Every show design starts with an attraction description. Once the desired guest experience, operator interface and performance requirements are known, they can be used to create a show equipment list. For our imaginary attraction we have chosen a motion-base theatre with a 12-track synchronized audio source, and a multi-screen video preshow area with stereo audio synchronized to the videos and continuously looping background music audio. Additional audio tracks are required for automated fill/spill spiels and a hearing impaired audio track. As with most shows of this type the preshow and theatre run in relative synchronization, allowing guests to accumulate in the preshow during the film presentation in the main theatre.
The theatre audio is required to be CD or better quality due to the wide dynamic range of the material, and SMPTE timecode is required to synchronize the show audio, film projector, motion base controller, and show control computer.
A single Digital Binloop provides all the audio and video tracks for our entire attraction. The Digital Binloop can playback up to 24 synchronized tracks of audio, up to 12 synchronized tracks of video, or any combination of both.
Over 1000 individual sound or video files on each track can be played back in response to serial or parallel inputs, or commands can be initiated from internally-stored SMPTE timecode triggers. Serial control can be either RS-232 or MIDI. Parallel inputs can be either dry contact closures or TTL. Sounds or videos can even be triggered from commands embedded in SMPTE user bits. Individual tracks can be grouped in software, to guarantee that they are always synchronized.
In our case, both synchronized and un-synchronized tracks are contained in the same unit. In some cases individual sounds within a specified track will be independently triggered. The Digital Binloop will also provide the SMPTE timecode for the motion base and show control computers.
The system architecture on the following page shows the partitioning of audio and video tracks amongst the Reproducers in the Binloop, and the various control interfaces.
The Digital Binloop is controlled with a combination of serial and parallel inputs. The main show audio is triggered using embedded SMPTE triggers.
The Digital Binloop can be configured to source SMPTE timecode or synchronize to externally sup-plied SMPTE. All standard frame rates are supported. The generator’s output level is adjustable. Any start, preroll, and stop times can be selected, and timecode can be programmed to loop or stop at the end.
For our sample show, the SMPTE timecode is sourced directly from the Digital Binloop. Our show uses 30 fps. Timecode is started with a contact closure from the operator. The Binloop is programmed so that timecode runs from 01:00:00:00 to 01:20:10:12.
Some show architectures may require that the Bin-loop synchronize to external SMPTE or video sync. Sound triggering when reading SMPTE is identical to that when generating.
In our sample show, an Alcorn McBride V16+ Show Controller serially controls the Binloop for the pre-show area. This allows easy interface to the operator consoles, door controls and other show elements. Alternately, any device which can generate RS-232 (38.4 K Baud N,8,1), MIDI, or discrete contact closures can control the Binloop. Alcorn McBride and MIDI show control protocols are both supported. The Digital Binloop can even be programmed to send SMPTE triggered serial messages to the V16 or other devices.
The Digital Binloop has parallel inputs for triggering sounds or videos from individual Reproducers or Groups of Reproducers. The exterior background music sounds for our sample show are triggered using these Group inputs. The Group inputs can be configured to play, stop or loop a specific track or group of tracks. Inputs are also available for muting audio tracks.
The Digital Binloop provides balanced and unbalanced audio outputs. The factory preset level is +4 dBm nominal with 20 dB of headroom, and achieves the high quality performance required of theatre au-do sources. Its frequency response is flat from 20 KHz down to DC. Of particular importance in a theatre environment, the Digital Binloop’s muted signal-to-noise ratio is 120 dB!
A composite video output with stereo audio is sour-cd from any Binloop slot populated with a Video Reproducer. Both PAL and NTSC are supported.
Here’s how we’ve laid out our theatre’s audio and video tracks:
Outdoor Background Music
Group 1, Reproducers 1-2
Two Reproducers are assigned to Group 1 and used to source two continuously looping stereo back-ground music tracks at the queue line entrance. It is started serially by the V16.
Preshow Audio & Video
Group 2, Reproducers 3-4,12
Three Reproducers are assigned to Group 2 and are serially controlled by the V16 to provide synchronized audio and video for the preshow area. Reproducers 3 and 4 provide 4 separate and independent tracks of audio, while Reproducer 12 provides video and stereo audio. A serial message from the V16 is sent to the Binloop in response to a contact closure input on the preshow operator’s console.
Group 3, Reproducers 5-10
The twelve tracks of main show audio are sourced from six Reproducers, all assigned to Group 3. The main show tracks are commanded to play using a Group 3 SMPTE trigger stored within the Binloop. The trigger time is selected to achieve perfect synchronization with the film and motion base profile. These Reproducers also contain additional sound files for fill/spill and emergency spiels. At the conclusion of the show a SMPTE trigger will rolls the fill/spill music. A contact closure from a show con-sole button to the V16 activates the emergency spiels, when required.
Hearing Impaired & Foreign Language Tracks
Group 3, Reproducer 11
This Reproducer contains a mix of all the main show tracks and also contains the fill/spill and emergency spiels in separate sound files. Since it is a member of Group 3 along with the main show audio Reproducers, it will be perfectly synchronized to the show.
Any digital audio source which outputs AES/EBU or S/PDIF data will work with the Digital Binloop.
The material for our show audio was provided by the sound producer in ADAT format. Two tapes each contained seven tracks of audio and one track of SMPTE. By using the SMPTE triggered recording feature of the Digital Binloop, the sound tracks were loaded via AES/EBU into the PCMCIA media using a 14 track Record-in-Place Digital Binloop and 2 ADAT recorders. Alternately, the recording could have been done using one ADAT (or any digital audio recorder) and multiple recording passes, one for each track or set of tracks.
The preshow video was encoded in a PC using an off-the-shelf MPEG encoder board and then just cop-i ed to the PC card.
The Compact Flash media used in the Digital Binloop is PC compatible. This means that the sound files for our show can be archived on any computer equipped with a PC-Card socket.
Because the Digital Binloop uses solid state flash cards or high reliability miniature hard drives, its mean time between failure is in excess of 14 years. No preventative maintenance is ever required.
We hope this application note has given you some insight into the power, flexibility and ease of use of the Alcorn McBride Digital Binloop. The Digital Bin-loop has many more features and applications not discussed in this application note. If you do not al-ready have a Digital Binloop programming disk, or to discuss your application, call or visit our web site at http://www.alcorn.com.