Preformat with Time Code

Preformat with Time Code

As an option to improve the reliability of video tape control, a number of the control operations in DigImage are able to use a series of pulse recorded on one of the audio channels - typically channel 1. The purpose of this option is to preformat a tape, on which the video signal (and maybe audio channel 1) is already recorded, by dubbing a pulse onto the audio channel every eighth video field. Provided the VTR is set up correctly (see below), this operation will not affect either the video signal or any audio signal or linear time code signal recorded on channel 1.

The VTR should be set up in the following manner for the front panel: 

           Front panel switch      Setting
           AUDIO MONITOR           CH1
           AUDIO MONITOR           NORM
           AUDIO OUT               NORM

           Input audio level       Setting
           CH1 NORM                Maximum
           CH1 HiFi                Minimum
           CH2 NORM                Minimum
           CH2 HiFi                Minimum

The relevant on-screen set-up menu (activated by pressing DOWN and SCREEN DISPLAY buttons simultaneously) should include the following: 

           Feature                 Setting         Notes
           AUDIO LIMITER           OFF
           DOLBY NR                OFF
           AUDIO CH2               TIME CODE
           AUDIO DUB               CH1             To record only audio
                                                   pulses
                                   CH1.CH2         To record audio pulses and
                                                   LTC track.
           HIFI REC                OFF

The interface cable should be connected to the audio channel 1 input phono socket and the audio monitor phono socket on the rear of the machine in addition to the normal (modified) RS-232 connection. Refer to installation documentation for further details.

NOTE: The audio pulses should be added to the tape prior to any processing. If the tape has become stretched due to repeated processing, the video and frame grabber will not be able to lock onto the sync pulses correctly, and as a result the audio pulses may not be accurate (typically they will appear more rapid than they should be).

For further details, refer to the Trouble Shooting section at the end of the help text for [X Examine time code pulses].

How long do you wish to record the time code signal for (seconds; 0 => for ever) ?

This entry governs how long DigImage will continue to record the time code pulses on the audio channel. The recording operation will finish when either the required time period has passed, or the user requests termination by pressing <Q> or <escape>. The period should be specified using the normal DigImage time format of minutes:seconds. A value of zero implies that the formatting is to continue forever (ie. 3 hours, the length of the standard tapes). See the <shift><f1> general help for more details on this format.

The time code will be recorded on audio channel Press any key to continue or Q to quit...

If any key other than <Q> or <escape> is pressed, then DigImage will place the VTR in audio dub mode and proceed to put an pulse on the audio channel every eight field. This process will continue until either Q or <escape> is pressed. If Q or <escape> are pressed in response to the original question, then no pulses are recorded.

Message:
Press any key to terminate tape formatting early

Reposition tape or Leave where it is ?

When DigImage exits the recording of time code pulses through Q being pressed, the user is given the option of repositioning the tape to the starting point of the preformatting (R), or leaving the tape where it is (L). Note that the repositioning is only approximate as DigImage is forced to STOP the VTR to terminate audio dub mode (STOPping the VTR causes the counter to loose track of some of the video fields).

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Stuart Dalziel, last page update: 19 February 1996