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Digital Transfer between SIGNAL and DAT Recorders

Application Note 10 5

Using the DAT File in SIGNAL

The Wave file received from the DAT is limited in length only by the recording program and

the available disk space. However, SIGNAL time buffers are limited to about 1.2 million

data points, or about 27 seconds at 44.1 KHz sample rate. Longer files can be read into

SIGNAL in segments using R /W /Q.

The Wave file will have the native sample rate of the DAT recorder, either 44.1 KHz or 48

KHz. Files at these sample rates can be viewed, measured, manipulated, modeled, edited, etc

with full accuracy in SIGNAL, but playbacks will be performed at the nearest sample rate

available on the SIGNAL I/O board, as indicated by the * in the connection diagram and

discussed earlier. If this sample rate error is unacceptable, for example when making

playback tapes, the Wave file can be resampled to an available sample rate such as 50 KHz

using an external software sample rate converter. Both cases are shown in the connection

diagram. See "Sample Rate Converter" for details.

Note that the sample rate of direct-from-DAT sound files may considerably exceed the

bandwidth requirements of the recorded material. This can waste SIGNAL buffer space, disk

space for storage, and computation time during analysis. In this case, sample rate can be

decimated (reduced) by an integer multiple without loss of information, provided the signal is

digitally filtered first. See "Time and Frequency Decimation" in Chapter 28, "Signal

Processing", in the

SIGNAL User Guide for details. Alternately, the DAT tape can be

played into SIGNAL and redigitized at an appropriate lower sample rate.

Using the DAT File in the RTS

The RTS can handle files up to 1 billion data points in length. It will detect the Wave file

type automatically and read it the same as a SIGNAL file.

As in SIGNAL, Wave files in the native sample rate of the DAT can be viewed and measured

in the RTS with full accuracy, but playbacks will be performed at the nearest available

sample rate, as indicated by the * in the connection diagram. This should suffice for most

purposes in the RTS. If exact playbacks are required, the Wave file can be resampled to a

sample rate such as 50 KHz, as described in "Sample Rate Converter". Note that the RTS

cannot write Wave files.

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Engineering Design NIDisk Betriebsanweisung Seite 21