GB2146458A - Improvements in or relating to video player control - Google Patents

Abstract

A position search control arrangement is provided which enables searching to be performed on video players not provided with this function together with automatic restoration of playing position upon power-up following a mains failure during play. A data stripper removes encoded data from the playback signal to produce a current value of a positional variable (frame number, chapter number or time code). This is compared with a desired value and the player controls actuated in accordance with the difference. This may be by operating semiconductor switches in parallel with the player's mechanical switches, or by feeding a signal which simulates remote control signals, or by actuating the player's keys by suitable electro-mechanical devices. The control arrangement includes a periodically updated non-volatile store which is used to set the desired value upon power-up following a mains failure. The control arrangement may be incorporated in an "intelligent" video disc player.

Description

SPECIFICATION Improvements in or relating to video player control This invention relates to control of video players.

There are commercially-available "intelligent" video disc players having position search facility, and there is also known a separate unit for use with a video disc player to provide such a facility. A feature common to these players is that the reading head starts at the edge of the disc upon power-up. Thus in the event of e.g. power failure to the player during play, the user will, upon restoration of power, need to search on a trial-and-error basis to restore the playing position.

It is therefore an object of this invention to enable a playing position to be substantially restored upon restoration of power. Such a facility may be incorporated in an "intelligent" player, or provided in a separate control arrangement for ordinary "nonintelligent" video players having just the normal control functions such as fast forward, reverse, triple play.

According to the present invention there is provided in or for a video disc player a position search control arrangement comprising means for receiving a desired value of a position indicator, means for extracting the position indicator from the playback signal, means for comparing the desired and extracted position indicators and producing a difference signal, means for producing control signals for use in controlling the video player in dependence upon the difference signal, non-volatile means for storing an extracted position indicator, means for updating the stored extracted position indicator at predetermined intervals, and means responsive to power-up of the control arrangement to enter the stored extracted position indicator as a desired value of position indicator.

The simplest form of position indicator is frame number, but some recorded material also includes chapter numbers. Another form of position indicator is a time code such as used in CLV type video players. It will be appreciated that the term "position" means a value of any of such forms of position indicator, depending on whichever system is adopted by the manufacturer of the relevant player.

Preferably the control signals respectively correspond to operational modes of the video player such as fast forward, reverse and triple play, and a respective control signal is produced in dependence upon the magnitude and sign of the difference.

Where there is a large difference a respective fast forward or reverse signal can be generated, which may take the form of jump movements of the laser head. When the difference becomes smaller than a predetermined value, then a slower speed can be selected, say triple play.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of the arrangement of a video player having an add-on search unit, and Figure2 is a schematic diagram of the circuitry of an add-on search unit.

In Figure 1 there is shown a video disc player 10 which is one of a large number of video disc players of a video library forming part of a video services network. One feature of the video library is that once a customer has sent his request through the network to the Headend for a particular programme from the video library to be transmitted to him, the customer can then control the video player just as if the video player was in his home. In other words, the customer can control such player functions as stop, fast forward, reverse, play and fast play (x3).

Each frame of the programme is numbered and some known video disc players have a frame search facility in which the laser reading head is rapidly moved to the appropriate part of the disc to get to a desired frame which can then be shown as a single stationary frame. However, video disc players are designed such as to move the reading head to a start position upon power-up of the player. The present invention relates to the provision of a position restoration facility, and whilst such a facility can be incorporated into an "intelligent" player i.e. one having picture search (position search), it is described below as incorporated into an add-on unit for use with "non-intelligent" players.

The video player 10 is linked to a video library control processor 11 by an interface unit 12 and a control network 13 by means of which control messages can pass between the video player 10 and the control processor 11. Closely associated with the interface unit is a frame search add-on unit 14.

In Figure 2 the add-on unit 14 comprises a data stripper 15 which receives the video output from the disc and extracts the encoded frame number (F). A comparator 16 receives F from the data stripper 15, and also receives a desired frame number (D) from the control unit 17 of the interface unit 12.

The difference between D and F is sent to a control circuit 18 which is arranged to actuate the fast forward or backward mode of the player depending on the sign of the difference. If there is convenient access to the switches of the player then this actuation can be by electrical signals applied to semiconductor switches in parallel with the manual switches, but alternatively actuation can be via an interface which physically actuates the press buttons of the player. Yet again, if access can be obtained to the servo control of the laser head, then a sophisticated control can be achieved in which the laser head is moved in steps which can be determined by the difference obtained each time the laser head reads the disc.

If the video player 10 is of the kind having an infra-red remote control, then the control circuit 18 can send suitably coded control signals to the player to emulate an actual signal, i.e. the repeats of code pattern and minimum duration. Again, the signals can be electrical if access can be obtained to the receive circuits, or an infra-red transmitter can be mounted in front of the player's receive panel and driven by the control circuit 18.

If the video output is available during say fast forward and the data stripper can operate then a continuous monitor of the difference can be done. If not, then control circuit 18 will have to actuate say fast forward mode for a suitable time, then the play mode in order to read F and see how close to D it is.

The duration of fast forward can be made a function of the difference between D and F.

After one or more bursts of fast forward as necessary the difference will then be small enough to permit the use of a triple play mode (or maybe a manual picture search mode - not related to position search facility of "intelligent" players) to approach even closer to D. A further change to normal play mode may be used, and then finally the player is commanded to stop when the difference becomes zero. If there is a noticeable lag resulting in an overshoot, this can be compensated for by commanding the player to stop when the difference becomes a predetermined amount, which itself may be a function of frame number if the overshoot differs between the inside and the outside of the disc.

Alternatively, a step frame mode can be used finally to adjust the player (if the player has such a mode).

If a video player is a CAV type then the reading head can be held stationary to produce a still frame.

However, a corresponding still frame facility is not possible on CLV type players, therefore to produce a pause the search unit can generate a short duration reverse signal followed by a play signal every time the extracted time code is equal to the desired time code.

If there is a failure of the mains supply to the video player, the current playing position will be lost since the player will start at the beginning of a disc when initially powered. To enable the player to recover from such a situation, the add-on unit 14 includes a timer 19 for causing a non-volatile memory 20, e.g.

battery-backed RAM, in the control unit 17 to be updated with the extracted frame number at regular intervals, e.g. every minute during play mode.

The control unit 17 further includes a circuit 21 responsive to power-up to interrogate memory 20 to see if there is a number stored in it, and if there is then circuit 21 enters this number as a desired frame number and instigates the frame search procedure wherebythe head is restored to the position corresponding to the last update of memory 20.

The timer 19 may be a frame counter providing a gating signal after a predetermined number of frames to cause memory 20 to read in the current extracted frame number. It will be appreciated that the predetermined numberwill not be too large to avoid the restored position being too far from the last playing position and the cost of the counter being high. In the limit the memory 20 could be updated at each extracted frame number.

If desired the add-on unit 14 can have a manual input, say a keypad, by means of which an operator can input data e.g. a disc code number or a desired frame number. In the context of the video library the customer will communicate a frame search request to the player via the library control processor 11 which can download the desired value to the control unit 17. In other applications not involving such a control processor, there will be a manual input to allow a user to input a desired frame number to allow the user to interact with the programme on the video disc.

Whereas the abovedescribed embodiment is one of a number of players of a video library, this is not restrictive of the present invention, and it will be appreciated that the present invention can be useful in applications such as teleshopping booths, or any such applications involving interactive video where in the event of a power failure (which could be mains failure, or even a blown fuse needing replacement) the user can be returned upon restoration of power to more or less the last playing position (depending on the frequency of update of the non-volatile memory 20).The restoration facility may even be useful in the domestic environment, thus in a player having a built-in position search facility with restoration facility there may be provision for resetting the memory 20 to zero upon operation of say a reject control, whereby the next time the player is powered-up with say a new disc the reading head does not move to the last playing position of the previous disc. However, if a user wants to view the remainder of a programme at a later time and switches the player off without using the reject control (i.e.

memory 20 is not reset), then upon power-up the reading head will start in accordance with the stored position indicator in memory 20. In the add-on unit 14, a similar facility can be obtained by providing a reject button (not shown) which when actuated causes the control unit 17 to reset memory 20 to zero and provide control signals to the player for stopping play and enabling the lid to be opened.

Claims (7)

1. In or for a video disc player a search arrangement comprising means for receiving a desired value of a position indicator, means for extracting the position indicator from the playback signal, means for comparing the desired and extracted position indicators and producing a difference signal, means for producing control signals for use in controlling the video player in dependence upon the difference signal, non-volatile means for storing an extracted position indicator, means for updating the stored extracted position indicator at predetermined intervals, and means responsive to power-up of the control arrangement to enter the stored extracted position indicator as a desired value of position indicator.

2. A control arrangement as claimed in claim 1 wherein the control signals respectively correspond to operational modes of the video player such as fast forward, reverse and triple play, and a respective control signal is produced in dependence upon the magnitude and sign of the difference.

3. A control arrangement as claimed in claim 2 wherein in use the control signals drive respective semiconductor switches connected in parallel with the manually-operable switches of the video player.

4. A control arrangement as claimed in claim 2 wherein the control signals are in the form of repective codes sent over a common transmission.

5. A control arrangement as claimed in claim 2 including means responsive to the respective control signals for actuating the manually-operable controls of the video player.

6. A control arrangement as claimed in any one of claims 2 to 5 wherein for producing a pause function for a constant linear velocity type video player, the means for producing control signals generates a short duration reverse mode control signal followed by a play mode control signal when the extracted position indicator becomes equal to a predetermined value.

7. In or for a video disc player in which the playback signal includes a position indicator, a position search control arrangement substantially as herein described.