WO1999012334A2 - Video tape and an arrangement for replaying such a video tape - Google Patents

Abstract

A pre-recorded video tape has a plurality of different language subtitles and/or audio channels which are encoded as standard teletext packets. To make them replayable by a VHS recorder they are encoded using a multilevel, for example four level, code at a reduced data rate. So that a single tape can be distributed over a wide geographical area, such as Europe, in which many languages are spoken the tape carries a plurality of subtitle pages, one for each language, and/or AUDETEL channels. The user can select the desired language on replay.

Description

DESCRIPTION

VIDEO TAPE AND AN ARRANGEMENT FOR REPLAYING SUCH A VIDEO

TAPE

The invention relates to a VHS video tape and an arrangement for replaying such a video tape.

In a culturally diverse area such as Europe there is a significant cost in producing different versions of pre-recorded video tapes for different languages. As many as ten different versions of the same material may be required dubbed on to the sound track in the required language or with sub titles added to the video as captions. Although the distribution of the correct version of these tapes is normally done by geographical area, that is French tapes to France, German tapes to Germany etc. this is not necessarily ideal for all of the potential audience. Countries may have significant immigrant populations or several languages may be spoken in the same area. All these factors lead to significant costs in manufacture and distribution channels which could be saved if it were possible to have only one version of the pre-recorded tape with the required language selected by the user on replay. French Patent Application No. 2586879 discloses a process which makes it possible to record several versions of subtitling on a single tape. The subtitles are transmitted in anticipation of the picture. The numerical data which represents the subtitles being modulated in a form compatible with the recording on one of the sound tracks of a consumer stereo video recorder, or with the aid of a sub carrier for recording on the sound track of a consumer mono video recorder. The said data are recorded at an instantaneous rate lower than the rate of the numerical data. The device may comprise a universal interface box connected to the SCART socket on a receiver and consisting of a display interface and a demodulator corresponding to the teletext standard used for broadcasts.

It is an object of the invention to enable the provision of a prerecorded video tape which contains a plurality of different language subtitles or sound channels in different languages and to enable a selected language to be used for replay.

The invention provides a VHS video tape carrying thereon a data signal having a given format and a data rate greater than that which can be reliably recorded and reproduced by a standard VHS video recorder, said data signal being encoded as a multilevel signal having a data rate which is lower than that of the original data signal and which is within the bandwidth of a VHS recorder, the data signal comprising a plurality of data streams, each representing dialogue in a different language or a different version of the same language, the dialogue being synchronised with a video programme recorded on the tape in association with the data signal.

The data may be in the form of a teletext signal and the data streams may be in the form of teletext pages each language dialogue being contained in a given numbered page.

As disclosed in our copending UK Patent Application No. 9605614.8 (PHB 34056) it is possible to record teletext or other data signals on a VHS tape using a multi-level code to reduce the data rate. Thus teletext data at the same information rate as that transmitted by a broadcaster or the subtitling system proposed to accompany digital terrestrial television in the UK can be recorded on the tape. Although teletext subtitles or subtitles in any other format on broadcast transmissions are normally provided in only one language for the hearing impaired, it is possible to provide subtitles in many languages for the general viewer. The language can be selected by the user by choosing an appropriate page number on the teletext TV receiver.

Since subtitles are relatively short, typically only one or two lines of text, and are updated every few seconds they occupy only a small data capacity. Typically for teletext format data, four data packets per second will be sufficient for subtitles in one language. Since the arrangement described in our copending application has a capacity of sixteen data packets per field or 800 data packets per second, it can be seen that subtitles in many languages are possible on a prerecorded tape. This is true even though the need to synchronise subtitles accurately to the dialogue is required.

The subtitles will be created by the media producer, tape distributor or an independent company. They are created on special subtitling equipment similar to that used by teletext broadcasters. The same subtitling equipment may be used to create subtitles for different languages, one language at a time. Alternatively different subtitling systems, possibly in different locations may be used to create the subtitles for each language. In either or both of these ways a complete data base of all subtitles can be built up for the particular video material on the tape.

When tapes are duplicated for production the subtitle data can be added to them by encoding equipment reading the information from the data base and using a different page number for each language.

The invention further provides an arrangement for replaying a VHS video tape carrying thereon a data signal having a given format and a data rate greater than that which can be reliably recorded and reproduced by a standard VHS video recorder, said data signal being encoded as a multilevel signal having a data rate which is lower than that of the original data signal, the arrangement comprising a decoder for decoding the data signal recorded on the tape and producing therefrom a data signal of the given format, a data decoder, means for selecting a data stream for decoding by the data decoder and means for reproducing the subtitle.

In one form the data decoder may be a teletext decoder and the data stream may be a given teletext page. When the viewer comes to play the tape she or he selects the page number for the desired language on the teletext TV receiver, either from information on the tape box or a paper insert or from an index teletext page describing the facilities available. The circuitry in the recorder converts the encoded data on the tape into standard teletext format and the subtitles may be displayed on the television screen in the desired language; provided that the teletext TV has the capability for displaying that language. In the European context most modern teletext decoders have facilities for a wide range of languages. More generally there is a trend towards wider language and geographical coverage as the technology becomes less expensive. For example, Chinese teletext decoders can normally cover English as well as Chinese.

It is not essential that each of the teletext pages produces subtitles in a different language. For example, for producing special prerecorded tapes for language teaching, subtitles could be provided in different languages, but also different subtitles streams in the same language could be provided on different page numbers. The viewer could then select the one most appropriate for his or her requirements. For example simple subtitles giving basic meaning at slow speed could be provided for early learners of a particular language or more comprehensive subtitles having a faster rate of change could be available for people with a clearer understanding of the language. The technique is not necessarily restricted to conventional subtitle displays of a few rows of text overlaid on the video. At a selected point in the dialogue a full or part screen could be provided containing all the text of the conversation and again the language or level of difficulty of the language could be chosen by the viewer. Another possibility is to mix the languages in the same subtitle stream. First one language appearing and then a translation perhaps underneath. All these options may be available depending on how the subtitles are created by the media provider and offer considerable scope for artistic creativity.

The dialogue may be encoded using an audio description code so that it can be reproduced by means of a speech synthesizer. An audio description code called AUDETEL was devised to provide an additional sound channel for visually impaired viewers which gives the description of what is going on in a TV programme during the gaps in the dialogue, for example "Bill walks through the door with a frown on his face pointing at Anne". The AUDETEL system works by transmitting data in a teletext format to a speech synthesizer built into the television and the output of the speech synthesizer can be added to the television sound. A description of the AUDETEL system has been published in a paper by J.G.W. Pledge entitled "The AUDETEL Audio Description Service for Visually Impaired People" in Proceedings of IEE Colloquium: Time between Pictures - The Vertical Blanking Interval, IEE Digest 1994/016. The present invention enables an audio description system such as

AUDETEL to be extended in two ways. First more than one sound channel can be made available and secondly the selected sound channel can be heard as an alternative to the normal sound not just in the gaps in the dialogue.

The AUDETEL system uses a packet format teletext coding method and consequently this can be extended with an additional data field to allow for different languages. A Hamming encoded byte yields four bits of data allowing separate identification codes for 16 different languages which is sufficient for most purposes. The capacity required per language depends on the speech synthesis algorithm and the audio quality required. Although AUDETEL as presently proposed uses only one data packet per frame, that is 25 packets per second, it is expected that higher sound quality would be desirable for multiple language audio description and it is proposed to use one data packet per field or 50 data packets per second. The data recording system has a capacity of 800 packets per second which will allow up to 16 languages to be recorded on one video tape. If a system like AUDETEL which uses teletext extension packets for the codes representing the audio dialogue is used it is, of course, necessary that the teletext decoder is capable of acquiring and decoding extension packets as well as the packets forming the displayed pages. Such teletext decoders are currently commercially available from the major manufacturers of teletext decoders.

The AUDETEL system has a mechanism for fading the AUDETEL sound channel in and out of the normal TV audio signal. This concept may be retained and used to replace the normal dialogue with the selected language rather than just to enable the AUDETEL sound signal to appear during gaps in the dialogue to describe the action of the actors. There are many possibilities for selecting the desired language for the audio description. Three examples of possible methods are indicated as follows. A first possibility is to use on screen displays generated by the TV software to guide the user to the selected language. A second option is to present the number of languages on a teletext index page recorded on the tape. The user would then select the page required for the desired language using direct page number selection or the Fastext or TOP colour buttons in conventional fashion and then press a key which down loads the language number from the spare packet 27 page link into the channel of the audio description decoder. A third possible method is that the language options are presented on a teletext page and are chosen in a PDC like way by moving a cursor to the desired position which then downloads the language choice. An example of such an arrangement is applied to the setting of VCRs to record a desired programme is disclosed in EP-A-0300562 (PHB 33373).

This audio description coding in different languages on the tape may be used both for the standard audio dialogue and for normal audio description purposes. That is the dialogue on the tape could be encoded purely as an audio description code and replace the normal audio signal. The actual location of the audio description decoder could be in the VCR rather than the TV, in which case the control methods would substantially identical. As with subtitles creative use of the facilities could give alternative types of dialogue as well as different languages for educational purposes.

Thus using the facilities of data recording plus some additional circuitry for audio description it is possible to provide prerecorded video tapes with user choices of dubbed languages and/or subtitles, one common tape being sufficient for a broad range of languages in a wide geographical area.

The above and other features and advantages of the invention will be apparent from the following description, by way of example, of embodiments of the invention with reference to the accompanying drawings in which:-

Figure 1 shows a standard broadcast teletext signal and the effect of the restricted bandwidth of a VHS recorder on this signal,

Figure 2 shows a four level code representing the broadcast teletext signal which is suitable for recording on and replay from a VHS recorder.

Figure 3 shows on an enlarged timescaie a portion of the signal shown in Figure 2.

Figure 4 shows in block schematic form an arrangement for replaying a VHS video tape according to the invention.

Figures 5 and 6 illustrate the selection of subtitles and audio description for replay using the apparatus shown in Figure 4.

Figure 1 shows a standard teletext signal as received by a receiver. The data rate of the teletext signal is greater than 5 MHz and consequently such a signal will be distorted when it is fed through a video recorder, such as one according to the VHS standard which has a channel bandwidth of around 3 MHz. Figure 1 b shows how the teletext signal is affected by the channel bandwidth of a typical VHS recorder. As can be seen the initial clock run-in information is lost and on replay such a signal would not be decodable by a standard teletext decoder. In order to overcome this problem our copending UK Patent Application No. 9605614.8 (PHB 34056) discloses the use of a multilevel code which has a data rate which is lower than that of the standard teletext data rate. Figure 2 shows a line of teletext data encoded according to a four amplitude level code. The initial clock run-in has been replaced by a lower frequency clock run-in while the framing code and data are replaced by the four level code. The four levels in this instance are four amplitude levels and consequently in each data period two bits can be encoded, the four levels giving the codes 00, 01 , 10, and 11. As a result the teletext signal re-encoded according to the multilevel code now has a data rate of half that of the standard teletext signal and now falls within the bandwidth of the VHS recorder.

Figure 3 shows the initial part of a teletext line using the multilevel code on an expanded time scale and indicates the cycles of the clock-run in the framing code and the data. In this case the clock run-in frequency is arranged to be half that of the standard teletext clock run-in frequency. Thus the method of recording teletext data on a tape disclosed in the above referenced patent application comprises the step of converting teletext data generated at the standard rate into a multilevel code at a data rate which is lower than that of the standard teletext signal. The multilevel code is then applied to the recording apparatus to enable the data to be recorded on the tape. In a particular embodiment a four level amplitude code is used and the data rate is half that of the standard teletext signal. If an 8 level code was used then the data rate could be reduced to one third of the standard teletext data rate since an 8 level code would allow each data period to encode three bits. Whilst it is preferred to use a multiple amplitude level code as this simplifies the recovery of data by a standard teletext decoder it is possible to use either a multilevel code comprising a number of different phases or to use a combination of phase and amplitude levels.

On replay the multilevel code is read from the tape and then converted to standard teletext data in an inverse operation to the conversion on recording. This data can then be fed into a teletext encoder to enable the teletext data to be reassembled with the video signal for transmission to an associated television receiver. The whole process of recording and replaying teletext data in this fashion using a VHS recorder is disclosed in our copending UK Patent Application referred to above, the contents of which are hereby incorporated by reference.

In the context of this application teletext refers to a system, such as World System Teletext, in which the teletext data has a binary data rate which is too high for a standard VHS recorder to record or replay. While the forgoing description with reference to Figures 1 to 3 has discussed the recording and subsequent replay of a teletext signal it will be apparent that teletext data encoded according to this procedure could be prerecorded on tapes for replay by a purchaser or renter of the tapes.

It will be apparent that other data representing subtitles or audio descriptions which have a data rate of greater than the bandwidth of a VHS video recorder could also be encoded and recorded and played back by a VHS video recorder in the same manner. For example it is already known that in the UK digital terrestrial television services will broadcast subtitling information in the VBI and by using an appropriate encoder and decoder subtitling information in this form may be recorded and replayed in a similar manner. UK Patent Application No. 9718326.3 (PHB34186) discloses a method of and apparatus for recording digital television signals on a VHS video recorder using a similar multilevel code to reduce the data rate of the digital television signal to within the bandwidth of a VHS recorder. Clearly the invention is applicable to any multi language subtitling or audio description which can be encoded and recorded on tape and replayed using a standard VHS recording mechanism with appropriate encoding and/or decoding circuitry. Thus while the specific description is based on examples using teletext format subtitling and audio description codes the invention is not limited thereto and the skilled person will be able to adapt the invention to subtitling or audio description information encoded in other formats.

Figure 4 shows an arrangement according to the invention for replaying tapes having multi-language facilities added thereto by means of data multiplexed with the video signal encoded according to a teletext standard. The arrangement is divided into a video recorder 1 and a TV receiver 2. The actual partition between the two is somewhat arbitrary and items could be transferred from the TV receiver to the VCR. The VCR 1 is arranged to replay a prerecorded tape 3 having multi-language facility encoded by means of teletext data packets. This is recorded on the tape using a multilevel code as described with reference to Figures 1 to 3. Tape replay heads 4 produce a first output which is fed to a video processor 5 and a second output which is fed to an audio processor 6. A control and timing circuit 7 receives an input from the video processor 5 from which it generates timing signals using the horizontal and vertical synchronising pulses. The output from the video processor 5 is also fed to a first input of a multiplexer 8 and to a decoder 9 which is arranged to decode the multilevel encoded teletext data and passes it to a buffer memory 10. The buffer memory is then read out into a teletext encoder 11 under the control of the control and timing circuit . Thus, as described in our co-pending application, the teletext data is reconstituted by the decoder 9, buffer ram 10, and teletext encoder 11 to form a standard teletext signal which is fed to a second input of the multiplexer 8. This teletext signal is selected during the vertical blanking interval and the video signal is selected during the active video lines. As a result the output of the multiplexer 8 is a CVBS signal which carries a standard teletext signal. The output of the multiplexer 8 is fed either to a modulator 12 whose output is connected to an aerial socket 13 of the television receiver 2 or may be connected directly via a SCART connection as a CVBS input to the television receiver 2. The output of the audio processor 6 is also connected to the modulator 12 or SCART connection.

The television receiver 2 comprises a tuner 13, IF stage 14, and demodulator 15. The output of the demodulator on a first line is fed to a video processor 16, a teletext decoder 17 and an audio description decoder 18. This output is the standard CVBS signal. In the alternative arrangement the SCART connector is connected to connect the CVBS signal from the video recorder to the video processor 16, teletext decoder 17 and audio description decoder 18. A second output from the demodulator 15 is fed to a audio processor 19 and again in the alternative the output of the audio processor 6 in the video recorder 1 is fed via the SCART connector to the audio processor 19 in the TV receiver 2.

A control circuit 20 which is a conventional television controller receives signals from a remote control handset 21 to enable the user to select the service required. The control circuit 20 has outputs which control the tuner 13 to enable a selected channel to be obtained, an output to the teletext decoder 17 to enable selected pages to be acquired and displayed, an output to the audio description decoder 18 to enable the audio description to be acquired and decoded and outputs to the video processor and audio processor. These control outputs and their functions are conventional and would be well known to the person skilled in the art of television receiver design. The teletext decoder 17 has an output which is fed to the video processor 16, the output normally being an RGB signal. Similarly the audio description decoder 18 has an output which is fed to an input of the audio processor 19. The output of the video processor 16 is fed to a display device 22 while the output of the audio processor is fed to either or both loudspeakers 23 or headphones 24.

The television receiver 2 as shown in Figure 4 is conventional apart from the audio description decoder 18 which retrieves the speech data from the composite video, selects the language required and has a speech synthesizer to generate the additional audio channel. This is then passed to the audio processor 19 and from there to the loudspeakers 23 and/or headphones 24. Codes sent with the audio description indicate when the main channel is to be faded up or down to allow the insertion of the additional audio channel.

The control circuit 20 selects the languages required for subtitles and/or audio description according to data in those services and to user commands from the remote control handset 21. So for example, an English family may watch an American film and listen to the dialogue via the loudspeakers while the French au pair wears the headphones and receives a French audio channel so that she can understand what is going on.

The control circuit 20 may be arranged so that it causes the AUDETEL sound channel to replace the main sound channel when it is required to change the language of the main sound channel. It is still possible to include the normal AUDETEL service in the silences between dialogue, both audio dubbing and AUDETEL description can be provided in each language if required. Thus the audio processor is arranged to be able to take either the demodulated sound signal from the demodulator 15 or from the audio processor 6 and use this as the output to the loudspeakers or headphones, or to select the audio description decoder output 18 and to feed this to the loudspeaker and or headphones. The normal sound channel may be used in conjunction with the audio description sound channel where an audio description service is required in the same language as the main sound channel. Thus the control circuit 20 will cause the main sound channel to fade out while the audio description is to be replayed; this is a standard use of the AUDETEL service. For other languages the audio description decoder will provide both the full sound channel and the audio description for the partially sighted. The control circuit 20 may be arranged to either select or not the audio description for the partially sighted depending on the wishes of the user.

Figures 5 and 6 illustrate how languages for subtitles and audio description could selected using a method like PDC where cursor positions on the screen are assigned data and the user can just move a cursor to select the desired item. In the case of PDC the data are programme labels for recording. Such a system is disclosed in European Patent No. 0300562 (PHB 33373). Using the same technique with different codes the cursor position can be assigned teletext page numbers, audio description channels, tape index positions, commands to a remote computer etc. In the case of multi-language subtitles, this mechanism selects a teletext page carrying the desired language subtitles and or audio description selects the desired audio channel and thus the language to be dubbed on to the sound output.

Thus on inserting a tape into the recorder an index page is brought up, an example of which is shown in Figure 5. The cursor is moved using up/down and left/right buttons on the remote control handset 21 , and in the example shown on activating a selected button on the remote control handset 21 the teletext page containing English language subtitles is selected as indicated by the cursor position. The next step is that the tape index service then gives what services are available on the tape in the English language and again the cursor can be moved to enable selection of any of these services. In the example shown subtitles are selected. However, the user may wish to look at some of the other services such as a synopsis of the plot, biographies of the performers, and details about the programme originator.

Figure 6 illustrates the situation when instead of an English language version being selected a German language version is selected. The next stage of the indexing again offers the viewer the possibility of various options and in this case the audio description service has been selected. Thus on replay of the tape a German sound channel will be produced using codes in the audio description to provide the sound channel.

Thus by encoding a plurality of different language teletext services on to the tape it is possible to produce a single tape for use in a number of different countries having different languages. It is also a useful facility for those who do not speak the native language of the country in which they are residing or for countries where a multiplicity of languages is used. Simple subtitling can be achieved by means of standard teletext techniques and since the normal broadcast teletext services will not be provided on a prerecorded tape it is possible to use many more pages for teletext subtitles thus enabling a multiplicity of languages to be encoded and selected by means of choosing the correct page number for the desired language. Again more space can be allocated to AUDETEL like services to enable not only an audio description of the scene to be provided but sufficient codes to be sent to enable a full audio channel to be created in the same way as the audio description. In practice there is sufficient capacity to enable the use of a multiplicity of audio channels using AUDETEL like coding.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the design and use of video tapes and tape recorders and data, including teletext and AUDETEL, encoders and decoders and component parts thereof and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation of one or more of those features which would be obvious to persons skilled in the art, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

1. A VHS video tape carrying thereon a data signal having a given format and a data rate greater than that which can be reliably recorded and

5 reproduced by a standard VHS video recorder, said data signal being encoded as a multilevel signal having a data rate which is lower than that of a standard data signal and which is within the bandwidth of a VHS recorder, the data signal comprising a plurality of streams of data each stream representing dialogue in a different language or a different version of the same language, ╬╣o the dialogue being synchronised with a video programme recorded on the tape in association with the data signal.

2. A tape as claimed in Claim 1 in which the data is in the form of a teletext signal and the data streams are in the form of teletext pages each i5 language dialogue being contained in a given numbered page.

3. A tape as claimed in Claim 1 or Claim 2 in which the dialogue is represented as subtitles.

20 4. A tape as claimed in Claim 2 or Claims 3 when dependent on

Claim 2 in which each language is recorded on a specific page number and the tape includes a teletext index page from which the page for a particular language can be selected for replay with the video programme.

25 5. A tape as claimed in Claim 1 in which the dialogue is encoded using an audio description code so that it can be reproduced by means of a speech synthesizer.

6. A tape as claimed in Claim 1 or Claim 5, in which the dialogue is

30 encoded using an audio description code in selected teletext packets and the data streams are in the form of teletext packets containing an identification code which identifies the language of the dialogue in that packet.

7. An arrangement for replaying a VHS video tape as claimed in any preceding claim, the arrangement comprising a tape decoder for decoding the data signal recorded on the tape and producing therefrom data having the given format, a data decoder, means for selecting a data stream for decoding by the data decoder, and means for reproducing the decoded data stream.

8. An arrangement for replaying a VHS video tape as claimed in Claim 2 or any claim dependent on Claim 2 wherein the data decoder is a teletext decoder and the data stream is a given teletext page.

9. An arrangement as claimed in Claim 8 in which the teletext page is a subtitle page and the reproducing means comprises means for superimposing the subtitles on a displayed picture.

10. An arrangement as claimed in Claim 7 in which the data stream contains audio description data and the reproducing means comprises a speech synthesizer for producing an audio signal synchronised with the video picture.

11. An arrangement as claimed in Claim 7 or Claim 10 for replaying a VHS video tape as claimed in Claim 1 or Claim 6 wherein the data decoder is a teletext decoder capable of decoding data packets containing an audio description code and an identification code identifying the language of the audio represented by the audio description code in the packet.

12. An arrangement as claimed in any of Claims 7 to 11 comprising a VHS video recorder connected to or combined with a television receiver, wherein the video recorder includes the tape decoder and the television receiver includes the data decoder.

13. An arrangement as claimed in Claim 12 when dependent on Claim in which the television includes the speech synthesizer.