View Full Version : Tearing and streaking in image

December 8, 2009, 05:10:05
We are testing a PC with 2 BT878 chipset video capture cards, there are 4 imaging crontrols on each tab, and when I load it up with 6 consumer digital video cameras the video image has tearing and streak lines with any movement.

Is this because the video capture card is not processing the raw video fast enough ?

We have set each camera YUV instead of RGB which has improved it a little,
and the cameras only expose 25 frames per second we can't reduce the frame rate.
We are only using the cameras to capture still images.

Any ideas ?

December 8, 2009, 05:44:55
The card is a PV-149 - 4 port video capture card
and we are using 2 in the same PC

December 8, 2009, 05:57:07
We have just done some more testing, when we still have 7 cameras connected to the video capture card, at 640 x 480 YUV2
but only preview 3 cameras in the imaging controls on one tab
there is no tearing, so is it the control not handling the previews ?

Stefan Geissler
December 8, 2009, 08:17:57

Please consider, the PCI bus has a limitation of data that can be transferred. If you get horizontal lines, that are not caused by interlacing effects, then the PCI bus bandwidth limit is achieved.

The control is handling as much previews as can be handled by the hardware. The maximum we tested were 12 FireWire cameras, 4 cameras per PCI FireWire board with external power supplies. All 12 images were displayed, but not at full frame rate. However, the bandwidth allocation of 640x480 UYVY at 25fps * 7 cameras is very high. You must calculate, whether your computer can handle this amount of data.

December 9, 2009, 00:34:16
Hi Stefan,

Do you know how we can reduce the Frame Rate.

Using the standard IcImagingControl1.ShowDeviceSettingsDialog()
the combobox only shows 25 fps

I also ran the Make Device Settings sample project, but the Frame Rate is
disabled with n/a

If I run Flash Media Encoder 2, there are frame rates available from 1.0 up to 60.0, why can't the ImagingControl see these available Frame Rates ?

DeviceFrameRateAvailable is returning False

Private Sub UpdateFrameRates()
If ImagingControl.DeviceFrameRateAvailable Then
Dim Item As Object

For Each Item In ImagingControl.DeviceFrameRates

cboFrameRate.SelectedItem = Str(ImagingControl.DeviceFrameRate)
cboFrameRate.Enabled = True
cboFrameRate.Enabled = False
cboFrameRate.SelectedIndex = 0
End If
End Sub

The command ImagingControl.DeviceFrameRate = CDbl(ComboBox1.Text) -- with say Combox1.Text = "10" does
not give an error although I am not sure it is having an effect on the Frame Rate.



Stefan Geissler
December 9, 2009, 09:48:45
Do you know how we can reduce the Frame Rate.

You can not reduce the frame rate, because it is determined by the video norm : PAL 25fps, NTSC 29.9 fps.

I guess, the Flash Media Encoder 2 frame rates are the play back frame rates saved in the AVI file, but not the frame rate of the grabber board.