GB2263576A - Method of automatically monitoring the quality of audio-video recordings - Google Patents

Description

2263576 Method of automatically monitoring the qualitv of audio-video

programs which are recorded on a magnetic recording medium The invention relates to a fully automatically 5 proceeding method of determining the quality of re-recorded audio and/or video information copied in large volume from a master tape to a magnetic recording medium in tape form by means of a high-speed copying process.

The widespread use of home video recorders has considerably increased the demand for prerecorded cassettes, in particular half-inch video cassettes. In order to satisfy this demand in a cost-effective way, it is necessary to produce in a short time a great number of copy tapes from a master tape. The production of such prerecorded cassettes is difficult, since video signals contain a large volume of information which has to be copied or duplicated with a high degree of accuracy in order to obtain appropriate picture quality.

A currently widespread tape copying process involves playing the master tape on a recorder, generally in real time, and connecting this recorder to a large number of L copying recorders, for example 1000, in which the tape copies are likewise produced in real time. The logistics required for such a copying process makes it very expensive.

Recently, two high-speed copying processes have become established on the market. These high-speed copying processes involve passing the master tape at high speed past, and in close contact with, the copy tape, the information on the master tape being transferred to the copy 30 tape. For this purpose, the master tape must contain mirror-invertedly applied information which is then transferred to the copy tape during high-speed copying.

1 One of these high-speed copying processes is based on an external magnetic field acting on the copy tape during its time of contact with the master tape and in this way - 2 transferring the information of the master tape onto the copy tape. The other high-speed copying process involves the use of a highly concentrated energy beam, for example a laser beam, acting through the transparent rear side of the copy tape during its time of contact with the master tape so as to heat the copy tape above its Curie point before it is cooled down, the information on the master tape being transferred to the copy tape in an analogous manner to that previously described. Both these known high-speed copying processes operate at more than 100 times the speed of the normal reproducing speed in helical video recording and reproducing processes.

The first-mentioned highspeed copying process is described in EP-A-0366531 and the last-mentioned thermomagnetic high-speed copying process is explained in detail in EP-A- 0113456.

In order to produce a large number of copies by highspeed processes of these types, the master tape runs past the copy tape in close contact and under high pressure in an endless loop.

In duplicator shops with high-speed copying systems (Sprinter, TMD), a mirror copy is taken from the master tape by means of a mirror master recorder. The master copy thus produced is used to record the information of the master as described above onto blank tapes several 1000 m long known as "pancakes". In this manner, a pancake can contain a large number of copies of a single film. In order to minimize as far as possible the reject rate caused by defects occurring during the creating of the mirror master copy, a first ',test" cassette is produced and assessed audiovisually by test personnel before the continuous loader process. However this test procedure is time-consuming, costly and extremely tiring for the test personnel.

There are a number of intellectual property rights concerned with the checking of analog or digital recordings 3 on magnetic tape, for example as a production control in the recording of magnetic tapes. According to EP 0083686 and EP 0309639, the input signal is compared fully automatically with the output signal. If a difference between the master tape and the copy tape is established when copying recordings, it is possible, according to GB 1158148, to compensate for this by changing the gain on the copying recorder. In FR 2420822, for checking the recording of the copying recorder, a test head is introduced in tape mode, permitting the necessary settings. In DE 1772155 a comparator circuit is described, in which the recording of the master tape is compared with the copying tape and is displayed.

GB 1408818 and US 3517305 describe apparatuses for checking the recording of digital data. DE 3242558 and DE 3314873 describe methods of detecting whether a video tape is an original or a copy.

PCT patent application WO 81/03591 describes a method and an apparatus for checking fully automatically whether a recording on video tape has been erased or copied over. This takes place by applying a low-frequency signal to the audio track. During fast rewind, the video and the audio check track are checked and any defects are registered fully automatically.

It is an object of the present invention to find a fully automatically proceeding method of the generic type referred to in the opening paragraph which is significantly more effective than the described prior art methods, which operates inexpensively and without unduly tiring the operator and in which the quality of the rerecorded information allows conclusions to be drawn with sufficient reliability as to the recording quality of the mirror master tape and of the copying tape material used.

Furthermore, it is an object of the present invention to determine unambiguously the cause of any established qualify defects which may occur when creating the mirror master tape.

Finally, the test device used for carrying out the method according to the invention is intended to be designed in such a way that a plurality of pancakes (different recordings), represented by in each case two cassettes from one pancake, can be tested.

We have found that these objects are achieved according to the invention by a fully automatically proceeding method of determining the quality of rerecorded audio and/or video information copied in large volume from a master tape to a magnetic recording medium in tape form by means of a high-speed copying process, comprising the method steps at least two copying tapes provided with identical copied-on information are made up into a corresponding number of commercially available cassettes and these are loaded into a corresponding number of test recorders (1,2) 20 the audio and/or -video signals emitted by the test recorders are passed to a testing unit (3,6,7), comprising a checking unit (3), a recorder control (6) and a change-over switch (7), which testing unit is connected to a computer unit (4) which controls 25 the test sequence and analyses the recorded-data and prints it out on a printer (15).

Further details of the invention emerge from the subclaims, the drawings and the description.

An embodiment of the invention will now be described, by way of example, with reference to accompanying drawings in which:

Figure 1 shows an exemplary embodiment of a measuring station for carrying out the method according to the invention, and Figure 2 shows a measuring data and analysis diagram for quality assessment.

The invention is based on the idea that the quality of re-recorded information can be tested and determined with sufficient certainty as well as without disturbance by the user and without additionally recorded-on spoken test sequences, by comparative measurements on the recorded audio and video signals.

The method according to the invention is explained in more detail below by the example of the copy of a pancake and two loaded cassettes.

As described above, a mirror master recorder is used to tape from an original film cassette or reel a mirror copy, the audio and video information of which is copied multiply onto a magnetic recording medium of relatively great length, known as a pancake. Two lengths are cut from this pancake, expediently the two first lengths each having the same information recorded from a common part of the mirror copy, are made up into commercially available cassettes (containing identical information) and are passed on to the measuring sequence to be described in more detail hereafter.

As can be seen from Figure 1, the test system for determining the quality of the cassettes produced by highspeed copying comprises at least two test recorders (1,2), the number of test recorders not having to be restricted to two.

Each of the test recorders has outputs for the recorded-on audio and video signals as well as for the RF and an input for recorder control (6) by the checking unit (3). These audio and video signals and the RF are passed directly to the testing unit and the measuring data 6 necessary for assessment of the audio and video reproduction characteristics is acquired there.

The test sequence and the analysis of the acquired measuring data is controlled and analyzed by means of a computer station (4) connected to the checking unit. For logging, a printer (5) is installed. For observing the reproduction, the signals are transferred via a manually operable switching unit (7) to a monitor (8) and/or to an oscilloscope (9).

The measuring sequence and the quality determination by means of the acquired measuring data takes place as represented in Figure 2.

The two created cassettes are loaded into the test recorders (1, 2). A starting signal from the computer unit (4) makes the test recorders run automatically to the beginning of the tape. When both test recorders have reached this point of the tape, they are simultaneously switched to reproduce or "play" mode and, after triggering the measuring data acquisition units (part of the checking unit (3)), they are started by the computer station. When the end of the recording is detected, the tape is automatically rewound to the beginning. The measuring data is acquired over the complete reproduction time and is analyzed in real time.

Measured are the reproduction of the longitudinal recording for channel 1 and 2 as well as the reproduction of the amplitude of the hi-fi recording for channel 1 and 2, the waveform of the hi-fi carrier frequency for channel 1 and 2, the waveform of the video carrier frequency and the dropouts, determined from the video carrier frequency. In addition, the information of the check track is assigned to the acquired measuring data for identification of points on the tape.

The acquired measuring data is investigated for 7 locationally fixed and extraneous defects by comparative measurements, firstly between test recorder 1 and test recorder 2 and secondly between reproduction of the amplitude of the longitudinal recording and reproduction of the amplitude of the hi-fi recording per channel and per test recorder.

From the type and locational relationships of the defects established, deteriorations in quality can be assigned to the sources of defects in the copying and loading process. Similarly, conclusions can be drawn as to the tape material used.

In the defect established is located at the same point in each case on both tapes or both cassettes, a defect of the mirror master tape must be concluded, thereby achieving the main object of the invention. If, on the other hand, defects are located at different points on the two tapes, a defect in the copying process and/or the copying tape can be concluded.

For repeated location and viewing of a defect which has been established, an automatic forward winding function is installed. The point of the tape to be wound to is entered via the computer and reached by counting the checktrack pulses. The check tracks are located on each copied tape alongside which the two longitudinal recordings are located. By means of the monitor, loudspeaker and oscillograph, the defect can be assessed visually and acoustically and it can be decided whether the defect is tolerable or prohibitive for the release of the cassette.

Since the defects which are possible and are established in the copying and loading operation are measured and analysed full automatically, testing of the cassettes with virtually no tiring of personnel is possible.

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Claims (9)

1. A fully automatically proceeding method of determining the quality of re-recorded audio and/or video information copied in large volume from a master tape to a magnetic recording medium in tape form by means of a highspeed copying process, comprising making at least two copy tapes provided with similar copied-on information from a common part of the master tape into a corresponding number of cassettes, loading the cassette S 4 Lnto a corresponding number of test recorders, passing audio and/or video signals emitted by the test recorders to a testing unit and controlling the test sequence and analysing the recorded - ing data by means of a computer unit connected to the test unit.

2. A method according to claim 1, in which the t recorded data is printed out on a printer.

3. A method according to claim 1 or 2, in which the testing unit comprises a checking unit, a recorder control unit and a change-over switch.

4. A method according to claim 3, wherein the checking unit, which includes an analog-digital converter for the carrier frequencies as well as for the audio signals and a dropout counter, in each case compares with one another the audio and video signals which are emitted by the test recorders and originate from identical parts of the two test tapes, and passes differences to the computer unit which prints out the differences on the printer.

5. A method according to any one of the preceding claims, wherein the measuring data is acquired over the complete reproducing time of the magnetic recording medium and is analyzed in real time.

6. A method according to claim 4 or claim 5 when dependent on claim 4, wherein a defect established by the computer unit is relocated by counting the pulses applied to a check track of the magnetic recording medium and is visually assessed on a monitor and/or oscilloscope selected via the change-over switch.

7. A method of automatically determining the quality of re-recorded audio and/or video information copied in large volume from a master tape, the method being substantially as herein described with reference to Figures I and 2 of the accompanying drawings.

8. A fully automatically proceeding method of determining the quality of re-recorded audio and/or video information copied in large volume from a master tape to a magnetic recording medium in tape form by means of a high speed copying process, comprising the method steps:

at least two copying tapes provided with identical copied-on information are made up into a corresponding number of commercially available cassettes and these are loaded into a corresponding number of test recorders (1,2); - the audio and/or video signals emitted by the test recorders are passed to a testing unit (3,6,7), comprising a checking unit (3), a recorder control (6) and a change-over switch (7), which testing unit is connected to a computer unit (4) which controls the test sequence and analyses the recorded data and prints it out on a printer (15).

9. A method of determining the quality of rerecorded audio and/or video information copied in large volume from a master tape to a magnetic recording medium in tape form by means of a high-speed copying process, comprising making at least two cassettes each having tape containing common audio and/or video information re-recorded from the same part of the master tape, and testing the at least two cassettes in a corresponding number of test recorders, the test sequence being automatically controlled v by computer means which also analyses during the test sequence audio and/or video signals emitted by the test recorders and derived from the re-recorded information on the cassette tapes.