Timecode Overview

Overview

Firing systems have various kinds of support for synchronizing the music and firing events in a pyromusical, from a low-tech approach of "press play on your firing system and audio system at the same time" to a more complex approach of synchronizing the firing system's clock to a "timecode" signal that is playing on one channel of the audio recording along with the music.

Timecode addresses both the synchronization problem of starting the music and firing event sequence at the same time, and the synchronization problem of keeping the firing events and music in sync over time. Back when audio was recorded on tape, variations in audio playback rate could cause the firing events and music to drift significantly out of sync. Since digital audio recordings today have precise playback rates, the problem of keeping the firing events and music in sync over time is not as significant as it used to be, but timecode is still commonly used, sometimes just to align the starting times and other times to keep firing events in sync over time.

Making a Timecode Recording

Timecode recordings have two channels, with a timecode signal on one channel and the music on the other channel. The timecode signal is an audible signal similar to the signal of an acoustic computer modem, which sounds like noise to the human ear. Firing systems use either of two timecode signal formats, FSK and SMPTE.

To make a timecode recording, use an audio editor like Gold Wave to combine a mono-channel recording of your music on the one channel with a recording of your standard timecode signal on the other. For some firing systems, if you are using timecode merely to synchronize the start time of the music and the firing events, then a minute or so of timecode signal will suffice; it does not need to extend for the full duration of the music. If you are using the timecode to synchronize the firing system's clock for the full duration of the music, then obviously the timecode signal must extend the full duration.

Aligning the Timecode Signal with the Music

Similar to computer modems, firing systems need to process some part of the timecode signal in order to get in sync with it, during which time the firing systems cannot be issuing firing events because their internal clocks are not yet keeping in step. To allow for this processing time, timecode signals generally begin with a short handshaking section that occurs before the time sequence starts (i.e., before "time zero"). Thus if you combine the timecode signal with the music both starting at the same time, the sequence of firing events will start late relative to the music. If the handshaking section is ten seconds, for example, then the sequence of firing events will begin late by ten seconds.

To address this problem, when you combine the timecode signal with the music you need to offset the music forward, after the handshaking period. If you know the exact duration of the handshaking section, you can align the start of the music to time zero in the audio editor. Otherwise, you can offset the music forward by an amount safely greater than the timecode handshaking section (e.g., a minute), and later get the exact alignment by adjusting an offset in the firing script.

Using Finale to Adjust the Script Offset

Once you have made your timecode recording with the timecode signal and music, play it back in your firing system and observe the synchronization between the music and firing events. If they are exactly in sync, you are done. If they aren't exactly in sync, then you can use a command in Finale called "Show > Set script export offset (for timecode)..." to add an offset to all the launch times and view times in the show's exported script. If, for example, you observe that the firing events are starting too late by 5.3 seconds, you can set the export offset to -5.3 to cause the firing events to occur earlier. Most firing systems cannot handle launch times before zero, so negative offsets must not be so large as to make launch times negative.

When you set the script export offset of your show, it will be saved as a property of that particular show. You will not see any difference in the timeline or music on the screen. The script export offset only affects exported scripts; it does not affect the editing window. After setting the script export offset, if you export a script or download a script to the controller, Finale will display a "Confirm Script Export Offset" dialog to remind you of the export offset that will be incorporated in the script.