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Switched Video through Asterisk

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N2MH's picture
Switched Video through Asterisk

Tim, N8NQH, was kind enough to lend me a Grandstream GXV3240 phone a few days ago. This is a nice phone and with it I was able to do normal pbx extension to extension voice calling. I was also able to do direct IP to IP video calling. Both types of calls worked ok.

Now that the holiday weekend is over and people are not out at barbecues forgetting about Mesh, I was able place a video call through my Asterisk switch to Tom, K1KY over the Mesh. Overall, the experience was enlightening! Voice quality and video quality was good. However, it seems that a really high quality link, even higher than needed for a voice call, is essential to sustain this kind of a call. I'm guessing that end to end link qualities need to be in the 90's for good results.

One thing left to try is voice mail, or should I call it, video mail. I think that with this setup, if a call gets unanswered and goes to voicemail, it might actually be video voice mail. In addition to the normal voice message, the video stream will be recorded also and be able to be retrieved by the person called. Stay tuned on this aspect as it has not been tried or tested yet.

Setting up asterisk was easier than I thought. There is much information about this on the 'Net. In sip.conf, in the


section you have to add a statement



In addition, you have to allow one video codec, again in the




(in this case)

Other codecs are available, but my version of asterisk does a poor job of negotiating them at call setup time. Finally, for each of the phones that will need video support, you have to do the same


statement (or put it in the template if you use templates).

73, Mark, N2MH


N8NQH's picture
info link

Here are  some details about this GXV3240 device:

and the GXP1630 model:

N2MH's picture
Video Mail

Video Mail, Video VoiceMail, (is there a proper name for this?) does work. I have successfully left messages for other videophone users and they have been able to retrieve those messages as video in addition to audio. The only quirk noticed is that the video only starts up a few seconds into the message and not right up front with the audio. Thus,  a quick message such as "Joe, please call me back" will only have an audio component. And, I guess for a short message like that, nothing more is needed. However, for longer messages, one must know about the delay and work with it when leaving a message.

N2MH's picture
Asterisk Loopback Feature - Video usage

Asterisk has a loopback feature to which one can assign an extension number. Normally, one calls this extension to guage his round trip delay to the pbx and back. Thus, when you speak into the loopback, you hear yourself come back a short time later.

This feature also works for video calls. You place a video call to this extension and you get to see what video your phone puts out. As noted in the comments about Video Voice Mail, there is a short delay for the video to appear. The voice starts looping immediately.

I noticed an interesting thing when I tried this. When using the GXV3240 phone, the screen is broken up into several sections. The left and largest section is the video coming in from the person to whom you are speaking. On the right, there is a smaller section that previews your image so that you can position yourself correctly in the camera, adjust lighting, and generally make yourself visible to the other end. When I called the loopback extension, my image came up on the left but was slightly different than the right (preview) image (and not just for the time delay). It turns out that the preview image is a mirror image of what the local camera sees and the larger image is exactly what the local camera sees.

Thus, for the purpose of adjusting your outgoing image, the preview works like a mirror on the wall. For example, if you move your hand to the right, the preview will also show you moving your hand in the same direction, just like a mirror. The loopback image shows you moving your hand to the left! Thus, the image on the left is what actually comes out of the camera, not a processed preview image.

This may seem strange, but think about it. If you are facing someone and having a conversation, if that person moves his hand to his right, you will observe him moving his hand to your left. This is exactly what you see coming in from the other end of the conversation. On the other hand (no pun intended) if you saw your actual image as sent to the other end in your preview screen, you would be very confused about positioning yourself in the camera and most likely would give up. By making it a mirror image, you are now doing something you have always done, looking in a mirror. And, seeing and positioning oneself in a mirror is second nature to everyone.

GXV3500 and AllStarLink
Since these should be asterisk-comparible, I wonder if anyone has had success?
N2MH's picture
Interesting Device

I found this description of the device on the Grandstream web site:

The GXV3500 is an IP video encoder and decoder that uniquely features a built-in public announcement system to offer a 3-in-1 combination device. The device decodes IP video streams to analog video in order to allow IP cameras to be used on an analog network and encodes analog video to allow analog cameras to be used in an IP network. Like all Grandstream IP Video Surveillance products, the GXV3500 is OnVIF compliant and includes built-in PoE.

With regard to compatibility with AllStarLink, you can't obviously pass video to or from an attached analog voice radio device.

However, with regard to using AllStarLink as a pbx and switching video calls, it appears that this device might work. The device supports H.264 and sip. And, so does the pbx. This is exactly what I am doing with the GXV3240 phones.

- The phones run the H.264 video codec.
- The pbx supports H.264
- The phones run sip and register OK with the PBX
- My pbx in this case is actually a "public" AllStar node with extra config files to turn it into a pbx along with keeping the AllStar functionality. I'm running the Acid distro from a few years ago on a pc.

As a plain sip phone, yes, it can be used to access an analog voice radio device through the AllStar app_rpt code. I'm not sure how the public address feature of this device would work (if at all).

I have also configured the WA3DSP/KB4FXC AllStar image for a Beagle-Bone Black to be both a pbx as well as an AllStar node (private node in this case) interconnected with my main, public AllStar node/PBX. I have not tested switched video on the Beagle-Bone device however. Voice works OK. I would expect the same results for Doug and Dave's raspberry pi 2 image.





K7OPA's picture
asterisk version
Mark - in your first post you mention 'my version of Asterisk'.  Which version are you using and why?
I have found install instructions for the older version (including a good youtube video) but no specific instructions for the newest version provided on the Asterisk-Pi site for configuring after install.

The pbx 'thing' is all Greek to me and while I have been successful in installing the older and new version it is the configuring that is unclear, especially in the new version.  I am unable to set up the phones - perhaps unclear with the terminology used.

tx, Ron
N2MH's picture
re: asterisk version


My version of asterisk is asterisk-1.4.23pre which is part of the AllStar Link "acid" distro from a few years ago. I installed it orginally as the software needed to participate in the AllStar Link network. I studied asterisk in the meantime and added config files which added conventional pbx functionality and support for telephones and trunking. I didn't pick this version - it was already there and usable for me.

I mentioned "my version" to try to differentiate it from the FreePBX verison of asterisk which is prevalent today. Configuring the old and new versions is not too difficult if you are running "raw" asterisk. Many commands are similar between old and new. There are several books out there as well as a ton of information available on the Internet. But this is only for raw asterisk.

FreePBX is what I would consider "non-raw" or "cooked" asterisk in that all configuration goes through a gui which actually manipulates an sql database which then eventually writes the actual asterisk config files. FreePBX is not very well documented and is heavily influenced by what someone thinks a pbx should be. This is not always what you or I would like it to be. It appears to try to be everything to everybody and in doing so, it is bloatware. So, if this is what you refer to, I can understand.

Also, FreePBX has its own terminology which may not be the same as raw asterisk or to terminology conventionally used by the voice telecomms business.

If you would like some further support, we can take this offline and go from there and address your concerns.


K7OPA's picture
Mark - thanks for this reply.
Mark - thanks for this reply.  Yes I have the FreePBX 'thing' I am trying to deal with.  Not being a command line person and since the Asterisk for Pi website bundles them together, I thought it would be easier - my mistake!
Let me know when you have time to discuss - shoot me an email at

73, Ron K7OPA

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