Re: [Ekiga-list] black video sent from ekiga on linux mint

[Alex Frase <atf3 psu edu>]

On 09/10/2013 10:58 AM, Eugen Dedu wrote:
> On 29/08/13 21:11, Alex Frase wrote:
> > Hi,
> >
> > (Apologies if this ends up posting twice; I sent it before subscribing
> > and it may have gotten lost in moderation)
> >
> > I'm trying to use Ekiga v4.0.1 on Linux Mint 15 (based on Ubuntu, based
> > on Debian) but can't seem to transmit video via h.323.
> >
> > I am able to connect to two different h.323 endpoints, and in both cases
> > I can see and hear the other side just fine, and they can hear me, but
> > they see only a black screen instead of the video from my side.
> >
> > I know that the camera works and Ekiga recognizes it, because I can see
> > my own video preview picture-in-picture. Skype also works just fine for
> > both audio and video in both directions.
> >
> > I can also successfully call the ekiga.net echo test
> > (sip:500 ekiga net), and I see my video echo (with a slight delay vs. my
> > local video picture-in-picture), so it seems to work okay via SIP. It's
> > just over h.323 that the other side does not receive my video.
> >
> > While connected via h.323, the call tooltip says "Codecs: PCMU - H264";
> > when I call the echo test via SIP, the tooltip instead says "Codecs:
> > PCMA - H261". I've tried disabling the H264 video codec, but then the
> > remote side reports not even seeing a black screen -- instead they just
> > see their own camera on the whole screen, as if no video signal is being
> > received by them whatsoever. When the H264 codec is enabled, then they
> > see their video picture-in-picture on top of a black screen. So perhaps
> > the problem is the H264 encoder producing only black frames?
>
> Sorry to answer so late.
>
> You wrote that you see video on your computer.  Do the others see their
> video too?  I ask this because a bug has recently been fixed about not
> seeing video on local computer.
>
> Do the other use ekiga too or not?
>
> So when you call them, nobody sees video, but see black as image, is
> that right?
>
> It is not an error to have H261 on sip echo test, and H264 with the
> others: very likely the others do not support (checked off) H261, hence
> the next one on the list (H264) is chosen.  If they check off H264 as
> well, then no common video codec is found: this is normal too.
>
> Finally, please send us/me a -d 4 log from your machine when you call
> and you see a black image.

A few clarifications first:

- I am testing with two call recipients: one uses a physical Polycom 
device and the other is a video bridge service which allows 3-way video 
calls, not sure what software/equipment is behind that

- on my end (Ekiga on Linux Mint) I see my own video, and I see remote 
video; I do not see any black image on my end

- on their end (Polycom device or video bridge service) they see their 
own video (and, via the bridge, eachothers video), but they do not see 
my video; they see black where my video should be

- when I disable H264 in the Ekiga preferences then I can call the 
Polycom using H261 video and it works correctly (they can see me), but 
the video bridge service does not support H261 so that workaround 
doesn't work there


However, this turns out to be a NAT/firewall problem and not a codec 
problem. I didn't mention that I'm behind a NAT because I had ruled that 
out previously, because a) putting my machine in my router's DMZ did 
*not* fix it, and b) changing the video codec to H261 instead of H264 
*did* fix it.

But apparently my router's DMZ does not do what I thought it did, and 
the choice of video codec affects the ports used during the call, 
because when I specifically forward all ports (1024-65535) to my local 
machine (in lieu of DMZ) then it works. However this also breaks almost 
all other network communication, not only for other machines on my local 
network, but even for the same machine which has all ports forwarded to 
it. Not sure why that is.

I had previously been forwarding only the ports listed in the Ekiga 
manual (1720, 3478-3479, 5000-5100, 30000-30010). That avoids 
interference with other applications and allows calls to be received by 
me, but the other end does not receive my H264 video.

What still puzzles me is that Ekiga on Windows on the same local network 
(a different machine behind the same NAT router) does not have this 
problem. I assume Windows must be doing something smarter about 
automatically configuring port forwarding (UPnP?) but I don't know how 
to configure Linux to do the same, or if it even can.

Any suggestions for negotiating the NAT for H264 video?

Thanks,
-alex