#>Video capture troubleshooter
{button ,ALink(trouble_cap_droppedframes)} I’m getting dropped frames during video capture.

{button ,ALink(trouble_cap_deviceabsent)} My capture device isn’t on the list.

{button ,ALink(trouble_cap_overlay)} I can’t get overlay working.

Video capture troubleshooter: dropped frames

Choose the option that best describes the problem.

{button ,ALink(trouble_cap_dropstart)} dropping frames immediately at start

{button ,ALink(trouble_cap_dropcont)} occasional dropped frames throughout capture

{button ,ALink(trouble_cap_droppoint)} frames being dropped at specific points in input video

Video capture troubleshooter: dropped frames at start
It’s not unusual to get one or two frames dropped at the start of the capture operation, to align the video to the audio track.  Usually this is the very first frame in the video, so no video data has been lost.  However, a large drop of 10 frames or more at the start could mean VirtualDub is having trouble starting the AVI file.  In this case, consider pre-allocating space through the Allocate option in the File menu, or enable the “wait for OK before starting capture” option in the Settings dialog.

Video capture troubleshooter: occasional dropped frames throughout capture

Try the capture operation using F7 (test capture).  This simulates the capture operation without writing data to disk.

{button ,ALink()} Frames are still being dropped.

{button ,ALink()} Few or no frames are being dropped.

Video capture troubleshooter: Source or device-based frame drops
If you 

Video capture troubleshooter: CPU or timing-based frame drops
Because test mode (F7) bypasses the disk, not dropping frames in Testing mode usually means your disk I/O system is not keeping up with the capture operation.  If you are using AVICap mode, try switching to
Internal mode.  If you are using Internal mode, check the Disk I/O settings.  Consider increasing the number of cache chunks to 4 and changing the cache chunk size.

This can also be a sign of excessive CPU usage.  If you are using video compression, reduce the load by switching to a faster codec or tweaking the quality and keyframe intervals.  Also, if you know how, check to see if bus mastering (DMA) is enabled on your capture drive.

Timing drops are rare but consistent.  Constantly drifting jitter and displacement values, shown in the status bar at the bottom of the window, indicate drifting video frame timing.  Subtly adjusting the frame rate until these values stay nearly constant should help.  If not, dropping one or two frames every few minutes is not a big concern.