WO1993024930A1

WO1993024930A1 - Digital compact cassette automatic search system

Info

Publication number: WO1993024930A1
Application number: PCT/US1993/002487
Authority: WO
Inventors: Daniel William Staudacher
Original assignee: Tandy Corporation
Priority date: 1992-05-27
Filing date: 1993-03-15
Publication date: 1993-12-09

Abstract

A system for effecting automatic program track searching functions for a digital compact cassette (DCC) tape operating in a playback deck. Facilities enable the automatic searching utilizing envelope detection of variable pulse width signals indicative of specific markers contained on the tape's auxiliary data track. Detection of the specific markers is utilized in the deck to control the movement of the tape relative to a tape head in stop/play and high-speed search modes of operation, in both forward and reverse directions, to locate desired program track selections. The facilities enable searching across both sectors of the tape, in a single automatic search operation. Searching is user-initiated from a front control panel of the deck by a serial front panel processor interfacing with a main control processor. A digital signal processor of the deck detects low-frequency envelopes or 'markers' on the tape used in controlling record and playback functions. The facilities are implemented by program logic executed in a main control processor of the deck.

Description

DIGITAL COMPACT CASSETTE AUTOMATIC SEARCH SYSTEM Field of the Invention

The invention relates generally to digital audio data processing and particularly to a system for automatically searching digital compact cassette (DCC) tape for desired program track selections.

Background of the Invention

Arrangements for recording and reproducing audio information have evolved through several stages including mechanical, magnetic and optical technology. Optical compact disks (CD's) which store audio data in digital form have replaced analog mechanical long-playing (LP) records as the preferred medium for music reproduction. Digital audio systems for playing CD's offer improved fidelity, increased dynamic range and extended longevity of the storage medium over prior analog systems. Analog magnetic tape (cassette) decks are also popular because they offer the capability to both play and record magnetic tape media, although they lack in the advantages of digital audio systems. Magnetic tape decks enable repeated recording, editing and multitrack recording capabilities.

The introduction of digital audio tape has brought magnetic media to the forefront of digital audio technology. One type of digital audio tape recorder mechanism utilizes a miniature helical-scan video cassette recorder with many precision parts, in conjunction with a digital audio tape cassette similar to a miniature videocassette, with a hinged door and numerous internal parts. This so-called recordable-digital audio tape (R-DAT) format has not been widely accepted because DAT-format recorders are relatively expensive when compared to CD or analog cassette players, and further the DAT-format tapes are relatively expensive when compared to compact disks or analog cassette tapes. As an alternative to the'DAT format, a digital compact cassette (DCC) format has been introduced which offers the sound reproduction quality of a digital audio system, yet which meets the pricing and adaptability requirements necessary for mass-market appeal.

The DCC tape format utilizes a cassette shell similar to that used by conventional analog audio cassettes. DCC recorder/playback devices ("decks") are designed with a compatible head configuration in order to play or record digital DCC tapes or play standard analog cassette tapes. The head contains a nine track (digital) section and a two track (analog) section mounted to a rotatable mechanism. The rotatable mechanism is required for bidirectional operation, since DCC tapes can only be inserted in recorders one way. The DCC tape is divided into a sector A and a sector B, corresponding to the side-A and side-B layout of an analog tape. Each sector includes eight tracks of digital data and a ninth auxiliary track which contains subcodes, timing codes, and up to four-hundred characters per second of text, which may be shown on an accompanying display.

The DCC format utilizes a low-bit rate encoding scheme referred to as precision adaptive sub-band coding (PASC) to compress incoming 16-bit digital data samples into a minimum representation of the sampled signal, resulting in a 2 to 5 bit data sample. The compressed sample is then given a scaling factor. The PASC sends the sample to an error correction device which adds error correction data to it or recording, and during playback, to reexpand the subband data back to 16-bit output codes. Redundant information is available for error detection and correction and the digital data is distributed amongst the eight data tracks in such a manner that large amounts of data can be lost to burst dropout errors without significantly affecting or altering the musical reproduction quality during playback.

The auxiliary track contains subcode information which contains time information, numbering of musical tracks, a table of contents (TOO . The main data area of the tape contains system information data, of which for prerecorded tapes, contain up to four-hundred characters per second of text, separated into different categories, which may be shown on an accompanying display. Further, the auxiliary track contains marker identification which enables the performance of automatic searching functions providing the same kind of access convenience found in CD players. Direct access, repeat, music scan and other familiar facilities are capable of being implemented in a DCC deck for playing desired music tracks in any order.

Specific "automatic search" techniques are known for implementation in DCC decks in order to locate the record/playback head relative to a particular location of the DCC tape. For example, certain techniques require the performance of search routines based on the use of table of contents (TOC) information, which is only contained on "prerecorded" and "super-user recorded" tapes. Thus, problems arise when the DCC tape is "user-mode" recorded which neither contains TOC information nor markers that are used for searching. Further, search techniques which rely on table of contents information, can experience errors when the tape encounters markers at extreme ends of the recorded portion, such as at the starting point of the recorded material, the auto-reverse position, or ending point of the recorded material. Other techniques do not adequately detect marker envelopes when tape degradation exists at the end of the recorded portions. Errors are especially notable using known search techniques when the search commands input by the user lag behind their implementation by the machine and require switching between sectors or reversing of tape direction.

Other search techniques implemented in DCC decks utilize schemes in which the desired track position is overrun, followed by the requirement of backing up to the correct position before play can begin. These procedures are time-consuming and place unnecessary wear on mechanical components. What is needed are efficient techniques for the implementation of automatic searching in a DCC deck which offer greater accuracy and reliability than those currently available.

Summary of the Invention The foregoing problems are solved and a technical advance is achieved by method and apparatus of the present invention for effecting automatic program track searching functions for a digital compact cassette (DCC) tape operating in a digital audio deck. In a departure from the art, the facilities of the present invention enable automatic searching in either a forward or a reverse direction for a desired program track selection on a DCC tape, utilizing envelope detection of variable pulse width signals indicative of specific markers contained on the tape's auxiliary data track. Detection of the specific markers is utilized in the deck to control the movement of the tape relative to a thin-film DCC head in stop/play and high-speed search modes of operation, in both forward and reverse directions, to locate desired program track selections. The facilities enable searching across both sectors of the tape, in a single automatic search operation.

The automatic search facilities are user-initiated from a front control panel of a DCC deck, the control panel being controlled by a front panel processor interfacing with a main control processor of the deck. A digital signal processor of the deck transfers low-frequency envelopes or "markers" on the tape to the main control processor for detection and is used in controlling record and playback functions. The facilities of the invention involve the envelope detection of the particular markers to control the custom playback of the tape. The facilities are implemented by program logic executed in a main control processor of the deck.

In one illustrative embodiment of the invention, a system is provided for searching a digital audio tape in either a forward or reverse direction to locate a desired program track selection during movement of the tape relative to a thin-film DCC head of a playback device. The system controls operation of the device responsive to marker information on the auxiliary data track of the tape, the marker information being indicated using a digital signal processor. Movement of the tape is initiated in a search mode of the device, in either a forward or reverse direction, responsive to a user input command. A track index is incremented representing the number of program track selections to be skipped during tape movement in the search mode. The main control processor monitors the tape during the search mode and detects time intervals between successive high and low signals on the auxiliary data track, such that the signals indicate the markers and the time intervals therebetween indicate the marker type. The track index is decremented upon indication of a start marker, such that once the track index is decremented to zero, the desired selection has been located. The tape is then returned to its previous mode of operation prior to the search mode. The previous mode may be a stop or a play mode, for example.

In another illustrative embodiment, a system is provided for locating program track selections of a digital audio tape during movement of the tape relative to a head of a playback device, while the device is operating in a play mode at a first tape speed. A digital signal processor monitors the tape during the play mode for detecting time intervals between successive high and low signals on the auxiliary data track, the signals indicating the markers and the time intervals therebetween indicating the marker type. The device enters a search mode at a second tape speed when a skip marker is indicated, and returns to the play mode when the beginning of the next program track selection has been located. The system also provides for reversing the direction of tape movement in the play mode when a reverse or lead-out marker is indicated, thus enabling the tape to automatically continue play on the next sector. Program logic is also provided to enable the tape to play one sector only, the full tape or continuously.

An important technical advantage achieved with the invention is that the system utilizes computer program logic stored in the device to implement the search functions with a minimum of input commands being required by the user.

Another important technical advantage achieved with the invention is that the search techniques are performed based on marker envelope detection techniques which do not require table of contents information, thereby simplifying the search process and reducing the occurrence of search errors.

Brief Description of the Drawings

FIG. 1 is a functional block diagram of a high fidelity stereo system including a digital compact cassette deck incorporating features of the present invention;

FIG. 2 is a perspective view of the front panel of the digital compact cassette deck of FIG.l;

FIG. 3 functional block diagram of the digital compact cassette deck of FIG.l;

FIG. 4 is a schematic representation illustrating the record and playback head design of the digital compact cassette deck of FIG.l;

FIG. 5 is a broken-away, schematic representation of the digital compact cassette magnetic tape shown in FIG. 3 illustrating the sectors A and B, and the format of the data tracks;

FIG. 6 is a broken-away and expanded schematic representation illustrating the format of an auxiliary data frame contained on the auxiliary data tracks on the digital compact cassette magnetic tape of FIG. 5;

FIG. 7 is a broken-away, schematic representation illustrating low-frequency envelopes of a labeled frame and a nonlabeled frame of the auxiliary data frame of FIG. 6;

FIG. 8 is a broken-away, schematic representation of marker envelopes comprised of the labeled data frames of FIG. 6;

FIG. 9 is a broken-away, schematic representation of the auxiliary data of FIG. 6 illustrating the data contents;

FIG. 10 is a flow chart illustrating the logic for implementing the user-initiated automatic search operation of the present invention;

FIGS, lla-lld are flow charts illustrating in greater detail the logic for implementing the user-initiated automatic search operation of the present invention in forward and reverse search directions; and

FIGS. 12, 12a and 12b are flow charts illustrating the logic for implementing the automatic search operations of the present invention initiated by markers contained in the auxiliary data track during the play mode; and

FIG. 13 is a flow chart illustrating the logic which interprets commands received from the front panel and the recording unit.

Detailed Description of the Preferred Embodiment

As discussed in detail below, the present invention relates to improved facilities implemented in a digital compact cassette (DCC) deck for effecting automatic program track searching functions for prerecorded and consumer recorded DCC tapes, in order to automatically fast-search a tape in forward or reverse directions to located desired program tracks for playback. More particularly, the facilities enable user-initiated fast searches over both sectors of a DCC tape in one automatic operation, skipping over selections until the desired selection is reached. The facilities also may be automatically initiated by lead-in, skip, reverse, lead-out or home markers residing on the DCC tape. In FIG. 1, the reference numeral 100 designates a high-fidelity stereo system embodying principles of the present invention. The system 100 includes a stereo amplifier 102, two speakers 104a, 104b, a compact disk (CD) player 106, a high-fidelity stereo record-player 108, and a digital compact cassette (DCC) deck 110. The deck 110 is utilized principally for the recording and playback of digital audio tape (not shown) configured in the DCC format, and may also be utilized for playback of standard, prerecorded analog cassette tapes. It is understood that multiple program track selections of music or other information may be played and/or recorded on the tape utilizing the deck 110.

The CD player 106 and the record player 108 are included as part of the system 100 to represent typical examples of digital and analog input sources, respectively, to the deck 110. The CD player 106 and the record player 108 provide the deck 110 with digital and analog inputs on lines 112 and 114, respectively, for purposes of recording a DCC tape using the deck 110. A line 116 connects the output of the deck 110 to the amplifier 102 which amplifies the output signal from the deck 110 and transmits the amplified signal to the speakers 104a, 104b via lines 118a, 118b, respectively. It is understood that FIG. 1 has been simplified for illustration purposes and that, in general, additional connectors would be utilized for connecting the amplifier 102 to the CD player 106 and to the record player 108.

FIG. 2 illustrates the front panel 200 of the deck 110. The panel 200 includes a vacuum fluorescent strip display 202 for the display of icons and alphanumerics, a tape drawer 204 for the loading and unloading of both analog and DCC tapes, a system control panel 206 for user interface and control of system functions, an edit control panel 208 for user interface and control of DCC tape editing -functions, a power switch 210 for turning the deck 110 on and off, and an input select switch 212 for selecting either the analog input from the record player 108, or the digital input from the compact disk player 106, to the deck 110.

The system control panel 206 includes an "open/close" switch 206a that controls the opening and closing of the tape drawer 204, a "record" switch 206b that places deck 110 in a record-pause mode, a "pause" switch 206c that places the deck in either a pause or an unpause mode, a "direction" switch 206d that controls the direction of motion of the tape during record and play-back modes of operation, a "stop" switch 206f to stop the operation of deck, and a "play" switch 206e to initiate the playing of a tape. The control panel 206 further includes a "reverse mode" switch 206g that sets-up the auto-reverse function of the deck 110 for automatic control of the playing of a tape, a "record mute" switch 206h for the recording of four seconds of silence, a "rewind" switch 206i for the rewinding of a tape, a "search reverse" switch 206j for automatic search to the beginning of the current or the previous track, a "search forward" switch 206k for the automatic search to the beginning of the next track, and a "fast forward" switch 2061 for fast forwarding of a tape.

It should be noted that once the the record switch 206b has been pressed, placing the deck 110 in a record-pause mode, either the pause switch 206c or the play switch 206e must be subsequently pressed in order to place the deck in the record mode.

The edit control panel 208 includes an "auto" switch 208a that takes the deck out of the default automatic mode of operation and activates the edit control panel, a "start ID write" switch 208b for placing a start marker on the tape to identify the start of a particular program track, an "start ID erase" switch 208c for the removal of a start marker, a "reverse ID" write switch 208d for placing a reverse marker on sector A of the tape to identify the point on the tape at which the deck 110 should reverse direction of play to sector B, a "reverse ID erase" switch 208e for removal of a reverse marker, and a "program" switch 208f for programming a desired sequential selection of the program tracks to be played. The panel 208 further includes a "renumber" switch 208g for the renumbering of program tracks, a "skip ID write" switch 208h for placing a skip marker on the tape to identify particular program tracks to be skipped over so that they will not to be played, a "skip ID erase" switch 208i for removal of a skip marker, a "reset" switch 208j for resetting the tape counter, a "mode" switch 208k for selecting the mode of the tape counter, such as track time, remaining track time, absolute time of the tape, or the total remaining time to be displayed on the display 202, and a "text" switch 2081 for selecting the text mode, such as track title, artist, credits, lyrics, or the like to be displayed on the display 202.

FIG. 3 is a functional block diagram illustrating the various components of the deck 110. It is understood that the deck 110 is utilized for the recording, playback and editing of audio information, such as high fidelity stereo music or the like, on a DCC tape 300 received in the tape drawer 204 (FIG. 2). It is also understood that the tape 300 is either prerecorded or consumer-recorded using a DCC deck, such as the deck 110. The deck 110 is also able to receive and playback standard analog cassette tapes (not shown) .

The front panel 200 of the deck 110 includes the vacuum fluorescent display 202, a select switch 212, a keyboard matrix 302, and a front panel processor 304. The deck 110 further includes a main processor 306, a digital drive signal processor (DDSP) module 308, a analog-to-digital (A/D) and digital-to-analog (D/A) converter 310, a digital compact cassette record/play thin film head 312, a recording unit 314, including a tape drive mechanism and a read/write amplifier (not shown) , a digital signal mute circuit 316, an analog signal mute circuit 318, an analog/DCC select circuit 320 and a precision rectifier 321. Two line input jacks 322a, 322b, a digital output jack 324a, a digital input jack 324b, and two line output jacks 326a, 326b are also provided, as discussed further below.

The keyboard matrix 302 includes the control panels 206 and 208 (FIG.2) and provides a user with a means to interface and interact with the deck 110. The front panel processor 304 is connected to the keyboard matrix 302 by a bus 328 that continuously strobes the keyboard matrix to determine when any of the switches 206a-206l or 208a-208l are pressed. Further, the processor 304 is connected to the display 202 by the bus 328 and controls the display of icons and alphanumeric information on the display and to the select switch 212 by a line 329 that is used to indicate the position of the switch 212. The processor 304 is connected to the main processor 306 by two serial bus lines 330a, 330b that are used for the transfer of information between the processors 304 and 306.

The main processor 306 has direct control over all system operations and functions within the deck 110 and contains the program instructions for implementing the automatic search functions of the present invention, described in detail below. The main processor 306 is connected to the recording unit 314 by a status line 332, a feedback line 334 and a data bus 336. The status line 332 gives the main processor 306 the current status of the tape 300. The tape status includes whether the tape 300 is a DCC or an analog cassette, whether the tape is record-prevented, and the time-length of the tape. The feedback line 334 indicates to the control processor 306 whether the tape 300 is moving, stopped or broken, the position of the head 312 (in, out, or in the search position), and whether the tape is transparent, thus indicating the end of the tape. A bus 336 is used by the main control processor 306 to control the functions of the recording unit 314. These functions include the speed and direction of movement of the tape 300, the position of the tape head 312 and the tension on the tape. A control line 338 connects the processor 306 to the select circuit 320 and enables the processor to select the output source depending on whether the tape 300 is analog or digital. Similarly, a control line 340 connects the processor 306 to the mute circuit 318 and enables the processor to mute the analog output.

While not shown, it is understood that the recording unit 314 includes a capstan drive, a reel drive, a head position solenoid, a read amplifier and a write amplifier. The recording unit 314 is connected to the head 312 by a write line 342 and a read line 344 which are used for the writing and reading, respectively, of digital data, including audio data, system information, containing the copyright protection status and recording-related text for display, parity codes for error detection and correction, and auxiliary data from the tape 300. The read line 344 is also used in receiving an analog signal from the head 312 during playback of an analog tape (not shown). The recording unit 314 is connected to the DDSP module 308 by a plurality of buses designated with the reference numeral 346. The buses 346 include a serial clock bus and nine parallel data buses that are used for the synchronous transfer of data to and from the recording unit 314. The recording unit 314 is connected to the select circuit 320 by a left channel output line 348a and a right channel output line 348b that are used by the recording unit 314 during the playback of an analog tape (not shown) and to the DDSP module 308 by a speed control line 350 that is used during playback to control the speed of motion of the tape 300 and, consequently, the rate in which data is transferred to the DDSP module via the buses 346.

The DDSP module 308 has direct control over the encoding, decoding, formatting and error correction of the data exchanged on the buses 346. While not shown, the module 308 includes five main components, which are a DDSP for the formatting and deformatting of data, an error correction device for error detection and correction, a sub-band codec device for the coding and decoding of sub-bands of the sampled audio data, a digital audio interface for interaction between the DDSP and the converter 310, and a digital equalizer to overcome the distortion made in the tape recording and playback processes. In the playback of the tape 300, digital data is transferred to the DDSP module 308 by the buses 346 and the DDSP module 308 deformats the data and corrects any correctable errors using a Reed-Solomon encryption code, well known in the art. The deformatted data is transferred to the main control processor 306 via a bidirectional bus 352. A determination is made from the deformatted data as to how the tape 300 was recorded and, consequently, the processor 306 transfers the appropriate digital equalizer filter (DEQ) coefficients to the module 308. It is understood that the digital equalizer consists of multi-taped filters used to optimize the digital signal and is well known in the art.

A synchronous start segment control line 354 connects the DDSP module 308 to the main processor 306 and indicates to the processor when it is time to either transmit or receive data. An asynchronous label control line 356 also connects the module 308 to the processor 306 and indicates to the processor the occurrence of a label on the tape 300, as will be discussed. A plurality of control lines 358 enable the processor 306 to select which of the aforementioned main components of the DDSP module 308 are to either receive or transmit data via the bus 352. The DDSP module 308 is connected to the converter 310 and to the mute circuit 316 by a serial data bus 360 and a control line 362 for the transfer of digital data and for muting the digital output from the deck 110, respectively. Further, the DDSP module 308 supplies a clock signal to the converter 310 via a line 364 for the clocking in and out of data via the serial bus 360, and receives digital data input from the jack 324b on a line 366 for subsequent PASC data compression.

The converter 310 is used to convert analog signals to digital signals and digital signals to analog signals. The converter 310 receives analog audio inputs for left channel and right channel from the jacks 322a, 322b via two lines 368a, 368b, respectively, and converts the signal to an 16-bit serial digital signal that is sent to the DDSP module 308 and to the mute circuit 316 on the serial bus 360. In addition, the converter 310 receives digital data that has undergone precision adaptive sub-band coding (PASC) data decompression via the serial data bus 360 and converts the data into left and right channel analog signals for output via two lines 370a, and 370b, respectively. Further, the analog output signal on the lines 370a, 370b can be inhibited or muted by the DDSP module 308 via a control signal on the line 362.

The digital mute circuit 316 is used by the deck 110 to mute the digital output from the jack 324a, as commanded by the main control processor 306 via the DDSP module 308 and the control line 362. Typically, the circuit 316 receives serial data from the DDSP module 308 on the serial bus 360 and outputs same from the jack 324a via a line 372.

The analog/DCC select circuit 320 enables the processor 306 to select either the inputs from the recording unit 314 on the lines 348a, 348b used during the playback of an analog tape or the input from the converter 310 on the line 370a, 370b used during the playback of the DCC tape 300 via the control line 338, and to output the left and right channels of the selected input to the mute circuit 318 on two lines 374a and 374b, respectively. Similarly, the mute circuit 318 is used by the deck 110 to mute the stereo output from the jacks 326a, 326b, as commanded by the processor 306 via the control line 340. Typically, the circuit 318 receives left and right channel inputs on lines 374a and 374b and outputs the same to the jacks 326a, 326b on two lines 376a, 376b, respectively.

The precision rectifier 321 is connected to the analog right and left channel output lines 374a, 374b and is used to convert the alternating output signal to direct current with a known conversion efficiency. The rectified signal is input to the front panel processor 304 via two input lines 380a, 380b. The processor 304 uses the rectified signal to determine the beginning of a new program track predicated on that both left and right channels exceed -lOdB, to arm the system, and on the assumption that the track is preceded by silence (-40dB) for a period of 4 seconds.

It is understood, although not shown, that the output of the record player 108 is input on the line 114 to the deck 110 via the jacks 322a, 322b and the CD player 106 is input on the line 112 to the deck via the jack 324b. Similarly, the output of the deck 110 is input on the line 116 to the amplifier 102 via the jacks 326a, 326b,

FIG. 4 is a schematic illustration showing details of the record/playback thin film head 312. The head 312 is a a thin film record and playback head comprising a set of nine inductive recording heads (IRHs) 400 for digital recording, a set of nine magneto-resistive heads (MRHs) 402 for digital playback and a set of two MRH's 404 for analog playback. The IRHs 400 include one IRH 400a for the recording of an auxiliary (AUX) data track on the tape 300 and eight IRHs 400b-400i for the recording of eight main data tracks (0-7) on the tape. The IRHs 402 include one MRH 402a for the playback of the auxiliary (AUX) data track and eight MRHs 402b-402i for the playback of the main data tracks (0-7). The MRHs 404 include an MRH 404a and an MRH 404b, for the playback of right channel and left channel tracks, respectively, of standard analog audio cassette tape (not shown). The IRHs 400 and the MRHs 402 are each approximately 185 and 70 microns wide, respectively, and the MRHs 404 are each approximately 600 microns wide. FIG. 5 schematically illustrates a portion of the tape 300 showing the digital compact cassette tape track format. The tape 300 is based on commercially available magnetic tape technology similar to the magnetic tape used in video cassette recorders and players, and is approximately 3.78 millimeters wide, 12 microns thick, and has a magnetic coating of chromium dioxide approximately 2.5 microns thick. The tape 300 is formatted into two main sectors, sector A 500 and sector B 502. The sector A 500 includes a track 500a which contains the auxiliary (AUX) data track and tracks 500b-500i which contain the main data tracks (0-7). The sector B 502 includes a track 502a which contains the auxiliary (AUX) data track and tracks 502b-502i which contain the main data tracks (0-7). The auxiliary data tracks 500a, 502a include information used by the deck 110 to inform the user of music-related items, such as time, track number, and table of contents. The tracks 500a, 502a further include markers, such as start, lead-in, lead-out, reverse, skip, mute or the like, used by the deck 110 for automatic response, as will be described, and other information. The direction of movement during playback and recording of the tape 300 for the sectors 500 and 502 is shown by two arrows 504 and 506, respectively. The main data tracks 500b-500i and 502b-502i contain encrypted audio data, including a Reed-Solomon code for error detection and correction, and system data, including copyright status, text, lyrics, credits, album title, track title, and the like.

In general, the two different kinds of data stored on the tape 300 are main data including system information stored on the tracks 500b-500i and on the tracks 502b-502i, and auxiliary data stored on the tracks 500a and 502a. The data format of the auxiliary data tracks 500a, 502a is similar to the data format of the main data tracks 500b-500i and 502b-502i, however, only one data track per sector is available for the storage of information on the auxiliary data tracks. As the present invention principally relates to utilization of data on the auxiliary data tracks 500a, 502a, and as the data format of the main data on tracks 500b-500i, 502b-502i is well known in the art, only the data format for the auxiliary data will be discussed further.

FIG. 6 schematically illustrates the manner in which data is arranged on the auxiliary data tracks 500a, 502a on the tape 300. The auxiliary data is recorded on the tape 300 as a plurality of successive data frames, one of which is represented by the reference numeral 600. An interframe gap (IFG) 602 is provided between successive data frames 600, to accommodate for small deviations in the length of the data frames due to small variations in sampling frequency and clock periods or the like, used during recording. The IFG 602 carries a signal that has an alternating polarity at every bit position and has a nominal length of eight bit periods. Each of the data frames 600 is divided into four data blocks 604a-604d (blocks 0-3, respectively). The blocks 604a-604d are each encoded using a standard look-up table, referred to in the art as an "8 to 10 modulation table" and stored in RAM memory (not shown) within the DDSP module 308. Each of the data blocks 604a-604d are divided into a header 608 and a body 610, as shown with respect to the block 604a in FIG. 6. The header 608 contains two 10-bit phase lock loop (PLL) sequences (not shown), that enable easy clock recovery and indicate whether or not the body 610 is recorded, and also contains a sync sequence (not shown), that is used to identify the start of each of the data block 604a-604d. The body 610 contains a single Reed-Solomon code word 614 consisting of twelve 8-bit parity bytes for error detection and correction of the auxiliary data in the block 604, and thirty-six 8-bit data bytes 614 containing the auxiliary data, as will be described. FIG. 7 illustrates schematically two of the possible low-frequency envelopes of the auxiliary data track 500a or 502a, used to enable easy detection of locations on the tape 300 during a search mode by monitoring the output of the label line 356 and without having to decode the auxiliary data. Ordinarily, auxiliary data is recorded only in the data block 604a and in the data block 604c. A data frame recorded in such a manner is referred to as a nonlabeled data frame and is designated by the reference numeral 700. In the nonlabeled data frame 700, the information on the tape 300 at the position of the data blocks 604b, 604d are erased by overwriting with eight binary ones (Hex FF) . Alternatively, a labeled data frame, designated by the reference numeral 702, is created by recording all of the data blocks 604a-604d of the frame. The labeled data frame 702 enables specific locations on the tape 300 to be located in both search-forward and search-reverse modes.

FIG. 8 illustrates schematically five possible low-frequency envelopes used as markers in the auxiliary tracks 500a, 502a on the tape 300. In general, marker envelopes are composed of a series of labeled and nonlabeled data frames of varying length and are categorized as being either "start" markers, "sector" markers or "feature" markers. Both the start marker and the sector markers can be detected during a search mode, whereas, feature markers can only be detected in the playback mode only. Sector markers function to define the start and end of a musical or program area on the tape 300 and also specify automated control of the deck 110. Start markers function to identify the start of a musical or program track. Sector markers may also function as start markers for the first musical track on both the sector A 500 and the sector B 502. Feature markers function to specify the automated control of the deck 110 during the playback of the tape 300 and is comprised exclusively of nonlabeled data frames. A start marker 800 is shown in FIG. 8 which has a length of a minimum of sixteen labeled frames 802. The start marker 800 can be detected in search modes and is used to indicate the start of a program track. On prerecorded DCC tapes, the start marker 800 is recorded before the start of the musical track and on consumer-recorded tapes the start marker 800 is recorded immediately after the start of the musical track. For consumer-recorded tapes only, the first start marker on Sector B, opposite the reverse marker on Sector A 500, is recorded for 32 frames within the MLI bit 932 set indicating that it is a long marker and it is the first track on Sector B 502. In the case of a reverse search operation this start marker can be detected causing the main control processor 306 to reverse direction of the head and continue the search in reverse down Sector A 500.

Sector markers include a "lead-in" marker 804, "lead-out" marker 806, "home and next markers 808 and a "reverse" marker 830. The lead-in marker 804 is used to indicate the start of the sector A 500 on both prerecorded and consumer-recorded DCC tapes. The lead-in marker is composed of an alternating series of 4-labeled frames 812 and 4-nonlabeled frames 814 that alternate for a total of 72 frames, followed by either 32 labeled data frames for prerecorded tapes or 16 labeled data frames for consumer recorded tapes, designated by the numeral 815. The lead-out marker 806 indicates the end of a sector, whereas, the reverse marker 830 indicates the point on the sector A 500 from which the deck 110 should continue to operate in the previous mode, but on the sector B 502. The reverse marker 830 is only applicable on sector A 500 of consumer-recorded tapes and is composed of 32 labelled data frames with the MLI bit 932 set. The lead-out marker 806 is composed of 32 labeled data frames 816 followed by an alternating series of 4-labeled frames 820 and 4-nonlabeled frames 822 that alternate for a total of at least 36 frames 818. The home marker 808 is used on consumer-recorded tapes to direct the deck 110 to search for the start of the first musical track on the sector A 500. The next marker 808 is used to indicate the point from which the deck should seach for the beginning of the musical track on the other sector. The home and next markers 808 are composed of a series of 4-labeled frames 824 and 4-nonlabeled frames 826 that alternate for a total of 16 data frames.

A skip marker 828 is a feature marker that is used on consumer-recorded tapes to direct the deck 110 to search for the next start marker 800. The skip marker 828 is unusual in that it is composed of 6-nonlabeled data frames and, consequently, is undetectable in a high speed search by the deck 110.

It is understood that prerecorded DCC tapes differ from consumer recorded tapes in that prerecorded tapes do not have all of the aforementioned markers and may only have the start marker 800, the lead-in marker 804, and the lead-out marker 806. Consumer-recorded tapes can further be categorized as having either "user" or "super-user" formats. The super-user and the prerecorded format differ from a user format in that a noninterrupted (absolute) time code is recorded over the entire length of the music/program area. Further, the super-user format differs from a user format in that all music tracks can be numbered in a noninterrupted ascending order, such as by a renumbering action, as will be described.

During search mode operation of the deck 110, the marker envelopes 800, 804, 806, 808, and 828 are passed from the DDSP module 308 to the main control processor 306 (FIG. 3). It is understood that the skip marker is detected only during the playback mode of operation of the deck 110. Further, it is understood that during the search mode, the envelope of the 16 labeled data frames 802 of the start marker 800, result in the label line 356 going high for a period of between 90 to 160 milliseconds (ms). Similarly, during search mode, the 4 labeled data frames 812 of the lead-in marker 804, results in the label line 356 going high for a period of between 20 to 55ms and the 16 or 32 labeled frames 815 of the lead-in marker 804, result in the label line 356 going high for a period of between 90 and 320 ms, respectively. Also during search mode, the 32 labeled data frames 816 plus the 4 labeled data frames 820 of the lead-out marker 806, result in the label line 356 going high for a period of between 210 to 425ms. Further, the alternating series of labeled and unlabeled data frames 820 and 822 of the lead-out and reverse markers 806, result in the label line 356 going high for a period of between 20 to 55ms and then low for a period of between 20 to 55ms, respectively. The reverse marker 830 is composed of 32 labeled frames which cause the label line 356 going high for a period of between 190 to 395ms.

FIG. 9 illustrates schematically the general organization of the contents of the thirty-six 8-bit data bytes contained in the auxiliary data block 612 (FIG. 6) of the data tracks 500a, 502a on the tape 300. A lower 4-bit nibble 900 contains tutorial information as to which of the 4 data blocks 604a, 604b, 604c, 604d the current data block 604 is, and in which direction as indicated by the arrows 504, 506 the sectors A 500 and B 502 were recorded. An upper 4-bit nibble 902 contains 4 mandatory binary zeros. An 8-bit byte 904 contains marker information including, whether or not the data block 604 is labeled, what kind of marker the data block 604 is contained in, whether the track is contained in the table of contents (TOC) and whether or not the tape 300 is in the super-user format. If the byte 904 indicates that the data block 604 is both labeled and a sector marker, then the DCC deck 110 must examine an 8-bit byte 906 to determine the sector marker type. The byte 906 is generally reserved for track numbering with values of 01 through' 99 (BCD) being valid track numbers indicating which musical track is currently being played. An 8-bit byte 908 is used for the index/chapter number. The index number divides a music track into separate parts and the chapter number combines various music tracks, for example because these have been performed by the same artist or are part of the same concert. On consumer-recorded tapes only chapter numbers are allowed. Three 8-bit bytes 910 are used to indicate the absolute time which is the total time elapsed since the beginning of the current program. A lower 3-bit nibble 912 are used for the hour units of the absolute time. A "start on B" (SOB) bit 914 is used to indicate whether or not the absolute time on the sector B 502 is independent from the absolute time on the sector A 500. A 3-bit nibble 916 is used to indicate the absolute frame count and the sector bit 918 indicates whether the sector A 500 or the sector B 502 is currently being played. A lower 4-bit nibble 920 is used to indicate the ones of minutes unit of the absolute time. An upper 4-bit nibble 922 is used to indicate the tens of minutes unit of the absolute time. A lower 4-bit nibble 924 is used to indicate the second units of the absolute time. An upper 4-bit nibble 926 is used to indicate the tens of seconds units of the absolute time. Three 8-bit bytes 928 are used to indicate the track time which is the elapsed time since the beginning of the current track. A lower 3-bits 930 is used for the hour units of the track time. A "marker length indication" (MLI) bit 932 is used to indicate whether the marker is a normal length marker (16 frames) or a long marker (32 frames), as in the case of a reverse marker or the first start marker on sector B. An upper 3-bit nibble 934 is used to indicate the track frame count. A "pause" (PAU) bit 936 is used to indicate that the current frame is not part of a musical track and is not to be included in the absolute time or in the track time. A lower 4-bit nibble 938 is used to indicate the ones of minutes unit of the track time. An upper 4-bit nibble 940 is used to indicate the tens of minutes unit of the track time. A lower 4-bit nibble 942 is used to indicate the ones of seconds unit of the track time. An upper 4-bit nibble 944 is used to indicate the tens of seconds unit of the track time. Ten 8-bit bytes 946 are used to indicate information regarding the table of contents (TOC) . As each table of contents entry requires 5 bytes, two table of contents entries can be stored in the bytes 946. The TOC is required to properly reflect the contents of the tape 300 and as the bytes 946 can only contain 2 TOC items in the single data frame 600, the first data frame contains the first 2 TOC items the second data frame contains the third and forth TOC items, and so forth, until all TOC items are extinguished. A table of contents sequence may be recorded at the start of both the sector A 500 and the sector B 502 only on a super-user formatted tape. The last sixteen 8-bit bytes contain an additional information specifier field 948 which is reserved for additional information. The field 948 can contain a catalog number, the data and time a recording was made, the remaining track time or consumer recorded characters.

FIGS. 10-12 are flow charts illustrating the control logic of the present invention used to implement an automatic search music system (ASMS) in the deck 110. The automatic search mechanism may be initiated in response to search commands from the control panel 200 input by the user (FIGS. 10 and 11) or may be initiated automatically by markers on the tape 300 (FIG. 12). It is understood that the control logic of FIGS. 10-12 is implemented using standard microprocessor instructions contained in the main control processor 306 (FIG. 3).

FIG. 10 illustrates generally the logic for performing a program track selection search of the tape 300 by the deck 110, in which the search is initiated by the user. The beginning of a flow chart is indicated at step 1000. At step 1002, an input is received by the user requesting the initiation of a program track selection search. The search is initiated when the user presses the appropriate keys on the keyboard matrix 302 of the front panel 200 (FIGS. 2 and 3). Specifically, a forward search is initiated by pressing the search-forward switch 206k or a reverse search is initiated by pressing the search-reverse switch 206j, respectively, indicating that the deck 110 is to fast forward to the beginning of next program track or fast reverse to the beginning of the previous program track. The current mode of the deck 110, such as whether the deck is currently playing, paused, or stopped, is stored in memory of the processor 306 as a variable called the "previous mode," so that the processor can return deck operation to the appropriate mode on completion of the search operation.

At step 1004, a determination is made whether the search request is in the forward or reverse direction. If a forward search has been initiated by actuation of the switch 206k, execution proceeds to step 1006 where a determination is made whether a valid command has been received. For example, if the deck is currently operating in the record mode, a search command is not valid and therefore execution continues in that same previous mode, as indicated at step 1008. If at step 1006 the command is valid, execution proceeds to step 1010. At step 1010, the audio output of the deck 110 is muted and movement of the tape 300 is started. At step 1012, a high speed tape search is initiated to the recording unit 314 and DEQ of the DDSP 308 in the forward direction.

At step 1014, a determination is made whether a labeled data frame on the tape 300 has been detected. In particular, the main processor 306 examines the status of the label line 356 (FIG. 3). The line 356 goes high when a labeled data frame 702 (FIG. 7) is detected. If at step 1014 a labeled data frame is not detected, execution proceeds to step 1016 where a determination is made whether an error has occurred or an abort instruction has been received. If at step 1016 an error or abort instruction is received, execution proceeds to step 1018 for return to the previous operating mode. If at step 1016 no error occurs or abort command is received, execution returns to step 1014. If at step 1014 a labeled data frame is detected, execution proceeds to step 1020.

At step 1020, a determination is made whether the track index is equal to zero. It is understood that the track index is initially set upon receipt of the search instruction to correspond to the number of tracks which must be skipped over to reach the desired program track selection. For example, if the user desires to skip a track, the switch 206k is pressed twice, thereby setting the track index equal to "1." It is understood that the first press initiates the search operation and the second press increments the track index. If at step 1020 the track index is not equal to zero, execution proceeds to step 1022. At step 1022, the labeled data frame is examined and determinations are made as to the type of marker present on the tape 300. If a detected marker is a "start" marker, the track index is decremented. Execution proceeds until a "start" marker is detected, the track index is decremented, and execution returns to step 1014. If at step 1020 the track index has been decremented to zero execution proceeds to step 1018 where operation returns to the previous mode. Thus, if the deck 110 was operating in the play mode when the search was initiated, upon completion of the search the deck will play from that location on the tape 300.

If at step 1004 a reverse search has been initiated by activation of the switch 206j , execution proceeds to step 1024 and it is understood that the search request is in the reverse direction. The steps 1024-1036 for performing a search operation in the reverse direction as shown in FIG. 10 are essentially the same as those just described for the forward direction, therefore will not be described further here. Differences in the logic required for performing forward and reverse searching will become apparent from the detailed discussion of FIGS. 11 and 12 which follows.

FIGS. 11a and lib describe in greater detail the logic for performing a program selection search of the tape 300 by the deck 110, in which the search is initiated by the user. The beginning of a flow chart is indicated at step 1100. It is understood that an input is received when the user requests the initiation of a program selection search by pressing either of the switches 206k or 206j on the panel 200, as described above.

At step 1102, a determination is made whether the search is in the forward or reverse direction, as previously described. If at step 1102 the search is in the forward direction, execution proceeds to step 1104. At step 1104, a determination is made whether the unit 314 is active, i.e., whether the tape 300 is moving. If at step 1104, a determination is made that the unit 314 is not currently active, execution proceeds to step 1106. At step 1106, the audio output of the deck 110 is muted via the mute circuits 316 and 318 (FIG. 3), and execution proceeds to step 1108. At step 1108, the processor 306 stores whether the previous tape movement was in the direction as indicated by the arrow 504 or in the direction as indicated by the arrow 506. The foregoing corresponds to whether the unit 314 was previously on sector A 500 or on sector B 502, respectively. This sector information is stored in the memory (not shown) of the processor 306 so that the processor can set up the play direction of the unit 314 once the search is completed. At step 1110, a determination is made whether the unit 314 is to be operating in sector A 500 or sector B 502. If at step 1110 it is determined that the recording unit 314 is to search sector A 500, execution proceeds to step 1112. At step 1112, the head 312 is positioned over sector A and the tape 300 is started in the forward direction. If at step 1112 it is determined that the recording unit is to the search sector B 502, execution proceeds to step 1114. At step 1114, the head 312 is positioned over sector B 502 and the tape 300 is started in the reverse direction. From step 1112 or step 1114, execution proceeds to step 1116, as will be discussed below.

If at step 1104 the unit 314 is active, the processor 306 must determine if the search command is valid before beginning the search. At step 1118, a determination is made whether the unit 314 is in the record mode. If the unit 314 is not in a record mode, execution proceeds to step 1120, where a determination is made whether the unit 314 is in either the fast forward or rewind mode. If at step 1118 the unit 314 is in the record mode or if at step 1120 the deck is in either the fast-forward or rewind mode, execution proceeds to step 1122. At step 1122, an invalid command error signal is sent to the front panel processor 304 and at step 1124 execution continues in the previous mode. If at step 1120 the unit 314 is neither in the fast forward mode nor in the rewind mode, then the command to search forward is valid, and execution proceeds to step 1126. At step 1126 the audio output is muted via the mute circuits 316 and 318, and execution proceeds to step 1116.

At step 1116, the digital equalizer (not shown) in the DDSP module 308 is placed in the search mode. At step 1128, the unit 314 is put into a high speed search of the tape 300. As indicated at step 1130, it is understood that the main processor 306 ignores any inputs from the label control line 356 for a period of 150 milliseconds (ms). This 150ms delay is provided so that the track index will not be decremented in the event that the tape head 312 is currently positioned on a start marker 800 when the search is initiated. This prevents the search from treating the current program selection (if at its beginning) as the next program selection for search purposes. After ignoring any inputs from the label control line 356 for a period of 150ms, execution proceeds to step 1132. At step 1132, the main processor 306 examines the control line 356 (FIG. 3) for the beginning of a labeled data frame 702 (FIG. 7). When a labeled date frame is detected, the line 356 goes high. If at step 1132 the control line 356 is not high, indicating that a labeled data frame 702 is not present, execution proceeds to step 1133. At step 1133, a routine "Y" in FIG. 13 is executed in which commands from the front panel 200 and the recording unit 314 are interpreted, as will be described. Execution then proceeds to step 1134. At step 1134, a determination is made whether there are any commands from the front panel 200. If there are no commands from the front panel 200, execution proceeds to step 1136. At step 1136, a determination is made whether the end of the tape 300 has been reached, via the feedback line 334. If at step 1136 it is determined that the end of the tape 300 has not been reached, execution returns to step 1132. If at step 1136 the end of the tape has been reached, execution proceeds step 1137. At step 1137, the unit 314 is commanded to exit the search mode, and the track index is set to zero. Execution then proceeds to step 1138 where the unit 314 is commanded to stop. If at step 1134 a valid command has been received from the front panel 200, execution proceeds to step 1140 where a determination is made whether the play switch 206e or the stop switch 206f has been pressed. If at step 1140 it is determined that the play switch 206c and the stop switch 206f have not been pressed, execution proceeds to step 1142. At step 1142, a determination is made whether the input from the front panel 200 was due to the forward search switch 206k being pressed. If at step 1142 a determination is made that the forward search switch 206k was pressed, execution proceeds to step 1144 and the track index is incremented prior to the execution returning to step 1132. If at step 1142 a determination is made that the forward .search switch 206k has not been pressed, the command from the front panel 200 is ignored and execution returns to step 1132. If at step 1140 a determination is made that either the play switch 206e or the stop switch 206f has been pressed, execution proceeds to step 1146. At step 1146, the command to stop or play is stored in memory as the "previous mode" of operation, and execution proceeds to step 1148. At step 1148, the unit 314 is commanded to exit the search mode and to set the track index to zero. Execution then proceeds to step 1150. At step 1150, a determination is made whether the previous mode is the stop, play or pause mode. If at step 1150 it is determined that the previous mode is the stop mode, execution proceeds to step 1142. If at step 1150 it is determined that the previous mode is the play mode, execution proceeds to step 1152 and the unit 314 is commanded to the play mode. If at step 1150 it is determined that the previous mode is the pause mode, execution proceeds to step 1154 and the unit 314 is commanded to the pause mode.

As previously stated, at step 1132 the main processor 306 examines the label line 356 for the beginning of a labeled data frame 702. If at step 1132 the label line 356 is high, indicating that the labeled data frame 702 is present, execution proceeds to step 1156. At step 1156, the processor 306 examines the current track index. If at step 1156 it is determined that the program track index is zero, then the unit 314 has completed the search forward operation, found the required track, and execution proceeds to step 1148.

If at step 1156 it is determined that the program track index is not zero, execution proceeds to step 1158. At step 1158, a determination is made as whether the label line 356 has gone low. If at step 1158 it is determined that the label line 356 has not gone low, execution proceeds to step 1159. At step 1159, it is determined if the label line has been high for 190mε, if not, execution proceeds to step 1160. If greater than 190ms, indicating that an end of sector (e.g., reverse) marker may have been detected, execution proceeds to step 1178 (FIG. lib). At step 1160, a routine "Y" (FIG. 13) is executed in which commands from the front panel 200 and the recording unit 314 are interpreted, as will be described. Execution then proceeds to step 1162. At step 1162 a determination is made whether a command has been received from either the front panel 200 or the recording unit 314 to which the deck 110 is to respond. If at step 1162 it is determined that a command has been received, execution proceeds to step 1134. If at step 1162 it is determined that a command has not been received, execution returns to step 1158.

If at step 1158 it is determined that the label line 356 has gone low, execution proceeds to step 1164. At step 1164, a 100 millisecond (ms) timer is initialized, and execution proceeds to step 1166. It is understood that if the label line 356 goes high within 100ms of when it went low, then a sector marker has been detected, whereas if the line does not go high within lOOms a start marker has been detected. At step 1166, a determination is made whether the control line 356 has gone high.

If at step 1166 it is determined that the control line 356 has not gone high, execution proceeds to step 1168. At step 1168, the routine Y is called, and execution proceeds to step 1170. At step 1170 a determination is made whether a command has been received from either the front panel 200 or the recording unit 314 to which the deck 110 is to respond. If at step 1170 it is determined that a valid command has been received, execution proceeds to step 1134. If at step 1170 it is determined that a valid command has not been received, execution proceeds to step 1172. At step 1172 a determination is made whether the 100ms timer has timed out without the control line 356 going high, as determined at step 1166. If at step 1172 it is determined that the 100ms timer has not timed out, execution returns to step 1166. If at step 1172 it is determined that the 100ms timer has timed out without the control line 356 going high, as determined at step 1166, then the pulse detected at step 1132 is from a start marker 800, and execution proceeds to step 1174 (if in forward search), 1174r (if in reverse search) .

At steps 1174, 1174r,the program track index is decremented and execution proceeds to step 1176, 1176r, respectively. At steps 1176, 1176r, the main control processor 306 sends a control signal to the front panel processor 304 to decrement the program track index, as displayed on the display 202, and execution returns to step 1132 (if forward search), ll32r (if reverse search).

If at step 1166 the control line 356 go high again within the 100ms as determined at step 1172, then the pulse detected at step 1132 is from a sector marker, such as the lead-in marker 804, the home marker 808, or the lead-out and reverse marker 806. Execution then proceeds to step 1178 (if forward search), 1178r (if reverse search). At step 1178, 1178r, the unit 314 returns to the play mode, and the processor 306 reads the labeled data frame 702 (FIG. 7) to determine the sector marker type from information contained in bytes 904 and 906 (FIG. 9). If in forward search, execution then proceeds from step 1178 to step 1180. At step 1180, a determination is made whether the frame 702 is contained in either a reverse marker or a lead-out A marker, indicating that the tape 300 is now at the end of sector A 500. If at step 1180 a determination is made that the frame 702 is contained in either a reverse marker or a lead-out A marker, execution proceeds to step 1182. At step 1182, the direction of play is changed from the sector A 500 to the sector B 502. Execution returns to step 1116 where the DDSP 308 is returned to the high speed search mode.

If at step 1180 a determination is made that the frame 702 is not contained in either a reverse marker or a lead-out A marker, execution proceeds to step 1184. At step 1184, a determination is made whether the frame 702 is contained in either a home marker or a lead-out B marker, indicating the tape 300 is now at the end of the sector B 502. If at step 1184 it is determined that the frame 702 is not contained in either a home marker or a lead-out B marker, execution returns to step 1116 where the DDSP 308 is returned to the high speed search mode. If at step 1184 it is determined that the frame 702 is contained in either a home marker or a lead-out B marker, then the unit 314 has reached the end of the tape 300 without finding the desired track and execution proceeds to step 1137 where the unit 314 exits the search mode and the track index is set to zero.

If in reverse search, execution proceeds from step 1178r to step 1180r. At step 1180r, a determination is made whether the frame 702 is contained in a lead-in B marker, indicating that the tape 300 is now at the beginning of sector B 502 or if it is contained in the first start marker on sector B indicated by having MLI bit 932 set. If at step 1180r it is determined the frame 702 is contained in a lead-in B marker, execution proceeds to step 1182r. At step 1182r, the direction of the search reverse operation is reversed. Execution returns to step 1116r where the DDSP 308 is returned to the high speed search mode. If at step 1180r it is determined that the frame 702 is not contained in a lead-in B marker, execution proceeds to step 1184r. At 118lr a determination is made whether the marker is the first start marker on sector B, in which case execution proceeds to step 1182r. If not, execution proceeds to 1184r. At step 1184r, a determination is made whether the frame 702 is contained in a lead-in A marker, indicating the tape 300 is now at the beginning of sector A 500. If at step 1184r it is determined that the frame 702 is not contained in a lead-in A marker, execution returns to step 1116r where the DDSP 308 is returned to the high speed search mode. If at step 1184r it is determined that the frame 702 is contained in a lead-in A marker, then the unit 314 has reached the beginning of the tape 300 without finding the desired track and execution proceeds to step 1137, where the unit 314 exits the search mode and the track index is set to zero. FIG. 12 describes the logic for performing a program selection search of the tape 300 by the unit 314, in which the search is automatically initiated according to special markers contained on the tape 300 and in response to detection of the physical end of the tape or the detection of the clear leader at the end of the tape. It is understood that the markers on the tape 300 for initiating the below-described automatic search functions may be placed on the tape by the user utilizing the custom tape editing functions of the edit control panel 208.

The beginning of a flow chart for performing the automatic search functions is indicated at step 1200. It is understood that the search functions are carried out by detection of selected markers recorded on the tape 300. At step 1200, the play switch 206e has been pressed by the user so that the unit 314 enters the play mode of operation. At step 1202, the processor 306 checks the feedback line 334 to determine whether the recording unit 314 has stopped, and consequently, whether the unit 314 has reached the end of the tape 300. If the unit 314 has not reached the end of the tape 300, execution proceeds to step 1204. At step 1204, the processor 306 reads the contents of the data bytes 904, 906 and determines whether the unit 314 has reached a reverse marker or a lead-out A marker. If the unit 314 has not reached a reverse marker or a lead-out A marker, execution proceeds to step 1206. At step 1206, the processor 306 examines the feedback control lines 334 and determines whether the transparent leader of the tape 300 has been reached, indicating that the unit 314 is approaching the end of the tape 300. If the unit 314 is not approaching the end of the tape 300, execution proceeds to step 1208. At step 1208, the processor 306 examines the contents of the data bytes 904, 906 to determine whether the unit 314 has reached a lead-in marker. If the unit 314 has not reached a lead-in marker, .execution proceeds to step 1210. At step 1210, the processor 306 examines the contents of the data bytes 904, 906 to determine whether the unit 314 has reached a home or lead-out B marker. If the unit 314 has not reached a home or lead-out B marker, execution proceeds to step 1212. At step 1212, the processor 306 examines the contents of the data byte 904 to determine whether the unit 314 has reached a skip marker, such as the skip marker 828 (FIG. 8). If a skip marker is detected, execution proceeds to step 1213. At step 1213, the unit 314 automatically skips to the next program track selection, as will be discussed. If the unit 314 has not reached a skip marker, execution proceeds to step 1212a. At step 1212a, the processor 306 examines the contents of the data byte 906 to determine whether the unit 314 has reached a next marker. If the unit 314 has not reached a next marker, execution returns to step 1202. If at step 1212a the unit 314 has reached a next marker execution proceeds to step 1212b. At step 1212b, the unit 314 reverses to the opposite sector and execution proceeds to step 1212c. At step 1212c a determination is made whether the unit is on sector A 500 or sector B 502. If at step 1212c it is determined that the unit 314 is on sector A 500, execution proceeds to step I212d. At step 1212d, the unit 314 searches for a lead-in-A marker, and execution proceeds to step 1212e. At step 1212e, the unit 314 searches forward to the end of the lead-in-A marker, and execution returns to step 1202. If at step 1212c it is determined that the unit 314 is on sector B, execution proceeds to step 1212f. At step 1212f, the unit 314 searches for a lead-in-B marker, and execution proceeds to step 1212g. At step 1212g, the unit 314 searches forward to the end of the lead-in-B marker, and execution returns to step 1202.

If at step 1202 the end of the tape 300 is reached the end of tape flag is cleared and execution proceeds to step 1214. If at step 1204 a reverse or lead-out A marker is detected, execution proceeds to step 1214. At step 1214, the processor 306 changes a status bit to indicate a reverse in the play direction in the event that it determined the the unit 314 is to continue playing and execution proceeds to step 1218. At step 1218, a determination is made whether the auto reverse mode was activated, via the reverse mode switch 206g, and consequently, whether the unit 314 is to continue to play. If it is determined that the auto reverse mode is set for playing a single sector, execution proceeds to step 1220 and the unit 314 stops playing the tape 300. If at step 1218 a determination is made that the auto reverse mode is set for playing more than a single sector, execution proceeds to step 1222.

At step 1222 a determination is made whether the auto reverse mode was set for playing the full tape, or alternatively set for "continuous play" mode. If at step 1222 a determination is made that the auto reverse mode was set for playing the full tape, execution proceeds to step 1224 where a determination is made as to the remaining number of times the unit 314 is to play the tape 300. If the number of times remaining for the unit 314 to play the tape 300 is zero, execution proceeds to step 1220, and the unit 314 stops playing the tape 300. If at step 1224, a determination is made that the number of times remaining for the unit 314 to continue playing is not zero, execution proceeds to step 1226. At step 1226 the unit 314 reverses the direction of play and continues playing the tape 300.

If at step 1222 a determination is made that the auto reverse mode was set in the "continuous play" mode, execution proceeds to step 1228. It is understood that in the continuous play mode, the unit 314 is to play the tape 300 eight times. At step 1228, the number of times the tape 300 has been played is determined. If the tape 300 has been played 8 times, execution proceeds to step 1220 and the unit 314 stops playing the tape. If the tape 300 has been played less than 8 times, execution proceeds to step 1226 and the tape direction is reversed.

If. at step 1206 the processor 306 examines the feedback control line 334 and determines that the transparent leader of the tape 300 has been reached, indicating that the unit 314 is either approaching the end of the tape 300 or has just started playing that sector at the beginning of the tape, execution proceeds to step 1230. At step 1230, the unit 314 will search for the end of the leader and execution returns to step 1202.

If at step 1208 the processor 306 reads the contents of the data bytes 904, 906, and determines that the deck 110 has reached the lead-in marker 804 (which is either a lead-in A marker or a lead-in B marker) indicating that the tape 300 is at the beginning of either sector A 500 or sector B 502, execution proceeds to step 1232. At step 1232, the processor 306 places the DEQ of the DDSP 308 and the recording unit 314 in a search forward mode, begins the search for the end of the lead-in marker 804, and execution proceeds to step 1234. At step 1234, the processor 306 examines the label control line 356 to determine whether the line is high. If the label control line 356 is high, the processor 306 continues to examine the line until the line is no longer high, at which time execution proceeds to step 1236. At step 1236, the processor 306 determines whether the control line 356 has not been high for 150 milliseconds (ms) indicating the end of the lead-in marker 804. If at step 1236 it is determined that the label control line 356 has gone high within a 150ms time frame, execution returns to step 1234. If at step 1236 the label control line 356 has been high within 150ms indicating the end of the lead-in marker 804, execution proceeds to step 1238. At step 1238, the processor 306 commands the recording unit 314 to exit the search mode and to return to the play mode, and execution returns to step 1202.

If at step 1208 the processor 306 reads the contents of the data bytes 904, 906, and determines that the unit 314 has not detected a lead-in marker 804, execution proceeds to step 1210. At step 1210, the processor 306 reads the contents of the data bytes 904, 906 to determine whether the unit 314 has reached a home or lead-out B marker. If it is determined that the unit 314 has reached a home or lead-out B marker, execution proceeds to step 1240. At step 1240, the processor 306 commands the recording unit 314 to reverse to sector A 500, and at step 1242, the processor reads the auxiliary data track 500a. At step 1244, a determination is made whether the recording unit 314 is reading a lead-in A marker. If the recording unit 314 is reading a lead-in A marker, execution returns to step 1232 and the processor 306 searches for the end of the lead-in A marker. If at step 1244 it is determined that the recording unit 314 is not reading a lead-in A marker, execution proceeds to step 1246. At step 1246, the processor 306 commands the recording unit 314 to enter the reverse search mode.

At step 1248, the processor 306 examines the label control line 356 to determine if the line is high. If the label control line 356 is not high, execution proceeds to step 1250. At step 1250, a determination is made whether the recording unit 314 is at the end of the tape 300 or whether the control panel 200 has received a command to stop. If at step 1250 it is determined that recording unit 314 is at the end of the tape 300 the processor sets the end of tape bit indicating the unit 314 is at the end of the tape, and execution returns to step 1202. If at step 1250 the control panel 200 has sent a command to stop, execution proceeds to step 1220 and the unit 314 enters the stop mode. If at step 1250 it is determined that the recording unit 314 is not at the end of the tape 300 and that the control panel 200 has not received a command to stop, execution returns to step 1248. If at step 1248 the label control line 356 has gone high, execution proceeds to step 1252. At step 1252, a determination is made whether the label control line 356 has been high for greater than 80 milliseconds (ms) . If at step 1252 the line 356 has been high for less than 80ms, execution returns to step 1248.

If at step 1252 it is determined that the label control line 356 has been high for greater than 80 ms, execution proceeds to step 1254. At step 1254,a determination is made whether the label control line 356 has gone high again within 100ms from the time in which the line went low. If at step 1252 the label control line 356 has not gone high again within 100ms, execution returns to step 1248 and continues searching. If at step 1252 the label control line 356 has gone high again within 100ms, execution returns to step 1202 to return to the play mode.

If at step 1210 the processor 306 reads the contents of the data bytes 904, 906 and determines that the unit 314 has not reached a home or lead-out B marker, execution proceeds to step 1212. At step 1212, the processor 306 reads the contents of the data byte 904 to determine whether the unit 314 has reached a skip marker, such as the skip marker 828. If at step 1212 a skip marker is detected, execution proceeds to step 1213. At step 1213, the unit 314 searches forward for the beginning of the next track where execution proceeds to step 1104 of FIG. 11a.

After the next track has been found, the processor 306 resumes the last play direction and execution returns to step 1202. If at step 1212, it is determined that the deck has not reached a skip marker, execution returns to step 1202.

FIG. 13 describe in greater detail the logic for interpreting commands received from the front panel 200 and the recording unit 314. The beginning of a flow chart is indicated at step 1300. It is understood that a call to this routine has been made by the control logic of FIGS, lla-llc, as described above.

At step 1302, a determination is made whether a command has been received from the front panel 200. If at step 1302 it is determined that a command has not been received from the front panel 200, execution proceeds to step 1304. At step 1304, a determination is made whether the end of the tape 300 has been reached, by examining feedback line 334. If at step 1304 it is determined that the end of the tape 300 has been not reached, execution proceeds to step 1306. At step 1306, a "no command or not end of tape" is returned, and execution proceeds to step 1308. At step 1308 execution is returned to the caller. If at step 1304 it is determined that the end of the tape 300 has been reached, an end of tape flag is set, and execution proceeds to step 1308.

If at step 1302 it is determined that a command has been received from the front panel 200, execution proceeds to step 1312. At step 1312, a determination is made whether a valid command has been received from the front panel 200. It is understood that valid commands include play, stop, forward search, and reverse search, only. If at step 1312 it is determined that a valid command has been received from the front panel 200, execution proceeds to step 1314. At step 1314 the "valid command" is returned and execution proceeds to step 1308.

If at step 1312 it is determined that a valid has not been received from the front panel 200, execution proceeds to step 1316. At step 1316, a determination is made whether the invalid command is an acknowledge by the front panel 200, to an "invalid command" error sent to the panel. If at step 1316 an invalid command error has not been acknowledged by the front panel 200, execution proceeds to step 1318. At step 1318, a "command invalid" error is sent to the front panel 200 and execution proceeds to step 1308. If at step 1316 the invalid command has been acknowledged by the front panel 200, execution proceeds to step 1320. At step 1320 the error flag is cleared, and execution proceeds to step 1308.

It is understood that variations may be made in the present invention without departing from the spirit and scope of the invention. For example, the DCC deck 110 may be alternatively configured so that the DDSP module and main controller are integrated into a single device, or may be embodied as a single integrated circuit chip with other components in any varying combination of discrete digital or analog components interconnected in a standard manner. The program instructions for implementing the foregoing search techniques may be stored in any suitable manner or location as would be understood by those skilled in the art for use in the deck 110.

Although illustrative embodiments of the invention have been shown and described, a latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A method of operating a digital audio playback device to locate a desired program track selection of a digital audio tape during movement of said tape relative to a tape head of the device, said device capable of operating in a play mode at a first tape speed and a search mode at a second tape speed, said tape including an auxiliary data track having at least start-type markers used in controlling operation said device, the method comprising: incrementing a track index representing the number of said selections to be skipped during movement of said tape at said second tape speed; monitoring said tape during movement at said second tape speed for detecting time intervals between successive high and low signals on said auxiliary data track, said signals indicating said markers and said time intervals therebetween indicating said marker type; and decrementing said track index upon indication of a start marker, such that when said track index is decremented to zero, said selection has been located.

2. The method of claim 1 wherein said auxiliary data track includes sector-type markers and said monitoring step further comprises: detecting a high signal time interval which is greater than a first value; and detecting a low signal time interval following said high signal time interval, such that when said low signal time interval is greater than a second value, a start marker is indicated, and when said low signal time interval is less than said second value, a sector-type marker is indicated.

3. The method of claim 2 further comprising: altering said tape movement from said second tape speed to said first tape speed upon indication of a sector-type marker; and reading said auxiliary data track to determine the type of said sector-type marker.

4. The method of claim 3 further comprising: reversing the direction of movement of said tape when said sector-type marker is either a reverse or lead out A marker.

5. The method of claim 3 further comprising: stopping movement of said tape when said sector-type marker is either a home or lead out B marker.

6. The method of claim 3 wherein said device includes a digital signal processor and said reading step further comprises loading PASC coefficients in said processor appropriate for said first tape speed.

7. The method of claim 1 wherein said tape monitoring is delayed for a predetermined time period following commencement tape movement at said second tape speed in order to prevent detection of a start marker of a program track selection currently located relative to said head.

8. The method of claim 2 wherein said first value is approximately 80 milliseconds.

9. The method of claim 2 wherein said second value is approximately 100 milliseconds.

10. A method of operating a digital audio playback device to locate a desired program track selection of a digital audio tape during movement of said tape relative to a tape head of the device, said device capable of operating in a play mode at a first tape speed and a search mode at a second tape speed, said tape including an auxiliary data track having at least start-type and sector-type markers for controlling operation said device, the method comprising: initiating movement of said tape relative to said head in either a forward or reverse direction at said second tape speed responsive to a user input command; incrementing a track index representing the number of said selections to be skipped during movement of said tape at said second tape speed; monitoring said tape during movement at said second tape speed for detecting time intervals between successive high and low signals on said auxiliary track, said signals indicating said markers and said time intervals therebetween indicating said marker type; decrementing said track index upon indication of a start marker, such that when said track index is decremented to zero, said selection has been located; and returning said device to its previous mode of operation prior to tape movement at said second tape speed upon location of said track.

11. The method of claim 10 wherein said previous mode is said play mode.

12. The method of claim 10 wherein said previous mode is a stop mode.

13. The method of claim 10 further comprising: muting the audio output of said device during tape movement at said second tape speed.

14. The method of claim 10 further comprising: aborting said user input command when said previous mode is a record, fast-forward or rewind mode.

15. The method of claim 10 wherein said tape monitoring is delayed for a predetermined time period following commencement of movement of said tape at said second tape speed in order to prevent detection of a start marker of the program track selection currently located relative to said head.

16. The method of claim 10 wherein said monitoring step further comprises: detecting a high signal time interval which is greater than a first value; detecting a low signal time interval following said high signal time interval, such that when said low signal time interval is greater than a second value, a start marker is indicated, and when said low signal time interval is less than said second value, a sector marker is indicated.

17. The method of claim 16 further comprising: reducing said high speed tape movement to a play speed upon indication of a sector-type marker; and reading said auxiliary data track to determine the type of said sector-type marker.

18. The method of claim 17 further comprising: reversing the direction of movement of said tape upon reading of a reverse or lead out A marker.

19. The method of claim 17 further comprising: stopping movement of said tape upon reading of a home or lead out B marker.

20. The method of claim 17 wherein said device includes a digital signal processor and said reading step further comprises loading PASC coefficients in said processor appropriate for movement of said tape at said first tape speed.

21. The method of claim 16 wherein said first value is approximately 80 milliseconds.

22. The method of claim 16 wherein said second value is approximately 100 milliseconds.

23. Apparatus for searching a digital audio tape to locate a desired program track selection, said apparatus capable of operating in a play mode at a first tape speed and a search mode at a second tape speed, said tape including an auxiliary data track having at least start-type and sector-type markers used in controlling search operations, the apparatus comprising: means for incrementing a track index representing the number of said selections to be skipped during movement of said tape at said second tape speed; a digital signal processor for monitoring said tape during movement at said second tape speed for detecting time intervals between successive high and low signals on said auxiliary data track, said signals indicating said markers and said time intervals therebetween indicating said marker type; means for decrementing said track index upon indication of a start marker, such that when said track index is decremented to zero, said selection has been located; and means for returning said tape to its previous mode of operation prior to said tape movement at said second tape speed.

24. The apparatus of claim 23 further comprising: means for detecting a high signal time interval which is greater than a first value; and means for detecting a low signal time interval following said high signal time interval, such that when said low signal time interval is greater than a second value, a start marker is indicated, and when said low signal time interval is less than said second value, a sector marker is indicated.

25. The apparatus of claim 24 further comprising: means for reducing said high speed tape movement to a play speed upon indication of a sector marker; and means for reading said auxiliary data track to determine said sector marker type.

26. The apparatus of claim 25 further comprising: means for reversing the direction of movement of said tape upon reading of a reverse or lead out A marker.

27. The apparatus of claim 25 further comprising: means for stopping movement of said tape upon reading of a home or lead out B marker.

28. The apparatus of claim 25 further comprising means for loading PASC coefficients appropriate for movement of said tape at said first tape speed.

29. The apparatus of claim 23 further comprising means for delay of said tape monitoring for a predetermined time period following commencement of tape movement at said second speed to prevent detection of a start marker of the current program track selection.

30. The apparatus of claim 24 wherein said first value is approximately 80 milliseconds.

31. The apparatus of claim 24 wherein said second value is approximately 100 milliseconds.

32. Apparatus for searching a digital audio tape to locate a desired program track selection, said apparatus capable of operating in a play mode at a first tape speed and a search mode at a second tape speed, said tape including an auxiliary data track having at least start-type and sector-type markers for controlling search operations, the apparatus comprising: means for initiating movement of said tape at said second speed in either a forward or reverse direction responsive to a user input command; means for incrementing a track index representing the number of said selections to be skipped during tape movement at said second speed; a digital signal processor for monitoring said tape during movement at said second speed for detecting time intervals between successive high and low signals on said auxiliary data track, said signals indicating said markers and said time intervals indicating said marker type; means for decrementing said track index upon indication of a start marker, such that when said track index is decremented to zero, said selection has been located; and means for returning said tape to its previous mode of operation prior to tape movement at said second speed upon location of said track.

33. The apparatus of claim 32 wherein said previous mode is said play mode.

34. The apparatus of claim 32 wherein said previous mode is a stop mode.

35. The apparatus of claim 32 further comprising: means for muting the audio output of said apparatus during tape movement at said second speed.

36. The apparatus of claim 32 further comprising: means for aborting said user input command when said previous mode is a record, fast-forward or rewind mode.

37. The apparatus of claim 32 wherein said tape monitoring is delayed for a predetermined time period following commencement of tape movement at said second speed in order to prevent detection of a start marker of the program track selection currently located relative to said head.

38. The apparatus of claim 32 further comprising: means for detecting a high signal time interval which is greater than a first value; means for detecting a low signal time interval following said high signal time interval, such that when said low signal time interval is greater than a second value, a start marker is indicated, and when said low signal time interval is less than said second value, a sector marker is indicated.

39. The apparatus of claim 38 further comprising: means for altering said tape movement to said first tape speed upon indication of a sector marker; and means for reading said auxiliary data track to determine said sector marker type.

40. The apparatus of claim 39 further comprising: means for reversing the direction of movement of said tape upon reading of a reverse or lead out A marker.

41. The apparatus of claim 39 further comprising means for stopping movement of said tape upon reading of a home or lead out B marker.

42. The apparatus of claim 39 further comprising a processor and means for loading said processor with PASC coefficients appropriate for said first tape speed.

43. The apparatus of claim 38 wherein said first value is approximately 80 milliseconds.

44. The apparatus of claim 38 wherein said second value is approximately 100 milliseconds.

45. Apparatus for operating a digital audio playback device to automatically locate program track selections of a digital audio tape during movement of said tape relative to a magnetic head of the device, said device operating in a play mode at a first tape speed and being capable of operating in a search mode at a second tape speed, said tape including an auxiliary data track having markers used in controlling operation said device, the apparatus comprising: means for monitoring said tape during said play mode for detecting time intervals between successive high and low signals on said auxiliary data track, said signals indicating said markers and said time intervals therebetween indicating the type of said markers; means for entering said search mode when a skip marker is indicated and returning to said play mode when the beginning of the next said program track selection has been located; and means for reversing the direction of movement of said tape in said play mode when a reverse or lead-out marker is indicated.

46. The apparatus of claim 45 further comprising means for entering said search mode when a lead-in marker is indicated and returning to said play mode when the end of said lead-in marker is indicated.

47. The apparatus of claim 46 wherein said end of said lead-in marker is indicated when said time interval between said high signals is greater than 150ms.

48. The apparatus of claim 45 wherein said reversing means further comprises means for terminating said play mode upon reversal of said tape when a single track mode has been selected.

49. The apparatus of claim 45 wherein said reversing means further comprises means for continuing said play mode in said reverse direction until said tape has played a selected number of times.

50. The apparatus of claim 49 wherein said selected number is eight.

51. Apparatus for operating a digital audio playback device to automatically locate program track selections of a digital audio tape during movement of said tape relative to a tape head of the device, said device operating in a play mode at a first tape speed and being capable of operating in a search mode at a second tape speed, said tape including an auxiliary data track having markers used in controlling operation said device, the apparatus comprising: a digital signal processor for monitoring said tape during said play mode for detecting time intervals between successive high and low signals on said auxiliary data track, said signals indicating said markers and said time intervals therebetween indicating the type of said markers; means for entering said search mode when a skip marker is indicated and returning to said play mode when the beginning of the next said program track selection has been located; and means for reversing the direction of movement of said tape in said play mode when a reverse or lead-out marker is indicated.

52. The apparatus of claim 51 further comprising means for entering said search mode when a lead-in marker is indicated and returning to said play mode when the end of said lead-in marker is indicated.

53. The apparatus of claim 52 wherein said end of said lead-in marker is indicated when said time interval between said high signals is greater than 150ms.

54. The apparatus of claim 51 wherein said reversing means further comprises means for terminating said play mode upon reversal of said tape when a single track mode has been selected.

55. The apparatus of claim 51 wherein said reversing means further comprises means for continuing said play mode in said reverse direction until said tape has played a selected number of times.

56. The apparatus of claim 55 wherein said selected number is eight.