Gilderfluke&Co 16 Bit CD-Quality Digital Audio Systems - Manual (Page 40)

using SMPTE at 25 FPS, donÕt try to trigger sounds on the 26th frame. The AB/DR-3000Õs SMPTE
input should follow SMPTE with a speed variation of approximately 25% from 30 FPS.
The AB/DR-3000s check for any spiels they might need to trigger one second ahead of the
SMPTE time they are receiving. If one is found then they use the incoming SMPTE frame num-
ber to trigger the spiel. This allows the SMPTE triggers to be handled at a high priority interrupt
level for the greatest possible accuracy.
The AB/DR-3000 needs to receive at least one second of timecode, including that sec-
ondÕs frame ÔzeroÕ, to trigger a spiel. i.e.: If the time code starts at 00:00:00.01, the first possi-
ble trigger would be at 00:00:02.00. A ÔprerollÕ, can be used if you need to trigger right at the
start of the received timecode. Unlike the timecode readers in our Animation Control Systems,
the AB/DR-3000s wonÕt be offended by receiving the end of the previous hour. Note that the
AB/DR-3000Õs reader expects 23:59:59 to roll over to 00:00:00.
If there is a glitch in the timecode which makes the SMPTE reader do a search for the sync
word after a trigger is found in the table but before it is played, the sound will not be played. If
for some reason the frame where a trigger is supposed to take place is missed, but no error is
generated, then the spiel will be played during the next good second. If the SMPTE is stopped
cleanly (without nay error) after an entry has been found in the table but before it has been
played, and then restarted cleanly (again without nay error) at a different time, the spiel will
play at the selected frame regardless of what the new time is. The odds of the latter two
events ever actually happening in the field are VERY small.
For those of you who want to know exactly when the sounds are triggered: It is two bits into
the SMPTE sync word that follows the frame upon which the sound is to be triggered. The
SMPTE triggers are handled at an interrupt level, and are the most time-accurate triggers avail-
able on these repeaters.
C) SMPTE Output: When the SMPTE Output is enabled, the AB/DR-3000 will act as a SMPTE time
code generator whenever the Left side (or a stereo spiel) is playing. When generating SMPTE
timecode the minutes, seconds and frames always start at 00:00.00. The ÔHourÕ digit of the
SMPTE will reflect the number of the spiel being played. As with the front panel display, decimal
numbers (01 to 99) will be used as long as there are less than 100 spiels on a repeater.
HEXadecimal numbers will be used if there are more than 100.
The only frame rate the AB/DR-3000s will generate is 30 FPS, non drop frame 23 . Note that
the actual frame rate generated by the DR-3000 is slightly off from an actual 30 Hz frequency
by -.0008. Over the course of a 20 minute spiel, the generated SMPTE will get off by about
one second from the actual time. Anything which is listening to the AB/DR-3000 timecode will
simply follow it, taking this error in stride. Additional timecode error can be generated by drift
between the crystal that is used for audio reproduction and the one that is used by the micro-
controller. The crystals we use are typically specified with accuracies of +/- .0001. Any equip-
ment which is synchronized to the AB/DR-3000 system should never so small an error.
Although the SMPTE generation is started right when a spiel is triggered, the end is treated
as a low priority by the AB/DR-3000. Depending on other tasks you have the AB/DR-3000 doing
at the time (scanning RTC, Status output or SMPTE tables, receiving or transmitting serial data,
running delays), the final time received from the SMPTE output may vary slightly.
D) IR Mode: This is a special mode to be used with the InfraRed Remote Control from Gilderfluke
& Company. It is typically used to trigger a sound system mounted on a vehicle, turntable, or
other installation where wires canÕt be used for the triggers. Any binary show spiel number re-
ceived by this serial port for more times than the value stored in the DEBOUNCE variable will
trigger that spiel. Typically the transmitters are placed along the path of the vehicleÕs travel to
trigger the appropriate spiels at the appropriate times.
The connections to the IR Remote Receiver are as follows (view is facing end of cable with
latch up):
G ILDERFLUKE & C O . ¥ 205 S OUTH F LOWER S T . ¥ B URBANK , C ALIF . 91502-2102 ¥ 818/840-9484 ¥ FAX 818/840-9485
32 of 92
23 ÔDrop FrameÕ time code literally ÔdropsÕ a frame every few seconds.