TSignalBrowseBuffer Class

Summary

Stores and buffers an overview of the incoming signal.

Hierarchy
TAnalysis <--TSignal <--TSignalBrowseBuffer

Subclasses
None

Description

The size of the preview is maintained small enough to allow quick redraw on a chart. At start the component holds the actual signal up to the size of the SpanLimit. Once SpanLimit is exceeded an overview of the signal is computed and the original is discarded. From that point on, only the overview of the signal is kept. Once the overview exceeds the SpanLimit a new signal overview is computed from the existing overview and this procedure repeats in to infinity allowing virtually unlimited length of the overview. The component allow's limited zoom-in in to the overview, because intermediate results are discarded, but the data discarded will not exceed a factor of sqr(Increment). The default value for increment is 20 and 20^2 = 400. For a 2GB long recording this will result in 5MB of the in-memory buffer. On the resulting overview PixelDownSample method should be applied again. For true navigation use TSignalBrowse component.

The purpose of this component is to allow an overview of already recorded data to be displayed to the user. The IsOverview function returns true, if the component stores an overview, otherwise it is still buffering the original signal. This is important to know because the drawing method may differ substantially for signal and overview. The overview stores Max and Min values interleaved. The Max values form the upper and the Min values from the lower envelope.

Calling Update or Pull method will return pipeOK, if the Data property has been updated. It will return pipeStream, if there is not enough data buffered yet to update.

Properties

Name	Summary
Increment	Defines the increment at which the overview is sampled.
SpanLimit	Defines the samples count at which an overview is computed.

Methods

Name	Summary
InternalUpdate
IsOverview	Defines, if the component already stores an overview.
Reset	Reset the buffering and overview.