MXPA96006554A - Screen deployment arrangement for a vi digital signal processing system - Google Patents

Abstract

The present invention relates to apparatus comprising: a source of digital packets representing analog video signals in compressed form; a decoder for producing a sequence of digital words representing respective components of a video image corresponding to the video signal; analog and organized in groups of repetitive video image in response to said digital packets, each of the video image groups that correpsonde to two image elements and which includes a first luminance component corresponding to a first image element of said two image elements, a second luminance component corresponding to a second image element of said two image elements and two color difference components for each of said two image elements, a memory for storing a sequence of words digital representations of respective components of a graphics image and organized into groups of repetitive graphics images, each of said graphics image groups corresponding to an image element and including a luminance component and two color difference components corresponding to said image element, a converter coupled to said image element; memory for converting respective pairs of sequential graph image groups stored in said memory for new graph image groups, each of said graph image groups corresponding to two pixels and including a corresponding first luminance component to a first image element of said two image elements, a second luminance component that corresponds to a second image element of said two image elements, and two color difference components that correspond to each of the image elements and a multiplexer that responds to said video image groups and said new graphics image groups s to select any of the video image groups or graphics image groups to produce a sequence of resulting image groups, each of the resulting image groups corresponding to two image elements and including a first image component. luminance corresponding to a first image element of said two pixels, a second luminance component corresponding to a second image element of said two pixels, and two components of color difference corresponding to each of the two elements of imag

Description

SCREEN DEPLOYMENT ARRANGEMENT FOR A VIDEO DIGITAL SIGNAL PROCESSING SYSTEM This request is related to the request for Patent of the United States of America with serial number RCA 87,686 entitled "On Screen Display Arrangement for a Digital Video Signal Processing System" presented in the name of B. Beyers, Jr., the same day as this application and assigned > . to the same transferee.

Field of the Invention The invention relates to an "on-screen display" (OSD) arrangement for a digital video signal processing system.

BACKGROUND OF THE INVENTION Screen display arrays employed in video processing systems include a switching network (or "multiplexing") for switching between representative graphic image signals and normal video signals so that a graphic image can be displayed on the screen of an image reproduction device either in place of the image represented by the video signals or together with (inserted in) the image. The graphic image can take the form of alphanumeric symbols or pictorial graphics, and can be used to indicate status information, such as channel numbers or time, or operating instructions. In an on-screen display array for use in an analog video signal processing system, the multiplexing network typically operates to switch at levels corresponding to the desired intensity of the respective portions of the graphic image at the time the portions of the graphic image will be displayed. In such an arrangement, the representative signals of the graphic image take the form of synchronization pulses that occur when the portions of the graphic image are to be displayed and used to control the multiplexing network. This display arrangement on analog screen can also be used in a digital video processing system, but requires that the video signals are first converted into analog form. While digital video signal processing systems typically include a digital-to-analog converter section in which digital video signals are converted to the analog form, it may be more cost effective than the screen display arrangement. Incorporate as an integral part of the digital video processing section.

SUMMARY OF THE INVENTION The invention relates to a screen display arrangement of a digital video signal processing system, and especially one for a digital video processing system in which digital video signals represent image information in compressed form. More specifically, the invention relates to a screen display arrangement for digital video processing that includes a source of a sequence of digital words representing respective components of a video image. The representative digital words of the video image component are organized into groups that correspond in a compressed form to more than one image element. For example, the groups may correspond to two image elements, and may include first and second luminance components corresponding to the respective of the two image elements, and two color difference signals corresponding to each of the two elements of image. A memory stores digital words that represent respective components of a graphic image. The representative digital words of the graphic image component are organized into groups corresponding in an uncompressed form to the respective image elements. For example, the groups may include the luminance and a pair of color difference components corresponding to the respective image elements. A converter converts groups of images representative of graphics stored in memory, in new representative groups of graphic images that are in the same way as representative groups of video images, to make it possible to multiplex representative groups of video images and representative groups of graphic images. For example, the converter produces new representative groups of graphics including first and second luminance components corresponding to the respective image elements of the two image elements, and a pair of color difference signals corresponding to each of the two image elements. A multiplexer selects any of the representative groups of video images, or any of the representative groups of graphic images, to produce a sequence of representative groups of resulting images. These and other aspects of the invention will be described with respect to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the Drawing: Figure 1 is a block diagram of a digital satellite television system that includes a digital signal processing section that includes a digital display array as an integral part in accordance with an aspect of the invention. Figure 2 is a block diagram which describes details of the digital video signal processing section of the digital satellite television system shown in Figure 1, the digital screen display arrangement; and Figure 3 is a block diagram of a converter used in the screen display array shown in Figure 2.

DETAILED DESCRIPTION OF THE DRAWING In the satellite television system shown in Figure 1, a transmitter 1, with an associated transmit antenna 3, transmits television signals including video and audio components to a satellite 5 in geosynchronous Earth orbit. The satellite 5 receives the television signals transmitted by the transmitter 1 and retransmits them towards the ground. The television signals transmitted by the satellite 5 are received by an antenna assembly or "outdoor unit" 7. The assembly of the antenna 7 includes an antenna in the form of a soup plate 9 and a frequency converter 11. The antenna 9 directs the television signals transmitted from satellite 5 to frequency converter 11 which converts the frequencies of all television signals received at respective lower frequencies. The frequency converter 11 is often called a "block converter" since it converts the frequency band of all television signals received as a block. The television signals produced by the block converter 11 are coupled via a coaxial cable 13 to the satellite receiver 15. The satellite receiver 15 is sometimes referred to as an "indoor unit" because it is located indoors. The satellite receiver 15 tunes, demodulates and otherwise processes the received television signal as will be described in detail below to produce video and audio signals with a convenient (NTSC, PAL or SECAM) format for processing by a receiver. conventional television 17 to which they are attached. The television receiver 17 produces an image on a display screen 19 as a response to the video signals and an audible response through the speakers 21a and 21b in response to the audio signals. The satellite television system shown in the Figure 1 is a digital television satellite system in which the television information is transmitted in compressed form according to a digital compression standard previously determined as MPEG. The MPEG is an international standard for the coded representation of moving images and associated audio information developed by the Motion Pictures Expert Group (Group of Experts in Moving Images). More specifically, within the transmitter 1, the analog video signals and the analog audio signals are converted into the respective digital signals. Digital video and audio signals are compressed and encoded according to the MPEG compression and coding standard. The resulting encoded digital signal is in the form of a series of packet streams correspng to the respective video and audio components. The type of package is identified by a header code. The packets correspng to the control and other data can also be added to the data stream. In the MPEG standard, the video information is transmitted in the form of a luminance component (Y) and two color difference components (U and V). For example, the first color difference component may represent the difference between the red information of the image and the luminance information of the image (RY) and the seccolor difference component may represent the difference between the information of the blue of the image and information of the luminance of the image (BY). further, the color information is compressed because the two color difference components correspond to more than one element of the image. The use of the color difference components and the sharing of the color difference components between the elements of the image reduces the bandwidth of the Transmission. The forward error correction data is added to the packets to make the error correction due to the noise within the possible transmission path. The well-known types of forward error correction coding Viterbi and Reed-Solomon can be conveniently employed. The digital information resulting from compression, coding and error correction operations is modulated on a carrier that is known in the digital transmission field as Quaternary phase shift modulation (QPSK). The satellite receiver 15 includes a tuner 1501 with a local oscillator and mixer (not shown to select the appropriate carrier signal from the plurality of signals received from the antenna assembly 7 and to convert the frequency of the selected carrier to a lower frequency to produce an intermediate frequency signal ( IF) The IF signal is demodulated by a phase shift demodulator 1503 to produce a demodulated digital signal A forward error correction decoder 1505 decodes the error correction data contained in the demodulated digital signal, and based on the error correction data corrects the demodulated packets representing video, audio and other information For example, the forward error correction decoder 1505 can operate according to the error correction algorithms of Viterbi and Reed-Solomon when employed the error correction coding of Viterbi and Reed-Solomon in transmitter 1. The tuner 1501, the quaternary phase shift demodulator 1503 and the forward error correction decoder 1505 can be included in a unit available from Hughes Network Systems of Germantown, Maryland or Comstream Corp., San Diego, California. A transport unit 1507 is a demultiplexer which routes the video packets of the error corrected signal to a video decoder 1509 and the audio packets to an audio decoder 1511 via a data bus according to the information of the receiver. header contained in the packages. The decoder 1509 cooperates with a direct access memory (RAM) 1513 for example, in the form of a dynamic direct access memory (DRAM), for decoding and decompressing the video packets to form a stream or sequence of digital words representing the respective luminance components (Y) and color difference (U and V). The sequence of the digital words representative of video components is coupled to a television encoder 1515 which converts the representative digital words of the component into a sequence of digital words that represent luminance information (Y) and a sequence of digital words that they represent chrominance information (C) according to the line and the field exploration format of a conventional television standard such as NTSC, PAL or SECAM. The television signal coder 1515 generates line speed (H) and field (V) signals and an image element clock (P) signal (pixel) which are coupled to a decoder to a video decoder 1509 to synchronize the representative sequence of components of the digital words. The digital words representative of the luminance and the chrominance are converted into analog chrominance luminance signals by the respective sections of a digital to analog converter (DAC) 1517. The audio decoder 1511 decodes and decompresses the audio packets and the audio signal The resulting digital is converted into a baseband analog audio signal by a digital-to-analog converter 1519. Although only a single audio channel is indicated in Figure 1, it will be appreciated that one or more channels can be provided in practice. additional audio, for example, for stereophonic reproduction, as indicated by loudspeakers 21a and 21b. The analog baseband video and audio signals are coupled to the television receiver 17 via the respective baseband connections. The baseband analog video and audio signals are also coupled to a 1521 modulator which modulates the analog signals on a radio frequency (RF) carrier according to a conventional television standard such as NTSC, PAL or SECAM. Attach to the antenna input of a television receiver without baseband inputs. A 1523 microprocessor provides frequency selection control data to the tuner 1501 to control the operation of the tuner 1501 to tune the channels selected by the user. The microprocessor 1523 also interacts with the transport 1507 to affect the routing of the data packets. The microprocessor 1523 also operates interactively with the transport 1507 to affect the routing of the data packets. The microprocessor 1523 additionally provides control data to the video decoder 1509 and the audio decoder 1511 via a control bus. Even more, the microprocessor 1523 generates the control data to cause graphic images, such as alphanumeric characters and / or pictorial graphics, for example, which represent status information and operating instructions, which are to be displayed on the screen 19 of the television receiver 17 The graphics data specifies the color and position of each image element (pixel) of the graphics that are to be displayed. The graphics data represent a pixel by pixel map or "bitmap" of the graphic image. Advantageously, the remaining portion of the screen display arrangement is integrally incorporated into video decoder 1509 and associated video direct access memory 1513, which are used primarily for decoding and decompressing video data packets. The graphics data is coupled to the video decoder 1509 via the control bus, as a result of the shared use of the video decoder 1509 and the associated video direct access memory 1513, a separate screen display arrangement is not necessary. The details of the screen display arrangement will be described with respect to Figure 2. Video decoder 1509 is incorporated into a single integrated circuit (IC). Similar decoding and decompression video circuits are commercially available, with the exception of the screen display provisions that will be described later. For example, an MPEG decoding and decompression integrated circuit, identified by part number ST3240, is available from SGS Thomson, France. Although it is not necessary to understand the details of the portions of the video decoder 1509 with respect to the decoding and decompression of the video data packets, of the provisions of the screen display, the following brief description of those portions is useful. Video decoder 1509 includes a FIFO buffer (first in, first out) 1509-1 which receives video data packets on request in relatively small segments of transport 1507 and which couples them into relatively larger segments via a controller of memory 1509-3 to a section 1513-1 of direct access memory 1513 reserved for decoding and decompressing. The video direct access memory 1513 is directed under the control of the memory controller 1509-3. The decode and decompression section 1513-1 of the direct access memory 1513 includes a buffer section of ratio 1513-1-3 for storing received video data packets and a frame store section 1513-1-2 to store video information frames during the decoding and decompression operation. A video image display unit 1509-5 decodes and decompresses the stored video data packets to form the sequence of digital words representative of the video image components (Y, U, V). To this end, the video display unit 1509-5 requests data from the decode and decompression section 1513-1 of the direct access memory 1513 via the memory controller 1509-3 as required. The generation of the digital words representative of the components is synchronized with the speed signals of the field (V), the line (H) and the pixel (PC) generated by the television signal encoder 1515. The control data generated by the microprocessor 1523 is received by a microprocessor interface unit 1509-7 and coupled to several portions of the video decoder 1509 via an internal control busbar. The number of bits contained in the digital words representative of the video image components determines the number of possible levels and by this the resolution of the respective components. For n-bit words there are 2n possible levels corresponding to the 2n possible binary states. As an example, in the present embodiment, the representative word of the video image component contains eight bits and therefore each component can have 28 or 256 possible levels. The sequence of representative digital words of video image components is organized into groups of components in which each group corresponds a plurality of pixels in sub-crushed or compressed form. More specifically, in the present embodiment, the representative groups of the video image correspond to two pixels, each of which includes a first digital word representative of luminance (Y ^ corresponding to a first pixel, a second digital word representative of luminance (Y2) corresponding to a second pixel, and a single pair of digital words representative of color difference (U12 and V12) corresponding to each of the first and second pixels.This has been called as a "4: 2" format : 2: "in the field of digital video signal processing." The sub-sampling or compression of the signals differs from color is related to the compression of image data which occurs in transmitter 1 in order to reduce the width of transmission band More specifically, the transmitted image data is organized in what is known as 4: 2: 0 format in which the representative words of the image correspond to or pixels in which there are four representative words of luminance corresponding to the respective four pixels and a single pair of words representative of the color difference corresponding to each of the four pixels. The representative groups of the 4: 2: 0 image are converted into representative groups of the 4: 2: 2 image by interpolation within the 1509-5 video display unit. A complete set (4: 4: 4) of components for each pixel is produced by the interpolation within the encoder of the television signal 1515. The display portion of the video decoder 1509 includes an on-screen display controller. 1509-9 which cooperates with a screen display section 1513-3 of the direct access memory 1513. The graphics-representative bitmap generated by the microprocessor 1523 is coupled via the microprocessor interface unit 1509-7 and the memory controller 1509-3 to the screen display section 1513-3 of the direct access memory 1513 for storage. For each pixel of the graphic image there is a digital word that represents a color for that pixel. The number of bits contained in the representative digital words of color determines how many different colors each pixel can have. if the representative color words contain n bits, then each pixel can have any of 2n colors corresponding to the 2n possible binary states of the n-bit color word. By way of example, in the present embodiment, the representative color words contain two bits. Accordingly, each graphics pixel can have any of four colors corresponding to the four possible binary states (00, 01, 10, and 11) of the two-bit color word. The pixel color information is organized as a component in which for each color word there is a unique group of digital words representative of components. The components are selected to be the same as the components used for the transmission of video image information: namely, luminance (Y) and a pair of color difference signals (U and V). The selection of the same components for video images and graphics images simplifies the screen display arrangement because it avoids the need to convert a set of components to gold. For example, in the present embodiment using two-bit color words, there is the following relationship between representative digital words of color and groups of representative digital words: color group of components 00 YA, uA, VA 01 YB, UB, VB 10 Yc, Uc, Vc 11 YD 'UD, VD The actual color (represented by the subscripts A, B, C or D in the table) of a graphics pixel depends on the value represented by the digital words representative of the components of the respective group. By way of example, in the present embodiment, the representative words of the graphic image component each contain four bits. Words representative of four-bit components provide 16 possible levels for each component. The four bits represent the most significant bits of an eight-bit word that is eventually formed by the screen display unit 1509-9, as will be described later. The representative words of graphic image components are transmitted and stored in the screen display section 1513-3 of the direct access memory 1513 from the microprocessor 1523 in groups of components as indicated in the table in the form of n heading for the bitmap. In the present embodiment in which each digital word representative of the graphic image component contains four bits, each group includes 12 bits. The colors of a graphics image can be changed by changing the four bits of one or more header words that represent components, depending on the nature of the graphics image to be displayed. Display display unit 1509-9 causes the bitmap to be read from section 1513-3 of random access memory 1513, and convert the representative color word for each pixel to the corresponding component representative group of the header. To this end the on-screen display unit 1509-9 requests data from the on-screen display section 1513-3 via the 1509-3 memory controller as required. Since, in the present embodiment, the representative words of the graphic image component contain only four bits while the representative words of the video image have 8 bits, the 1509-9 display unit converts the representative words of components of four-bit graphic image in eight-bit words by simply adding four binary "0" s as the four least significant bits of the four-bit words. The generation of the representative digital words of graphic image components by the screen display unit 1509-9 is also synchronized with the field (V), line (H) and pixel (PC) speed signals generated by the encoder the television signal 1515. As noted above, the representative groups of video image components generated by the video image display unit 1509-5 represent video image information in a compressed form in which for every two pixels there are two respective words representative of luminance and a pair of representative words of color difference in a format known as 4: 2: 2. On the other hand, representative groups of the graphic image component stored in the screen display section 1513-3 of the direct access memory 1513 and generated by the display unit 1509-9 represent image information of graphics in a non-compressed form in which for each pixel there is a representative word of luminance and a pair of words representative of color difference (or for each two pixels there are two representative words of respective luminance and two respective pairs of words representative of color difference ). The last uncompressed format is known as the "4: 4: 4" format in the field of digital video signal processing, the 4: 4: 4 graphics image sequence is desirable since it allows as many colors as possible for be defined with a given number of bytes, because it provides a single luminance component and two unique color difference components for each graphics pixel. However, the 4: 4: 4 graphics image sequence is not compatible with the 4: 2: 2 video image sequence and can not easily be multiplexed with it in order to insert a graphics image into a video image . To solve this problem, the video decoder 1509 includes a converter 1509-11 for converting the 4: 4: 4 sequence used for the graphic image components in the 4: 2: 2 sequence used for the video image components. As indicated in Figure 2, for each two graphics pixels, the converter 1509-11 selects the pair of color difference components for the first pixel and erases the pair of the second pixel. As shown in Figure 3, the screen display converter 1509-11 may comprise a holding circuit 1509-11-1 for storing two groups of words representative of graphic image components, and a multiplexer 1509-11-3 the which selects the appropriate words representative of the component in sequence from those stored in the holding circuit 1509-11-1 at the output speed. It is desirable that the number of 4: 4: 4 groups of representative components of graphic image per line be an even number because two of the groups in the graphic image 4: 4: 4: or-iginal are used to produce each new one of the groups of graphic image 4: 2: 2. While the output sequence is shown as being, in the order named, a first luminance component (Y) for a first pixel of two pixels, a first color difference component (U) for each of two pixels and a second color difference component (V) for each of the two pixels, and a second luminance component for the second of the two pixels. An output multiplexer 1509-13 selects either word groups representative of video image components provided by video display unit 1509-9 or groups of words representative of graphic image components provided by the 1509 display display converter -11 under the control of the display unit 1509-9. In a video image-only operation mode, the output multiplexer 1509-13 selects only the video image groups. In a graphics image-only operation mode, the output multiplexer 1509-13 selects only graphics image groups. In an "superimposed" operating mode, in which the graphic image is inserted into a video image, the output multiplexer 1509-13 selects either the video image groups or the graphics image groups on a base of pixel by pixel. The 4: 2: 2 output sequence of the representative words of components produced by the output multiplexer 1509-13 is coupled to a television signal encoder 1515.

Claims (10)

1. An apparatus comprising a source of digital packets (1) representing analog video signals in compressed form; a decoder (1509) for producing a sequence of digital words representing respective components of a video image corresponding to said analog video signal, and organized into groups of repetitive video images corresponding to two picture elements, and including a first luminance component (Yl) corresponding to a first image element of the two image elements, a second luminance component (Y2) corresponding to a second image element of the two image elements, and two components of color difference (Ul, VI, U2, V2) that correspond to each of the two image elements; a memory (1513) for storing a sequence of digital words that represent respective components of a graphic image, and organized into groups of repetitive graphic images; each of the groups of graphic images corresponding to an image element, and which include a luminance component (Y) and two color difference components (U, V) corresponding to said image element; a converter (1509-11) coupled with memory (1513) for converting respective pairs of groups of graphic images into sequence stored in the memory (1513) in new groups of graphic images; each of the new groups of graphic images corresponding to two image elements, and which include a first luminance component (Yl) corresponding to a first image element of the two image elements, a second luminance component (Y2) corresponding to a second image element of the two image elements, and two color difference components (Ul, VI, U2, V2) corresponding to each of the image elements; and a multiplexer (1509-13) that receives the groups of video images and the new groups of graphic images, and that responds to a controller (1523) that also couples with the memory and with the converter, to select the groups of video images or groups of graphic images, to produce a sequence of groups of resulting images, -corresponding each of the groups of resulting images to N image elements, and including N luminance components (Y) corresponding to the respective elements of the N image elements, and two color difference components (U, V) corresponding to each of the N image elements.

2. The apparatus as described in claim 1, which further includes: a second converter that responds to the sequence of the resulting image groups to produce a sequence, of groups of output images wherein the respective groups of images Resulting image groups have been converted into pairs of respective output image groups; each of the pairs of groups of output images corresponding to an image element; including a first group of the groups of output images to the first luminance component and to the two color difference components of a respective group of the resulting image groups; including a second group of the groups of output images to the second luminance component and to the two color difference components of the respective group of the resulting image groups. The apparatus described in claim 2, which further includes: a digital-to-analog converter (1517) for converting the sequence of groups of output signals into respective analog video signal components. The apparatus described in claim 1, wherein: a first component of the two color difference components (Ul, VI) represents the difference between the respective luminance component (Yl) and the first primary color; and a second component of the two color difference components (U2, V2) represents the difference between the respective luminance component (Y2) and the second primary color. The apparatus described in claim 1, wherein: the memory (1513) includes a section (1513-1) operatively coupled with the decoder (1509). 6. An apparatus comprising: a source of a sequence of digital words representing respective components (Y, U, V) of a video image, and organized into groups of repetitive video images; each of the groups of video images corresponding to two image elements, and which include a first luminance component (Yl) corresponding to a first image element of the two image elements, a second luminance component (Y2) corresponding to a second image element of the two image elements, and two color difference components (Ul, VI, U2, V2) corresponding to each of the two image elements; a memory (1513) for storing a sequence of digital words representing respective components (Y, U, V) of a graphic image, and organized into groups of repetitive graphic images; each of the groups of graphic images corresponding to an image element, and which include a luminance component (Y) and two color difference components corresponding to that image element; a converter (1509-11) coupled with the memory (1513) for converting the respective pairs of the groups of graphic images into sequence stored in the memory, in new groups of graphic images; each of the new groups of graphic images corresponding to two image elements, and which include a first luminance component corresponding to a first image element of the two image elements, a second luminance component (Y2) corresponding to a second image element of the two image elements, and two color difference components (Ul, VI, U2, V2) corresponding to each of the two image elements; and a multiplexer (1509-13) that receives the groups of video images and the new groups of graphic images, and that responds to a controller (1523) that also couples with the memory and with the converter, to select the groups of video images or groups of graphic images, to produce a sequence of groups of resulting images; Each of the resulting image groups corresponding to N image elements, and including N luminance components (Y) corresponding to the respective elements of the N image elements, and corresponding two color difference components (U, V ) to each of the N image elements. The apparatus described in claim 6, which further includes: a second converter that responds to the sequence of the resulting image groups to produce a sequence of groups of output images, wherein the respective groups of image groups resulting ones have become pairs of groups of respective output images; each of the pairs of groups of output images corresponding to an image element; including a first group of the output image groups to the first luminance component (Yl) and to the two color difference components (Ul, VI) of a respective group of the resulting image groups; including a second group of the groups of output images to the second luminance component (Y2) and to the two color difference components (U2, V2) of the respective group of the resulting image groups. The apparatus described in claim 7, which further includes: a digital-to-analog converter (1517) for converting the sequence of groups of output signals (Y, C) into respective analog video signal components. The apparatus described in claim 6, wherein: a first component of the two color difference components (Ul, VI) represents the difference between the respective luminance component (Yl) and the first primary color; and a second component of the two color difference components (U2, V2) represents the difference between the respective luminance component (Y2) and the second primary color. 10. An apparatus comprising: a source (1) of a sequence of digital words that represent respective components of a video image, and organized into groups of repetitive video images; each of the groups of video images corresponding to a number N, greater than one, of picture elements, and including a number N of luminance components (Y) corresponding to the respective elements of the N picture elements, and two color difference components (U, V) that correspond to each of the N image elements; a memory (1513) for storing a sequence of digital words that represent respective components of a graphic image, and organized into groups of repetitive graphic images; each of the groups of graphic images corresponding to an image element, and which include a luminance component and two color difference components corresponding to that image element; a converter (1509-11) coupled with the memory for converting the respective groups of groups of graphic images into sequence stored in memory, into new groups of graphic images; N each of the new groups of graphic images corresponds to N image elements, and which include N luminance components (Y) corresponding to respective elements of the N image elements, and two components of color difference (U, V) which correspond to each of the N image elements; and a multiplexer (1509-13) that receives the groups of video images and the new groups of graphic images, and that responds to a controller (1523) that also couples with the memory and with the converter, to select the groups of video images or groups of graphic images, to produce a sequence of groups of resulting images; Each of the resulting image groups corresponding to N image elements, and including N luminance components (Y) corresponding to the respective elements of the N image elements, and corresponding two color difference components (U, V ) to each of the N image elements.