This submenu allows the specification of the basic timing parameters for the particle tracking process.
This option specifies the time, relative to the start of an experiment, at which the tracking process is to begin. Before starting the tracking process, the VTR should be synchronised with the start of the experiment. The tracking program would then reposition to tape to the required location before commencing tracking.
This option may be used to configure DigImage to track from a sequence of images recorded at a frame rate other than the standard video rate of 25 (PAL) or 30 (NTSC) frames per second.
This option is used to enable or disable the interlace filters. An interlace filter will generally be required if the velocities are sufficiently high that the two video fields which make up a single video frame register the particles at different locations. Note that the interlace filter will always be applied if single field sample spacing is requested.
This option specifies the speed of or inhibits the rewinding of the video tape in the background while the recently acquired sequence of frames is being processed. Under normal circumstances the rewinding should be enabled as this will significantly increase the throughput of the tracking.
This entry specifies the frequency at which the sequence of particle images, recorded on video tape, is to be sampled. The Sample spacing may be specified from every video field (1/50s or 1/60s, depending on the video system) up to a spacing of 10s. The sample frequency sets an upper bound on the velocity frequencies which may be resolved. During subsequent analysis (eg. with Trk2DVel), the particle velocities may be calculated over an arbitrary number of sample periods. Note that specification of a negative value for the sample spacing allows DigImage to track particles backwards through time.
This option allows the total (experimental) time the particles will be tracked for to be specified. The tracking will proceed for the desired period from some starting time, unless premature termination is requested, or an unrecoverable error occurs. The amount of storage required for the tracking process is determined by combination of this entry and [S Sample spacing]. For each frame sampled during the total tracking time, 80+6*nPart bytes are required, where nPart is the average number of particles in each sampled frame.
This option allows the images to be tracked to be acquired from video (the normal operation) or read from the hard disk.