Microsoft KB Archive/111974

= Microsoft Knowledge Base =

Video: Vertical Sync Error When Capturing Audio and Video
Last reviewed: November 22, 1994

Article ID: Q111974

The information in this article applies to:


 * Microsoft Video for Windows, versions 1.0, 1.1

SUMMARY
The VidCap utility that is provided with Video for Windows may give you the following error message when you attempt to capture video and audio:

No frames were captured; confirm that vertical sync interrupts are configured and enabled.

MORE INFORMATION
All existing capture drivers use the Vertical Sync (VSYNC) as an interrupt to determine when to capture a frame. (The Intel ActionMedia II card uses an interrupt on the i750 to trigger frame processing, so the motherboard does not see the interrupt directly; however, the outcome is basically the same). Therefore, if there is no VSYNC, no frames will be captured.

Below is a potential list of problems that can generate the Vertical Sync error:


 * 1) A jumper on the capture card may need to be installed to enable interrupts.
 * 2) The software interrupt setting (set by choosing Drivers from Control Panel and choosing Setup) does not match the hardware jumper setting.
 * 3) The selected interrupt may be in use by another device.
 * 4) The capture card may have difficulty generating internal video timing signals (VSYNC) if no video source is connected.
 * 5) The driver is out of date.
 * 6) The hardware is defective.