Data tape recorder having a data compressor/expander

Abstract: A data tape recorder having a data compressor/expander for recording digital information on a magnetic recording tape and for reproducing it therefrom. In a digital audio tape having 4-head deck each provided with two recording heads and two reproducing heads, a switching pulse interval is channel-counted to a multichannel interval, and if the channel count signal and a channel selection signal by user are identical, only a reproducing signal of the selection channel among the signals being reproduced from the reproducing heads is expanded and reproduced. Moreover, in order to record data to a corresponding channel, the expanded reproducing data and compressed input data are multiplexed by the channel selection signal. Thus, the record/reproduction of a multichannel for a long time is possible.

Description: BACKGROUND OF THE INVENTION The present invention relates to a data tape recorder for recording digital information on a magnetic tape recorder and for reproducing digital information out of the tape recorder, and more particularly to a tape recorder having a data compressor/expander, which is capable of recording and reproducing digital information for a long time with multichannel. Presently, a digital recording and reproducing system such as a DAT (Digital Audio Tape) system which records and reproduces audio signals by digitally processing the signals, is divided into two main classes: normal mode and long time mode. The normal mode has a sampling frequency of 48KHz and two channels of 16 bits whilst long time mode has a sampling frequency of 32KHz and two channels of 12 bits. If the long time mode is permitted in the above DAT system, the record and reproduction with a 4mm tape (60 minutes) is possible at maximum four-hour. Since the sampling frequency of the long time mode is 32KHz, an actual audio bandwidth becomes about 14.5KHz. And since the DAT has 12-bit quantization, the tone quality is deteriorated in comparison with 16-bit quantization. That is, when recording the audio signals for a long time with a multichannel, there is a disadvantage in that the tone quality is degraded. US-A-4,542,419 discloses an apparatus for recording and reproducing an analog audio signal in a plurality of successive tracks on a magnetic tape, including a PCM processing circuit for converting the analog audio signal into a PCM audio signal and a video signal processing circuit for processing a video signal. A rotary magnetic head assembly records the video signal and the PCM audio signal in the plurality of successive tracks on the tape. This prior art apparatus already comprises substantially all the features as indicated in the precharacterizing part of claim 1. It is the object of the invention to improve a data tape recorder as indicated in the precharacterizing part of claim 1 such that also in its long time mode the tone quality of the reproduced audio signal is not degraded, and to allow monitoring of the recorded signal as well as rerecording of selectable channels of the reproduced signal. In a data tape recorder as indicated above this object is solved in accordance with the invention by the features as claimed in the characterizing part of claim 1. Further developments of the invention are claimed in the subclaims. By the first and second multiplexing means it is possible to monitor during the recording mode the time compressed signal to be recorded in a selected channel after time expanding this compressed signal in accordance with the channel selection control signal and to record during the recording mode in the selected channel only the time compressed input signal and during the remaining channels not selected by the channel selection control signal the reproducing signal as processed by the second processing means. The delay means ensures during the recording mode that the reproduced and processed signals together with the input digital signal to be newly recorded in one selected channel of the plurality of channels are recorded in the successive tracks on the tape. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, advantages and features of the present invention will be more apparent from the detailed description taken with the accompanying drawings, in which: Figure 1 is a block diagram showing a data tape recorder according to the present invention; Figure 2 is a block diagram showing a data compressor/expander circuit of figure 1; Figure 3 is diagrams showing a head drum and a format of a tape of figure 1, respectively.; Figure 4A to figure 4E are diagrams showing recording/reproducing waveforms of figure 1; Figure 5A to figure 5L are diagrams showing output waveforms of a channel counter and a comparator of figure 2; Figure 6A to figure 6E are diagrams showing waveforms for the recording operation of figure 2; and Figure 7A to figure 7D are diagrams showing waveforms for the reproducing operation of figure 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to figure 1 of the accompanying diagrammatic drawings, a rotary head mechanism 10 having a drum provided with two recording heads and two reproducing heads, records input information on a magnetic recording tape and reproduces the recorded information from the tape. An input analog signal is converted into a digital signal in an analog to digital converter (ADC) 16, and then supplied to a first digital filter 18 (DF1) for filtering the output data of the ADC 16. The output data of a second digital filter 20 (DF2) for filtering input digital data, is converted into an analog signal in a digital to analog converter (DAC) 22. The compressed input recording data is signal-processed in a first signal processor (DSP1) 24. Recording amplifier 28 amplifies the output of the DSP1 24 to provide the amplified output to the rotary head mechanism 10, and the reproducing amplifier 30 amplifies a reproducing signal originated from the head 10. A data strobe 32 extracts a clock from the reproducing signal of the reproducing amplifier 30, and generates the extracted clock together with the reproducing signal. A second digital signal processor (DSP2) 34 signal-processes the reproducing signal produced from the data strobe 32. A system controller 40 produces a recording/reproducing mode control signal, a multichannel selection control signal and servo control signal, in response to a key input of a keyboard 38. A servo 42 controls the rotary head mechanism 10 by the control of the controller 40 and simultaneously generates a switching pulse SWP. A data compressor/expander (DCE) circuit 41 which is connected between the DSP1 24 and the DF1 18 and between the DSP2 34 and the DF2 20, compresses the input data in accordance with the control of the controller 40 to generate a record signal of an assigned channel. By the DCE circuit 41, only a signal of the assigned channel among the signals being reproduced is expanded. Figure 2 of the accompanying diagrammatic drawings shows a block diagram of the data compressor/expander circuit 41 of figure.1. A channel counter 48 receives a switching pulse SWP and a sampling frequency 2f S and generates a channel count signal determining a channel interval during a switching pulse period by counting the sampling control signals FS and S of the controller 40. A comparator (CMP) 50 compares the channel count signal of the channel counter 48 with a channel selection signal CS of the controller 40. If the signals Q1, Q2, Q3 and CS are the same, the comparator 50 produces a channel enable signal CMPO. A data compressor 52 compresses input data at a predetermined compression rate. A data expander 54 operates in response to the channel enable signal CMPO of the comparator 50 and expands the input data at a predetermined expansion rate. Either one of the reproducing signal obtained from the DSP2 34 and a signal produced from the data compressor 52 is selected in a first data multiplexer 56 by the reproducing control signal PB/ REC , being fed to the data expander 54. A recording data selection circuit 66 receives and selects either one of the outputs of the compressor 52 and the DSP2 34 in response to the channel enable signal CMPO, and provides its output signal to the DSP1 24. The channel counter 48 includes a falling edge detector 43 for detecting a falling edge of the switching pulse SWP, a first counter 44 which is cleared by the output of the falling edge detector 43, for counting the sampling clock 2f S to a signal of 200Hz, and a second counter 46 which is cleared by the output of the falling edge detector 43, for counting the output of the first counter 44 to produce a channel count signal CNTO. Next, the compression reproducing/recording operation will be described. In the embodiment of this invention, data recording/reproducing apparatus having N times or N times x 2 channels, as contrasted with a standard DAT tape, can be described by the data compressor/expander algorithm. However, for the convenience of the description, recording/reproducing apparatus having data compressor/expander with 6-time channels will be described. It is assumed that the compressed data with 6 channels has been recorded on the tape by the recording operation which will be described later. If user selects a channel by using a keyboard 38 and applies a read (reproduce) mode control signal to the keyboard 38, the controller 40 connected to the keyboard 38 provides a servo control signal to the servo circuit 42. Simultaneously the controller 40 generates the reproducing mode PB/ REC of a logic "high" state, and supplies a channel selection signal CS to the DCE circuit 41. In this case, if reproducing heads a and b of figure 3 pick up a compress-recorded signal by the switching pulse SWP obtained from the servo circuit 42, as shown in figure 4B, the reproducing amplifier 30 amplifies the signal and supplies the amplified signal to the data strobe 32. The output of the data strobe 32 is applied to the DSP2 34 as a pulse signal. The DSP2 34 signal-processes the input signal to apply the output signal like the reproducing signal PBD indicated in figure 4C to a terminal X0 of the first multiplexer 56. Then, the first multiplexer 56 selects the reproducing signal applied to the terminal X0 by the reproducing mode control signal PB/ REC of the controller 40, providing the reproducing signal to the data expander 54. Meanwhile, the falling edge detector (FED) 43 of the pulse counter 48 detects a falling edge of the switching pulse SWP shown in figure 5A, to generate a signal as shown in figure 5B of the accompanying diagrammatic drawings. Thereby the first and second counters 44 and 46 are cleared. Moreover, the first counter 44 divides an input sampling clock, supplying a pulse shown in figure 5C to the second counter 46. The second counter 46 counts the output of the first counter 44 by 3-bit binary notation and supplies channel counting data Q1, Q2 and Q3 shown in figure 5D to figure 5F to the comparator 50. If the channel selected by the user is 0 channel (0 is channel number), the channel selection signal CS originated from the controller 40 becomes 000. Then, the output of the channel enable CMPO of the comparator 50 becomes a logic "high" state as shown in figure 5G. Therefore, the expander 54 to which the reproducing signal of 6 channels is applied as shown in figure 4C expands only 0 channel data by the channel selection signal CS=000, supplying its output to the second digital filter 20 and a digital out (DOUT) 14. That is, as shown in figure 7C, the expander 54 receives only 0 channel data among the reproducing data PBD of 6 channels of figure 7A by the channel selection enable signal CMPO of figure 7B generated from the comparator 50. Thereafter the expander 54 produces the expanded data as shown in figure 7D. In this case, the data transmitted from the DCE circuit to the second digital filter 20 is converted into an analog signal in the DAC 22. The expanded reproducing data from the DCE circuit is applied to the digital out 14 to generate a digital signal. The channel enable signal CMPO produced from the comparator 50 is converted into waveforms indicated in figure 5G to figure 5L by the channel selection signal CS generated from the controller 40 in response to the channel selection of the user. Here respective channel of the reproducing data PBD having 6 channels can be expanded by the varied channel enable signal CMPO such as figures 5G to 5L. Therefore, if the reproducing operation is carried out with the channel enable signal CMPO alternatively and successively changed from 0 channel up to 5 channel by the proper channel selection, the expansion and reproduction of 6 times in comparison with conventional reproducing time is possible. Next, the compression recording operation is described. If the user selects a recording mode, analog/digital input and recording channel by means of the keyboard 38, the controller 40 generates control signals in response to an input signal applied from the keyboard 38. In case of selecting 1 channel under the condition that digital input is selected, the controller 40 produces the reproducing control signal PB/ REC of a logic "low" state, a digital/analog signal D/AS of a logic "high" state and the channel selection signal CS of 001 state. Hence, the first multiplexer 56 generates data of the input terminal X1 through its output terminal X, and the second multiplexer 51 selects the output of a digital in 12 to be produced to its output terminal X. Input data as indicated in figure 6A, which is applied to the data compressor 52 from the digital in 12 by the selective operation of the second multiplexer 51, is compressed through the data compressor 52 and then supplied to a third multiplexer 62 and the first multiplexer 56. In this case, the comparator 50 compares the output of the second counter 46 with the channel selection signal CS=001 generated from the controller 40. If they are the same, the channel enable signal CMPO indicated in figure 5H is varied as shown in figure 6B. In this case, if the rotary head mechanism 10 is operated by the operation of the servo circuit 42, the reproducing heads a and b of figure 3 reproduce the signal shown in figure 4B. The signal of figure 4B is signal-processed by the DSP2 34. Then the signal- processed signal as shown in figure 6C is applied to the input terminals X0 of the first and third multiplexers 56 and 62. The reproducing data of 0 channel among the reproducing data PBD indicated in figure 6C is produced as shown in figure 6D through the terminals X0 and X of the third multiplexer 62, by the channel enable signal CMPO of a logic "low" state shown in figure 6B. After the reproducing data of 0 channel of figure 6C is supplied to the third multiplexer 62, if the channel enable signal CMPO of the comparator 50 becomes a logic "high" state as shown in figure 6B, the third multiplexer 62 selects the data of the input terminal X1 and produces it through the output terminal X. Moreover, the data expander 54 receives the compressed data from the compressor 52 through the first multiplexer 56 and expands the compressed data. Therefore, if the output of the comparator 50 becomes a logic "high" state as indicated in figure 6B, the compressed data by the compressor 52 is produced as the recording data RCD as shown in figure 6D through the third multiplexer 62 at 1 channel region of the reproducing data PBD. Simultaneously the compressed data is expanded in the data expander 54. That is, the user comes to monitor the compressed and recorded data with the data generated from the data expander 54. If the channel enable signal CMPO indicated in figure 6B becomes a logic "low" state, the reproduced data of 2 to 5 channels shown in figure 6C is produced through the third multiplexer 62. The recording data RCD of figure 6D produced from the third multiplexer 62 is delayed as much as about 5 milliseconds by a delay random access memory 64 as shown in figure 6E, and then is recorded through the DSP1 24 and the recording amplifier 28. Hence, the reproducing heads a and b reproduce the track data of tracks T3 and T4 and applies the reproduced data to the DSP2 34. The recording heads A and B record the data which is presented at terminal X0 and generated at terminal X of multiplexer 62 and the compressed data through the data compressor 52, corresponding to the channel selection signal, which is generated through terminal X of multiplexer 62 onto the tracks T3 and T4 as shown in Fig. 4D. As described above, since the compressing/expanding operation of data is carried out and simultaneously the data is recorded on a magnetic tape and reproduced therefrom with a multichannel, there is no deterioration of the data, and data process of large capacity is possible.

Claims: A data tape recorder having a rotary head mechanism (10) which has a drum provided with at least one recording head and at least one reproducing head, selectively recording input data of a plurality of data channels in successive portions in a track on a magnetic tape and for selectively reproducing the recorded data channels from the respective portion of the magnetic tape, said data tape recorder comprising: filtering means (18) for filtering a given digital input signal; time compressing means (52) for compressing the filtered input signal at a given rate; first processing means (24) for signal processing the time compressed signal; first amplifying means (28) for amplifying an output of said first processing means (24) and forming an input signal to said recording head; second amplifying means (30) for amplifying a reproducing signal from said reproducing head; data strobe means (32) for extracting a clock from said reproducing signal obtained from said second amplifying means (30) and providing both a clock and said reproducing signal; second processing means (34) for signal processing said reproducing signal; time expanding means (54) for expanding the processed reproducing signal at a given rate; system controlling means (40) for producing a recording/reproducing mode control signal (PB/ REC ), a channel selection control signal (CMPO) and a servo control signal in response to a key input (38); servo means (42) for controlling said rotary head mechanism (10) in response to said servo control signal and for producing a switching pulse; wherein time compressing of said digital input signal being in response to said recording/reproducing mode control signal (PB/ REC ) of said system controlling means (40), and time expanding of a signal of a selected channel from said reproducing signal being in response to a channel selection control signal (CMPO); characterized by first multiplexing means (56) for alternatively selecting the reproducing signal obtained from said second processing means (34) or the compressed input signal generated from said time compressing means (52) in response to said recording/reproducing mode control signal (PB/ REC ) of said system controlling means (40) and for supplying the multiplexed signal to said time expanding means (54) being controlled by a channel control signal (CMPO); second multiplexing means (62) for alternatively enabling transmission of said processed reproducing signal and said compressed input signal in response to a channel enable signal (CMPO) to generate an output signal for said first processing means (24), and delay means (64) for delaying transmission of said output signal of the second multiplexing means (62). A recording as claimed in claim 1, wherein said data compressing/expanding means (41) includes: a channel counting means (48) receiving a switching pulse (SWP) and assembling frequency, for generating a channel count signal by determining a channel interval during the switching pulse period in response to a sampling control signal of said system controlling means (40); and comparing means (50) for comparing said channel count signal of said channel counting means (48) with said channel selection signal of said system controlling means (40) and producing a channel enable signal when said channel count signal and said channel selection signal are the same. A recorder as claimed in claim 2, wherein said channel counting means (48) is comprised of: falling edge detecting means (43) for detecting falling edge of said switching pulse; first counting means (44) being cleared by an output of said falling edge detecting means (43), for counting a sampling clock of said sampling frequency to a signal of 200Hz in accordance to the length of a channel; and second counting means (46) being cleared by said output of said falling edge detecting means (43) for counting an output of said first counting means (44). A recorder as claimed in claim 3, wherein said delay means (64) is a delay random access memory of 5 m sec delay. .

Inventors: RO IL-YOUNG, RO, IL-YOUNG
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1992
Main classification: G11B20
IPC codes: G11B5, G11B20, G11B15