IE20070242A1 - Presentation storage device - Google Patents

Abstract

A portable device (20) comprises a non-volatile memory (25) for storing compressed image file data and a data interface (26, 27) for transferring image file data to the device. In one embodiment a decoder (e.g. JPEC decoder) decodes compressed image file data into a frame buffer. There are at least two frame buffers which allow the decoding of a selected compressed image file into one of the frame buffers while generating a video output by reading data from another one of the frame buffers. In another embodiment, image data is stored in the non-volatile memory (25) in decoded form and the memory (25) is directly used as a frame buffer. The decoder can be switched off when not required to conserve the limited power supply of the device.

Description

. PRESENTATION STORAGE DEVICE FIELD OF THE INVENTION This invention relates to a portable device which can be used to store images for presentation.

BACKGROUND TO THE INVENTION A popular way to make visual material for presentation to an audience is to prepare a set of electronic slides on a personal computer (PC) using a software package such as Microsoft PowerPoint™. The set of slides can be arranged in a desired presentation sequence for display as a slide show.

When the presenter delivers their presentation to an audience, there are several options for accessing the set of slides that they previously created. Firstly, the presenter can store the set of slides on a portable computer, such as a laptop or handheld computer, and take the portable computer to the presentation. During the presentation, the computer executes the same presentation software that was used to create the slide show, and plays the slides under the presenter’s control. The portable computer is connected to a video projector using a VGA (Video Graphics Array) lead. This has disadvantages of requiring the presenter to carry the portable computer. It also has the disadvantage of requiring the presenter to ensure the battery of the portable computer is suitably charged to last the duration of the presentation or, alternatively, requires the presenter to carry a mains adaptor and power lead to connect the portable computer to a mains supply during the presentation.

Secondly, the presenter can transfer the set of slides onto a storage medium such as an optical disc (e.g. a recordable CD) or solid state memory chip (e.g. a USB pen drive). The user takes the storage medium to the presentation and, in a similar manner to the first method, uses a computer at the presentation to execute presentation software, l’his has disadvantages of requiring the presentation organiser to supply a computer and requires the presenter to use an unfamiliar computer at the presentation. There is also a risk that the version of presentation software used to create the slide show is * /¼ f : ure *°70242 computer. There is also a security risk in that a copy of the presentation may be created and reside on the unfamiliar computer.

Thirdly, the presenter can store the set of slides on a network server and can remotely access the slide show from a computer at the presentation. This has disadvantages of requiring the organiser to supply a computer, it requires the computer to support a connection to the server where the slides have been stored, and requires the presenter to enter passwords on a machine which may not be secure. Again there is a security risk in that a copy of the presentation may be created and reside on the unfamiliar computer.

WO 02/01545 Al describes an electronic presentation system using a portable device in place of a personal computer. Various embodiments are described, one of which requires the device to execute presentation application software such as PowerPoint™. Other embodiments describe a device in the form of a video recorder or camera which can capture, and store, a presentation.

Portable media players are known. These typically comprise a high-capacity hard disk store for storing a mix of media content, such as audio, video and still images. The player has a display and a processor to decode and output stored media content. These players arc typically high cost devices, with substantial power consumption requirements, and are usually intended for personal use, or connection to a domestic television set or hi-fi system.

There is a need for a portable device for storing presentations which is low cost, low power and of small physical size, which minimises or overcomes the various disadvantages outlined above.

In particular, the present invention seeks to provide a simple, portable, presentation device which can be manufactured at low cost but which does not suffer from excessive processing delays when displaying images. £θ7Ο?42 SUMMARY OF THE INVENTION A first aspect of the present invention provides a portable device for storing images for presentation, comprising: a non-volatile memory for storing compressed image file data; a data interface for transferring image file data to the storage device from an external device; a video output interface; a decoder for decoding compressed image file data; at least two frame buffers for storing decoded data; a video controller for generating a video output signal for display by reading data from one of the frame buffers; and a controller arranged to cause the decoder to decode a selected compressed image file and store the decoded data in one of the frame buffers while causing the video controller to generate a video output by reading data from another one of the frame buffers.

The portable device has advantages over the conventional ways of transporting a set of slides to a presentation that are described in the background to the invention. It does not require a portable computer to execute presentation software, it avoids the presenter having to use an unfamiliar computer at the presentation, and it avoids security risks of the presenter having to enter passwords in a computer which is possibly insecure. The use of two frame buffers allows the portable device to use a decoder with a modest performance (i.e. relatively low processing speed) without having a detrimental effect on the presentation. A presenter will be able to step through the presentation without experiencing long pauses while the decoder decodes the next image into the frame buffer. The use of a decoder with modest performance has the advantage of reducing the power requirements of the device, which in turn allows the device to have a longer operating duration for a given capacity of the power source, or to use a power source having a smaller capacity to achieve a given operating duration. All of these factors help to reduce the cost of the device, and to make the device physically smaller and hence more portable.

Preferably, there are least three frame buffers which can respectively store the current image in the presentation sequence, the next image in the presentation sequence * ο 7 Ο 2 4 2 and the previous image in the presentation sequence. This allows the benefits of the invention to be enjoyed, irrespective of whether the presenter steps forwards or backwards through the set of images forming the presentation.

Preferably, the frame buffers comprise storage areas within a common memory device. The common memory device can be a volatile memory which forms part of an FPGA or ASIC which implements the decoder, or the frame buffers can comprise storage areas within the non-volatile memory. The use of the non-volatile memory for the frame buffers further reduces the cost and size of the portable device.

Preferably, the controller is arranged lo turn off the decoder for periods between occasions when it is used to decode compressed image file data. This can have a significant power saving which allows the device to have a longer operating duration for a given capacity of the power source or to use a lower capacity power source to achieve a given operating duration.

A second aspect of the present invention provides a portable device for storing images for presentation, comprising: a non-volatile memory for storing image file data in decoded form; a data interface for transferring the decoded image file data to the memory from an external device; a video output interface for generating a video output signal; and a controller arranged to cause the video output interface to generate a video output signal by reading the decoded image data directly from the memory.

This aspect of the invention has the same advantages over the conventional ways of transporting a set of slides to a presentation as the first aspect of the invention. In essence, the non-volatile memory is used as a frame buffer. Decoded image data is store in the memory in readiness for being read for display. This has an advantage of minimising the amount of processing capability required in the device. There is no need for a decoder, and the device will not suffer from delays between displaying images, since image data is stored in the exact form in which it needs to be output. Preferably, the decoded, data for an image is stored contiguously within the memory, and consecutive images in a presentation sequence are stored contiguously within the IEO 7 Ο 2 4 2 memory. Software executed by the portable device and/or an external device (e.g. a PC) causes the decoded image data to be stored in the contiguous format.

Preferably, the video output interface is as a Video Graphics Array (VGA) interface, with a VGA connector, such as is found on all projectors likely to be used at a presentation. The video output interface can be Digital Visual Interface (DVI) or another format.

It will be appreciated that both aspects of the invention address a single technical problem of providing a simple, portable, presentation device which minimises the delays experienced by a user when displaying images in a presentation.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 schematically shows a first embodiment of the portable device; Figure 2 shows use of the device at a presentation; Figure 3 shows multiple frame buffers within a memory; Figure 4 shows the use of a set of frame buffers over a period of time; Figure 5 schematically shows a second embodiment of the portable device for storing images; Figure 6 schematically shows a third embodiment of the portable device which can store and decode video content.

DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 schematically shows a first embodiment of a portable storage device. A solidstate non-volatile memory store 25 (e.g. Flash memory) is provided. The memory has a size which is sufficient to store a set of compressed image files for a typical presentation. The memory is connected to a USB interface 26 having a USB port 27 for connection to an external device. Processing functions are provided by an ASIC or a FPGA 30. The main processing functions arc an image decoding/decompression function (JPEG decoder) 32 and a video output controller (VGA controller) 33. RAM 31 is also provided on the ASIC/FPGA 30. The ASIC/FPGA also connects to a control interface 28 which, in a simplest form, comprises manually-operable buttons for stepping through the slide sequence. The ASIC/FPGA also connects to a digital-toanalog converter 34 and an output VGA connector 35. A power source (e.g. battery) 23 is provided on the device 20. The power source is controlled by power control unit 24.

The FPGA 30 includes sub-modules to act as a USB master (allowing access to the shared flash memory), a memory controller for DRAM access, and general I/O pins to allow monitoring of the control interface buttons. In addition, it has a small PIC CPU core, which is used to implement the logic that renders JPEG images on the display. For performance reasons, JPEG decode acceleration logic can be included on the FPGA.

The device 20 is primarily designed to display Microsoft PowerPoint™ presentations on a standard VGA display connected to port 35. The device 20 should be small, portable and self-contained. Presentations are first converted to a set of compressed images on a separate host PC, and the resulting compressed image files are written to memory 25 on the device 20. The most common form of image compression coding is Joint Photographic Experts Group (JPEG), although the invention is not restricted to this. Some presentation packages, such as Microsoft PowerPoint™, provide an option to save a set of slides as a set of JPEG images. Alternatively, a software utility can be used to convert the set of slides into a set of JPEG images. Each of the slides can be assigned a sequential number and stored in a particular directory.

In use, a user connects the device 20 to a spare USB port on a PC where the set of JPEG slides is stored. The device 20 will be recognised by the host PC and a USB connection will be set up between the device 20 and host PC, in a conventional manner. The slide set can then be transferred to the memory 25 by the USB connection, preferably to a default directory. The device 20 is then disconnected from IΕ ο 7 0 2 4 2 the PC and carried to the place where the presentation is to be given. As shown in Figure 2, the device 20 is connected to a projector 10 or a large display using a standard VGA lead 22 usually attached to all presentation projectors. Alternatively, the device could plug directly into the projector. When a user is ready to give a presentation, the device is turned on. Slides are retrieved from memory 25 and decoded (decompressed) into a video buffer, as described more fully below. Data is retrieved from the video buffer by VGA controller 33, converted to analog form 34, and output via the VGA connector 35 and lead 22 for display 14 on a screen 12. The firmware on the device 20 begins displaying the presentation from slide 1. Buttons on the control interface 28 are used to instruct the device 20 to display the next slide in the presentation sequence, or to display the previous slide in the presentation sequence, l he device can also be programmed to advance the slides automatically. Optionally, a simple configuration file can be stored alongside the JPEG images, to allow the user to define default behaviour for the slideshow (e.g. display each slide for five seconds before advancing). In a basic form of the device 20, no video transitions are supported. Each slide is simply replaced by its successor at the appropriate time.

To allow smooth navigation both forwards and backwards through the presentation, three video frame buffers are provided. Referring to Figure 3, the video frame buffers can comprise areas of RAM 30. The three video frame buffers respectively store: the current slide in the presentation sequence, the next slide in the presentation sequence and the previous slide in the presentation sequence. As the presenter steps forwards, or backwards, through the presentation, the contents of the buffers are updated such that store the current slide, next slide and previous slide. Figure 4 illustrates how the set of frame buffers are used over a period of time, shown as steps 100-105. When the device 20 is initially turned on, at step 100, slide 1 in the presentation sequence is read from memory 25, decoded by the decoder 32 and the resulting decoded data is stored in one of the buffers. Slide 1 can either be output as the decoded image data is written to the buffer, or the controller may prevent the slide from being displayed until a complete image has been decoded to the buffer. As soon as the first slide has been decoded, the next slide in the sequence is similarly read from memory 25, decoded 32 and stored in another buffer (step 101). It should be noted that the device 20 does not wait until the user requests the next slide is displayed. Instead, the next slide is automatically decoded in advance of when it is needed so that when the user requests ΙΕΟ 7 0? & 9 the next slide, it can be output immediately. At step 102, the previous slide in the sequence (slide -1) is similarly read from memory 25, decoded 32 and stored in another buffer (e.g. buffer #3). When a user does request the next slide is displayed, the contents of video buffer #2 can be immediately used, and the next slide is read from memory 25, decoded 32 and stored in buffer #3, overwriting the previous contents of that buffer. In this manner, whenever a user requests that the next slide, or the previous slide, is displayed, one of the buffers always has that slide ready for immediate output, and one new slide is then decoded. At step 103 the presenter requests that slide 2 is displayed. Slide 2 can be immediately output for display.

While this occurs, slide 3 is decoded into buffer previously occupied by slide -1. At step 104 the presenter requests that slide 3 is displayed. Slide 3 can be immediately output for display. While this occurs, slide 4 is decoded into buffer previously occupied by slide 1. At step 105 the presenter requests that slide 2 is displayed (stepping backwards in the presentation sequence). Slide 1 can be immediately output for display. While this occurs, slide 1 is decoded into buffer previously occupied by slide 4, in anticipating that the presenter may step backwards again.

It will bc appreciated that there is no need to physically swap the contents of the buffers alter each change in the presentation. Instead, the control logic maintains a pointer to the beginning of the video frame buffer which currently represents the current slide, next slide and previous slide (ptr eurrent slide, ptrnextslide, ptr previous slide). The three video frame buffers are preferably implemented as different regions within a common memory device although they could, less preferably, be implemented as separate physical devices.

A 1024 x 768 24-bit true-colour VGA display requires 2.3MB of memory. A 16 bitcolour display of the same resolution requires at least 1.5MB of memory. 8 MB of RAM would be sufficient to provide three frame buffers although 16 MB is recommended as it provides much greater flexibility. It is generally not cost-effective to include this quantity of RAM in a FPGA. A cheaper, but slower, alternative is to use the Flash memory 25 as a frame buffer. The number of slides that are decoded can be increased beyond three slides. This is particularly desirable to compensate for the slower access to Flash memory 25. he power source can take the form of single use batteries but preferably comprises a rechargeable battery which can be recharged via the power supply line of the USB interlace when the device 20 is connected to an external USB device. The power consumption of the device is dependent on factors such as the frequency at which processing circuitry is clocked. It is possible to improve power consumption by turning olf portions of the FPGA when they are not being used. For example, once a JPI'XJ image has been decoded, only the video controller portion of the FPGA need remain active; the JPEG decoder and other portions can be shut down. This can help increase battery life significantly.

At a battery voltage of 3.3V, and assuming some known components for the first aspect of the present invention, one hour of operation will require approximately (1400 mW / 3.3V) 424 mAmp-hours of current. Thus, a 1200mAh battery should provide approx three hours of operating time, which will be sufficient for most presentations. Alternatively, a pair of Nickel Metal Hydride (NiMH) rechargeable AA batteries could be used. These would occupy more physical space, but have the advantage that normal AA alkaline batteries can be substituted at short notice in the event of a dead battery.

When the device 20 is connected to an external USB device, the battery can be tricklecharged using an output from the USB controller 26. Voltage conversion from the 5V USB voltage to the voltage required by the battery can be provided as part of the USB controller 26. or power control 24.

The control interface 28, in a basic version of the device, comprises buttons on the device itself. In a more advanced version of the device, the control interface 28 includes a receiver for receiving commands from a wireless remote control. The remote control can use infra-red or an RF technology such as Bluetooth.

Figure 5 schematically shows a second embodiment of a portable storage device. The main difference of this embodiment is that slides are stored in memory in a decoded form. The device does not require a JPEG decoder or separate video buffer memory. The Flash memory in which the image is stored is used directly as the video buffer. This embodiment recjStoes a*larger memory 25, but performs less computation and therefore uses substantially less power, allowing a much smaller and cheaper battery to IE 0 7 0 2 4 2 be used. Ihe removal of a need to decode JPEG slides allows slides to be displayed more rapidly, thereby allowing a user to quickly step through a presentation without waiting for decoding to a video buffer.

As before, a solid-state non-volatile memory store 25 (e.g. Flash memory) is provided. T his memory is larger than required in the first embodiment as the slides are stored in decoded form. The memory is connected to a USB interface 26 having a USB port 27 for connection to an external device. A video output controller (VGA controller) 33 and DAC 34 are linked to an output connector 35. The decoded image data is stored directly in frame-buffer format, i.e. the Flash memory is used as the video buffer. For performance reasons, a Flash memory is typically addressed in 32 bit segments. If the colour resolution of the image data requires less than 32 bits (e.g. true-colour 24 bits, 16 bits or 8 bits), then either a single pixel of image data can be stored in each 32 bit segment of memory, or image data can be stored contiguously in memory, with no gaps between adjacent blocks of pixel data. It is noted that for typical slide-based presentations, a reduction in the colour palette is unlikely to be discernible to most viewers.

A tiny CPU 41 provides logic to control where in Flash memory the image data should be read from. Generally, a modem VGA memory controller 33 allows a frame buffer lo be located anywhere within memory. If necessary, some small external banking logic can be implemented with the CPLD 42, to allow the VGA controller 33 to access a larger address space than that normally supported by the video controller 33.

A common way of storing data on a storage device is to use the FAT32 file storage system. However, this does not guarantee that files will be stored contiguously in RAM. Since, in this embodiment, the video display will be rendered directly from Flash memory 25, it is important that the video data is laid out in a contiguous format within the Flash memory 25. Thus, a standard FAT32 filing system is not sufficient.

Logic on the device CPU (or in the driver software running on an external PC) supports the function of copying files directly to Flash memory. This can take the form of a Windows Explorer-style interface to a proprietary flash file system devised specifically lor the portable device or, alternatively, the portable device can be used ^070242 simply as a dedicated, extensible frame buffer to store rendered presentation slides, as produced on the PC. In either case simple software functionality can be used to support the device and enable it to be used similar to standard USB flash drives.

The CPU 41 provides sequencing of the display. It configures the VGA controller 33 for the correct resolution and steps through the Flash-based frame buffer 25 in response to button presses, etc.

The CPLD 42 is used to replace several discrete components on the board (multiplexors, and/or gates, inverters, buffers, etc.) to facilitate physically connecting all the chips together. The use of the CPLD 42 is optional.

Figure 6 shows a more advanced version of the portable device which includes the ability to play back compressed video, such as MPEG-encoded video. An MPEG decoder 51 performs decoding of compressed video and audio content. The device includes an audio DAC 52 and an audio output connector 53. This version of the device also shows a wireless remote controller 54 and a wireless interface 55 on the portable device, although this is optional. The rechargeable power supply 23 can be charged via the data interface 27. The functionality shown in Figure 6 can be provided in addition to that shown in Figures 1 or 5. The compressed video can be used only where it is needed in the presentation, such as to present animated transitions between slides, or short sections of video footage in presentations. Software which converts the presentation creates a mix of JPEG files (static slides) and MPEG files (animated slides and video content), or creates a mix of decoded image file data for storing directly in the frame buffer, and MPEG file data. In use, the device can switch between displaying still images full-screen and displaying video full-screen, or it can display a combination of a still image, full-screen, with a smaller video overlaid upon part of a still image. Phis can be achieved by writing video data into a part of the frame buffer where the moving image is required to be displayed. In this way, the amount of video processing is reduced, which can allow a smaller (simpler processor) MPEG chip to be used, with a lower power consumption.

IE Ο 7 0 2 4 2 Using a mix of image file data and compressed video helps to conserve the limited power supply of the device. Preferably, the MPEG decoder 51 is turned off whenever it is not required, thus further conserving power.

Asa further option, the apparatus shown in Figure 6 can replace that shown in Figures 1 and 5 and the entire presentation can be encoded as an MPEG video. The combination of features of the video-only version of the device, shown in Figure 6, provide a low-cost device suitable for displaying presentations.

The invention is not limited to the embodiments described herein, which may be modified or varied without departing from the scope of the invention.

Claims (19)

Claims:

1. Λ portable device for storing images for presentation, comprising: a non-volatile memory for storing compressed image file data: 5 a data interface for transferring image file data to the storage device from an external device; a video output interface; a decoder for decoding compressed image file data; at least two frame buffers for storing decoded data; 10 a video controller for generating a video output signal for display by reading data from one of the frame buffers; and a controller arranged to cause the decoder to decode a selected compressed image file and store the decoded data in one of the frame buffers while causing the video controller to generate a video output by reading data from another one of the 15 frame buffers.

2. Λ device according to claim 1 wherein the controller is arranged to use the frame buffers to store decoded data representing consecutive images in a presentation. 20

3. A device according to claim 1 or 2 wherein the controller is arranged to use at least three frame buffers, the controller being arranged to use a first frame buffer for storing a decoded version of the current image in the presentation sequence; a second frame buffer for storing a decoded version of the next image in the presentation sequence; and, a third frame buffer for storing a decoded version of the previous image 25 in the presentation sequence.

4. A device according to any one of the preceding claims wherein the frame buffers comprise storage areas within a common memory device. 30 5. A device according to any one of the preceding claims wherein the frame buffers comprise storage areas within the non-volatile memory. ΙΕΟ 7 0 2 4 2 6. Λ device according to any one of the preceding claims wherein the controller is arranged to turn off the decoder for periods between occasions when it is used to decode compressed image file data.

5. 7. A device according to any one of the preceding claims wherein the controller is arranged to select a default storage location within the storage device as the location where a first image in the presentation is stored.

6. 8. A device according to any one of the preceding claims wherein the controller is 10 arranged to find a presentation configuration file in the storage device which specifies parameters of the presentation.

7. 9. A device according to claim 8 wherein the configuration file specifies presentation duration of an image.

8. 10. A device according to any one of the preceding claims further comprising a user interlace for receiving input commands from a user.

9. 11. A device according to any one of the preceding claims further comprising a 20 rechargeable power source which is rechargeable via the data interface.

10. 12. A device according to any one of the preceding claims wherein the video output interface is a VGA interface. 25

11. 13. A device according to any one of the preceding claims wherein the data interface is a Universal Serial Bus interface.

12. 14. A portable device for storing images for presentation, comprising: a non-volatile memory for storing image file data in decoded form; 30 a data interface for transferring the decoded image file data to the memory from an external device; a video output interface for generating a video output signal; and a controller arranged to cause the video output interface to generate a video output signal by reading the decoded image data directly from the memory. IE Ο 7 0 2 4 2

13. 15. A device according to claim 14 wherein decoded data for an image is stored contiguously within the memory. 5

14. 16. A device according to any one of the preceding claims further comprising a compressed video decoder for decoding compressed video file data.

15. 17. A device according to claim 16 wherein the controller is arranged to turn off the compressed video decoder for periods between occasions when it is used to decode 10 compressed video data.

16. 18. A device according to claim 16 or 17 wherein the controller is arranged to cause the compressed video decoder to decode a selected compressed video file and to overlay the decoded video data on decoded image data within one of the frame buffers 15 or the non-volatile memory, with the video data occupying a portion of an output frame.

17. 19. A portable device for storing video content for presentation, comprising: a non-volatile solid state memory for storing compressed video data;

18. 20 a data interface for transferring video data to the storage device from an external device; a video output interface; a decoder for decoding compressed video data; a frame buffer for storing decoded data; 25 a video controller for generating a video output signal for display by reading data from the frame buffer; and a rechargeable power source for powering the device which is rechargeable via the data interface. 30 20. A portable device for storing images for presentation, substantially as hereinbefore described with reference to and/or as illustrated in Figures 1 to 4 or Figure 5 of the accompanying drawings. ΙΕ Ο 7 ο ί

19. 21. A portable device for storing video content for presentation, substantially as hereinbefore described with reference to and/or as illustrated in Figure 6 of the accompanying drawings.