Record Movie - Multi Pass.

This option provides an alternative computer controlling recording facilitiy which will achieve up to the full video frame rate by executing multiple passes until all the images are recorded. Note that the frame rate for a single pass is slightly lower than that achieved by [R Record movie - single pass].

DigImage movie files normally have a .MOV extension and consist of a sequence of images stored in a single file. They are accessed as a direct access binary file with one byte per record. The file format consists of four blocks of header information followed by the raw image data:

GeneralHeader 256 bytes

                   Contains general information

HistoryHeader 256 bytes

                   Contains information about the file history

MovieHeader 1024 bytes

                   Contains information about the images and movie sequence

MovieFrameTable 32768 bytes

                   Stores pointers to each frame (maximum of 2048) in the
                   movie

For complete details on each of these headers, refer to DigImage\Include\Headers.INC.

Name of movie to be created (.MOV default extension) ?

The images acquired as part of the movie will be stored in the file specified here. For full details of the format of this file, refer to DigImage\Include\Headers.INC.

Set recording window using which buffer ?

Only the region of the image falling within a user specified window will be recorded. The smaller this window is, the closer the samples may be together without loosing data. The buffer specified here will be displayed while the window is being specified.

Window Selection: Region to record in movie

The Window Selection submenu is produced to allow the desired region to be selected. For further information on the use of windows, refer the [H Help] within the Window Selection submenu. Note that the number of rows will be rounded up to the next multiple of two and the number of columns to the next multiple of four (with this option it is necessary for the total number of pixels to be a multiple of 8).

Horizontal step ?

By sampling the image on a coarser grid the frame rate of the recording may be increased. This entry specifies the horizontal spacing between samples to be included in the movie image.

Vertical step ?

This entry specifies the vertical spacing between the samples to be included in the movie image.

Spacing between images ?

This entry specifies the temporal sampling frequency or frame rate of the movie. If the requested frequency is too high (spacing too small), then the computer will control the video recorder to make multiple passes until all the images have been captured (in contrast, [R Record movie - single pass] will make only a single pass at a reduced frame rate).

Duration of movie ?

The duration of the movie is fixed by this entry. The duration is converted into the number of samples to be recorded.

Start time (offset from current position) ?

The movie recording will start at the specified offset from the current position of the VTR. If positive the movie will start after this point, while negative will make the movie start before this point.

On completion Reposition video tape or Leave it where it is ?

Once the acquisition has been completed, the video tape may be either repositioned to its initial location (<R>), or simply left where it is. In both cases the location may be obtained through the !!V system variable.

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DigImage User Documentation

Stuart Dalziel, last page update: 19 February 1996