Author Topic: Critical! AVAST (and AVG) are stopping video streams from local USB cameras  (Read 19710 times)

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Offline chris..

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port COM device , port USB device , More than one Network card and/or devices (NAS , Tuner TV , particular cam or alarm)
Already a lot of problems encountered with the web shield of the latest version of avast
Pending that avast restore order in all that, it seems that they proposed a version beta  ???

It almost looks like the web shield functions as a (failing) firewall
« Last Edit: May 04, 2017, 10:51:32 PM by chris05 »


  • Guest
We have the same issue on our customer's PC.
- It was reported on Windows7 (WIndows update enabled) with a Logitech C310 and a Sweex webcam
- Today I tested it with a newly installed Avast Free with default settings
- The issue can be reproduced with the old AmCap.exe from the Windows DirectX9 samples (I can't find exe on the net, its size is 6963 bytes and the timestamp is 2001.11.05)
  The preview doesn't appear, and displays a dialog with error code 0.
- But the most recent AmCap demo version works well: ""
- The Delphi Jedi JvAviCapDemo that uses AviCap32.dll also produces the error: ""
  With Avast installed, the preview screen will be green.
- I tried to disable all protection from Avast popup menu, but it doesn' solve the problem.

So I recommend to our customers to uninstall Avast.


  • Guest
I have the same problem.  I'm a developer of  two programs for webcam control:

    Splitcam -
    KVYcam -

These programs are used thousands of users and have a digital sign - OMT-LIDER, TOV.
Since April I have gotten many complaints from my users with one issue: Avast blocks a webcams access for my programs. Why?,  before we didn't have any problems with  Avast!
I produced that situation and tested  the Avast Free Antivirus 17.4.2294 (build 17.4.3482.0,   virus version 170505-2) in our lab. My users were right - the problem in Avast.
You can test my programs in your lab too.  These programs are free for usage and can be gotten by using those URLs, see above.


  • Guest
We got same issue, I am Sr. Tech Support for Video Relay Service company for deaf and hard of hearing users, we got several reports from our clients about local screen being not displayed with our videophone application since last week. We are encouraging our clients to uninstall Avast or enable Passive mode.

For Windows 10 only, interesting part is after uninstalled KB4015217 under Windows Updates and this resolve our local screen issue.


  • Guest
FYI, OBS users are experiencing the same blocks on their video software.

Lets snowball this to get some attention.


  • Guest
Hi there, I am the author of the OBS Project, an open source video compositing/capturing/streaming/recording tool with a few million users.

The other day, I released (or was going to release) a new update for my software, version 18.0.2.  When I sent out the update, webcams and capture devices mysteriously stopped working completely for everyone on Avast and AVG.  After a lot of debugging, I determined that my new executable would cause Avast to block webcams and video devices completely.  If I moved my old 18.0.1 executable back over that version, they would start working again.  I did have to renew my code signing certificate with 18.0.2, so that may have triggered Avast/AVG to block them prematurely.  I had to turn off my auto-update and roll back to 18.0.1 for my users.

"Disable for one hour" does not work (edit: apparently passive mode does?) -- but I don't care about disable/passive mode so much, this feature or bug really needs to be fixed or removed from Avast/AVG.

If Avast/AVG blocking video devices is a bug, this needs to be fixed ASAP because I am unable to make updates to my software while this is happening, and clearly it's affecting medical software as well.

If Avast/AVG are now by design intentionally blocking webcams and video devices of non-whitelisted code certs or (even worse) non-whitelisted executable hashes, then this is a very poor design decision that is going to cause a lot of problems for a lot of people and have major unintended consequences.  Medical software as described above are now at your mercy if they want to be functional on a computer with Avast/AVG installed.  Again this is an extremely poor design decision.  Please, we beg of you, revert this change and stop trying to block video devices if this is the case.  It invokes very strong emotions with me.

Right now I am waiting for whitelisting in the mean time, but currently have had no response.  We've tried several avenues to try to get in contact and explain the problem with no feedback.  Please I beg of you -- fix this problem.  Do not do this.

Please, I beg of you, have mercy on those of us and your users whose livelihoods are so heavily dependent on video capture devices functioning properly.  Stop blocking video capture devices.
« Last Edit: May 07, 2017, 04:17:20 AM by Jim (OBS Project) »


  • Guest
Jim from OBS, thank you for your support in this matter! Note that the AVG forums are beginning to get more posts regarding the issue:


  • Guest
My users found how to resolved this problem:

Hi Viktor

Yep, uninstalling Avast fixed the problem. In a way I'm glad that it turned out to be that simple. If I'd had to go back to a restore point, I would have had to re-install a lot of software.

Thanks very much

What do i must tell  my users?


  • Guest
Official answer of AVG: Temporarily to run AVG in the Passive mode.

This is true and for Avast too. For run in the Passive mode you need make the following operations:

1. Call the Avast control window
2. Run Settings
3. Click on Troubleshooting
4. Find the Passive mode and turn on it
5. Restart PC.

Offline igor

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Would you have download links for the affected software (other than the three mentioned on this page)?


  • Guest
Would you have download links for the affected software (other than the three mentioned on this page)?

Hi there Igor, here you go:

That's our 18.0.2 version.  Just as a note, for 18.0.2 we have a new recently-renewed code signing certificate on the executables and installer.  I apologize if I got a bit heated.  This situation is just really stressful for me at the moment.  I would really prefer it if webcams are not being blocked by anti-virus software.  I hope it's a bug and not intentional.  I really need this situation resolved for my users because as of right now I cannot release new versions of my software without major problems for my users.

Thank you for responding, I really appreciate it.

(EDIT: oh I apologize if you weren't referring to my software, I'm just really frustrated and hope this situation gets resolved)
« Last Edit: May 06, 2017, 10:31:05 PM by Jim (OBS Project) »


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OmniJoin is one of the programs that have been blocked by this. I believe you can get a 14-day trial of OmniJoin v7 here:

Offline pk

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It seems there was a problem with some webcam apps which avast could block. This will be fixed with a VPS update on Tuesday. It didn't affect well-known webcam apps (Skype, ...), but only new/uncommon webcam apps, this was caused by a bug in our rating system.
« Last Edit: May 07, 2017, 05:58:46 PM by igor »


  • Guest
The issue is caused by the exe displaying the video not being signed. I downloaded a shareware AmCap from here
As installed, it works.

I used the Reshacker (resource editor) to remove the version information resource from amcap.exe which invalidated the signature. After that, it stopped working if AVAST is enabled and works if Avast is in Passive mode.


  • Guest
I also have this problem but with a BlackGold BGT3620 TV card rather than a webcam. I use a program called DV Scheduler which suddenly stopped recording. The TV card tunes a frequency but does not output any data.

I tried to use the TV Card with some other software, some work and some have the same issue. Eg. MPC-HC ( works fine but Mediaportal ( does not.

Uninstalling AVAST fixes the issue completely.