Blank Purple Screen When Capturing Webcam from VirtualDub

[aesthetic]

Hi guys,

I have tried many webcam software that horribly lag soon as you hit the record button for resolutions above 1090x1080. But then I found the wonderful program named "VirtualDub". I have currently set my webcam resolution to 2304x1296 and its running very smooth but then when i click on record/capture button it stlll starts to lag.

So I came up with an idea to use a separate screen capture software to capture the webcam motion in virtualdub without compromising it by hitting record. For example I open up virtualdub and run the webcam and then I open Camtasia and begin screen capture to catch the webcam.

I have been trying many screen capture programs but they all fail to catch the virtualdub's webcam screen. During the recording I can see the webcam is working fine but its after I go back to watch the recoded file I find it is blank. The capture software successful records everything on the desktop and even the window from of virtual dub but everything inside the webcam frame is just appearing as a blank solid purple screen.

What is causing this and how to fix it? Thanks

[jagabo]

Just use a faster codec for capturing in VirtualDub.

The screen capture method isn't working because the video you see on the monitor is not on the Desktop. VirtualDub creates a hole in the Desktop and the graphics card displays the video in that hole -- but only on the monitor. Screen capture software just sees the hole. I'm not sure, but you might be able to capture the video rather than the hole by turning off Video -> Overlay, and turning on Video -> Preview.

[aesthetic]

jagabo,

You sir are a genius. I tried what you suggested and changed it from "overlay" to "preview" and it WORKED !

THANK YOU SO MUCH!

[aesthetic]

jagabo, you seem to have a lot of knowledge on this topic so if you don't mind there are a few more question I would like to ask you.

I noticed that once I changed over to the "preview" option the picture quality became worse and every time there is movement the screen flickers and some screen tearing lines occur. I managed to find the problem was occurring from an option that was ticked under the category:

Video -> Preview acceleration -> Interlaced - frames

Turning off the option fixed it immediately and the webcam screen became excellent quality again, however turning the "Preview acceleration" off has once again caused the same original problem where the screen capture is failing to see the active webcam.

There is always a catch to everything that happens to me in life

I realize I need to enable the "Preview acceleration" to resolve the issue however there are 8 different option in there, ranging from:

Progressive...
Interlaced...
Non-Interlaced...

Which one should I select? I am also considering your initial advice to "Just use a faster codec for capturing in VirtualDub." I also noticed major problem with audio being way out of sync when I use compression.

I was currently using the "x264vfw codec". Which codec would you recommend? Keep in mind though that my computer is very old and outdated. I only have:

4GB of ram,
Nvidia GeForce GTS250,
Intel DuoCore E6750 2.66Ghz

So based on those poor specs which codec is best suitable for my slow PC?

[jagabo]

Webcams typically are progressive -- so for Preview Acceleration select Progressive Both Fields. I think that will use least CPU cycles and give the best quality.

x264vfw is too slow unless you use ultrafast settings. Try huffyuv (fast, lossless, not much compression). Another very fast codec is PicVideo MJPEG (I don't know if they support very large frame sizes though). That one has different quality settings so you can specify low quality (lots of compression) to high quality (not much compression) with about 20 steps between them. With your 2304x1296 frame size disk I/O might be a problem if you don't compress enough.