Amiga Video Toaster / Flyer FAQs
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      Why Should the A/V Drives be Short-Stroked?

Product: Flyer

Platforms: 2000 3000 3000T 4000 4000T

In order to perform A/B roll edits when clips which are adjacent in a sequence reside on the same video drive, A/V temp headers from one of the video clips must be copied to a drive on the opposite video drive chain. If drives have not been tested and short-stroked, then the temp files may be writing to an area that does not actually support the playback speed needed for the given temp file. This is especially the case when the clips are in HQ5 mode, as opposed to Standard mode.

The reason for this is that the temp files are always copied to the innermost available tracks of the target drive, so as not to interfere with recording new material to the drives, which are recorded from the outermost (fastest) tracks working inward. The innermost tracks are the slowest tracks, and if these inner tracks transfer data below the required speed for playback of a given clip, then the sequence will fail, exhibiting stuttering or dropouts.

The need to short-stroke can be worked around to some extent by alternating the clips which are used in a sequence between the two video drives. No header is needed if each successive clip is on the opposite drive to the clip which preceeded it. However, the user would still need to avoid filling the drives past the point where the tracks are fast enough to play back the clips. That still requires testing the drive, and leaving the portion of the drive unable to sustain the required transfer rate unused. At that point, you might as well short-stroke the drives.

Update, 6-21-2001: This issue is moot with the newest generation of drives on the market, which have sustain rates even on their slowest tracks that far exceed the Flyer's requirements. Modern drives also typically have RAM buffers several times the size that drives had when the Flyer was first issued, which means that time-out functions such as thermal recalibration now have virtually no chance of affecting data delivery. However, it is still wisest to test a new drive when mounting it, in order give the drive a little burn-in exercise right at the start just to make sure it is good.