Created attachment 78277 [details]
gabble log from ktp-debugger

Created attachment 78278 [details]
google-talkplugin log

P.S: After G+ said that the call failed, ktp-call-ui still says it is connecting -- apparently not realising that the other end gave up.

I tried a few more combinations.

1) Desktop+KTp -> Laptop+Google fails - that is what I previously posted about.
2) Laptop+Google -> Desktop+KTp fails - KTp does not even show an incomming call.

3) Desktop+Google -> Laptop+Empathy fails - Empathy shows no incomming call.
4) Laptop+Empathy -> Desktop+Google fails - the call is established, but both ends appear to receive nothing at all (they show a placeholder image), while their previews are fine.

5) Desktop+KTp -> Laptop+Empathy fails - KTp does not allow a video call (greyed out), while Empathy would allow one (see 6).
6) Laptop+Empathy -> Desktop+KTp works.

google-talkplugin is at version 3.15.2.0 on both machines. Empathy on the Laptop is at 3.4.2.3 (Ubuntu 12.04 / Bodhi Linux).

KTp was generally using an account on my own server running ejabberd-2.1.11, while G+ or Empathy were using the Google account.

media-plugins/gst-plugins-ffmpeg-0.10.13_p201211(0.10)(20:18:56 23/02/13)(orc)
media-libs/gst-plugins-ugly-0.10.19(0.10)(23:43:41 03/12/12)(nls orc)

If you need versions and compilation options of other software to debug this, please let me know.

My next test will use the following software.

Software on Laptop:
* google-talkplugin-3.17.0.0
* empathy-3.4.2.3-0ubuntu1
* telepathy-gabble-0.16.0-0ubuntu2
* libtelepathy-farstream2-0.4.0-0ubuntu1
* libgstreamer0.10-0-0.10.36-1ubuntu1
* gstreamer0.10-plugins-ffmpeg-0.10.13-1
* gstreamer0.10-plugins-bad-0.10.22.3-2ubuntu2.2
* gstreamer0.10-plugins-bad-multiverse-0.10.21-1
* gstreamer0.10-plugins-ugly-0.10.18.3-1ubuntu1

Software on Desktop:
* google-talkplugin-3.16.0.0
* ktp-call-ui-0.6.0(4)[1](20:38:39 04/04/13)(v4l -aqua -debug LINGUAS=...)
* telepathy-qt-0.9.3(00:09:01 13/01/13)(farstream -debug -farsight -test)
* telepathy-gabble-0.16.4(00:00:34 11/02/13)(jingle -gnutls -test)
* telepathy-farstream-0.4.0(22:57:49 12/01/13)(-examples -python)
* net-libs/farstream-0.1.2-r1(0.1)^t(20:13:00 30/03/13)(introspection upnp -msn -python -test)
* gstreamer-0.10.36(0.10)(23:34:51 03/12/12)(introspection nls orc -test)
* qt-gstreamer-0.10.2(23:19:54 29/07/12)(-test)
* media-plugins/gst-plugins-ffmpeg-0.10.13_p201211(0.10)(20:18:56 23/02/13)(orc)
* media-libs/gst-plugins-bad-0.10.23-r1(0.10)(12:39:15 08/12/12)(nls orc)
* media-libs/gst-plugins-ugly-0.10.19(0.10)(23:43:41 03/12/12)(nls orc)
Format is: ...-$version($slot)[$overlay]($build_date)($useflags)

1) Laptop/G+ -> Desktop/KTp: fails -- G+ plays ringtone, but KTp shows no reaction whatsoever
2) Desktop/KTp -> Laptop/G+: fails -- G+ plays ringtone for a split second, but then shows an error message: "Der Video-Chat mit ... ist aufgrund eines Serverproblems um ... fehlgeschlagen" (video chat failed due to a server problem), while KTp still shows "Verbindung wird aufgebaut" (connecting) without any error message

3) Laptop/Empathy -> Desktop/KTp: works partly -- Empathy shows fluid preview of myself and view of the other person, but KTp shows only a fluid preview and the view of the other person got "stuck" on a still image right after connection -- after closing the window in Empathy, KTp does not notice that the other side hung up and still claims "es wird gesprochen" (someone is talking) -- even closing the video call window does not work but instead brings up the kwin program killer
4) Desktop/KTp -> Laptop/Empathy: works -- both show preview and view and neither gets stuck as before. (Though this is apparently too much for my Laptop's CPU...) -- this time KTp even realises that Empathy hung up, even though the message is misleading and has a typo: "Verbindung getrennt: Die Gegenstelle hat den Anruf angelehnt." (disconnected: peer has rejected the call)
5) Laptop/Empathy -> Desktop/KTp repeated: works -- unable to reproduce the problem in (3) -- both sides show preview and view and do not get stuck

(In reply to comment #8)
P.S: Both machines (Laptop and Desktop) were on the same network. This might or might not explain why it fails with G+ -- depending on how it is implemented on Google's side, there might or might not be my firewall in between.

I tested again with rdieter, who is neither firewalled nor NATed. He was using KTp 0.6.0.

1) rdieter/KTp -> Desktop/KTp: works partly -- he saw my video and we could hear each other, but I saw no video of him (just black - apparently there was a video being transmitted, but it was black)
2) Desktop/KTp -> rdieter/KTp: works partly -- neither of us saw a video of the other (for me it his video was black like before), but I could hear him, while he could not hear me

(In reply to comment #10)
> I tested again with rdieter, who is neither firewalled nor NATed. He was
> using KTp 0.6.0.
P.S: This obviously does relate only partially to this bugreport, which is primarily about G+/GoogleTalkPlugin

(In reply to comment #10)
rdieter had his webcam open in another application, so we tried again without that.

It turns out that Desktop/KTp -> rdieter/KTp works now, too. (We did not try the other way round due to time constraints.)

So basically what is still broken (but completely) is KTp <-> GoogleTalkPlugin.

As it was recommended by alin_ on IRC to try not G+/GoogleTalkPlugin <-> KTp, but GMail/GoogleTalkPlugin <-> KTp, I did that:
1) Laptop/GMail -> Desktop/KTp: fails -- KTp does not even show that someone is calling
2) Desktop/KTp -> Laptop/GMail: fails -- KTp still thinks the connection is being established, while GMail already aborted with a serverproblem error message

So all the same as it was with G+. Please also note that I did not use the G+ Hangout feature, but the plain old Video Call.

Google is going to deprecate GTalk in favor of Hangouts, which have no public API (yet). Also our Call UI desperately needs a maintainer and a port to GStreamer 1.0.

Given these facts, I don't see this bug getting fixed, sorry.