FI110376B - A method for transferring a computer resolution image in MPEG2 in real time - Google Patents

Description

110376

A method for transferring a computer resolution image in MPEG2 in real time.

The present invention relates to a method for transmitting a computer resolution image in a MPEG2 system in real time. (MPEG = Moving Pictures Expert Group) MPEG2 has not previously been used to transfer computer-resolution images. The method of the invention enables multiple computer resolutions (e.g., 640 x 480, 800 x 600, 1024 x 764, 1280 x 1024) to be transmitted in real-time up to several hundred meters of connection using a preferred pair-of-10 cable or coaxial cable. The invention is based on converting a computer resolution image to a suitable MPEG2 transmission system. The conversion uses the memory to which the image is transferred. From memory, the image is read interleaved and at a different output frequency adapted for the MPEG2 transmission system.

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The first major international digital standard for compressing, storing and transferring moving images is MPEG1 (ISO / IEC 11172). MPEG1 enables video transmission typically at a resolution of 352 x 240 (previously known as MPEG1).

Extensions have been made to the 20 'MPEG2 standard (ISO / IEC 13818) over the MPEG1-' t standard. The primary application in MPEG2 is the transfer of professional video deo · · · · · · · · · · · · · · · typically at a 4-9 Mbit sirit rate. Extensions are defined in the MPEG2 standard so that 25-level HDTV (High Definition TV) transmission is also possible. Typical MPEG2 video resolutions used are 720 x 480 and 720 x 576. MPEG2 also defines ... higher resolutions such as 1920 x 1080, 1440 x 1080 and 1280 x 720.

US-5,410,354 discloses a method and apparatus for producing II * 30 compressed and non-interlaced video signals. • •; * * MPEG1 system that only supports non-interlace: .i .: signal. This patent discloses a method for transmitting a non-interleaved signal to a TV system.

EP-0926898 discloses image encoding and decompression methods and an image processor. The publication discloses a method for transferring video images from different image sources to different display devices for viewing at the receiving end. Image coding is used to scale the image to 5 screens of different resolutions. This publication discloses a method for transferring a 640 x 480 resolution image in an MPEG system. The method is based on the use of an image processor and does not disclose the transfer of larger computer resolutions (such as 800 x 600, 1024 x 764, and 1280 x 1024) in an MPEG2 system.

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It is an object of the present invention to provide a method for transmitting a plurality of computer resolutions (e.g., 640 x 480, 800 x 600, 1024 x 764, 1280 x 1024) using the MPEG2 transmission system over long distances in real time using a preferred pair or coaxial cable.

This object is achieved by the invention on the basis of the features set forth in claim 1. Preferred embodiments of the invention are disclosed in the dependent claims.

The present invention is not based on the use of an image processor or on the exploitation of image scalability, but in the invention, the original computer resolution image is returned at the receiving end. To this end, the information '' '**. the machine resolution image is converted to be suitable for the MPEG2 transmission system.

The conversion uses the memory to which the image is transferred and from which !!! The 25 images are read interleaved and at a different frequency matched to the frequency values of the picture frame used in the MPEG2 image transfer system. In this case, the computer ..... resolution image can be placed in the MPEG2 resolution image frame, »» · · '·, part of the MPEG2 resolution image and the MPEG2 resolution image frame can be used to transfer the computer resolution image.

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In the following, the invention will be illustrated by means of an exemplary embodiment with reference to: .l .: In the accompanying drawings, in which: 3 110376 Fig. 1 shows a block diagram of an encoder used in a transmission system according to the invention; Fig. 1A shows an alternative embodiment of the memory used in the encoder of Fig. 1; Figure 1B illustrates the placement of a computer-resolution image in an MPEG2 resolution picture frame in an encoder of Figure 1; and FIG. 2 shows one possible embodiment of a decoder used in the receiving end of the transmission system of the invention.

The following describes a typical embodiment of the invention, which does not limit the use of the invention in other applications of the same type.

The image compression unit 4 (Encoder) receives its signal from the display connector 3a (e.g., the Digital Visual Interface) of the video card 3 of the PC 2 equipped with a computer monitor 1. The signal at the DVI connector 3a is 20 serially encoded and TMDS (Transmission Minimized Digital Sig - 1 »'·: nai) encoded In the picture compression unit 4, the signal from the video card 3a

The signal is then decoded by the receiver circuit 5. The signal is then typically in the form of a · · * digital R, G, B, 8 bits each. This signal is supplied to the memory unit 6a, 6b.

25 '** ·' The system can use so-called field memories 6a, 6b. Field memory is a 2 .., step-by-step serial memory that acts like FIFO (First In! First Out) memory. Generally, one port acts as a write port for data and the other port serves as a read port for data. Both ports can be used simultaneously and asynchronously independently of the other. Field memories are originally designed to store »· '; video images such as still images in the VCR. Field memory controls are ', ·,: limited compared to standard SRAM and DRAM, but sufficient and: simple to control video in and out. The field memory 4 110376 forms two memory banks 6a, 6b to which the computer-generated non-interlaced image is digitally transmitted such that even lines are transferred to one and odd lines are transmitted to another field memory bank 6a, 6b. Thus, transferring the image from the field memory banks interlaced is easily accomplished.

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If SDRAM, DRAM, or SRAM based memories are used, the non-interlaced image is interleaved to control interleaved memory, e.g., in the order of the pixels in the memory, but odd lines are read first and then even lines are output. 10 {SDRM = Synchronous Dynamic Random Access Memory.

The memory 6a, 6b (or 6) also implements a frequency conversion: f (computer monitor) to f (video). The frequency conversion is used to change the frequency values of the image signal to match the frequency values of the icon frame used in the MPEG2 transmission system.

MPEG2 resolutions (e.g., 720 x 480, 720 x 576, 1920 x 1080, 1440 x 1080, and 1280 x 720) are used as frames for transferring typical computer-resolution images. The following table provides a list of examples of which MPEG2-20 resolution frames can be used to migrate computer resolutions. . images.

r Portable computer resolution image used MPEG2 frame:,; 640 x 480 720 x 480 or 720 x 576 800 x 600 1920 x 1080 or 1440 x 1080 1024 x 768 1920 x 1080 or 1440 x 1080 1280 x 1024 1920 x 1080 or 1440 x 1080 •

The computer resolution image is placed in an MPEG2 resolution image frame as part of the MPEG2 resolution image, and 25 frames of the MPEG2 resolution are used to transfer the computer resolution image. Fig. 1B shows: - an example of how a computer-resolution image can be placed e.g. in the center of a 5,117,376 MPEG2 resolution frame, leaving areas at the bottom, top and sides that can be filled with e.g. black.

Thus, the image signal is made suitable for the MPEG2 encoder 7. If the MPEG2 encoder circuit 7 accepts the non-interleaved signal, only a change in frequency values is made with the memory. The MPEG2 encoder circuit 7 compresses the image for transmission. The output is a clock signal and a serial data signal which is converted to differential by a separate conversion circuit 9 before transmission to the transmission line.

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In the image decompression unit 10-13 shown in FIG. 2, the signal first enters a conversion circuit 10 which converts the differential image signal into a MPEG2 decoder circuit 11. After the MPEG2 decoder circuit 11, the image is transferred to the memory bank 12a, 12b if displayed on a non-interlaced display.

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By means of memory bank 12a, 12b, the frequency values of the image signal are changed to correspond to the frequency values of the computer resolution image frame and the interlaced image is rendered non-interleaved. If the MPEG2 encoder circuit 7 accepts the non-interleaved image signal, only a change in frequency values 20 is made with the memory. Blank black areas at the top, bottom and sides of the image »[will be deleted. Field memories 12a, 12b or * DRAM or SRAM type memories can be used as memory banks.

* *! r I · l t ,,, The signal is then supplied, for example, to a D / A converter 13, which outputs *! 25 an analog RGB signal. The signal can also be supplied to a transmitter * * circuit which generates a suitable signal for the DVI connector. So the decoder can. . (be digital or analog output and control TV, monitor or flat panel displays.

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Claims (7)

A method of real-time transmitting a computer resolution image in an MPEG2 system, in which method a digital image signal representing the image with the data resolution is transmitted to the memory (6; 6a, 6b), and by means of the memory (6; 6a , 6b), the frequency value of the image data signal is converted to correspond to the frequency values of the image frame used in the MPEG2 image transmission system, characterized in that said frequency converted computer resolution image is placed in an MPEG2 resolution image frame as part of an MPEG2 resolution image used in MPEG2 resolution. to transfer the computer resolution image. Method according to the claim, characterized in that the uninterleaved image with computer resolution representing the digital image signal is converted by the memory (6; 6a, 6b) into an interleaved image representing image signal before said computer resolution image is placed in the MPEG2 image. resolute picture frame. Method according to claim 1 or 2, characterized in that the data is packed with an MPEG2 encoder (7) for transmitting the image and the The MPEG2 encoder received data clock signal is converted to differential and the differential signal is measured into the transmission line. Method according to any of claims 1 to 3, characterized in that the image signal is received from the transmission line to the image unpacking unit 25 (10-13), where the image signal is converted to suit the MPEG2 decoder circuit (11). Method according to claim 4, characterized in that the frequency values of the received 'I' image signal are converted by means of a memory bank (12a, 12b) to correspond to the frequency values of the computer-resolved picture frame. 110376; 9 ί Method according to claim 4 or 5, characterized in that the empty image portions p1 of the edge portions of the image frame are removed from the image signal. Method according to claims 2, 4, 5 and 6, characterized in that, in order to display the image in an uninterleaved display, the image signal received from the MPEG2 decoder (11) is transmitted to the memory bank (12a, 12b), by means of which the interleaved image is transformed into uninterleaved.