Time Series at Single Point(s)

Time series may be generated, with a sampling rate of even multiples of the field rate (ie. multiples of the frame rate). Multiple points may be processed (the maximum number depends on the speed of the PC - if too many are specified, then an error message is generated), with up to 256K individual readings. The time series are optionally available in an INTEGER*1 binary file (which also stores the number of points and the number of samples) and/or displayed on a buffer. The option [W Time series of window means] performs a similar process, but sampling the mean intensity of a list of windows rather than individual points.

Define sampling points using which buffer ?

The locations at which the time-series of intensities is given is specified interactively using the cursor submenu within DigImage. This entry may be used to specify a buffer containing a suitable image to aid the specification process.

Cursor Positioning: Locate sample point number ##

The cursor submenu is used to specify the location of each of the points at which a sample is to be taken. Operation of the cursor is in the normal manner with further information available from [H Help] within the submenu.

Another point ?

DigImage is capable of simultaneously sampling a large number of points. If a further point is to be added to the sample list, then a response of yes (<Y>) will return to the cursor submenu. Once all the points have been specified, <N> will continue with the time series process. Note that if more points than DigImage is able to sample within one frame period (1/25s or 1/30s) are specified, then an error message will be generated.

Number of samples ?

The number of samples required should be specified. The maximum number depends on the number of points at which samples are being taken. If the image is being sampled at n points, then up to INT(262144/n) samples may be taken at each point. Note that the sampling process may be terminated early by pressing <Q> once it has started.

Sample spacing (even number of video fields) ?

This entry specifies how frequently the points are to be sampled. All the points are sampled for the same video frame (two video fields) within 1/25s or 1/30s (PAL or NTSC, respectively), but need not be sampled for every frame. A spacing of two video fields means that every video frame will be sampled, four fields for every second frame and so on.

Manual or Computer control of VTR ?

The VTR may be controlled either manually (<M>), or automatically by the computer (<C>). The latter choice will be required for operation from a command file.

{If computer control}

Start time (offset) ?

The time series will be started at a specified time relative to the current point. The time offset should be specified using the normal DigImage time format of minutes:seconds (see the <shift><f1> general help for more details). A negative time represents offsets to earlier times on the tape.

{If computer control}

On completion Reposition video tape or Leave ?

The answer to this question dictates how the VTR is handled at the end of the time series. If <R> is selected, then the video tape is repositioned to its initial position, while <L> causes the tape to be left where it finished. Once this choice has been made, the computer will take over control of the VTR and process the time series.

Display samples using what buffer (-1 to suppress) ?

As an option, the time series may be written to a frame buffer to create a visual display of the data. This entry specifies the buffer to which the data is written. Note that the data will not be written to the buffer until the time series acquisition is complete. A value of -1 suppresses this display.

{If manual control}

Press any key to start acquisition (<escape> to abort)

Pressing any key will start the acquisition of the time series.

Collecting ## samples for ## points Press <Q> to quit early...

Once the time series sampling has started, it may be terminated early by pressing <Q> or <escape>. The difference lies in that <Q> will still allow the display of the samples and optional saving to a file, while <escape> simply returns control to the previous menu.

Name of file to save data to (blank to suppress) ?

As an option, the time series data may be written to a formatted or a binary file. The name of the file is specified by this entry; the data is not saved if no file name is given.

Use Formatted or Binary file ?

This entry specifies whether the data is to be written to a formatted or a binary file.

If a formatted file is created, it contains columns for the point number, an index, the time and the intensity. This format may be readily plotted using DigiPlot.

The format of this binary file is as follows:

           nSamples, nPoints,
           iValue(0,0), iValue(1,0), ...
           ... iValue(iPoint,iSample) ...
           ... iValue(nPoints-1,nSamples-1)

where nSamples is INTEGER*4, nPoints is INTEGER*2 and each iValue is unsigned INTEGER*1. The location of each of the points is as specified earlier through the cursor.

Errors, Warnings and Messages

Error Message:
Unable to open output data file

DigImage was unable to open the specified output data file. This may be due to an invalid filename or path, or insufficient disk space.

Error Message: Unable to sample required list

There are either too many windows, or the windows are too large for all the mean intensities to be evaluated within the required time period.

Parent menu

Main Menu

DigImage User Documentation

Stuart Dalziel, last page update: 19 February 1996