GB2252864A

GB2252864A - Converting tape speed

Info

Publication number: GB2252864A
Application number: GB9200372A
Authority: GB
Inventors: Tae Suk Bae
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1991-01-09
Filing date: 1992-01-09
Publication date: 1992-08-19
Anticipated expiration: 2012-01-09
Also published as: DE4200359A1; GB9200372D0; KR920015318A; GB2252864B; JPH06168504A; KR930007793B1; JP2655775B2

Description

-)")c 25 64 CONVERTING TAPE SPEED The present invention relates to tape

speed conversion apparatus (hereinafter called a converter) and methods for example, for use in a video cassette recorder.

In a known video cassette recorder (hereinafter called a VCR) adopting a stepwise slow play mode, when the video tape is reproduced at a different speed from the tape record speed during a slow play mode, the reproduced video signal may be destroyed. This occurs because there is a lack of synchronization between the record speed and the reproduction speed when the video tape is not reproduced at the same speed as the record speed. The reason for this is that, when the tape speed is changed in the existing VCR, it is impossible to determine the tape reproduction speed.

is Preferred embodiments of the present invention aim to provide an apparatus and method for converting a tape reproduction speed according to the variation of the tape speed by determining the tape reproduction speed of the VCR during a slow play mode, based on the possibility of the determination of the tape reproduction speed.

According to a first aspect of the present invention, there is provided an apparatus for converting video tape reproduction speed according to a video tape record speed during a stepwise slow reproduction in a video tape recorder, the apparatus comprising:

a control head which reproduces a control pulse from a control track of a video tape; a capstan motor for running said video tape according to a drive signal of a capstan motor driver; a capstan frequency generator for generating a frequency pulse corresponding to a tape running speed during the rotation of said capstan motor; and means for instructing said capstan motor driver with a command for converting the reproduction speed, when the tape reproduction speed does not match the tape record speed, by receiving said control pulse and said capstan frequency pulse and comparing them with a specific design value.

Preferably, said instructing means comprises: a microcomputer for producing data and control signals corresponding to a tape reproduction speed matching a tape record mode by comparing the reproduction speed with the tape record mode according to stored data; and a servo mechanism for receiving said control pulse and said capstan frequency pulse and supplying both pulses to said microcomputer, and then for receiving data corresponding to the tape reproduction speed from said microcomputer and for supplying a speed command signal to said capstan motor driver.

According to another aspect of the present invention, there is provided a method for converting video tape reproduction speed according to a video tape record speed during a stepwise slow reproduction in a video tape recorder, comprising the steps of..

receiving a control pulse and a capstan frequency pulse and determining a mode of the video tape reproduction speed; counting the number of said capstan frequency pulses when the video tape reproduction speed is that determined mode; comparing the counted result with a specific design value; maintaining the current reproduction mode when the number of said capstan frequency pulses is the same as the specific design value of the reproduction mode; and otherwise converting the reproduction speed to a speed corresponding to the tape record speed.

Preferably, said mode of the reproduction speed is one of SP, LP and SLP modes.

is Preferably, said number of capstan frequency pulses is 36, 18 or 12, when the record mode of the video tape is SP, LP or SLP respectively.

According to a further aspect of the present invention, there is provided apparatus for controlling reproduction speed in a video tape recorder during slow play mode, the apparatus including means for detecting a speed of recording of a tape being reproduced, and means for matching the speed of reproduction to the speed of recording.

Such apparatus may further comprise any one or more of the features disclosed in the accompanying specification, claims, abstract and/or drawings, in any combination.

The invention extends to a video tape recorder provided with an apparatus, or adapted to operate in accordance with a method, according to any of the preceding aspects of the invention.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 is a block diagram showing one example of an apparatus for converting tape speed according to the present invention; Figure 2 is a flowchart diagram showing one example of a method for converting tape speed according to the present invention; Figure 3 is a timing diagram for explaining operation of a stepwise slow play mode in a VCR; and Figure 4 is a timing diagram showing some of the waveforms of Figure 3 in a larger scale.

First, prior to a description of the illustrated tape speed conversion apparatus and method, the operation of the stepwise slow play mode in the VCR to which the illustrated embodiments of the present invention are adapted, will be described below with reference to the accompanying 25 drawings.

In the stepwise slow play mode, the VCR performs continuously the operations "PLAY", "STILU, "PLAV, "STILL", etc., whereby the video tape is reproduced at a speed slower than normal play speed.

Referring to Figure 3, (a) is a waveform diagram of a head switching signal, (b) is a waveform diagram of a control pulse, (c) is a waveform diagram of a capstan motor driving signal, (d) is a waveform diagram representing a rotation direction (F/W) of the capstan motor, (e) is a view representing an actual rotation direction of the capstan motor, and (f) is a view representing operational intervals of the stepwise slow play mode. The VCR performs a play mode in interval A of the head switching signal, a still mode in interval B, a play mode in interval C, a still mode in interval D, and so on. That is, the VCR performs a "play mode" and a "still mode", alternately. Since one frame picture (picture on the TV screen) is composed of one period of head switching signal (a), the slow play mode in this embodiment is realized by displaying one piece of the reproduced picture and four pieces of the still pictures, subsequently. Accordingly, the slow play operation is effected at one fifth of the normal play speed.

Figure 4 is a timing diagram showing the enlarged waveforms (a), (b), (c) and (d) shown in the interval A of Figure 3.

In Figure 4, rising edge R1 of head switching signal (a) represents a start of the play operation. The next rising edge R2 represents a start of the still operation. Interval Cl (a motor acceleration interval) of capstan motor drive signal (c) represents the acceleration interval of the capstan motor.

Accordingly, the actual tape run is done at point R1 of head switching signal (a). Interval C2 (a play interval) represents a control interval during the reproduction.

Interval C3 (a motor brake interval) represents a forced stop interval of the capstan motor. The actual tape stop is done at point R2 of head switching signal (a). The capstan motor is controllably driven along the intervals Cl, C2 and C3.

Accordingly, the reproduction operation is done between points R1 and R2 of head switching signal (a).

Meanwhile, in Figure 4, interval B2 of control pulse (b) represents the time it takes the tape to stop after the control Pulse is input. The interval B2 depends on the tape speed. This is because the amount of the tape run depends upon the record speed according to the tape record modes SP, LP and SLP. Here, SP is standard play, LP is long play, and SLP is super long play.

Thus, if the current tape reproduction speed is a speed corresponding to SP mode, and on the other hand the tape recorded speed is a speed corresponding to SLP mode, the synchronization is broken since the intervals corresponding to B2 of Figure 4 do not coincide with each other. Here, the interval B2 differs from the tape record speed according to the design condition. The number of capstan frequency pulses generated during the interval A shown in (a) of Figure 4 is consistent according to the tape record mode as shown in Table - I when the tape record speed is the same at the tape reproduction speed.

Table - 1

Mode Number of Capstan Frequency pulses SP 36 LP 18 SLP 12 1 However, when the reproduction speed is different from the tape record speed, the reproduction and record speeds are combined by modes as shown in Tables II and III.

First, when the reproduction speed is faster than the tape record speed, the combination of the tape reproduction and record speeds follows as shown in Table -11.

Table - II

Reproduction Speed SP SP LP Record Speed LP SLP SLP 1 - 11 As can be seen in Table - II, the tape reproduction speed is faster than the record speed. For this reason, the time B2 shown in (b) of Figure 4 is longer than the actually required time corresponding to the tape record speed.

Accordingly, in the play interval, more tape is run than that of the interval marked with 'W' shown in (a) of Figure 4. Thus, since the number of the capstan frequency pulses is not constant, the synchronization is not consistent.

Next, when the reproduction speed is slower than the tape record speed, the combination of the tape reproduction and record speeds follows as shown in Table - III.

Table - III

Reproduction Speed SLP SLP LP Record Speed LP SP SP 1 1 As can be seen in Table - III, the tape reproduction speed is slower than the record speed. For this reason, the time B2 shown in (b) of Figure 4 is shorter than the actually required time corresponding to the tape record speed. Accordingly in performing the reproduction mode of the next stage, the interval B1 shown in (b) of Figure 4 is lengthened.

Finally, the intervals B1 + B2 shown in (b) of Figure 4 become constant. Accordingly, the number of the capstan frequency pulses can be obtained as shown in Table - I. In conclusion, when the tape reproduction speed is faster than the record speed, there is no synchronization.

Up to now, the operation of the stepwise slow reproduction of the VCR has been described. Hereinafter, an example of the operation of the illustrated embodiments of the present invention will be described in detail with reference to Figures 1 and 2.

The apparatus of Figure I is for converting tape speed during - a stepwise slow reproduction of a VCR. Referring to Figure 1, the control pulse reproduced from the video tape (not shown) through control head 1 is supplied to servo mechanism 2. Also, the capstan frequency pulses generated in the capstan frequency generator 4 during rotation of the capstan motor 3 are supplied to servo mechanism 2. Then, servo mechanism 2 supplies a capstan motor drive signal for capstan motor driver 5. At the same time, servo mechanism 2 transmits the control pulse and the capstan frequency pulses to microcomputer 6. Here, microcomputer 6 instructs capstan motor driver 5 to drive capstan motor 3 which makes the video tape run. Also, microcomputer 6 supplies the data signals for servo mechanism 2 and performs the method for converting the tape speed according to the control flowchart shown in Figure 2.

Referring to Figure 2, when slow reproduction starts during the reproduction of the tape in step 101, microcomputer 6 detects whether or not the current reproducing speed matches the tape record speed in accordance with the data in Table - I. When the current reproducing speed of the tape is in the SP mode in step 102, microcomputer 6 detects if the number of the capstan frequency pulses is 36. Here, when the number of the capstan frequency pulses is 36, the tape reproduction speed is maintained in the SP mode, otherwise microcomputer 6 converts the tape reproduction speed to the SLP mode in step 104. That is, in step 104, microcomputer 6 supplies the data signal to servo mechanism 2 in order to convert the tape reproduction speed into the SLP mode. Then, servo mechanism 2 supplies the control signal to capstan motor driver 5 to drive capstan motor 3.

On the other hand, when the current reproduction speed is not in the SP mode, microcomputer 6 proceeds to step 105 from step 102 and determines if the reproduction speed is in the LP mode. If the reproduction speed is in the LP mode in step 105, microcomputer 6 counts the number of the capstan frequency pulses in step 106. Here, when the number of the -10capstan frequency pulses is 18, the tape reproduction speed is maintained in the LP mode, otherwise microcomputer 6 converts the tape reproduction speed into the SLP mode in step 104.

If, in step 105, the current tape reproduction speed is not in the LP mode, the microcomputer 6 checks if it is in the SLP mode in step 107. If the tape reproduction speed is in the SLP mode in either step 104 or 107, microcomputer 6 proceeds to step 108. In step 108, microcomputer 6 determines if the number of the capstan frequency pulses is 12. Here, when the pulse number is 12, the current tape reproduction speed is determined to be in the SLP mode. Otherwise, microcomputer 6 proceeds to step 109. Then, when the number of the capstan frequency pulses is determined to be 18, microcomputer 6 recognizes that the reproduction speed is in the LP mode. Therein microcomputer 6 converts the reproduction speed into the LP mode in step 110. When the number of the capstan frequency pulses is not 18 in step 109, microcomputer 6 proceeds to step 111 and determines if the number of the capstan frequency pulses is 36. Then, when the number of the capstan frequency pulses is 3 6 in step 111, microcomputer 6 advances to step 112 and recognizes that the reproduction speed is in the SP mode. Therein, microcomputer 6 converts the reproduction speed into the SP mode. However, when the frequency pulse number is not 36 in step 111, microcomputer 6 proceeds to step 108 from step 111 in order to count again the number of the frequency pulses, and to repeat the above-described processes.

As described above, the apparatus and method for converting the tape reproduction speed during the stepwise slow reproduction of the VCR may have the advantage that sharpness of the picture is obtained since the tape - ll- reproduction speed is easily determined even in slow reproduction and converted into the speed corresponding to the tape record speed by comparing the number of the capstan frequency pulses generated in the tape run with a specific design value. That is, there is provided an exact reproduction control function for the different record mode programs during the stepwise slow reproduction using the VCR.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel -12combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. An apparatus for converting video tape reproduction speed according to a video tape record speed during a stepwise slow reproduction in a video tape recorder, the apparatus comprising:

2. An apparatus as claimed in claim 1, wherein said instructing means comprises: a microcomputer for producing data and control signals corresponding to a tape reproduction speed matching a tape record mode by comparing the reproduction speed with the tape record mode according to stored data; and a servo mechanism for receiving said control pulse and said capstan frequency pulse and supplying both pulses to said microcomputer, and then for receiving data corresponding to the tape reproduction speed from said -14microcomputer and for supplying a speed command signal to said capstan motor driver.

3. A method for converting video tape reproduction speed according to a video tape record speed during a stepwise slow reproduction in a video tape recorder, comprising the steps of.

receiving a control pulse and a capstan frequency pulse and determining a mode of the video tape reproduction speed; counting the number of said capstan frequency pulses when the video tape reproduction speed is that determined mode; comparing the counted result with a specific design value; is maintaining the current reproduction mode when the number of said capstan frequency pulses is the same as the specific design value of the reproduction mode; and otherwise converting the reproduction speed to a speed correspond ing to the tape record speed.

4. A method as claimed in claim 3, wherein said mode of the reproduction speed is one of SP, LP and SLP modes.

5. A method as claimed in claim 4, wherein said number of capstan frequency pulses is 36, 18 or 12, when the record mode of the video tape is SP, LP or SLP respectively.

6. Apparatus for controlling reproduction speed in a video tape recorder during slow play mode, the apparatus including means for detecting a speed of recording of a tape being reproduced, and means for matching the speed of reproduction to the speed of recording.

7. Apparatus according to claim 6, further comprising any one or more of the features disclosed in the accompanying specification, claims, abstract and/or drawings, in any combination.

8. Apparatus for controlling reproduction speed in a video tape recorder, the apparatus being substantially as hereinbefore described with reference to Figure 1 or to Figures 1, 3 and 4 of the accompanying drawings.

9. A method of controlling reproduction speed in a video tape recorder, the method being substantially as hereinbefore described with reference to Figure 2 or to Figures 2, 3 and 4 of the accompanying drawings.

10. A video tape recorder provided with an apparatus, or adapted to operate in accordance with a method, according to any of the preceding claims.