Entries for month: September 2014

No webcam Image on USB webcam for Ubuntu 14.04

I have been doing google hangouts more for work, and most folks who use Google hangouts also have a webcam setup so you can see the person you're speaking with. This is useful because as most communicators know, so much communication is non-verbal. It's helpful to have an image of the person you're talking to.

webcamI have just recently changed out my PC case and motherboard for an older server board. The server board, while being slower on the MGhz and RAM speeds, had a lot more CPU cores and RAM amount. On my previous PC, running an older version of Ubuntu (13.04), my USB webcam worked flawlessly. However, on this "newer" PC, my webcam no longer works. First my USB camera didn't even register. I had to unplug it and replug it in for it to register at all. IE: nothing was showing up when I entered the following:

ls /dev/video*

As soon as I unplugged and replugged in the USB video camera, I would get a device here, but when I started up "cheese" (a cam viewer for Linux), I got nothing but a black screen. What was going on?

Looking up some articles on debugging Ubuntu camera issues, I happened on an article that mentioned I try a camera app called "guvcview". I did, and when I ran it, I got the following error message over and over:

Could not grab image (select timeout): Resource temporarily unavailable

Mkay... why can't you grab an image if you see that I have a camera now?

Turns out, the bottom of the article that I found earlier had the answer:

"Some newer webcams produce high resolution images at 30fps. This is a lot of data. If your USB cable path is too long or convoluted, frames can drop causing flicker or no picture. If you find MJPG format mode produces less flicker than YUYV format mode, then this could be the case. Try plugging the webcam directly into the computer. Then try progressively reconnecting your extension cables or hubs to see how the picture changes. Check you don't have a low speed hub.

You may also see:

Could not grab image (select timeout): Resource temporarily unavailable

This could indicate the frame data not arriving down the long cable fast enough. Check also for cable kinks and tight loops, which like ethernet, cause delayed packets."

BINGO! Apparently my older server board only had the earliest USB ports, which means they are really, really slow. I tweaked with the settings on the "Video" tab in guvcview and was able to get a picture of some kind by dramatically lowering the resolution and camera output type. Unfortunately the camera is still barely usable. Couple that with the relatively low Ghz value of the CPU and slow RAM, I'm not so sure this old server board is worth being a desktop.

Methods to address a slow Tomcat/Railo startup

Recently my technicians and I encountered an issue with a hosting customer who had an interesting situation between two VPS Accounts that he owns. The first VPS had a relatively quick startup time (under a minute), and the second VPS had an extremely slow startup time (above 5 minutes). Both VM's were relatively similar, and both served a great number of sites. The following are the two options that corrected the issue:


Slow Railo/Tomcat Server

Option 1

Set property in TOMCAT_HOME/conf/catalina.properties:

org.apache.catalina.startup.ContextConfig.jarsToSkip=*.jar

This will turn off jar scanning during the Tomcat startup.

Option 2

Configure the number of concurrent threads for Tomcat to use to create new contexts by adding the "startStopThreads" attribute to the <engine> tag in the Tomcat server.xml file. The number of threads should not be higher the number of CPU cores available to your server or the threads might overlap and you probably won't get the speed boost you were hoping for.

 

Once these options were implemented, both servers started up in just a few seconds.

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