360 Systems Instant Replay DR-552 - Manual (Page 10)

Instant Replay Owner’s Manual page 5
Recording Formats and Sample Rate Conversion
There are three recording formats available. The standard format used is 48K AC-2. This uses
the Dolby AC-2 encoding system to allow five times the audio storage of 48K Linear format
recording. The AC-2 system is of very high quality and is recommended for all but a few
applications:
•
When the Instant Replay will be required to provide a digital output at 44.1 K. (Format and
Sample Rate are determined at the time of recording and cannot be changed.)
•
When the audio being reproduced may be subjected to other forms of data compression as
part of the transmission path, for example a satellite link or telephone codec.
•
In applications where the exact same digital data must be reproduced. An example of this is
when using digital audio test signals to test the digital I/O or other performance factors.
AC-2 has been successfully used in applications with recorded SMPTE Time Code paired with
mono audio. This has been applied to the synchronization of lighting and show controllers with
Instant Replay.
WARNING
Note that while you can have Cuts recorded in any of the three formats stored in the unit, it is
best not to mix formats on a particular project. Switching from a 48K Linear or 48K AC-2 to
44.1 will cause the output sample rate to change, causing possible disturbance of equipment
monitoring the digital outputs. (The analog and headphone outputs will not be affected.)
When playing Hot-Keys in rapid sequence, (three or more keys pressed within one second)
changing between formats can cause playback errors which result in momentary noise output or
momentary playback at an incorrect sample rate.
When using 48K Linear or 44.1K Linear formats, playback and recording can only be
performed on the internal hard drive. Linear Cuts can be copied to and from the External drive
for backup and data transport. See the section on “Using an External Drive” on page 24.
The Sample Rate Converter is a hardware device available on the Digital Inputs. It is normally
enabled. It allows digital recordings made from any source to end up at the sample rate defined
by the selected Recording Format. When it is disabled, the digital input requires that the
incoming digital audio signal match the currently selected format. See page 21, "Record Setup"
to disable the converter. The Sample Rate Converter can be used by itself to convert a digital
input to 48K or 44.1K output by simply putting Instant Replay into record ready.
Table of Recording Time Capacity and Recording Format
Times listed are approximate. Some space is used for data storage functions, so the total record
time is decreased by approximately 2 seconds for each Cut in addition to the space used by the
Cut’s audio data. Also, the amount of time may vary depending on specific model of hard drive
used in the unit.
MODEL AC-2 48K LINEAR 44.1K LINEAR
DR554 24 HOURS 4 HOURS 41 MIN. 5 HOURS 5 MIN.
ZIP 100 DISK 46 MIN. 8 MIN. 9 MIN.
ZIP 250 DISK 1 HOUR 55 MIN. 20 MIN. 22 MIN.