METHOD OF VIDEO INFORMATION TRANSMISSION, AS WELL AS AN INFORMATION CARRIER, A DEVICE FOR RECEIVING AND A DEVICE FOR TRANSMITTING VIDEO INFORMATION

Abstract

Video information intended to be reproduced on a television screen often includes additional information such as graphics information or subtitles in addition to the main information such as film images. This additional information is transmitted separately, so that the user may choose whether the additional information is to be displayed or not. According to present embodiments, the transmitted video signal includes information relating to the duration for which the additional information is to remain on the display. The additional information can be displayed exactly for the duration of the desired time. When a video disc or tape is used for transferring video information, this is advantageous in trick modes, such as Fast Forward.

Description

In the drawings:

FIGS. 1A, 1B, 1C show television screen displaying video information,

FIG. 2 shows a system for transmitting video information,

FIG. 3 shows a Table of duration-information,

FIG. 4 shows an information carrier,

FIG. 5 shows a device for receiving video information,

FIG. 6 shows a device for reacting an information carrier,

FIG. 7 shows a device for transmitting video information, and

FIG. 8 shows a device for transmitting video information via information carriers.

Elements corresponding to elements described in previous Figures carry like reference characters.

FIGS. 1A, 1B, 1C show a television screen 1 on which video information is displayed. This video information comprises basic information 2 displayed over the entire surface of the television screen as shown in FIG. 1A. The basic information 2 may be formed by moving images, such as film images or a television program. The basic information may also comprise animations or still, photographic images. FIG. 1B shows the same basic information 2 on which graphics information 3 is displayed as overlay information. For example, the basic information 2 may remain the same in the background, whereas repeatedly new musical notes may be displayed as overlay information. FIG. 1C shows a subtitle text 4 as overlay information such as can be used for films. In a television system the overlay information is combined with the basic information prior to transmission and this overlay information is transmitted along in each image of the basic information. By transmitting the overlay information in a separate manner as is done, for example, in said WO 92/00647, more than one piece of overlay information can be transmitted along. The user may then choose, for example, from several languages, or omit the subtitles 4 entirely.

FIG. 2 shows a system for video information transmission. The video information is transmitted via an information signal such as, for example, a television signal, a digitally modulated signal via a network, or a recorded signal on a magnetic tape, such as VCR (Video Cassette Recorder) or on an optical disc such as a laser disc or digital video disc. The device 21 for transmitting the information signal will transmit the video information signal to the receiving device 23 by the transmission channel 22. The receiving device 23 reproduces the video signal for the user. The information signal comprises at least a representation of the basic information such as, for example, an analog PAL or NTSC video signal or an MPEG-1 or MPEG-2 digitally encoded and compressed video signal. In addition, the information signal comprises a representation of the overlay information encoded by information symbols which symbols may be separately recovered from the basic information. A page of overlay information will be replaced if after a while a next page of overlay information is received. Another option is transmitting the overlay information along with every new image. However, this is at the cost of much transmission capacity, especially if, for example, subtitles for a plurality of languages are to be transmitted. In a video signal the symbols may be transmitted along in the form of digital signals during the horizontal or vertical blanking. In fully digitized information streams a separate user data stream may be transmitted by multiplexing, for example, by subdividing the digital data stream into packets and providing them with headers which denote the type of information. In the case of MPEG-2, the video information is encoded as described in ITU/ISO 13818-2 international standard. In ITU/ISO 13818-1 is described how elementary streams of encoded video data are multiplexed together with other encoded data representative of, for example, audio and subtitles into an MPEG-2 program stream. Information of a type not specified by MPEG can be included in ‘private packets’ in a format to be chosen at will. MPEG-2 then distinguishes packets carrying an additional header of a prescribed format as “private stream 1”, and without a prescribed format as “private stream 2”. The subtitles may be included, for example, in private stream 1 packets; these packets may comprise an optional presentation time stamp which denotes the initial presentation time on the television screen. A subtitle will not be replaced until the presentation time of a next subtitle has come.

In the information signal according to the invention, the overlay information comprises time information indicating a duration for which the overlay information is to be displayed on the television screen. Symbols described above intended for the overlay information are included in the information signal, for example, in private packets in a MPEG-2 stream. These packets now contain a time code. FIG. 3 shows in a Table an example of an information signal with a time code according to the invention which can be added to the overlay information to control the display of an overlay page. The available number of bits is given per parameter. A page_start_code denotes the beginning of the page, a page_data_length denotes the amount of information of the page and there is room for other control information, for example, the duration 25. The time code may denote, for example, the duration in seconds (or parts thereof). A different suitable time unit such as the number of frames or the number of units of an available system clock, for example, 90kHz in MPEG, may also be selected. This duration starts when the overlay information is displayed on the television screen, for example, after the presentation time stamp in MPEG-2.

In the case of a basic information signal which comprises time codes indicative of a relative time of the basic information, there is a time indication available in a relation to the displayed basic image. In this case the time information may be indicated by a time of removal, which is indicative of the (relative) instant from which the particular overlay information is no longer to be displayed on the television screen. The time information for MPEG-2 may be included, for example, in the extension of the packet header or in the user data.

FIG. 4 shows a disc-shaped optically readable information carrier 30 such as a CD or laser disc. In a helical or concentric track 31 is recorded the information signal which represents video information to be displayed on a television screen. A description of the reading of a CD can be found in the title “Principles of optical disc systems” by Brouwhuis et al., ISBN 0-85274-785-3. The video information and the information signal are described with reference to FIGS. 1A, 1B, 1C and 2. The overlay information then comprises in a manner described with reference to FIG. 3 time information which is indicative of a duration for which the overlay information is to be displayed on the television screen.

FIG. 5 shows a device for receiving video information, such as a satellite receiver or a television signal decoder also referenced set-top-box. The transmitted signal arrives at the receiving means 42 via an aerial 41 (no part of the device) or via a cable connector. In the receiving means 42 the information signal is recovered and fed to combining means 42 in which a video signal is generated from the basic information combined with the overlay information. The information signal is also fed to means 44 for recovering the time information, while these means 44 at the appropriate instants give a command to the combining means 43 to remove the overlay information from the television screen in dependence on the time information. The video signal may be supplied to the user through output 46. In another embodiment the device also comprises a display 45 on which the image can be reproduced direct.

FIG. 6 shows a device for reading an information carrier 30, such as, for example, a CD. The device comprises scanning means 51 for scanning the track 31 via an optical beam 50. The device further corresponds to the device of FIG. 5. The received signal goes to the receiving means 42 and, subsequent thereto, to the combining means 43 and the means 44 for recovering the time codes. The information signal processing has been described with reference to FIG. 5.

FIG. 7 shows a device for transmitting video information such as, for example, a television transmitter. The video information is fed to image generator means 62; the basic information is fed through an input 60 and the overlay information through a separate input 62. The image generator means 62 encode the video information and generate the information signal. Information about the display of overlay information is fed through input 67 to the time code generator means 63 which generates time codes for the duration of the display. The duration may, for example, be predefined and stored in a computer file, but the duration may also be automatically derived from the length of a subtitle or manually by an operator. In a multiplexer 64 the generated time codes are added to the overlay information, after which the complete information signal is amplified in the transmitting means 65 to be transmitted via antenna 66. If subtitle texts for a film are available in two languages, the time code generator means 63 will generate separate time codes for the two languages. In the receiver there may then be selected between no subtitling or subtitling in either language.

FIG. 8 shows a device for transmitting video information via information carriers, such as, for example, for CD-ROMs. First a master information carrier is made by the device shown. From this master information carrier are then produced a multiplicity of information carriers with a customary process with moulds and presses (not shown). The complete information signal is generated by generator means (62, 63, 64) as described with reference to FIG. 7. The channel encoding unit 70 encodes the information signal in a manner customary to the disc-shaped carrier and passes this information on to the radiation unit 71. Radiation unit 71, by means of radiation beam 72, for example, a high-intensity laser beam, introduces effects on the master information carrier 73. A system controller of a customary type (not shown) provides the control of the speed of rotation of the disc and the positioning of the radiation unit 71 over the track 31. For a further description of the CD system reference be made to the title stated with reference to FIG. 4. In another embodiment a similar device is suitable for recording the information signal on a record carrier which is directly recordable, such as a CD recordable, a VCR tape or an optical tape.

The embodiments for devices are not restricted to the examples of FIGS. 5, 6, 7 and 8 and comprise any device for receiving and/or transmitting video information while overlay information comprises time information indicating the duration of display.

Claims

1. A method of producing a presentation, comprising: providing basic information including information frames during the presentation of the basic information to an audience; andproviding overlay information during the presentation of the basic information, the overlay information including a predetermined duration of time indicating the duration during the display in which a portion of the overlay information is substituted for a portion of each respective frame of a plurality of the information frames.

2. A method of producing a presentation, comprising: providing basic information including a series of subsequent frames during the presentation of the basic information to an audience, each frame being presented for a predetermined nominal frame period;providing overlay information during the presentation, the overlay information including a predetermined overlay duration of time during which the presentation of the overlay portion is substituted for respective portions of the presentation of a plurality of the subsequent frames, the overlay duration exceeding the nominal frame period.

3. A method of producing a presentation, comprising: providing basic information to be presented at a variable presentation rate; andproviding overlay information including a predetermined overlay duration of time during which the overlay information is substituted for portions of the basic information during the presentation, the overlay duration being independent of the presentation rate.

4. A method of producing a presentation, comprising: providing a series of frames;providing overlay information; substituting the overlay information for a portion of each respective frame of multiple frames depending on a predetermined overlay duration during a presentation of the series of frames.

5. A presentation device, comprising: an input for receiving a series of frames and overlay information including a duration;means for presenting the frames to an audience;means for substituting, during the presenting, the same portion of the overlap information for a portion of each frame in the same area of each frame of multiple subsequent frames during the presenting.