High speed recorded information duplicating equipment

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This invention relates to recording systems and more particularly to systems for custom recording "tape cassettes or other recording media by recording a number of specific selections taken from a repertoire of selections which is stored in a library or libraries.

For convenience of expression, this specification may refer to music, tape, libraries, albums and the like However, it should be understood that these and similar expressions should be construed broadly enough to cover all equivalent items and structures. For example, the recorded information may be, not only music, but also a recorded foreign language lesson, poetry, telemetry, sound effects, or any other suitable items. The recording media could be tape, records, compact discs, optical tracks on film, or the like. The "library" could be any suitable data base, including satellite, slave or other distributed libraries. For example, each recording company may have a remote library of its musical selections which the inventive recorder may reach via a telecommunication network. The term "album" is used herein to mean a certain batch amount of recorded information items, regardless of whether the items are music, voice, or some other material. Long play records and tape cassettes are examples of albums; however, there may also be other examples.

One example of the invention is found in the recording industry which issues "singles" and "albums". If singles are played, the listener hears exactly what he wants to hear, but he has to continuously change records or tapes, which is a bother. On the other hand, if an album is played, the listener usually likes one or two of the many selections which are recorded thereon and is indifferent to or positively dislikes the remaining selections in the album. The alternative is to buy expensive play back equipment which can pick one of many selections in an album. However, this, in effect, reduces the album to one or two singles with all of the same problems that singles present.

Within a few years after a recording is first made, it is "cut out" of the music catalogs which list the records that are then being offered to the general public. After it becomes a "cut out", the musical selection may be included in albums at a very low cost, and often is offered as a special issue to a select audience, such as the listeners of a TV station, but the question of taste remains and not all of the records are enjoyable to everyone. After a few more years, recorded music tends to become unavailable at any cost. Then, those who are in their nostalgia years do not have the option of playing a recently acquired record containing the music of their youth.

Thus, there are many reasons why there is a need for a system which enables one to select only his favorite music for inclusion in a custom recorded album. This way, everyone may then have a customized album of selections of his own taste which may be totally different from the albums which anyone else may select.

U.S. Pat. No. 4,410,917 has a capability of recording from a master medium onto a slave medium but it does not provide a random selection capability and does not provide a sufficient flexibility. The structure of this patent can not rearrange, edit, or modify the stored information items. It is strictly a duplicator of recorded media.

A desirable kind of master-slave recording system is one which might eventually become almost as commonplace as record stores. Still, the growth of such an industry may be relatively slow; therefore, the same system should also be adaptable to use in a single central location where custom recorded albums are made for distribution via the mail.

Accordingly, an object of this invention is to provide new and improved means for and methods of distributing recorded music. Here, an object is to provide systems for preparing customized recorded albums containing only recorded information selected by an individual.

In keeping with an aspect of the invention, these and other objects are accomplished under the control of a microprocessor or mini-computer. A master library, libraries, data base or storage medium contain recorded information which may originate from any suitable source, such as phonograph records, tapes, sound tracks, compact discs, telemetry sources, or the like. Each recorded information item in the library is stored under its own address. On read out, an operator keys in the addresses identifying the selected recorded information item. The selected items are read out of the library medium and stored in a large capacity memory, usually to provide a total of about forty-five minutes of listening time. Then, all of the items are read out of that large capacity memory and recorded at a high speed onto a suitable album size medium, such as a tape cassette, for example. The various transfers of recorded information items from the master storage to the recorded album, may be accomplished at a high speed.

An embodiment of the invention is shown in the attached drawings, wherein:

FIG. 1 is a block diagram of a first embodiment of the inventive system for storing recorded information items, such as musical selections, for example, in a master library;

FIG. 2 is a block diagram of the inventive system for retrieving recorded information items from the master library;

FIG. 3 is a block diagram of a first embodiment of an analog-to-digital module for converting the analog source music into digital data for processing within the inventive system;

FIG. 3a is a block diagram of a low pass filter used in the ANDI and the DIAN modules;

FIG. 3b indicates a clock rate caused roll off in the upper frequency range of signals passing through said low pass filter;

FIG. 4 is a timing chart for the operation of the analog-to-digital converter of FIG. 3;

FIG. 5 is a block diagram of a command control computer for use in the circuit of FIG. 1;

FIG. 6 is a block diagram of a master storage circuit for use in FIG. 1;

FIG. 7 is a block diagram of a master storage controller circuit used in FIG. 1;

FIG. 8 is a block diagram of a source media for use in FIG. 1;

FIG. 9 is a block diagram of a first embodiment of a digital-to-analog module for converting the digital data processed by the inventive system into an analog form for recording;

FIG. 10 is a timing diagram for the digital-to-analog converter of FIG. 5;

FIG. 11 is a destination controller for directing data taken from the master library to the album sized recording medium;

FIG. 12 is a block diagram of an intermediate storage circuit for buffer storing digital data relating to recorded information items which are read out of the master library and prior to its recording on the customized album;

FIG. 13 is a block diagram for a destination medium on which the custom album is recorded;

FIG. 14 is a graph illustrating, by best case and worst case examples, a loss of fidelity in a conventional prior art PCM recording;

FIG. 15 is a similar graph showing how a second embodiment of the invention improves the fidelity of the PCM signal;

FIG. 16 shows the high frequency end of a recorded characteristic curve that illustrates how the second embodiment of the invention improves the recorded fidelity;

FIG. 17 is a block diagram of a second embodiment of the analog-to-digital converter;

FIG. 18 is a block diagram of a second embodiment of a digit-to-analog converter;

FIG. 19 is a graph similar to FIG. 15 showing how the digital-to-analog circuit converts the digital signals back into an analog signal with improved fidelity;

FIG. 20 is a timing chart for the converter of FIG. 18;

FIG. 21 is a block diagram of a destination controller for use in the information retrieving system of FIG. 2;

FIG. 22 is a flow chart for the circuit of FIG. 21, showing the state of the circuit responsive to a request control logic;

FIG. 23 is a flow chart for the circuit of FIG. 21, showing the state of the circuit during bus control;

FIG. 24 is a block diagram of a master storage controller for use in connection with the information retrieving circuit of FIG. 21;

FIG. 25 is a flow chart showing the state of the circuit of FIG. 24 in a request for control condition;

FIG. 26 is a flow chart showing the state of the circuit of FIG. 24 during bus control;

FIG. 27 is a block diagram showing the intermediate buffer storage of FIG. 2; and

FIG. 28 is a flow chart showing the control over the random access memory of FIG. 26.

FIG. 1 shows a system which may be used to store or create a master library containing a repertoire of recorded information items, such as musical selections, for example. The major parts of this system are a central controller 40 operating in response to a command control computer 42, a master storage medium 44, a source medium 46, and an analog to digital conversion module 48. The master storage medium 44 could be a laser disc, or the like. Any suitable source medium 46 may be used such as records, tapes, compact discs, optical tracks, or the like. Usually the pertinent playback device at 46 has an analog output at 50 which ANDI module 48 converts into digital data. The digital data is then transferred over a data input bus 52 and through storage controller 40 to the master storage medium, via a data bus 54. The storage of each recorded information item or selection is at its own individually identified address location in the master storage medium 44. All of this happens in response to control signals transmitted from a microprocessor or mini-computer 42 over control busses 56-60.

In FIG. 2, the selections stored in the master storage medium 44 are retrieved for assembly as an album which is recorded on any suitable destination medium 62, such as on a tape cassette, for example, or the like. In greater detail, the digital data taken from the master storage medium 44 are sent over data bus 54, through the master storage controller 40, and bus 65 to an intermediate buffer storage circuit 64. After an album amount of music (about forty-five minutes) is assembled in the intermediate storage circuit 64, it is sent over a data bus 66 to a digital-to-analog converter module ("DIAN") 68, from which an analog signal is sent via bus 70 and recorded onto medium 62.

The data retrieval circuit (FIG. 2) is controlled by a destination controller 72, which is driven from the microprocessor 42 via data bus 56 and master storage controller 40. Connected to the input/output ports of the destination controller 72 are data request 74 bus, digital-to-analog control commands bus 76, destination medium control bus 78, storage/retrieval address bus 80, and intermediate buffer storage control bus 82.

In operation, an operator simply applies any suitable recorded information in the source medium 46 (FIG. 1) by playing a recording, tape, or the like. For example, the operator may place a phonograph record on a turn table and play it back. The command control computer 42 assigns suitable addresses to each recorded information item that is played back and stored at 44. This address assignment may be done either automatically or in response to operator entered command signals. Any suitable printer 83 may print out a master list of recorded items and their addresses in the master storage 44. An automatic address assignment and print out is all done in approximately the same manner that a word processor assigns document numbers and prints out documents.

When a customer provides a list of items for inclusion in a single album, an operator consults the master list and enters the indicated addresses on a keyboard 85 (FIG. 2) associated with the command control computer 42. Responsive thereto, the master storage controller 40 reads stored data out of the library or libraries at master storage 44, where the digital data is that stored under each selected address. That read out data is then stored in the intermediate buffer storage circuit 64, at an address selected by the destination controller 72. After all of the digital data required to record an entire album is read from the master storage circuit 44, the destination control 72, acting responsive to computer 42, causes the intermediate buffer storage circuit 64 to transmits the entire album of data through the digital to analog "DIAN" module 68 for storage on medium 62, such storage being in an analog form.

In an alternative system, the intermediate buffer storage memory 64 (FIG. 2) may have a much smaller capacity. Then, the system may operate on a demand and fetch basis. That is, the master storage circuit 44 reads out a burst of data which is put into intermediate buffer storage at 64. In this alternative system, the resulting stored data immediately begins to be read out of buffer 64 for storage at the destination medium 62. As the data is being so read out, the intermediate buffer storage 64 makes repeated demands for more data from the master storage 44. As each demand is made, more data is fetched from the master storage circuit 44, which is used to replenish the data being taken from the intermediate buffer storage and recorded in the destination medium.

FIGS. 3, 4 show the details of a first embodiment of the "ANDI" analog to digital module 48 and of the timing of the module operation. This module 48 converts the analog information, taken from the source medium 46 (FIG. 1) into the digital data information that is processed and stored on the master storage device 44.

More particularly, the analog signal which is taken from a record or tape, for example, enters the module 48 through input port 84 and the input amplifier 86, which sets a uniform input signal level by providing a suitable gain. Also amplifier 86 isolates the input port 84 from the next stage 88 which is a low pass filter that rolls off or drops out the high frequencies.

The next stage is the sample and hold amplifier 90, which holds a sample of the input signal at a constant level while the analog-to-digital converter 94 is making its conversion. At 92, a mode input control signal is applied to the sample and hold amplifier 90 to select between the sample mode and the hold mode. In the sample mode, amplifier 90 reads the input signal and stores it inside the amplifier 90. In the hold mode, it holds the previously sampled voltage at a constant level, to prevent the analog-to-digital converter 94 from trying to convert an input signal with a level that is changing. In this particular system, the sample and hold amplifier 90 has a very high output impedance. The analog-to-digital converter 94 has a very low input impedance. Therefore, to compensate for this, a buffer stage 96 is coupled between these two devices. Of course, the buffer may not be required if the impedances match.

The signal which reaches the analog-to-digital converter 94 is converted into digital data, such as a 16-bit digital word, for example. When the analog-to-digital converter 94 completes the conversion, it strobes the digital word into a first-in first-out ("FIFO") buffer memory 98. This buffer stores the samples in aligned rows, which may be 1,024 samples long, for example. Then, on a first-in first-out basis, the command control computer 42 (FIGS. 1, 2) retrieves the stored data, on a word by word basis. The read-out data is transmitted through the digital buffer 100 to the master storage controller 40. This buffer storage enables the two systems to operate at speeds that are not synchronized.

The bandwidth is selected at 99 by sample and filter clock divisor signals sent over data bus 56 and received in the ANDI module 48. In greater detail, two of the more important circuits shown in this block diagram of FIG. 3 are the timing generator 101 and the clock divider unit 102. The timing generator 101 places the sample and hold amplifier 90 in a particular mode and starts the analog-to-digital converter 94. The timing generator 101 and the clock divider unit 102 are controlled via bus 56, by a signal which is sent under the control of the master microprocessor or minicomputer 42. In this particular embodiment, the source clock 104 is a 5.64480 MHz crystal oscillator which has an output that is an exact multiple of the industry standard sampling rate. Other frequencies may be used in other systems. Thus, the divider 102 provides a divided sample rate which is equivalent to or any multiple of the industry standard rate. The timing generator 101, in effect, retimes the clock pulses divided by circuit 102 in order to accommodate circuit delays, such as the finite time required for a signal to transfer from the input of amplifier 86 to the input of sample and hold circuit 90, for example.

The divided sample clock rate pulse stream is sent from clock divider unit 102 over wire 103 to drive the low pass filter 88.

In operation, clock controlled low pass filter 88 (FIG. 3a) switches a capacitor back and forth between its input and an output. Its effect is to start a process whereby the analog signal is divided into a plurality of pulses representing the intelligence in the analog signal. In greater detail, the low pass filter 88 includes a switched capacitor network 105 driven from clock pulses on wire 103, via divider circuit 106, and clock generator 107. The divider circuit 106 may be set to divide by 1, 2, or 4. The switching circuit 105 alternately connects a small capacitor to the input terminal "IN" and the output terminal "OUT". FIG. 3b shows a roll off characteristic wherein the frequencies passing through the low pass filter circuit fall off sharply after some frequency which is set by a ratio between the frequency of the input signal divided by the frequency of clock pulses delivered from the clock 107. Therefore, the roll off frequency may be changed by changing the dividing factor of the divider 106. This filter may be low pass filter LTC 1062 made by Linear Technology Corporation of Milpitas, Calif. 95035-7487.

Before the analog-to-digital conversion in converter 94, a small segment of the analog signal is fed to a sample and hold capacitor in circuit 90 where it is held long enough to accumulate a charge that represents the instantaneous amplitude of a generally analog wave shape during that segment.

The timing requirements for the embodiment of the analog to digital module that is shown in FIG. 3 can be seen in the timing diagrams of FIG. 4, which are thought to be self explanatory.

The command control computer module 42 (FIG. 5) includes a commercially available computer system 110 which should have multi-user capability. That is, the computer should be able to sort and segregate data into a number of different categories. Each of many clients and copyright owners has a separate record keeping memory to make royalty accounting possible. Thus, as each recorded information item is read out of the master storage, a record company or other person owning the copyright on that particular selection receives an accounting credit. In one system, the command control computer was a four-user Maxicom/DL computer with an 85-megabyte, hard disk drive. This unit has a general purpose parallel interface card 112 which sends commands and receives responses from commands over the various data buses. Any suitable interface circuit 112 may be provided to integrate this computer into the over all system. In general, these interface circuits meet the SCSI (small computer system interface) standards.

The master storage circuit 44 (FIG. 6) includes any suitable recording device, such as a commercially available twelve or fourteen inch laser read-write device 114 with a removable disc. One system used an Alcatel Thomson Gigadisc. Data is stored on and retrieved from the disc by the master storage circuit 44 in response to standard industry commands. Both the data and the master storage commands are sent over the data bus 54.

The master storage controller 40 (FIG. 7), uses custom software with a commercially available 32-bit central processor unit 116 which may be a Motorola MVME-130, for example. An SCSI interface card 118, and a general purpose parallel interface card 120, interconnect the controller 40 with other circuits via standard data buses.

The source medium 46 (FIG. 8) is any suitable commercially available, studio quality, reel-to-reel player, phonograph disk player, cassette player, CD disk player, or any other suitable device 126 that can supply suitable audio output signals, usually analog signals. Once the source medium 46 has received its command, regardless of whether it is "start", "stop", "rewind" etc. . . . , over the source medium control bus 58, it responds as directed and sends analog output signals over the source medium output bus 50 to the next stage.

Under the control of the command control computer 42, the storage controller 40 selects the bandwidth. Then, controller 40 starts the source medium 46 by sending signals over the source medium control bus 58. Once the master storage controller 40 has started the source medium 46, it begins receiving samples which are sent from the ANDI module 48 over the input data bus 52. These samples are forwarded through the bus 52 to the master storage circuit 44 by way of the data bus 54.

After the command control computer 42 commands a read-out, controller 40 sets up the destination controller 72 (FIG. 2) by way of the command bus 56. After the destination controller is initialized, it begins a retrieve cycle in order to take data from master storage circuit 44 by way of the master storage data bus 54 and the SCSI interface card 118 (FIG. 7). The information that is being received from master storage circuit 64 is sent over the data bus 54 to the intermediate buffer storage circuit 64, where it is stored.

FIGS. 9, 10 show details of a first embodiment of the digital-to-analog (DIAN) module 68 and of the timing of the module operations. This module 68 translates the digital data as it is received from the destination controller circuit 72 (FIG. 2) into the analog information that is required for the destination medium 62.

The digital-to-analog conversion process starts with the destination controller circuit 72 setting a clock divider unit 130 in the module of FIG. 9 to operate at the desired output sample rate. The command signals that set the sample rate are sent via the command control bus 76. After a period which is long enough for this clock rate to stabilize, the destination controller 72 (FIG. 2) starts the destination medium via bus 78. The intermediate buffer storage circuit 64 continuously sends 16-bit samples to the first-in first-out buffer circuit 132 (FIG. 9), over the data bus 66.

Two critical circuits in the digital-to-analog module (FIG. 9) are the timing generator 134 and the clock divider unit 130. The timing generator retimes the divided clock pulses in order to accommodate the circuit delays. For example, there is a circuit delay that is required for a signal to transfer from the FIFO buffer 132 to the converter 142, which the retimed pulse accommodates.

The master clock 136 has a frequency of 5.64480 MHz in this embodiment. This frequency is divided by the clock divider unit 130. The destination controller 72 sends a divisor control signal to the clock divider unit 130 which is used to divide the master c