REPRODUCTION DEVICE WITH A SEARCH-REPRODUCTION MODE

Abstract: In a reproduction device (1) with magnetic tape transport means (17) for transporting a magnetic tape (4) at a first transport speed (V1) and at least a second transport speed (V2) which is higher than the first transport speed (V1), and reproduction means (8) for reproducing a digital video signal from a magnetic tape (4) transported at the first transport speed (V1) by the magnetic tape transport means (17), and control means (16) for controlling the magnetic tape transport means (17) for periodically alternately transporting the magnetic tape (4) at the first transport speed (V1) during a first time interval (T1) and at the second transport speed (V2) during a second time interval (T2), and with supply means (26) for supplying a reproduced digital video signal, the reproduction means (8) are adapted to reproduce a digital video signal recorded on a magnetic tape (4) and comprising an MPEG transport stream (MPEG Standard (System): ISO/IEC13.818-1), and the supply means (26) are adapted to supply a reproduced digital video signal only during first time intervals (T1).

Description: Reproduction device with a search-reproduction mode The invention relates to a reproduction device comprising magnetic tape transport means for transporting a magnetic tape at a first transport speed and at least a second transport speed which is higher than the first transport speed, and reproduction means for reproducing a digital video signal from a magnetic tape transported at the first transport speed by the magnetic tape transport means, and control means for controlling the magnetic tape transport means for periodically alternately transporting the magnetic tape at the first transport speed during a first time interval and at the second transport speed during a second time interval, and supply means for supplying a reproduced digital video signal. A reproduction device of this type described in the opening paragraph is known from US-A-5,239,429 and is constituted as a video recorder for reproducing digital video signals. The known video recorder comprises magnetic tape transport means with which a magnetic tape of a magnetic tape cassette inserted in the video recorder is transportable at a first transport speed which corresponds to the transport speed when recording a digital video signal on the magnetic tape. Reproduction means of the known video recorder are adapted to reproduce a digital video signal from a magnetic tape transported at the first transport speed by the magnetic tape transport means. The magnetic tape transport means are further adapted to transport a magnetic tape at a second transport speed which is higher than the first transport speed and corresponds to, for example, seven times the value of the first transport speed. The known video recorder further comprises control means with which a search-reproduction mode of the video recorder is realized, with which a user gets a quick survey of television broadcasts recorded as digital video signals on the magnetic tape, which broadcasts are quickly retrievable with the desired magnetic tape positions of the magnetic tape. The control means for controlling the magnetic tape transport means are constituted for this purpose, so as to achieve a periodically alternating transport of the magnetic tape at the first transport speed during a first time interval and at the second transport speed during a second time interval. The known video recorder further comprises a picture memory in which a part of a digital video signal reproduced during a first time interval and representing at least a television image of a reproduced television broadcast is stored during the first time interval. At the end of the first time interval, the storage of a reproduced video signal in the picture memory is ended, and during a subsequent second time interval, during which the magnetic tape is transported at the second transport speed, one or more television images stored in the picture memory are repeatedly supplied by the supply means of the video recorder. The supply means are constituted by address means for generating read address information for addressing television images stored in the picture memory and formed by the picture memory and are adapted to supply a reproduced digital video signal during first and second time intervals. The known video recorder has the drawback that the supply means, and particularly the picture memory, is very expensive. Moreover, only few television images can be stored in the picture memory because a picture memory for storing a sequence of television images is very expensive. It is an object of the invention to eliminate the above-mentioned difficulties and provide an improved reproduction device in accordance with the embodiment described in the opening paragraph. This object is achieved in a reproduction device in accordance with the embodiment described in the opening paragraph in that the reproduction means are adapted to reproduce a digital video signal recorded on a magnetic tape and comprising an MPEG transport stream (MPEG Standard (System): ISO/IEC13.818-1), and in that the supply means are adapted to supply a reproduced digital video signal only during first time intervals. This has the advantage that a part of a digital video signal reproduced during a first time interval by the reproduction means is directly supplied from an output terminal of the reproduction device constituting a supply means to, for example, a set-top box. During second time intervals, no digital video signal is supplied from the reproduction device to the set-top box and it is left to the set-top box whether it indicates, for example, an "On-Screen Display" with the text "no input signal" during second time intervals. In this way, a search-reproduction mode can be realized in a reproduction device for reproducing a digital video signal, without an expensive picture memory being required for one or more television images. Furthermore, arbitrarily long sequences of a reproduced television broadcast can be reproduced by a magnetic tape advantageously during first time intervals. In a recording device as defined in claim 1, it has proved to be advantageous to provide the measures as defined in claim 2. This yields the advantage that at least a so-called I-frame is reproduced during a first time interval, which I-frame is comprised once in a "Group of Pictures" and comprises picture information required for reproducing a television image of a reproduced television broadcast. A processing device for processing an MPEG transport stream is also adapted to supply a short sequence of consecutive television images when there is an I-frame for supplying a television image and when there is a complete "Group of Pictures", by evaluation of B-frames and P-frames possibly comprised in the "Group of Pictures". Time-control information may be advantageously supplied by a time stage to be provided in a video recorder, which measures first time intervals and supplies time-control information to the control means only after termination of a duration of the first time interval during which at least a complete "Group of Pictures" and hence certainly an I-frame has been reproduced by the reproduction means, so as to terminate the first time intervals at the earliest after this duration. Since the time interval for reproducing a complete "Group of Pictures" is dependent on the coding mode of an MPEG transport stream, the first time interval should be dimensioned to be large in this case. Time-control information may also be advantageously supplied by an I-frame detection stage to be provided in a video recorder, which stage recognizes the start and the end of a "Group of Pictures" with reference to header information of an I-frame laid down in the MPEG standard. It is, however, particularly advantageous to provide the measures as defined in claim 3 in a reproduction device as defined in claim 2. A processing device may be constituted, for example, by a set-top box or by a television apparatus and is adapted to process an MPEG transport stream. Since reception and processing of a complete I-frame of a "Group of Pictures" must be detected for processing an MPEG transport stream in the processing device, this detection result, which can be supplied to the reproduction device, can be used as time-control information. This is particularly advantageous because no additional means have to be provided in the reproduction device and substantially no additional means have to be provided in a processing device. Furthermore, this has the advantage that a reproduction of a digital video signal during the first time interval is only terminated when the reception of at least one complete I-frame of a "Group of Pictures" with a satisfactory reproduction quality is confirmed by a processing device by supplying time-control information. In a reproduction device as defined in claim 2, it has been found to be advantageous to provide the measures as defined in claim 4. When, in a search-reproduction mode, at least a television image last reproduced during a previous first time interval is to be reproduced repeatedly also during second time intervals, then it is particularly advantageous to use a reproduction memory of a processing device connectable to the reproduction device for processing a reproduced digital video signal as a picture memory for reproducing at least a television image stored in the reproduction memory during second time intervals. This yields a particularly low-cost reproduction device which uses a reproduction memory provided in each processing device for processing an MPEG transport stream during the search-reproduction mode of the reproduction device. In a reproduction device as defined in claim 4, it has proved to be advantageous to provide the measures as defined in claim 5. This yields the advantage that memory blocking information is directly inserted into a reproduced MPEG transport stream and that additional data bus means for transmitting memory blocking information to a processing device can be dispensed with. In a reproduction device as defined in claim 1, it has proved to be advantageous to provide the measures as defined in claim 6. This yields the advantage that time-control information or memory blocking information can be transmitted to a multitude of processing devices via a standardized data bus. Information can then be transmitted via a data bus, both in the case of an isochrone data transmission and in the case of an asynchronous data transmission in accordance with the IEEE-1394 standard. In a reproduction device as defined in claim 1, it has proved to be advantageous to provide the measures as defined in claim 7. This yields the advantage that text information can be inserted in an "On-Screen Display" generated by the OSD-generating means. For example, the title of a television broadcast reproduced in first time intervals, a count of an internal tape-counting mechanism or other additional information can be inserted as text information. Such an "On-Screen Display" can be indicated on a TV apparatus connected to the reproduction device in second time intervals for the purpose of additional information for a user. In a reproduction device as defined in claim 1, it has proved to be advantageous to provide the measures as defined in claim 8. This yields the advantage that a reverse-search- reproduction mode in the direction of the start of the magnetic tape is possible. These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. In the drawings: Fig. 1 is a block diagram of a reproduction device for reproducing digital video signals recorded on a magnetic tape in a search-reproduction mode, Fig. 2 shows diagrammatically the sequence of I, B and P-frames of a "Group of Pictures" in a digital video signal encoded in accordance with an MPEG standard, Fig. 3 shows diagrams of signal curves occurring with an activated search- reproduction mode of the reproduction device. Fig. 1 shows a reproduction device 1, a set-top box 2 and a television apparatus 3. Analog video signals recorded on a magnetic tape 4 are reproducible by means of the reproduction device 1 in a reproduction mode of this device and can be supplied from an analog output 5, while digital video signals recorded on the magnetic tape 4 are reproducible and can be supplied from a digital output 6. The set-top box 2 is connected to the analog output 5 and the digital output 6 of the reproduction device 1. The set-top box 2 constitutes a processing device and is adapted to process analog and digital video signals applied thereto and to supply an analog output signal AS from a first output terminal 7. The television apparatus 1 is connected to the first output terminal 7 and is adapted to optically indicate and acoustically reproduce television broadcasts reproduced by the output signal AS. The reproduction device 1 comprises reproduction means 8 which are adapted to reproduce analog video signals recorded on the magnetic tape 4 in accordance with the VHS standard and digital video signals recorded in accordance with the DVHS standard (Victor Company of Japan, no. 07015 of 25 July 1997). For this purpose, the reproduction means 8 comprise a scanner 9 on which a rotatably driven head disc 10 with a first magnetic head pair 11 and a second magnetic head pair 12 is provided. The magnetic tape 4 is guided along the scanner 9 and the head disc 10 by means of tape-guiding rolls 13 and 14 in a reproduction mode of the reproduction device 1. In a reproduction mode of the reproduction device 1, reproduction signals WS can be supplied from a second output terminal 15 alternately by one of the magnetic heads of the magnetic head pairs 11 and 12, which reproduction signals comprise analog or digital video signals recorded on the magnetic tape 4. The reproduction means 8 are also adapted to reproduce a digital video signal comprising an MPEG transport stream (MPEG Standard (System): ISO/IEC13.818-1) recorded on the magnetic tape 4 in accordance with the DVHS standard. It may be noted that an MPEG transport stream is constituted by transport stream packets in which video packets comprising encoded video data, audio packets comprising encoded audio data, data packets comprising additional data and table packets comprising table information are laid down in the MPEG standard. An MPEG transport stream may comprise one program stream or a plurality of program streams, with table information determining which video packets, audio packets and data packets are to be assigned to a program stream. A program stream comprises the picture information and sound information required for the optical indication and acoustical reproduction of a television broadcast. Data packets may comprise additional information relating to the television broadcast which may be formed, for example, by the title of the television broadcast or by a survey of contents of the television broadcast. The reproduction device 1 further comprises first control means 16 and magnetic tape transport means 17. The magnetic tape transport means 17 are adapted to transport the magnetic tape 4 at a first transport speed VI and at a second transport speed V2 which is higher than the first transport speed VI. For this purpose, the magnetic tape transport means 17 have a motor 18, a capstan 19 and a pressure shaft 20. In a reproduction mode of the reproduction device 1, the motor 18 is adapted to drive, via a connection 21, the capstan 19 against which the magnetic tape 4 is pressed by the shaft 20. As a result, the magnetic tape 4 is transported at a transport speed VI or V2, dependent on the rotational speed of the motor 18. The magnetic tape transport means 17 are adapted to transport the magnetic tape 4 in a first transport direction Rl during first time intervals Tl, and to transport the magnetic tape 4 in the first transport direction Rl but also in a second transport direction R2 during second time intervals T2, which will be further described hereinafter. The first control means 16 are also adapted, inter alia, to control the magnetic tape transport means 17 and to supply motor control information MSI to the motor 18. In a search-reproduction mode, the control means 16 are adapted to control the magnetic tape transport means 17 for periodically alternately transporting the magnetic tape 4 at the first transport speed VI during a first time interval Tl and at the second transport speed V2 during a second time interval T2, which will be described in further detail hereinafter. The first control means 16 have time means 22 constituted by a timer with which the first time interval Tl and the second time interval T2 are predeterminable, which will hereinafter be described in greater detail. The first control means 16 further have insertion means 23 which are adapted to insert insertion information DEI constituting memory blocking information in a table packet of an MPEG transport stream comprised in a reproduced digital video signal. The bit sequence "010" constitutes insertion information DEI and can be inserted as "trick-mode control" information in a PES table, which will be further described hereinafter. The reproduction device 1 is adapted, in a manner not further shown in Fig. 1, to detect whether a video signal recorded on the magnetic tape 4 was recorded as an analog video signal in accordance with the VHS standard or as a digital video signal in accordance with the DVHS standard. In a reproduction of an analog video signal recorded in accordance with the VHS standard, a reproduction signal WS supplied by the reproduction means 8 from the second output terminal 15 can be supplied to VHS processing means 24. The VHS processing means 24 are adapted to process a reproduction signal WS comprising an analog video signal and to supply a first television signal FS1 to the analog output 5 of the reproduction device 1, as is generally known. The reproduction device 1 further comprises OSD-generating means 25 which are adapted to generate "On-Screen Display" comprising text information. Such text information may be constituted, for example, by additional information for a television broadcast of a reproduced analog or digital video signal. Such additional information may be determined, for example, from teletext information comprised in a reproduced television signal and may be constituted by the title or the recording date of the television broadcast. Furthermore, such text information may be constituted by the count of a tape-counting mechanism not shown in Fig. 1, indicating the magnetic tape position from which a reproduction signal WS is reproduced by the magnetic tape 4. An "On-Screen Display" generated by the OSD-generating means 25 can be inserted in the first television signal FS1 or forms a first television signal FS1 by means of the first control means 16 by supplying OSD insertion information OSD at given time intervals. When reproducing a digital video signal recorded in accordance with the DVHS standard, a reproduction signal WS supplied by the reproduction means 8 from the second output terminal 15 can be supplied to supply means 26. The supply means 26 are adapted to supply an MPEG transport stream comprised in a reproduced digital video signal to the digital output 6 of the reproduction device 1. The supply means 26 comprise DVHS processing means 27 and first data bus means 28 for this purpose. The DVHS processing means 27 are adapted to process a reproduced digital video signal comprising an MPEG transport stream corresponding to the DVHS standard, as is known, for example, from the document with the application no. 98 201 959.8 (European patent application). For this purpose, the DVHS processing means 27 comprise, inter alia, error correction means 29 and time stamp means 30. The error correction means 29 are adapted to evaluate error correction information comprised in a reproduced digital video signal in accordance with the DVHS standard and to supply a corrected reproduced digital video signal to the time stamp means 30. The error correction means 29 are further adapted to supply a valid information DG to the time means 22 of the first control means 16, which will be described in greater detail hereinafter. The time stamp means 30 are adapted to evaluate time stamp information comprised in a reproduced digital video signal so as to supply transport stream packets of an MPEG transport stream comprised in the reproduced digital video signal with the distances in time which these transport packets had when the digital video signal was recorded. An MPEG transport stream supplied by the time stamp means 30 and the DVHS processing means 27 can be supplied to the first data bus means 28. The first data bus means 28 are adapted to communicate with further data bus means corresponding to an IEEE-1394-standard via a data bus 31. In accordance with the IEEE-1394-standard, an isochrone and an asynchronous data transmission is provided. In the isochrone data transmission, time critical data such as, for example, an MPEG transport stream can be transmitted. In the asynchronous data transmission, less time-critical control information such as, for example, reproduction device control information WSI can be transmitted. Reproduction device control information WSI received in the case of asynchronous data transmission can be supplied by the first data bus means 28 to the first control means 16, which will be further described hereinafter. The first data bus means 28 are connected to the digital output 6. Second data bus means 32 of the set-top box 2 are connected via the data bus 31 to the digital output 6 and adapted to communicate with the first data bus means 28 of the reproduction device 1. In the case of isochrone data transmission, an MPEG transport stream comprised in a reproduced digital video signal is transmissible from the first data bus means 28 via the digital output 6 and the data bus 31 to the second data bus means 32. By complying with the IEEE-1394- standard in a data transmission with the first data bus means 28, the advantage is obtained that the data bus means 28 are adapted to communicate with a multitude of other data bus means of processing devices because a multitude of data bus means complies with the IEEE- 1394- standard. The set-top box 2 comprises a demultiplexer 33, decoding means 34, a switch 35, second control means 36 and a key block 37 for processing an MPEG transport stream received with the second data bus means 32 and for supplying an output signal AS. The key block 37 has a plurality of keys for controlling the set-top box 2 and the reproduction device 1. Input information El can be supplied from the key block 37 to the second control means 36. When input information El supplied with the key block 37 to the second control means 36 is provided for controlling the operating mode of the reproduction device 1, reproduction device control information WSI can be supplied by the second control means 36 in the case of asynchronous data transmission via the second data bus means 32 and the data bus 31 to the data bus means 28 of the reproduction device 1 and, from this device, to the first control means 16. When input information El supplied with the key block 37 to the second control means 36 is provided for selecting a program stream comprised in an MPEG transport stream received by the second data bus means 32, program control information PSI can be supplied to the demultiplexer 33 by the second control means 36. When there is program control information PSI, the demultiplexer 33 is adapted to select the program stream characterized by the program control information PSI from program streams comprised in a received MPEG transport stream. A program stream selected by the demultiplexer 33 can be supplied to the decoder means 34 for decoding video data and audio data comprised in the program stream. For this purpose, the decoder means 34 have a decoder stage 38, a reproduction memory 39 and table means 40. A program stream supplied by the demultiplexer 33 can be applied both to the decoder stage 38 and to the table means 40. The decoder stage 38 is adapted to decode video data comprised in video packets of a program stream and coded in accordance with the MPEG video standard (MPEG Standard (Video): ISO/IEC13.818-2). Fig. 2 shows the sequence of picture information comprised in video packets and formed by coded video data of a video signal coded in accordance with the MPEG video standard. Picture information is comprised in I-frames, B-frames and P-frames. An I-frame, one or more B-frames and one or more P-frames constitute a "Group of Pictures". When coding video data, it is fixed every time whether and how many B-frames and P-frames are comprised in a "Group of Pictures". An I-frame comprised in each "Group of Pictures" comprises the picture information which is sufficient for displaying a television picture of a television broadcast by means of the television apparatus 3. A B-frame only comprises modification information relating to a previous and a subsequent frame. The picture information comprised in a B-frame is not sufficient for displaying a television picture of a television broadcast by means of the television apparatus 3 without the picture information of an I-frame. A P-frame comprises modification information relating to a previous I-frame and a subsequent I-frame. The picture information comprised in a P-frame is not sufficient for displaying a television picture by means of the television apparatus 3 without the picture information of an I-frame. The decoder stage 38 is adapted to decode video data for storing received video data in the reproduction memory 39. Video data of at least one "Group of Pictures" are stored in the reproduction memory 39 because video data of a "Group of Pictures" are only jointly decodable. With the picture information comprised in a "Group of Pictures", a plurality of television images, constituting a scene, of a television broadcast can be displayed with the television apparatus 3. The decoder stage 38 is also adapted to decode audio data comprised in a received program stream. Decoded video data can be supplied as analog video signals and decoded audio data can be supplied as analog audio signals to the switch 35 in the form of a second television signal FS2. The second control means 36 are adapted to supply switching control information USI to the switch 35. In dependence on switching control information USI supplied thereto, the switch 35 is adapted to supply a first television signal FS1 or a second television signal FS2 as an output signal AS to the first output terminal 7. The table means 40 are adapted to evaluate table information comprised in table packets and laid down in MPEG system standard (MPEG Standard (System): ISO/EEC 13.818- 1). The table means 40 are adapted, for example, to evaluate "trick-mode control" information of a PES table. The bit sequence "010" of the "trick-mode control" information stands for a "freeze-frame" command in which a processing device such as, for example, the set-top box 2, is assigned to freeze the last supplied picture information stored in the reproduction memory 39 and to supply it in a further sequence as a second television signal FS2 for displaying a television picture on the television apparatus 3. To ensure a freeze of last supplied picture information, the table means 40 are adapted to supply "freeze-frame" information FF1 to the second control means 36. When "freeze-frame" information FFI occurs, the second control means 36 are adapted to supply storage blocking information SSI to the decoder stage 38. When there is storage blocking information SSI, the decoder stage 38 is adapted to block an overstorage of video data stored at this instant in the reproduction memory 39 and to supply picture information, stored in the reproduction memory 39, of an I-frame as a second television signal FS2. The decoder stage 38 is adapted to detect header information of an I-frame received in a video packet. When the decoder stage 38 detects such header information, which means that the video data of an I-frame have been received by the decoder stage 38 and are stored in the reproduction memory 39, and a "freeze-frame" command can be given, then the decoder stage 38 is adapted to supply detection information DI to the second control means 36. When there is detection information DI, the second control means 36 are adapted to supply time-control information ZSI to the second data bus means 32. In the case of asynchronous data transmission, the second data bus means 32 are adapted to supply the time-control information ZSI to the first data bus means 28 which constitute receiving means for receiving the time-control information ZSI from a connected processing device and are adapted to supply the received time-control information ZSI to the first control means 16. With the key block 37 of the set-top box 2, a search-reproduction mode of the reproduction device 1 can now be activated. In the case of an activated search-reproduction mode, a part of a television broadcast reproduced by means of the reproduction device 1 is displayed on the television apparatus alternately during first time intervals Tl, during which the magnetic tape 4 is transported at the first transport speed VI, and a last displayed television picture is frozen as a still picture during second time intervals T2 during which the magnetic tape 4 is transported at the high transport speed V2. A user thereby obtains a quick survey of television broadcasts which are recorded as digital video signals on the magnetic tape 4. Furthermore, desired magnetic tape positions of the magnetic tape 4 can be quickly retrieved. The magnetic tape 4 is searched in the direction towards the end of the magnetic tape 4 in the first transport direction Rl when the search-reproduction mode is used. It may be noted that a "trick play" reproduction for reproducing a digital video signal recorded on the magnetic tape 4 in accordance with the DVHS standard, in which the magnetic tape 4 upon reproduction of a reproduction signal WS is transported at a multifold value of the first transport speed VI, is only possible with the reproduction device 1 when "trick play" data are recorded in special "trick play" recording areas on the magnetic tape 4, as is known, for example, from the document with application no. 98.201.959.8 (European patent application). A search-reproduction mode is advantageously also possible when no "trick play" data are recorded on the magnetic tape 4. When input information El is supplied by the key block 37 to the second control means 36 for activating the search-reproduction mode, the second control means 36 are adapted to supply corresponding reproduction device control information WSI via the data bus 31 to the first data bus means 16. When such reproduction device control information WSI occurs, the first control means 16 are adapted to supply motor control information MSI for controlling the magnetic tape transport means 17 for periodically alternate transport of the magnetic tape 4 at the first transport speed VI during a first time interval Tl and at the second transport speed V2 during a second time interval T2. A diagram in Fig. 3A shows the variation with respect to time of the transport speed V of the magnetic tape 4 from an instant ti at which the search-reproduction mode in the reproduction device 1 was activated. From the instant t|, the reproduction means 8 supply a digital video signal recorded on the magnetic tape 4 in accordance with the DVHS standard as a reproduction signal WS to the DVHS processing means 27. From an instant t , transients in the reproduction means 8 and the DVHS processing means 27 have diminished to such an extent that the error correction means 29 determine a low rate of non-corrigible errors, whereupon the error correction means 29 are adapted to supply the valid information DG to the time means 22 of the first control means 16. A diagram in Fig. 3B shows the variation with respect to time of the valid information DG which remains valid until there is a change of the transport speed V. From the instant t , a reproduced MPEG transport stream is supplied by the supply means 26 via the data bus means 28 and 32 and the demultiplexer 33 to the decoder means 34. As is shown in Fig. 2, the video data comprised in video packets of the MPEG transport stream from the instant t 2 initially comprise picture information of a B-frame stored in the reproduction memory 39. Subsequently, picture information of a P-frame and another two B-frames is received by the decoder stage 38 and stored in the reproduction memory 39. At an instant t 3 , picture information of an I-frame is received by the decoder stage 38 and stored in the reproduction memory 39. From the instant t 3 , the decoder means 34 are adapted to supply a first television image of the reproduced television broadcast as a second television signal FS2. As explained hereinbefore, the decoder stage 38 is adapted to detect the header information of an I-frame and to supply detection information DI to the second control means 36. This detection information DI is supplied by the second control means 36 directly as time-control information ZSI via the data bus 31 to the first control means 16. As is shown in Fig. 3C, time-control information ZSI remains valid up to an instant t 4 when the transport speed V of the magnetic tape 4 is changed. The time-control information ZSI, characterizing a complete reproduction of at least an I-frame of a reproduced MPEG transport stream, can now be supplied to the first control means 16. Even when the duration of the first time interval Tl is very short, the first control means 16 is now adapted to end the first time interval Tl only after the occurrence of the time-control information ZSI. This yields the advantage that, at the end of the first time interval Tl and at the instant t 4 , always at least an I-frame is stored in the reproduction memory 39 of the set-top box 2 for reproducing a television picture of a reproduced television broadcast. As is shown in Fig. 2, the duration of the first time interval Tl is adjusted in such a way that, during the first time interval Tl, even further frames also constituting an overall "Group of Pictures" GOP are reproduced and stored by the decoder stage 38 in the reproduction memory 39. At the instant t 4 , the time means 22 determine the end of the first time interval Tl. Since at this instant t 4 also already time-control information ZSI has been supplied to the first control means 16, the first control means 16 supply motor control information MSI to the magnetic tape transport means 17 for transporting the magnetic tape 4 at the second transport speed V2. Furthermore, the insertion means 23 of the first control means 16 are adapted at the instant t to insert the insertion information DEI in a PES table of the reproduced MPEG transport stream. The insertion information DEI already constitutes storage blocking information SSI and is used for freezing picture information stored at the instant t 4 in the reproduction memory 39 and displayed on the television apparatus 3 during essentially the second time interval T2. A diagram in Fig. 3D shows the variation with respect to time and the validity of the storage blocking information SSI. As explained hereinbefore, insertion information DEI inserted in a PES table of an MPEG transport stream is detectable by the table means 40 which thereupon supplies "freeze-frame" information FFI to the second control means 36. The second control means 36 are adapted to supply the actual storage blocking information SSI to the decoder stage 38 for freezing the storage contents of the reproduction memory 39 and thus for preventing overstorage of picture information of the frames shown in Fig. 2. During the period of validity of the storage blocking information SSI, the decoder stage 38 is adapted to read from the reproduction memory 39 and to decode the picture information of the I-frame decoded at the instant t 4 . This yields the advantage that, also during second time intervals T2, a television picture of a television broadcast reproduced during first time intervals Tl is reproduced without a reproduction memory in the reproduction device 1 being required for this purpose. By inserting insertion information DEI in a reproduced MPEG transport stream, the advantage is obtained that the insertion information DEI is detected by the table means 40 exactly at the instant when no further picture and sound information is comprised in the MPEG transport stream, because the magnetic tape 4 is transported at the second transport speed V2. When the time means 22 determine the end of the second time interval T2 at the instant t 5 , the first control means 16 supply motor control information MSI to the magnetic tape transport means 17 for transporting the magnetic tape 4 at the first transport speed VI. At the instant t , the error correction means 29 again determine a low rate of non-corrigible errors, whereupon the error correction means 29 supply the valid information DG to the time means 22 of the first control means 16. At an instant t , the decoder stage 38 receives picture information of an I-frame and detects header information of the I-frame. A time interval between the instants ti and t 3 may deviate from a time interval between the instants t 5 and t 7 in this case, because the reproduction may start at a different position within a "Group of Pictures". Time-control information ZSI supplied after the detection of header information of an I-frame by the second control means 36 to the first control means 16 has the result that no insertion information DEI is inserted any longer by the insertion means 23 in a PES table of a reproduced MPEG transport stream. From the instant t 7 , the television picture of the television broadcast reproduced on the television apparatus 3 during the second time interval T2 is no longer displayed, but a scene of the television broadcast reproduced between the instants t 7 and t 8 is displayed. When the search-reproduction mode is activated, OSD insertion information OSD is supplied during second time intervals T2 to the OSD-generating means 25 for generating and inserting "On-Screen Displays" comprising text information. Text information can be determined, in a manner not shown in Fig. 1, for example from the data packets of the reproduced MPEG transport stream. This "On-Screen Display" is supplied as a first television signal FS1 to the switch 35 of the set-top box 2. Advantageously, it is thus possible that the second control means 36 of the set-top box 2 supplies switching control information USI to the switch 35 during the validity of the storage blocking information SSI - thus, for example, between the instants t 4 and t - and the "On-Screen Display" is reproduced with additional information relating to the reproduced television broadcast during essentially the second time interval T2. From the instant t 8 up to the end of the validity of the storage blocking information SSI, a television picture stored in the reproduction memory can be reproduced. This yields the advantage that a user also receives additional information relating to a reproduced television broadcast during a part of the second time intervals T2, enabling him to retrieve a desired magnetic tape position even more rapidly. In the reproduction device 1, a reverse-search reproduction mode can be activated in a manner not shown in Fig. 1, in which the magnetic tape 4 is transported in the first transport direction Rl during first time intervals Tl and in the second transport direction R2 during second time intervals T2. Apart from the transport direction R during second time intervals T2, the processing in the case of the reverse-search reproduction mode corresponds to the processing in the case of the search-reproduction mode. This yields the advantage that the user can also search the magnetic tape 4 in the second transport direction R2 towards the start of the magnetic tape 4. It may be noted that "On-Screen Display" with additional information relating to a reproduced television broadcast can also be generated in the set-top box. Advantageously, additional information may be determined from data packets of a reproduced MPEG transport stream. It may be noted that the duration of the time intervals Tl and T2 and the second transport speed V2 can be adjusted by a user. In this case, the user can determine, for example, that a television broadcast is reproduced and displayed on the television apparatus 3 during a time interval Tl of 3 seconds. During a subsequent, second time interval T2 of, for example, 5 seconds, the magnetic tape can then be transported at the second transport speed V2 which might correspond to, for example, 20 times the value of the first transport speed VI. Dependent on the desired search mode of a desired magnetic tape position, a multitude of further time intervals T and second transport speeds V2 is feasible such as, for example, Tl = 10 seconds, T2 = 40 seconds and V2 = 50 x the first transport speed VI. It may be noted that a set-top box may also be adapted to reproduce scenes of a reproduced television broadcast - whose picture information in one or more "Groups of Pictures" may be stored in a reproduction memory of the set-top box - during second time intervals T2. It may be noted that, when "trick play" data for reproduction at, for example, the 12-fold transport speed are recorded on a magnetic tape, the first transport speed VI may also correspond to this 12-fold transport speed and the second transport speed V2 may then correspond to, for example, 3 times the value of the first transport speed VI. It may be noted that reproduction means of a reproduction device with a search- reproduction mode may also be adapted to reproduce an analog video signal. It may be noted that additional information, which can be inserted as text information in an "On-Screen Display", may also be determined from VASS data (Video Address Search System) of an analog video signal or from sub-code data or main-code data of a digital video signal corresponding to the DVHS standard, and, for example, may also comprise archive information about television broadcasts recorded on magnetic tapes. It may be noted that only I-frames of a plurality of "Groups of Pictures" may be stored in a reproduction memory, which I-frames are then reproducible as a sequence of television pictures during second time intervals T2. It may be noted that storage blocking information may also be supplied by the first control means of the reproduction device in the case of asynchronous data transmission via the data bus means and the data bus to the second control means of the set-top box. Furthermore, the insertion means may also be adapted to insert storage blocking information in data packets of a reproduced MPEG transport stream.

Claims: CLAIMS 1. A reproduction device (1) comprising magnetic tape transport means (17) for transporting a magnetic tape (4) at a first transport speed (VI) and at least a second transport speed (V2) which is higher than the first transport speed (VI), and reproduction means (8) for reproducing a digital video signal from a magnetic tape (4) transported at the first transport speed (VI) by the magnetic tape transport means (17), and control means (16) for controlling the magnetic tape transport means (17) for periodically alternately transporting the magnetic tape (4) at the first transport speed (VI) during a first time interval (Tl) and at the second transport speed (V2) during a second time interval (T2), and supply means (26) for supplying a reproduced digital video signal, characterized in that the reproduction means (8) are adapted to reproduce a digital video signal recorded on a magnetic tape (4) and comprising an MPEG transport stream (MPEG Standard (System): ISO/_EC13.818-l), and in that the supply means (26) are adapted to supply a reproduced digital video signal only during first time intervals (Tl). 2. A reproduction device (1) as claimed in claim 1, characterized in that time- control information (ZSI) can be supplied to the control means (16), which information characterizes a complete reproduction, realized during the first time interval (Tl), of at least an I-frame of a "Group of Pictures" (GOP) of an MPEG transport stream laid down in the MPEG standard, and in that the control means (16) are adapted to terminate the first time interval (Tl) only after the occurrence of time-control information (ZSI). 3. A reproduction device (1) as claimed in claim 2, characterized in that the supply means (26) are adapted to supply a reproduced digital video signal to a processing device (2) which is connectable to the reproduction device (1), and in that receiving means (28) are adapted to receive time-control information (ZSI) from a connected processing device (2) and to supply received time-control information (ZSI) to the control means (16). 4. A reproduction device (1) as claimed in claim 2, characterized in that, at the end of the first time interval (Tl), the supply means (26) are adapted to supply storage-blocking information (SSI) to a processing device (2) connectable to the reproduction device (1) for the purpose of blocking overstorage of picture information of at least a television picture (I-frame) of a reproduced digital video signal stored at this instant (t 4 , t 8 ) in a reproduction memory (39) of the processing device (2). 5. A reproduction device (1) as claimed in claim 4, characterized in that insertion means (23) are provided which, at the end of every first time interval (Tl), are adapted to insert storage-blocking information (DEI, SSI) in an MPEG transport stream reproduced as a digital video signal. 6. A reproduction device (1) as claimed in claim 1, characterized in that the supply means (26) are adapted to supply information in accordance with an IEEE-1394-standard. 7. A reproduction device (1) as claimed in claim 1, characterized in that OSD- generating means (25) are provided which are adapted to generate "On-Screen Displays" comprising text information which can be supplied by the reproduction device (1) in second time intervals (T2). 8. A reproduction device (1) as claimed in claim 1, characterized in that the magnetic tape transport means (17) are adapted to transport a magnetic tape (4) in a first transport direction (Rl) during first time intervals (Tl) and in a second, opposite transport direction (R2) during second time intervals (T2).

Inventors: RICHTER MANFRED, RICHTER, MANFRED
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 1999
Main classification: H04N5
IPC codes: G11B7, G11B20, G11B27, H04L12, H04N5