Due to continual spamming, forum registrations are now by Invitation Only. Hopefully this will be only a temporary measure to combat spammers.

If you want an invitation contact forumapplication @ camstudio . org

Sorry for the inconvenience.

Interference with keyboard [EDIT] even if not [/EDIT] recording

Hi there and thank you for this great piece of software!!

Currently I'm testing CamStudio 2.6b r294 and 2.6c r303 recorder on my dual-monitor desktop PC running Windows 7 x64 SP1 and got ONLY ONE problem that anybody else couldn't have seen before because of my own particular, daily usage.

The screen recorder is very useful for my data-entry-based job, because I can keep track of all web-based form-filling, have an evidence of what I did, day by day, and have the opportunity to countercheck in case my boss says I have did some mistakes.

To speed-up the form-filling process I use some browser extensions and a couple of useful tools: a very good keyboard with programmable macro functions and an extended clipboard manager.

Since my work is made of hundreds copy+paste combos in a day, I have easily and repeatedly experienced lost keystrokes while CamStudio recorder is running: Windows didn't catch a lot of CTRL+C and CTRL+V and the consequence is that the extended clipboard (Ditto-CP) missed some clips.

So, even if CamStudio recorder is using a lightweight video compression codec, grabbing only 5 screenshots per second and taking approximately between 5% and 10% of my CPU resources, it seems to interfere with other programs based upon keyboard events.

I have also tried to disable ALL of the recorder keyboard shortcuts, but nothing changed.

Can you help me in any way?
Thank you in advance for your valuable support.


  • LanX,

    I've copied your post and will send it to the developers. This is unusual, as one wouldn't think that key-polling by the program would interfere with basic system key-polling like CTRL-C. Still, it is resource intensive while grabbing frames, and even at 5 frames per second is grabbing resources for each moment it is doing a capture.

    I'll let you know what comes out of this discussion - thanks!

  • You may give a shot to “PassThrough true;” in config file. There is no GUI option for this. It should be added into the same section where hotkeys are defined.

    This setting is read in HotKey.cpp and is respected in hook.cpp from hook folder.

    Though it doesn’t explain how some CTRL+Cs are caught. This is the only setting that allows for keyboard shortcuts to pass through camstudio to reach other applications as well. It is unlikely that this option will help, but there may be a bug. This setting helps if you want let’s say to have F11 as a hotkey and the same time want firefox to go fullscreen instead of F11 being eaten by camstudio only.
  • Thank you tbritton and mlt.

    I know that grabbing a dual-monitor desktop could be a resource intensive activity, especially if both monitors are working at 1280x1024 giving a whole area of 2560x1024 pixels... but I have a six-core CPU, 16GB DDR3 RAM and a really powerful graphic adapter, so I don't think this 5fps video grabbing applied to a low-resource demanding desktop activity like filling forms in a web browser could be that compromising for keyboard input stability.

    I also tried the trial version of a well known commercial product, and didn't encounter any keystroke loss or delay.

    Well... I'll try to apply mlt's suggestions and make some in-deep test, then I'll let you know the results asap!!

    Once again, thank you for your kind support.
  • @LanX

    Are you using some kind of automation as key firing loggers and scripts to ease your work. Maybe a keyboard buffer overflow occurred?
  • Ok guys... here is my test report after applying "PassThrough = true;" option to config file, just like suggested by mlt.

    I tried to work, as usual, with Ditto-CP extended clipboard and the driver-integrated macro support for my Microsoft Natural Ergonomic Keyboard 4000, and after many hours I have experienced only a few keystrokes lost somewhere in outer space, which normally happened even without a screen recorder running in background.

    No more hassles with a "C" letter appearing instead of a CTRL+C command which should have sent the selected text to the clipboard, no more "V" letters appearing instead of the clipboard content when pressing CTRL+V... that's simply fantastic!!

    Since I'm not interested at all in having Camstudio catching my keystrokes and not simply having a "passthrough" option, I would like to ask you if there's also a setting to completely exclude or disable such a feature.

    Keyboard buffer overflow??
    Why should this occur ONLY and exclusively if Camstudio is running and recording?
  • I made camstudio use low-level keyboard hook to be able to set arbitrary hot keys (e.g. key by itself). It may be somewhat related to that hook.
    6 cores are not of much help in my understanding.
    IIRC there are just 2 threads. 1 worker thread and GUI one. Also IIRC hooks are called by OS in yet another thread. So theoretically if hook code is fast enough nothing bad should happen.
    I'm busy (even besides dshow version:-) ) so I'm not sure if I can add an extra option entirely disable lowe-level keyboard hook. Though in my opinion it is better to see why it eats up keystrokes that are not hotkeys.
    P.S. If I don't reply for a long time, send a message to mailing list.
  • bummer... this forum ate angle brackets around word ctrl in "e.g. ctrl key by itself"
  • Whoooops... it seems I have believed in a miracle prematurely.

    Well, after longer and deeper testing I have found that:

    (1) this keystroke loss issue seems to become more and more frequent and persistent as the time passes and the video file size grows.

    (2) it seems to affect ONLY the "function" keys such as CTRL, ALT and SHIFT; but I'm only 100% sure about the CTRL key because is the most used during my sessions.

    Why so sure about this? Because I have carefully and closely monitored all of the combo-keystrokes typed during the last recording sessions, and I have clearly seen that the alphanumeric keys associated to CTRL+something combos always reached the foreground running application.
    Only the CTRL key, after hundreds of copy+paste, has not been properly catched with an increasing frequency depending on recording time.

    So, a wrongly catched copy command ALWAYS produced a "C" letter, just like a paste command ALWAYS made a "V" letter to appear on my forms.

    Hope this would help you in better addressing this issue and release a small fix.

    Thanks for your patience.

  • Took some few more days to see if CamStudio could interfere with keyboard even if simply loaded in memory but not recording, and... oh gosh...

    YES!! I have ran the recorder and minimized to tray and it have still eaten my keystrokes!!

    Well, at this point I think an option to completely disable hotkeys support should be almost mandatory... don't you?
Sign In or Register to comment.