than video / audio, there is data for data broadcasting, which is processed by display software called a browser, combined with video data as necessary, and displayed on the screen.

  Data handled by the browser includes characters, graphics, bitmap images, and the like. Bitmap images are sent after being compressed by a standard method such as JPEG in order to reduce the amount of transmission data. The browser decompresses this image data, converts it into a data format corresponding to the hardware, and displays it.

  FIG. 9 shows memory management when general-purpose memory management is used. In the physical address space 901, the reserved memory is discontinuously mapped 902 in the physical address space 901, and these memories are mapped 904 in the continuous logical address space 903 in the logical address space 903. In other words, when general-purpose memory management secures an image display memory in a data format suitable for the hardware, it is not always assigned to physically continuous addresses, and address conversion and memory copying occur during memory transfer for display. In addition, the display speed is reduced.

FIG. 10 shows memory management when memory transfer is performed during drawing. In the memory transfer at the time of drawing, in order to avoid the above problem, special memory management for securing the memory in the image display memory 1003 at physically continuous addresses 1004 is necessary. Under the memory management, the memory is originally secured in a fixed-length unit called a page, and this may be further managed in a power-of-two unit and assigned to a higher system (see, for example, Patent Document 1). .
Japanese Utility Model Publication No. 5-43246

  However, it is normal that there is a difference between the amount of memory actually required in the host system, whether it is a page unit or a power of two unit. This wasteful area will cause the memory efficiency of the system to decrease.

  In response to a request from the application, the maximum memory that can be allocated is secured, only the necessary amount is returned to the application from the memory block, and the remaining is divided and managed as a free area.

  According to the present invention, memory management by simple list processing is possible, and efficient high-speed image display memory management can be performed with a small number of additional programs without significantly changing the structure of an existing application.

  In addition, processing performed in general memory management, such as defragmentation and garbage collection, has been omitted. This is because the purpose of use is for data broadcast display, and almost all of the image memory is changed due to screen transitions. Because it is refreshed (released), no effect can be expected even if it is introduced.

  FIG. 1 shows a schematic diagram of the present invention. The present invention relates to a memory management device 101 for dynamically securing a memory, a memory management device 102 according to the present invention, an application 103 for securing an image display memory, and a memory secured by the memory management device 101. The block 104, a used area 105 that is a memory actually used by the application 103, a free area 106 in the memory block 104, a video RAM 107, and a display device 108.

  FIG. 3 shows an initial state of memory management. The memory management device 102 creates a list-structured memory area management structure 302 at the time of memory allocation, and associates the free area 301 with the memory block management structure 302 with the entire fixed-length memory block as the free area 301. The memory area management structure 302 includes a start address, a size, and a flag indicating free / busy. Usually, since the number of fixed-length memory blocks that can be secured is limited to a finite number, parameters (pointer, size, etc.) for memory block management can be handled as a fixed-length array. In addition, since the management in the memory block is also managed as a list structure connected in the order of addresses, at least a pointer to the start address, the capacity of the memory block, and a use flag (free or in use) are taken. ) Only information can be managed.

  FIG. 4 shows a memory management state of memory management. When there is a memory request from the application 103, a necessary amount of area is allocated from the free area 301. Then, a memory area management structure 402 associated with the allocated area (in-use area 401) is newly created as a list structure in which the memory area management structure 404 of the free area 403 and the address order are connected. The memory securing process will be described in detail later with reference to FIG.

  FIG. 5 shows the memory release state of memory management. When the used area becomes unnecessary in the application 103, the flag of the memory area management structure 503 corresponding to the area 504 to be released is cleared (the flag is set to “free”). Also, as shown in FIG. 6, when there are free areas 502 before and after the area 504 to be released, these areas are integrated into a free area 602. The memory release process will be described in detail later with reference to FIG.

  Next, the memory securing process will be described with reference to the flowchart shown in FIG. Here, if the requested memory amount is larger than the size of the fixed-length memory block, an error is determined (No in S701).

  If the requested memory amount is less than or equal to the size of the fixed-sized memory block (Yes in S701) and there is no fixed-sized memory block already secured (No in S702), a new fixed-sized memory block is secured as a free area. Management is performed (Yes in S706, S707), a necessary amount is allocated from the free area, and a corresponding memory area management structure is created (S704). If the reserved free area is larger than the requested memory (Yes in S705), the remaining area is set as a free area, and a memory area management structure corresponding to the allocated area is newly arranged in the order of addresses. A body is created (S708).

  If the requested memory amount is less than or equal to the size of the fixed-sized memory block (Yes in S701) and there are already secured memory blocks (Yes in S702), the free space of each memory block is searched to find a free space larger than the requested memory. If there is no area (“not found” in S703), a memory block in which the requested memory is newly entered is secured and managed as a free area (Yes in S706, S707), and a necessary amount is allocated from the free area and a response is made. A memory area management structure is created (S704). If the reserved free area is larger than the requested memory (Yes in S705), the remaining area is set as a free area, and a memory area management structure corresponding to the allocated area is newly arranged in the order of addresses. A body is created (S708).

  On the other hand, if there is a free area in which the requested memory is stored ("found" in S703), the free area closest to the requested memory capacity is allocated among them, and the memory area management structure associated with the free area is split. The above processing (S705, S705) is performed. As an allocation method, for example, during free space search of each memory block, if there is a free space that can contain the requested memory, it is determined as an allocation candidate, and the free space is compared while looping, and the smaller one is selected as a candidate. . If memory is allocated and there is not enough free space, a fixed length memory is newly secured and a memory block management structure is created. If a new fixed-length memory cannot be secured, an error is assumed that the memory cannot be secured (No in S706).

  Next, the memory release process will be described with reference to the flowchart shown in FIG. First, a memory area management structure is searched, and a memory block to which a memory to be released belongs is searched (S801). This can be easily determined because the memory area management structures are arranged in the order of addresses.

  When the memory area management structure of the memory to be released is found (“found” in S801), this area is set as a free area, and the flag of the memory area management structure is set to a value indicating the free area (S802). ). Then, the vacant states of adjacent memory blocks before and after are checked, and if they are vacant areas, these areas are integrated and managed (S803 to S806).

  If all the memory secured in the fixed-length block is an empty memory, it is released (Yes in S807), and the memory area management structure is initialized (S808).

  In this embodiment, the memory area management structure has a list structure. At this time, however, care must be taken not to dynamically secure the memory area management structure itself with this mechanism. This is because an infinite cycle of creating a memory area management structure to secure the memory area management structure occurs. One way to avoid this is to attach a memory area management structure to the head of the memory block to be secured.

  The image display memory management device according to the present invention secures the maximum allocatable memory in response to a request from the application, returns only the necessary amount from the memory block to the application, and divides the remaining as a free area for management. Therefore, it can be applied to all television broadcast receivers.

The figure which shows the outline | summary of this invention Block diagram showing the structure of a digital TV The figure which shows the initial state of the memory management which concerns on embodiment of this invention The figure which shows the memory allocation state of the memory management based on the embodiment The figure which shows the memory release state of the memory management which concerns on the same embodiment The free area integration status at the time of memory release for memory management according to the same embodiment A flowchart showing a memory securing process according to the embodiment Flow chart showing memory release processing according to the embodiment Diagram showing memory management status when using conventional general-purpose memory management The figure which shows the memory management state when performing the memory transfer at the time of conventional drawing

Explanation of symbols

101, 102 Memory management device 103 Application 104 Memory block 105, 401 Used area 106, 403, 502, 602 Free area 107 Video RAM
108 display device 301 fixed-length memory block 302, 402, 404, 501, 503, 601 memory area management structure 504 freed area

Claims (2)

When securing and managing the image display memory in a continuous area of physical addresses that can be transferred at high speed, the allocated memory block is divided into multiple areas for efficient use with simple logic and minimal management information Memory management device. A memory management device for managing memory in page (block) units, power-of-two units, etc., and dividing the reserved memory blocks into a plurality of areas for efficient use with simple logic.

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