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About Menelaos Bakopoulos

Mr. Menelaos Bakopoulos is currently pursuing his PhD both at Center for TeleInFrastruktur (CTiF) at Aalborg University (AAU) in Denmark and Athens Information Technology (AIT) in Athens, Greece. He received a Master in Information Technology and Telecommunications Systems from Athens Information Technology and a B.Sc. in Computer Science & Management Information Systems from the American College of Thessaloniki. Since April 2008 he has been a member of the Multimedia, Knowledge, and Web Technologies Group.

Posts by Menelaos Bakopoulos:

Opening multiple VLC windows for different RTSP Streams from AXIS camera

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

Today I wanted to open asap 4 RTSP streams using VLC.
I ended up copying and pasting the following in the command prompt caused 4 background instances of VLC to appear and read from 4 different AXIS cameras.


"C:Program Files (x86)VideoLANVLCvlc.exe" -vvv "rtsp://username:password@IP_ADDRESS:PORT/axis-media/media.amp?videocodec=h264&resolution=768x576&compression=30&fps=10&textstring=cam1&text=1&textpos=1"&

"C:Program Files (x86)VideoLANVLCvlc.exe" -vvv "rtsp://username:password@IP_ADDRESS:PORT/axis-media/media.amp?videocodec=h264&resolution=768x576&compression=30&fps=10&textstring=cam2&text=2&textpos=1"&

"C:Program Files (x86)VideoLANVLCvlc.exe" -vvv "rtsp://username:password@IP_ADDRESS:PORT/axis-media/media.amp?videocodec=h264&resolution=768x576&compression=30&fps=10&textstring=cam3&text=3&textpos=1"&

"C:Program Files (x86)VideoLANVLCvlc.exe" -vvv "rtsp://username:password@IP_ADDRESS:PORT/axis-media/media.amp?videocodec=h264&resolution=768x576&compression=30&fps=10&textstring=cam4&text=4&textpos=1"&

echo done

Enjoy!

Calculating required upload bandwidth for Axis IP Camera

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.
SVGA_10FPS_StationWhat must someone consider for calculating required bandwidth for IP cameras?

It is not only resolution, but also FPS, the amount of activity (motion), and the compression level which determine the bandwidth required.

Obviously, when the frame doesn’t have so much traffic there is less data to transfer (due to the compression in H.264).
There is a very nice Axis Design tool which estimates bandwidth based on various scenario videos located at:
Within the tool you can select from various videos (“Scenario Combobox”) and view how the bandwidth requirements change based on the activity.
The train station is the extreme example with movement everywhere.The amount of activity within the video makes a tremendous difference as well as the compression, so you need to test reading at multiple compression to see what is acceptable 
in order to not undermine results especially if you are using video analytics software

Also, instead of viewing using RTSP over HTTP it is optimal to view through VLC and RTSP using the axis rtsp api.
The API is available at:  ( http://www.axis.com/files/manuals/RTSP_API_2_01.pdf – page  PDF 14 – parameter specification ) and specifies options to build URLs such as:
rtsp://IP:PORT/axis-media/media.amp?videocodec=h264&resolution=768×576&compression=10

 

XDebug in XAMPP and Netbeans

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

Having written a lot of PHP code for a project using Notepad++, I got tired with the limitations of not having an IDE containing a debugger, and refactoring tools.

Quick post mostly for myself to have a reference on how to setup XDEBUG (which was quite easy using XAMPP).
If you don’t want to go the long road download the full version of XAMPP here 🙂

1) First off as the DLL is already located it does not need to be downloaded.
2) Open php.ini and make the following edits:

A) Uncomment the line zend_extension = “Somethingphp_xdebug.dll”
B) Uncomment the variables and set them as specified by netbeans …
More

2012 in review

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

The WordPress.com stats helper monkeys prepared a 2012 annual report for this blog.

Here’s an excerpt:

600 people reached the top of Mt. Everest in 2012. This blog got about 3,800 views in 2012. If every person who reached the top of Mt. Everest viewed this blog, it would have taken 6 years to get that many views.

Click here to see the complete report.

Running Java on Fujitsu Q700 NAS Server

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

NAS+JavaSmall post how I got java to work on Q700 NAS Server.
If you check the Datasheet for the server ( here ), you will see the Processor is a  Marvell 6281 1.2 GHz  . Essentially, this is a ARM 5 processor.
Based on some instructions from here , I navigated to http://www.oracle.com/technetwork/java/javase/downloads/embedded-jsp-135769.html ,
and downloaded the version ARMv5 Linux – Headless EABI, SoftFP, Little Endian2 .

All that remained was untar-ing the content onto the NAS, and executing  java – version.
JavaEmbedded

How to move “Virtualbox VMs” files

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

I came across a situation where my VMs were taking too much space from my C drive. The instructions below are from the forum post here.

“The most common I found is to remove your VMs from the manager without deleting the files. “Remove the VMs from the manager without deleting the files. You can then move the entire VM folder (not just the bare VDIs) to a new location, before adding them back to the manager.”

Here’s how I did it… Use these instructions at your own risks ;-)

More

Easily validating your Varnish cache VCL file and other quick tips

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

I’ve been playing around with varnish lately and had to make a change in a VLC file to perform URL re-writing before following with “hashing”, lookup, and if necessary forwarding to tomcat.
For anyone wanting further information on the varnish pipeline, as well as why someone should use varnish I recommend the following two articles:

1) http://open.blogs.nytimes.com/2010/09/15/using-varnish-so-news-doesnt-break-your-server/?smid=tw-share
2) https://www.varnish-software.com/static/book/VCL_Basics.html

More

Dealing with FFMPEG Error while opening codec for output stream…

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

Quick post about the ffmpeg error message: “Error while opening codec for output stream #0.0 – maybe incorrect parameters such as bit_rate, rate, width or height” .

We received some video files from a partner in the Safecity project, which did not play in all media players.
We tried VLC, windows media player, and a variety of other players but nothing worked.

Checking the file with a hex editor, I saw there was data within the video, and thought to try converting with FFMPEG using commands such as:

ffmpeg -i “damaged_file.avi” converted_file.mp4

However, ffmpeg  failed with the following error message:

Error while opening codec for output stream #0.0 – maybe incorrect parameters such as bit_rate, rate, width or height

More

Logging in VLC 2.0.3 not working in Windows 7 and Fix

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

Working on a project, I noticed that I could not access the VLC 2.0.3 log (or even see it).

I had followed the instructions related to the Tools>Messages dialog, and changed the Verbosity level to enable the logging but it was not working.

After some thought I realized that as these configurations are stored as files within the VLC program files folder.

VLC must be run as administrator for the logging to actually work due to the windows 7 security restrictions.

Google hiding search parameters in referer address

This specific content was written 9 years ago. Please keep this in mind as it may be outdated and not adhering to best-practices.

Greetings,

While checking my statscounter/analytics today and noticed that the number of links starting with the following had increased:
www.google.gr/url?sa=t&rct=j
OR
www.google.com/url?sa=t&rct=j

What I don’t like with these links is that I can no longer know what search was used to land the users on my page, in order to be able to tweek my SEO, and know what content is more demanded.

Reading a bit more about this I found out its’ google’s new policy to hide the search parameters for users privacy – Ok I can understand that.

There is however the opinion that this data is for sale if your an advertiser who is paying them (I have not confirmed this).

More information on this from designer Tim Minor in his blog post: Deconstructing Google url search parameters .