Data AcQuisition And Real-Time AnalysisScope - Spectrum - Spectrogram - Signal Generator
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Spectrogram / Pitch Track of File Data
Spectrograms or Pitch Tracks of long files of wave data (.DQA, .WAV, or .DAT) can be viewed just like live signals by hitting unPause once the file is opened. In this condition normal Trigger operation is available, if desired. The progress of the Spectrogram or Pitch Track display is then controlled by the Trace Update Interval, as usual.
When Trigger is toggled off, the timing between spectra (Sgram/PT vertical columns) of file data is that of the Read Step Size in the DDisk Controls dialog. This defaults to 512 input samples, which means that the spectra overlap: Each spectrum uses 512 new data points and 512 prior data points.
You can move through the file manually in Paused Sgram/PT mode, with the cursor keys or by direct entry of the desired file position, as explained under Reading DDisk Files. The timing in Pause mode always uses Read Step Size.
Setting Read Step Size to smaller values gives better Spectrogram time resolution, usually much better that you can obtain in real-time viewing. This can be very important if you are trying to analyze the fine structure of speech, for example. (You may also wish to reduce Spectrum Window Width for possible further improvements in time resolution at the expense of frequency resolution. See the Screen Shots section of the Daqarta Website for examples of wide and narrow Width applied to a speech spectrogram.)
For file data, Single trigger mode behaves like it is unPaused only until is finds the initial trigger event; the actual Spectrogram is created using Read Step Size as if Paused.
When viewing the Spectrogram or Pitch Track of a file, the file position readout/control below the right end of the X axis shows the start position of the displayed screen within the file. The end position is shown by a separate readout-only panel below that.
Whether live or from a file, Spectrograms or Pitch Tracks only show one channel at a time. If only one Display button is active, that will be the channel used. If both Left and Right are active, only the Left is shown. If both Input and Output are active, only the Input is shown.
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