Encoded data stream recording and reproducing apparatus

Abstract: According to the present invention, a recording and reproducing apparatus for an input encoded data stream having two different bit rates of N 1 and N 2 (where N 1 < N 2 ) is provided. The recording and reproducing apparatus includes: an input interface (2) having two outputs for outputting the input encoded data stream to two channels, the input interface dividing and outputting the input encoded data stream to both of the two channels when the bit rate of the input encoded data stream is N 1 , while the input interface outputting the input encoded data stream to only one of the two channels when the bit rate of the input encoded data stream is N 2 ; a first recording processor (3) and a second recording processor (4) for converting the input encoded data stream into a signal suitable for being recorded so as to supply the signal to a recording head (6,7), the first recording processor and the second recording processor being connected with the two outputs of the input interface; a recording head (6,7) for writing the signal onto a magnetic tape; a tape speed controller (5) for varying a speed for transporting the magnetic tape in accordance with the bit rates of the input encoded data stream; a reproducing head (9,10) for reading the signal from the magnetic tape; a first reproducing processor (11) and a second reproducing processor (12) for performing a predetermined reproduction processing for a signal reproduced from the reproducing head (9,10); and an output interface (13) having two inputs for inputting the signals from two channels, the input interface integrating and outputting the signals input from the two channels when the bit rate of the reproduced encoded data stream is N 2 , while the output interface outputting the signal input from only one of the two channels when the bit rate of the reproduced encoded data stream is N 1 .

Description: 1. Field of the Invention: The present invention relates to an input encoded data stream recording and reproducing apparatus. More specifically, the present invention relates to an input encoded data stream recording and reproducing apparatus for correcting a reproduced data where an error has been generated, and a recording and reproducing apparatus allowing for reproducing a trick play video of satisfactory quality. 2. Description of the Related Art: Nowadays, a multi-channel satellite broadcasting service is available in the United States. Such a multi-channel satellite broadcasting is realized by considerably compressing a video signal or an audio signal by utilizing digital compression technologies. In the multi-channel satellite broadcasting, the bit rate for the channel to be transmitted is varied in accordance with the contents of the program to be broadcast and the like. For example, in the case of broadcasting a movie or the like, the bit rate for the channel is set to be low, e.g., 3 Mbps, while in the case of broadcasting a live video or the like, the bit rate for the channel is set to be high, e.g., 6 Mbps. A similar service based on conventional technologies utilizing a ground wave, a communication satellite, a cable network and the like is going to be available in the near future in Japan and Europe, too. In other words, such a multi-channel broadcasting is on the point of being put into practice by reducing the communication cost for each channel by utilizing the newest digital compression technologies. On the other hand, the introduction of the digital technologies into a recording and reproducing apparatus has remarkably been developed these days. As a result, several kinds of recording and reproducing apparatuses allowing for a digital recording are practically used now. In a digitally recording type recording and reproducing apparatus for performing a helical recording on a tape-shaped recording medium, in order to perform a high-speed reproduction by transporting the tape-shaped recording medium at a faster speed as compared with the speed for a normal reproduction, the data for the high-speed reproduction is repeatedly recorded in the high-speed reproduction regions on the tape-shaped recording medium several times. According to such a method, it is possible to stably perform the high-speed reproduction by simplifying the control of the heads and the magnetic tape during the high-speed reproduction. Since the above-mentioned service was begun, currently available video tape recorders (VTRs) for a home-use, e.g., VTRs of VHS, S-VHS, and 8 mm, record an analog video signal obtained by decoding the received digital signal. Accordingly, it is impossible to vary the recording time period in accordance with the bit rate of the input encoded data stream. For example, the recording time period required in the case of receiving a broadcasting at a bit rate of 3 Mbps does not become twice as long as that required in the case of receiving a broadcasting at a bit rate of 6 Mbps, but becomes the same length as in a 6 Mbps. In addition, although a large number of programs are simultaneously broadcast by the above-mentioned service, it is still impossible to simultaneously record a plurality of programs by using one and the same VTR. The problem lies in the method for recording the digital data in conventional VTRs. More specifically, although the digital data, obtained by converting an analog video signal, an analog audio signal or the like, is transmitted after compressing the digital data so as to have the bit rate reduced as described above, the conventional VTRs record an analog video signal or an analog audio signal obtained by decoding the transmitted digital data, not the digital data itself. SUMMARY OF THE INVENTION According to one aspect of the present invention, a recording and reproducing apparatus for an input encoded data stream having two different bit rates of N 1 and N 2 (where N 1 < N 2 ) is provided. The recording and reproducing apparatus comprises: an input interface having two outputs for outputting the input encoded data stream to two channels, the input interface dividing and outputting the input encoded data stream to both of the channels when the bit rate of the input encoded data stream is N 2 , while the input interface outputting the input encoded data stream to only one of the two channels when the bit rate of the input encoded data stream is N 1 ; a first recording processor and a second recording processor for converting the input encoded data stream into a signal suitable for being recorded so as to supply the signal to a recording head, the first recording processor and the second recording processor being connected with the two outputs of the input interface; a recording head for writing the signal onto a magnetic tape; a tape speed controller for varying a speed for transporting the magnetic tape in accordance with the bit rates of the input encoded data stream; a reproducing head for reading the signal from the magnetic tape; a first reproducing processor and a second reproducing processor for performing a predetermined reproduction processing for a signal reproduced from the reproducing head; and an output interface having two inputs for inputting the signals from two channels, the input interface integrating and outputting the signals input from the two channels when the bit rate of the reproduced encoded data stream is N 2 , while the output interface outputting the signal input from only one of the two channels when the bit rate of the reproduced encoded data stream is N 1 , wherein the speed for transporting the magnetic tape and a number of the channels used for recording and reproducing operations are varied in accordance with the bit rates of the input encoded data stream. In one embodiment of the present invention, the recording and reproducing apparatus for an encoded data stream includes: an input terminal for inputting an analog video signal; an output terminal for outputting the analog video signal; an analog recording processor for processing the analog video signal so as to record the analog video signal onto the magnetic tape; and an analog reproducing processor for processing the analog video signal so as to reproduce the analog video signal from the magnetic tape, wherein a rotation speed of a cylinder, on which the recording head and the reproducing head are mounted, is not varied in both cases of recording the analog video signal and the encoded data stream. According to one embodiment of the present invention, the recording and/or reproducing apparatus for an encoded data stream further comprises: an error detection means for detecting an error from a reproduced signal and outputting error detection information when the error is detected; a refresh information detection means for outputting a refresh information signal indicating a timing of a refresh performed in a differential pulse coding from a reproduced signal; and a correction means for generating a signal in a refresh period during which no error is generated from the reproduced signal by using a signal output from the error detection means and the signal output from the refresh information detection means so as to substitute the signal in the refresh period during which no error is generated for the signal in a refresh period during which the error is generated. According to another embodiment of the present invention, the recording and/or reproducing apparatus for an encoded data stream further comprises: a memory means for storing the reproduced signal; and a controller for controlling the memory means so that a signal in a refresh period during which no error is generated is output in place of the signal in a refresh period during which an error is generated, by using the output from the error detection means and the output from the refresh information detection means. According to still another embodiment of the present invention, the recording and reproducing apparatus for an encoded data stream further comprises: a data bit number converter for converting a bit number of the signal in a refresh period during which no error is generated into a bit number of the signal in a refresh period during which an error is generated, by using the signal output from the memory means as an input. In order to solve the above-mentioned problems, an encoded data stream recording and reproducing apparatus of the invention includes a plurality of recording processors and reproducing processors so as to vary the tape transporting speed and the number of the channels to be used for the recording and reproducing operations in accordance with the bit rate of the input encoded data stream. The recording and reproducing apparatus of the present invention having the above-described configuration performs the recording and reproducing operations by using recording and reproducing processors for one channel in the case where the bit rate of the input encoded data stream is low, and using recording and reproducing processors for multiple channels while varying the tape transporting speed in the case where the bit rate of the input encoded data stream is high. In other words, the recording and reproducing apparatus of the present invention realizes highly efficient recording and reproducing operations by varying the amount of the consumed tape in accordance with the bit rate of the input encoded data stream. In addition, the recording and reproducing apparatus of the present invention can also record and reproduce plural kinds of encoded data with a low bit rate by using the recording and reproducing processors for multiple channels. Furthermore, the recording and reproducing apparatus of the present invention can also record and reproduce the data while maintaining the data in the state of a digital signal, so that the quality of the video is hardly degraded unlike currently available VTRs for recording and reproducing the data after decoding the digital signal into an analog signal. Thus, the invention described herein makes possible the advantage of providing a VTR allowing for recording a data for a long time period in the case where a program with a low bit rate is input, and simultaneously recording a plurality of programs. This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram schematically showing a configuration of an encoded data stream recording and reproducing apparatus according to an example of the present invention. Figure 2 shows a configuration of a cylinder for the recording and reproducing apparatus according to the example of the present invention. Figures 3A and 3B show recording track patterns in the recording and reproducing apparatus according to the example of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, an encoded data stream recording and reproducing apparatus according to the present invention will be described by way of an illustrative example with reference to accompanying drawings. The same reference numerals denote the same components throughout the drawings. It is noted that a "recording and reproducing apparatus" refers to an "encoded data stream recording and reproducing apparatus". Figure 1 is a block diagram schematically showing a configuration of a recording and reproducing apparatus according to an example of the present invention. An input terminal 1 receives an encoded data stream. An input interface 2 detects a bit rate of the input data stream so as to distribute and output the data stream to two channels in accordance with the detected bit rate of the data stream. Recording processors 3 and 4 convert the two divided data streams into a signal suitable for being recorded on a magnetic tape. A tape speed controller 5 varies the speed for transporting a magnetic tape 8 in accordance with the detected bit rate of the data stream. Recording heads 6 and 7 record the signals output from the recording processors 3 and 4 onto the magnetic tape 8 , respectively. Reproducing heads 9 and 10 reproduce and output the signal recorded by the recording heads 6 and 7 from the magnetic tape 8 . Reproducing processors 11 and 12 receive the signals output from the reproducing heads 9 and 10 , process the signals in a predetermined manner, and output the processed signals. An output interface 13 receives the signals output from the reproducing processors 11 and 12 , restores the signals into the same encoded data stream as the recorded one and outputs the restored data stream to an output terminal 14 . In Figure 1 , the recording processor 3 , the recording head 6 , the reproducing head 9 and the reproducing processor 11 will be regarded as a first channel and the recording processor 4 , the recording head 7 , the reproducing head 10 and the reproducing processor 12 will be regarded as a second channel. Both bit rates cf the encoded data streams to be recorded and reproduced by using the first and the second channels will be assumed to be N Mbps. Figure 2 schematically shows a configuration of the heads to be used for the recording and reproducing operations. As shown in Figure 2 , the heads 6a, 6b, 7a and 7b are mounted on a cylinder 15 . The heads 6a and 6b are used for the recording and reproducing operations performed by the first channel, while the heads 7a and 7b are used for the recording and reproducing operations performed by the second channel. Hereinafter, the operation of the recording and reproducing apparatus having the above-described configuration will be described as being applied to the case where encoded data streams with two kinds of bit rates, i.e., N Mbps and 2N Mbps, are input to the input terminal 1 . The input interface 2 outputs the data stream only to the first channel when the bit rate of the input encoded data stream is N Mbps, and outputs the data stream to both the first and the second channels when the bit rate of the input encoded data stream is 2N Mbps. First, the case where the data stream with the bit rate of N Mbps is input will be described. The input interface 2 detects the bit rate of the data stream to be N Mbps. Based on the detected bit rate, the input interface 2 outputs the encoded data stream only to the recording processor 3 . The recording processor 3 processes the input encoded data stream so as to record the data stream on the magnetic tape 8 . For example, the processings include: an encoding using an error correction code (ECC); an addition of a sync (synchronization) data and an ID data; a modulation; a recording equalizaticn; and a recording amplification. The processed signal is recorded on the magnetic tape 8 by the recording head 6 . In this case, the recording processor 4 is not required to operate and the recording head 7 is not required to record the signal, either. In other words, the data stream can be recorded and reproduced by using only the first channel. Figure 3A shows the pattern of the track recorded on the magnetic tape 8 when the recording and reproducing operations are performed by using only the first channel. In performing the recording operaticn, two recorded tracks are formed by the recording heads 6a and 6b during one rotation of the cylinder 15 . In performing the reproducing operation, the signal reproduced by the reproducing head 9 is subjected to the predetermined processings, e.g., the detection and the protection of the sync data and the ID data, an ECC decoding and the like by the reproducing processor 11 . The output interface 13 restores an encoded data stream complying with a predetermined standard from the reproduced data stream so as to output the restored data stream. In this example, the recording and reproducing operations are assumed to be performed by using only the first channel. However, the same operations can be performed by using the second channel only instead of the first channel. Next, the case where the encoded data stream with a bit rate of 2N Mbps is input will be described. The input interface 2 detects the bit rate of the data stream to be 2N Mbps. Based on the detected bit rate, the input interface 2 distributes the input encoded data stream to two channels end outputs the divided data streams to both the recording processors 3 and 4 . As described above, the recording processors 3 and 4 process the data stream so as to record the data stream onto the magnetic tape 8 . The processed signal is recorded on the magnetic tape 8 by the recording heads 6 and 7 . Figure 3B shows the pattern of the track recorded on the magnetic tape 8 when the recording and reproducing operations are performed by using both the first and the second channels. Since the bit rate of the input data stream is 2N Mbps, the tape speed controller 5 transports the tape at a speed twice as fast as the speed when the bit rate is N Mbps. The rotation speed of the cylinder 15 is the same as that in the case where the bit rate of the data stream is N Mbps. In performing the recording operation, four recorded tracks are formed by the recording heads 6a, 6b, 7a and 7b during one rotation of the cylinder 15 . In this case, the width of each of the four tracks is the same as the width T w in the case of recording by using only the first channel. If the transportation distance of the tape per unit time period is denoted by L in the case where the bit rate of the encoded data stream is N Mbps, then the transportation distance of the tape per unit time period is denoted by 2L in the case where the bit rate of the encoded data stream is 2N Mbps. In performing the reproducing operation, the predetermined reproducing processings to be performed for the first channel only when the bit rate is N Mbps are performed with respect to both the first and the second channels. The output interface integrates and outputs the encoded data streams output from the two channels into one data stream. As described above, the recording and reproducing apparatus of the present invention makes it possible to record and reproduce both a data stream with a bit rate and a data stream with a bit rate twice as high as the bit rate by selecting the number of the channels to be used. In the foregoing description, in order to reccrd and reproduce the encoded data stream by using the first channel only, the bit rate of the input encoded data stream is set to be N Mbps. It is obvious that the same operations can be performed for the case where an encoded data stream with a bit rate lower than N Mbps is input. In this first example, the two kinds of bit rates of the encoded data stream to be recorded and reproduced are set to be N Mbps and 2N Mbps. However, the ratio of the two kinds of bit rates is not limited to two. Even when the ratio is larger than two, or in a range of one to two, the same operations can be performed by selecting the number of the channels to be used for the recording and reproducing operations. In this example, the recording and reproducing apparatus has a configuration where the recording heads and the reproducing heads are separately provided. Alternatively, a recording and reproducing apparatus including a head functioning both as a recording head and a reproducing head can also be used. In addition, the recording medium is not limited to a magnetic tape. The recording medium may also be a hard disk, a semiconductor memory or the like. As described above, according to a recording and reproducing apparatus of the present invention, even if the bit rate is varied, the data can be processed in a constant state by changing the number of the recording and reproducing channels to be used without varying the operational frequency of the respective recording and reproducing channels or the rotation speed cf the cylinder.

Claims: A recording and reproducing apparatus for an input encoded data stream having two different bit rates of N 1 and N 2 (where N 1 < N 2 ), comprising: an input interface (2) having two outputs for outputting the input encoded data stream to two channels, the input interface (2) dividing and outputting the input encoded data stream to both of the channels when the bit rate of the input encoded data stream is N 2 , while the input interface outputting the input encoded data stream to only one of the two channels when the bit rate of the input encoded data stream is N 1 ; a first recording processor (3) and a second recording processor (4) for converting the input encoded data stream into a signal suitable for being recorded so as to supply the signal to a recording head (6,7), the first recording processor (3) and the second recording processor (4) being connected with the two outputs of the input interface (2); a recording head (6,7) for writing the signal onto a magnetic tape (8); a tape speed controller (5) for varying a speed for transporting the magnetic tape (8) in accordance with the bit rates of the input encoded data stream; a reproducing head (9,10) for reading the signal from the magnetic tape (8); a first reproducing processor (11) and a second reproducing processor (12) for performing a predetermined reproduction processing for a signal reproduced from the reproducing head (9,10); and an output interface (13) having two inputs for inputting the signals from two channels, the input interface (2) integrating and outputting the signals input from the two channels when the bit rate of the reproduced encoded data stream is N 2 , while the output interface (13) outputting the signal input from only one of the two channels when the bit rate of the reproduced encoded data stream is N 1 , wherein the speed for transporting the magnetic tape (8) and a number of the channels used for recording and reproducing operations are varied in accordance with the bit rates of the input encoded data stream. A recording and reproducing apparatus for an encoded data stream according to claim 1, comprising: an input terminal (16) for inputting an analog video signal; an output terminal (14) for outputting the analog video signal; an analog recording processor (17) for processing the analog video signal so as to record the analog video signal onto the magnetic tape (8); and an analog reproducing processor (20) for processing the analog video signal so as to reproduce the analog video signal from the magnetic tape (8), wherein a rotation speed of a cylinder, on which the recording head (6) and the reproducing head (9) are mounted, is not varied in both cases of recording the analog video signal and the encoded data stream. A recording and/or reproducing apparatus for an encoded data stream according to any one of the previous claims, further comprising: an error detection means (45) for detecting an error from a reproduced signal (a) and outputting error detection information (c) when the error is detected; a refresh information detection means (43) for outputting a refresh information signal (b) indicating a timing of a refresh performed in a differential pulse coding from a reproduced signal (a); and a correction means (44) for generating a signal (d) in a refresh period during which no error is generated from the reproduced signal by using a signal (c) output from the error detection means (45) and the signal (b) output from the refresh information detection means (43) so as to substitute the signal in the refresh period during which no error is generated for the signal in a refresh period during which the error is generated. A recording and/or reproducing apparatus for an encoded data stream according to claim 3, further comprising: a memory means (50) for storing the reproduced signal (a); and a controller (54) for controlling the memory means (50) so that a signal in a refresh period during which no error is generated is output in place of the signal in a refresh period during which an error is generated, by using the output (c) from the error detection means (45) and the output (b) from the refresh information detection means (43). A recording and reproducing apparatus for an encoded data stream according to claim 3, further comprising: a data bit number converter for converting a bit number of the signal in a refresh period during which no error is generated into a bit number of the signal in a refresh period during which an error is generated, by using the signal output from the memory means as an input.

Inventors: HAMAMOTO YASUO, IKETANI AKIRA, KOBAYASHI MASAAKI, KUNIHARA TADASHI, MORIMOTO KENJI, OCHI ATSUO, OKAYAMA MUTSUYUKI, TAKEUCHI AKIHIRO, YAMADA MASAZUMI, HAMAMOTO, YASUO, IKETANI, AKIRA, KOBAYASHI, MASAAKI, KUNIHARA, TADASHI, MORIMOTO, KENJI, OCHI, ATSUO, OKAYAMA, MUTSUYUKI, TAKEUCHI, AKIHIRO, YAMADA, MASAZUMI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1995
Main classification: G11B15
IPC codes: H04N9, G11B27, H04N5, G11B20, G11B15