I am looking for an open source Skype replacement that will work on Linux systems. I think that SIP-based services are the way to go. I set up 2 accounts on linphone.org and another on ekiga.net. I made a call between two Linphone users and between Ekiga and Linphone users using H264 codec. Results were pretty bad - audio was ok, but video was very laggy, with a delay up to a few seconds. I made these calls using two computers with Slackware installed, both in the same LAN, both on cable connection. As a softphone I picked linphone, mainly for its command line interface. I also tried Jitsy but the results were the same. On a contrary, Skype works ok in the same conditions - no HD video, but also no lag. I already used local SIP provider to call peers in my country including mobile phones for very low fees when abroad using Linphone and it worked very well. There is a potential in SIP. But for video calls I've always used Skype. Based on your experience, what SIP provider and software would you recommend to make free good qualiy video calls?

Software:
http://qutecom.org/
SIP providers:
http://snapvoip.blogspot.com/2013/01...ders-2013.html
Note that the SIP provider is very important, and I've found the quality to vary greatly with them.

Some other things you can do:
Latency is very important to VOIP, so you don't want packets to stall anywhere along the line, not at your firewall, router, or SIP provider.
Check your router settings and make sure SIP is fully allowed, and if it has quality of services settings put SIP on top. Also make sure to open the port used by your software, or add it to application settings.
Make sure your firewall is setup properly and allows the right ports for SIP and software.

I set up 2 accounts on iptel.org and called each other with Linphone on 2 computers in the same LAN connected by a cable. I had mixed results - video was ok only occassionaly, most of the time there was a lag and artficats. On my way to replace Skype with SIP I also tried several different providers: linphone.org, ekiga.net, sip2sip.info. I have never been able to make a good video call comparable to Skype.

I could not install qutecom program you recommended. When compiling it manually I got this error:

I tried to download rpm from their site but link is broken. After installing rpm downloaded from another source it turned out that my libboost is too old:

Of course I have ports open for SIP because I can use SIP services. I have a usual DSL cable modem connection, I have Netgear modem with OpenWRT installed. As I said, I can use Skype with no problems.

I would like to ask - what quality video call did you have with your provider and software? Was it nearly real-time talk like Skype, were there any artifacts, was it stable? I am looking for someone to say "Yes, this is possible with SIP, I did it, I will show you how I do" or "No, it's not possible with SIP yet, it's not ready yet, Skype is evil but it's better"

I used antisip for a while and although it wasn't as good as skype, it was close enough. The latency varies, I mean I used it to talk between US and Europe so latency was around 4-5 seconds but could be higher. skype had somewhat less latency like 3-4 seconds and the picture had less artifacts, but that's probably down to codecs and protocol.

skype is better unfortunately, but you can get close.

If you want to compile qutecom, you need these dependencies including ffmpeg:
http://qutecom.org/wiki/HowToBuildFromSource

Skype is a protocol/application that "just works" usually, SIP is NOT very reliable compared to it.
Thats the way it is - SIP is developed for telephony applications and it needs clear routing to work properly. It has some features "bolted on" later for NAT traversal, video etc. Yes, it does work over NAT, but not always - for example it works perfectly from your home, you go to another network and it doesnt work there.
Also, as previously noted, not all SIP providers are created equal. In addition to this, not all softphones wwork equally well.
I have tested most available soft phones out there (for use in an internal Asterisk server) and Linphone is one of the best. Ekiga doesnt really work well if you have more than 1 network interface (Same for Qutecom). Sflphone is ok, but i couldnt get it compiled with video support. KDE's Twinkle worked ok, but on GTK it has a very bad looking interface. Jitsi works well mostly with SIP, but in certain cases it didnt register incoming calls, probably because of a stricter SIP header inspection.

In conclusion, i wouldnt advise SIP as a replacement for Skype.

But there is the jabber/XMPP protocol - that was built on the same idea as Skype (audio/video over the internet), it has file transfer and whatnot. I use Jitsi with Google Talk (it uses XMPP too, at least for now) and coupled with the Opus wideband codec the call quality is just as Skype's. Bandwidth usage is very low too.
Additionally the video and audio is encrypted (optionally, default is on) between the endpoints (using zrtp, needs Jitsi on both sides), so the Google servers receive already encrypted data, making eavesdropping much harder. Optionally (default is off) you can use something similar (OTR) for text messaging too. This goes for any Jabber server (jit.si for example), not just Google Talk (which, i hear, is in process of stopping support for XMPP, so much for openness...).

Besides Jitsi, jabber/XMPP is supported by other messengers like Pidgin, Psi and some others i dont remember now. I use Jitsi because (besides supporting every protocol Pidgin can and SIP too) it has many options, wide built in codec range and permits codec selection/prioritization.

I need to check XMPP,maybe I will have more luck with video calls using this protocol. Do you use it yourself for video calls?

And do you also use it with video? Did you try other providers apart from Google Talk?

On a sidenote, a few days ago a new version of Linphone was released: http://lists.nongnu.org/archive/html.../msg00036.html. They now support HD video call. So that must means that video calls through SIP actually work well for them. Maybe it's intended to be used in LAN only. But, once I connected to my home router via VPN from a distance of a few thousand kilometres (Asia->Europe) and made a video call with another machine in the same LAN with Linphone. Sound quality was, as every time with SIP, very good but video was poor. I saw the other side clearly only sometimes but the other side said they just saw a big artifact all the time. And when either side made a movement, turned down or stood up, video quality dropped. Later we switched to Skype and when voice quality wasn't so perfect from what I remember video was so good that I even could detach my USB camera from my netbook, point it in different directions, point it at the window and walk around my hotel room and the other side saw everything well. I used VPN so it could be a partial reason of a bad quality but OTOH a good video quality on such a long distance is technically possible these days as shown with Skype.

But I really, really don't want to use Skype. I want something more open, something to learn and more fun to hack. SIP seems not good enough for long distance video calls. Maybe XMPP would be better as you suggested.

EDIT: I just found this: http://tox.im/. It's supposed to be a free as in freedom p2p replacement for Skype. Can be cool.

I think the VPN may have affected the quality. Also try to get a wired connection rather than wireless as it adds latency.

You should try XMPP, but I couldn't get it to work last time I tired.

I used wired connection both with Linphone over VPN and Skype. I found what difference in speed an ethernet cable can make after trying to stream HD videos from my OpenWRT router to LG Smart TV via Wifi in the other room - it was unwatchable, video stopped every few seconds. After connecting ethernen cable everything was going smoothly.

I use Google Hangouts for voip video calls. It works. The quality is far superior to Skype, which I abandoned long ago due to poor performance and quality.

Yes, video calls. But since i have low end crappy webcams on both sides, cant say much about it except Skype doesnt look better with them. Also, the video is mostly "lip synced", but this may vary with the used client/codec and network latency.
I use only Google Talk for now. I am lazy to search for something else but i have to do it anyways since Google is using that hangout thingie that isnt XMPP xompatible anymore and they are in process of dropping support...