Detailed Contents
Preface
1 Microsoft Language Utilities
2 Board Installation
3 Operating System Setup
4 Installing Software
5 Configuration Utility
6 Setting up the Video Tape Recorder
7 Other Software
8 Other Hardware
In order for DigImage to control the Panasonic AG-7330 or AG-7350 Super VHS video tape recorder with the required degree of accuracy, it is necessary to modify and fit the optional AG-IA232 (AG-7330) or AG-IA232TC (AG-7350) RS-232C interface between the VTR and the host computer. This section deals with the modification required to the interface, the DIP switch settings, the wiring of the cable, connecting the computer and VTR, some basic warnings about the usage of the VTR and interface, and finally some notes about the connection of video sources.
Using the standard AG-IA232 or AG-IA232TC interface, the computer is able to control the VTRs state through a simple command protocol, and inquire from the VTR what it is doing, how it is set up, and where it is. Unfortunately the VTR is only able to tell the computer where it is in units of one second; this does not offer sufficient resolution for DigImage to operate successfully. Moreover, the VTR is subject to the occasional error when reversing direction, so that even if the computer were to have full access to the VTR's own internal clock or strobe, there would still be some positional error.
DigImage has adopted a combination of two techniques to ensure sufficiently accurate positioning of the video tape. The first is a modification to the interface to make the VTR's own internal strobe available (the modification is covered in this section), and the second is a consistency check produced by recording tone pulses on one of the two audio tracks (see section 6.2 and the DigImage Help System).
Figure 2 is a schematic of the modification required to either the AG-IA232 or the AG-IA232TC interface. Any general purpose npn transistor could be used in place of the specified BC547, provided it has sufficient current capacity and power dissipation. The purpose of the transistor is to convert the TTL level voltages (a 5V square wave at 25Hz while in PLAY mode) supplied through pin 7 of the internal connector to the interface to the RS-232 level voltages required to communicate with the computer's serial ports. Care must be taken with this modification to ensure that none of the other electronics in the interface are affected. The output from the transistor (a 12V square wave) will be connected to the CTS hand-shake line of COM2: (or COM4:, if a mouse is connected) and used to generate an interrupt which will in turn allow the computer to keep track of each passing video field. Pin 14 is not normally used on the RS-232 connector and so is a convenient point to make the signal available.
For the AG-IA232TC used with the AG-7350, the 12V supply at pin 8 of the internal connector must be made available at pin 25 of the serial D socket (this is not necessary for the AG-IA232 with the AG-7330 as 12V is already available on this pin). In order to make these modifications for the AG-IA232TC, it will be necessary to temporarily remove the piggy-backed circuit board from the interface. This board unplugs after squeezing the plastic mounting pins to release it. After the modification has been made to the inner board, the interface must be reassembled prior to installing in the AG-7350.
In addition to this modification, the DIP switches
on the interface should be set up in the following manner:
| AG7330 | ||||
| SW1: * | SW2: 1 | SW3: 1 | SW4: 1 | |
| SW5: 0 | SW6: 1 | SW7: 1 | SW8: * |
| AG7350 | |||
| Switch One | |||
| SW1.1: 1 | SW1.2: 0 | SW1.3: 1 | |
| SW1.4: 1 | SW1.5: 1 | SW1.6: 1 | |
| Switch Two | |||
| SW2.1: 0 | SW2.2: 0 | SW2.3: 0 | |
| SW2.4: 0 | SW2.5: 0 | SW2.6: 1 |
where 1 is on, 0 is off and * means "do not care" (these switches are not used by the interface). Note that this set up is for the preferred 4800 baud with the AG-7330 or 19200 baud with the AG-7350 (the baud rate is controlled by the DIP switches; consult the VTR's manual for more details).
Due to the requirements of the computer over to control the VTR, DigImage requires a non-standard cable to connect them together. Figure 3 gives a schematic for the wiring of this cable. Note that some electronics must be included in the plug shell at the VTR end (Plug A). Shielded cable should be used for the video strobe and two audio pulse lines to prevent interference from the computer and between each other. At the computer end, Plug B and Plug C are connected to two of the computer's serial ports. These ports may be either COM1: and COM2: or COM3: and COM4:. The serial ports may have either 25 pin or 9 pin connectors. Pin numbers are given first for 25 pin connectors with the 9 pin equivalents indicated in brackets. The socket on the back of the VTR interface, to which Plug A is connected is always 25 pin.
Plug E and Plug F are used to record and read the audio pluses DigImage records on the audio channel to ensure correct synchronisation between computer and VTR.
Plug D, marked optional, may be used to connect a serial device (such as a printer or another computer) into COM2: or COM4: at the same time as the computer is connected to the VTR. Both XON/XOFF and RTS/CTS handshaking are supported. When fitted, the serial device should be connected to Plug D instead of directly to the computer. If you do not wish to connect an additional serial device to the computer, or use the computer as a terminal over a serial line, there is no need to fit Plug D. As before, pin numbers are given for both 25 pin and 9 pin variants.
If you have a serial mouse connected to COM1: or COM2: then it will be necessary either to disconnect the mouse prior to using DigImage, or to install a second serial card and utilise COM3: and COM4: for controlling the video recorder. DigImage For details on how to configure DigImage to utilise the different combination of serial ports, please consult the help on the [;T Configure serial ports] option in the configuration utility. Note that if you have three or more serial ports, then DigImage is able to make use of a mouse connected to COM1: or COM2: for positioning the cursor and specifying windows. See the System Overview for details.
Once the VTR and computer are connected through the above interface and cable, the computer is able to control most of the features of the VTR. With the AG-7350 the computer and the keys on the front of the VTR may be used interchangeably to control the VTR. However you should not normally use both forms of control at the same time. As an option the keys on the VTR may be disabled by setting the MODE LOCK switch to the ON position.
With the AG-7330 simultaneous computer and front panel operation is not possible. The OPERATION switch, located near the right-hand end of the closing control panel on the VTR is used to switch the VTR between LOCAL (i.e. from the VTR's own keys) and REMOTE (i.e. using the RS-232 adapter) control. When DigImage is exerting control over the VTR this switch must be set in the REMOTE position. Failure to do so will prevent DigImage from being able to exercise the required control.
For details on the operation of the VTR from DigImage refer to [f1 Help] within [;V: Video tape recorder control].
Normally DigImage will take control of the VTR whenever [;V: Video tape recorder control] is entered, or any other option which implicitly requires control of the VTR (such as [;UH Start particle tracking]). While DigImage has control of the VTR, the second last character in the top row of the screen will flash with each passing frame and an arrow in this position will indicate the direction DigImage believes the tape to be moving. If this character does not flash while in PLAY mode, check the wiring of the serial cable to COM2: and the modification to the interface. These may be checked using an oscilloscope.
If DigImage is unable to complete an operation for one reason or another then it will produce the message "VTR not responding...". Should this occur, check the cabling and, for the AG-7330, the position of the OPERATION switch. Note that manual repositioning of the VTR (switched to LOCAL for the AG-7330) is allowable while the computer has nominal control of the VTR, but such repositioning may cause the record of the position stored by DigImage to disagree with the true position of the tape, especially if rapid tape movements or sudden changes of direction are used.
The DT-2861 and DT-2862 are grey-scale devices. They operate best when they receive a simple monochrome signal without any colour information. While there are links on the frame grabber board to filter out any colour signal present, installing these links; reduces the spatial resolution of the board. Moreover, particularly at low signal strengths, there can be an interference between the intensity and chrominance signals. Experience has shown that better results may be achieved by filtering out the chrominance signal at the VTR. With the AG-7330 the MODE switch should be set to MONO. For the AG-7350 you must use the video's on-screen menu to change between colour and mono. Results are also improved if the frame grabber is connected to the SVHS output socket of the VTR rather than the BNC output connector. The connection should be made to the Y (luminescence) signal and Y ground pins of the miniature DIN plug, with a 75 ohm terminator across the other pair of pins (chrominance). Looking into the socket with the notch to the top and the locating pin to the bottom, the signal pins are the top pair with the chrominance to the left and luminance to the right. The lower pair are the ground pins, again with chrominance to the left and luminance to the right.
When recording the video, unless it is desirable to maintain colour information, it is again preferable to have the MODE switch in the MONO position (AG-7330) or on-screen menu set to mono (AG-7350). When using a monochrome source, connect it through the luminescence pins of the SVHS input socket rather than the BNC socket. As before, terminate the chrominance pins with a 75 ohm terminator. Connecting some high resolution monochrome cameras via the BNC connector can confuse the video recorder into thinking a colour signal is connected if the video recorder MODE switch is left in the AUTO position. This is due to the high bandwidth of the monochrome camera overlapping the frequencies used to carry colour information in composite video output from colour video cameras.
This section summarises the necessary settings for the switches (both mechanical and software) on the supported video recorders.
The front panel switches should normally be set as follows:
| Switch | Setting | Notes |
| CH2 METER | TRACKING | The meter may be used to monitor the video tracking. |
| AUDIO MONITOR | CH1 | Audio channel 1 is connected to the computer through the audio monitor socket on the rear of the VTR. |
| AUDIO MONITOR | NORM | DigImage uses the audio channels as part of the control system. The conventional linear tracks should be used rather than the hi-fi. |
| AUDIO OUT | NORM | Normally only the conventional linear audio tracks will be recorded. |
| HIFI REC | OFF | Normal audio sufficient. |
| INPUT | SVIDEO | The four pin SVHS input socket should be used in preference to the composite video BNC socket (line). |
| TV SYSTEM | PAL | Whichever system is to be used. |
| SYNC | NORM | The sync signal is normally embedded in the video signal. |
| VIDEO MODE | B/W | Monochrome is preferred for most applications. |
| AUTO | When colour signals must be used. | |
| NOTCH | OFF | The notch filter should not be required. |
| SVHS | ON | Record as SVHS when SVHS tapes are used. |
| IMAGE | DETAIL | Use as much of the information in the image as possible. |
| SENSOR REC | OFF | Prevent the VTR entering record mode due to some external event. |
| AUDIO DUB | CH1 | When dubbing the DigImage time code pulses. |
| OPERATION | LOCAL | For operating VTR manually. |
| REMOTE | For computer controlled operation. | |
| EXT TIMER | OFF | This switch should be covered to prevent accidental setting to rec (in the rec position the VTR automatically enters record mode when it is switched on). |
| CH1: AUDIO LEVEL - NORM | maximum | DigImage uses this audio channel to record time-code pulses to aid with the control of the video recorder. |
| CH1: AUDIO LEVEL - HIFI | minimum | The hifi channel is not used. |
| CH2: AUDIO LEVEL - NORM | minimum | ch2 is used for linear time code signals instead of audio - see below. |
| CH2: AUDIO LEVEL - HIFI | minimum | The hifi channel is not used. |
The set up menu (entered by simultaneously pressing the DOWN and SCREEN DISPLAY buttons) should be set as follows:
| Item | Setting | Notes |
| AUDIO LIMITER | OFF | Need to make audio pulses as loud as possible. Distortion is not a problem. |
| DOLBY NR | OFF | No need for noise reduction. |
| AUDIO CH2 | AUDIO | The VTR does not have a time code generator. |
| TAPE SELECT | NORMAL | Unless 240 minute tapes are being used (not advisable). |
| TAPE IN MODE | STOP | The tape does not start to play when inserted. |
| TAPE END MODE | REW | When the tape gets to the end, rewind to the beginning. |
| AUTO BACKSPCE | ON | This prevents gaps between sequences of recordings. |
| FRAMING | ON | It is not clear what effect this has. |
| DIRECT SEARCH | OFF | The tape does not go into shuttle mode automatically on start up. |
| REMOTE PIN | Does not matter. |
The front panel switches should normally be set as follows:
| Switch | Setting | Notes |
| CH2 METER | TRACKING | The VTR is set up for linear time codes to be recorded on audio channel 2. Hence the meter may be used to monitor the video tracking. |
| AUDIO MONITOR | CH1 | Audio channel 1 is connected to the computer through the audio monitor socket on the rear of the VTR. |
| AUDIO MONITOR | NORM | DigImage uses the audio channels as part of the control system. The conventional linear tracks should be used rather than the hi-fi. |
| AUDIO OUT | NORM | Normally only the conventional linear audio tracks will be recorded. |
| INPUT | SVIDEO | The four pin SVHS input socket should be used in preference to the composite video BNC socket (line). |
| SYNC | NORM | The sync signal is normally embedded in the video signal. |
| TV SYSTEM | PAL | Whichever system is to be used. |
| REMOTE REC | OFF | In the video mode the VTR will automatically record whenever a video signal is detected, erasing any existing contents of the video tape. |
| EXT TIMER | OFF | This switch should be covered to prevent accidental setting to rec (in the rec position the VTR automatically enters record mode when it is switched on). |
| MODE LOCK | OFF | The computer may control the VTR without changing this switch. In the on position manual control is not possible. |
| CH1: AUDIO LEVEL - NORM | maximum | DigImage uses this audio channel to record time-code pulses to aid with the control of the video recorder. |
| CH1: AUDIO LEVEL - HIFI | minimum | The hifi channel is not used. |
| CH2: AUDIO LEVEL - NORM | minimum | ch2 is used for linear time code signals instead of audio - see below. |
| CH2: AUDIO LEVEL - HIFI | minimum | The hifi channel is not used. |
The set up menu (entered by simultaneously pressing the DOWN and SCREEN DISPLAY buttons) should be set as follows:
| Item | Setting | Notes |
| AUDIO LIMITER | OFF | Need to make audio pulses as loud as possible. Distortion is not a problem. |
| DOLBY NR | OFF | No need for noise reduction. |
| AUDIO CH2 | TIME CODE | We will record the linear time code track on audio channel 2. |
| AUDIO DUB | CH1 | If wanting to dub DigImage time code pulses only. |
| CH2 | If wanting to dub linear time code track only. | |
| CH1.CH2 | If the linear time code track is to be rewritten at the same time as the DigImage time code pulses. | |
| HIFI REC | OFF | The standard audio track is better for the DigImage time code pulses. |
| S-VHS | ON | The VTR will automatically record as Super VHS if a Super VHS tape is used. |
| EDIT | ON | Allows edit operations. |
| VIDEO MODE | MONO | For most applications a mono signal is preferred, but the auto option is also acceptable. |
| AUTO | When a colour signal is required, set to auto detection. | |
| NOTCH | OFF | The notch filter should not normally be required. |
| TAPE IN MODE | STOP | The tape does not start to play when inserted. |
| TAPE END MODE | REW | When the tape gets to the end, rewind to the beginning. |
| AUTO BACKSPCE | ON | This prevents gaps between sequences of recordings. |
| DIRECT SEARCH | OFF | The tape does not go into shuttle mode automatically on start up. |
DigImage documentation page
DigImage home page
Stuart Dalziel's home page