Subject: Re: ISDN, Mbone gateway

From: Soghra Zamani <[email-masked]>
Date: Tue, 11 Feb 1997 12:08:59 +0000 (GMT)

Craig,

>If I understand correctly, then you are attempting to do the same thing
>we are.  You want to build a gatway from your ISDN based videoconferencing 
>system to the mbone.
>

Yes, This is exactly what we want to do at the moment. Our requirement
might change in the future to have a two way gateway between ISDN and the
Mbone. 

>It is easy if you are just trying to build a one-way feed from the ISDN 
>Codec to the mbone.   You just need to connect the video out on your codec 
>with the video in on any video capture card supported by the mbone tools and 
>the audio out to the line in on the workstation, and then run the mbone 
>tools on that workstation.

This sounds quite straight forward, thanks. This is the answer I was
looking for. Am I correct to assume that video and audio out of the codec
to the workstation is in the analog domain and therefore, no conversion
between different video and audio standards is necessary? Sorry if this 
sounds a very simple question. We don't have any videoconferencing 
devices yet as we are in the process of purchasing one.

Regards,

Soghra
 
>
>It is more difficult to get the mbone video feed back to the ISDN codec.
>This is what we want to do for our ISDN Video conferencing to mbone gateway.
>
>We had such a gateway working in test mode using a DEC 3000/300LX with
>two J300 cards.  The vic utility is capable of sending the mbone feed
>to the video out on the J300, so we connected the video out on the J300
>with the video in on our codec.  This provided the path from the mbone 
>back to the ISDN videoconferencing system.
>
>This gateway would work quite well for 5-10 minutes before the jv2driver 
>would leak enough memory to crash the system.  I asked Lance Berc from DEC, 
>who wrote the jv2driver, about this and he said that he is no longer making 
>improvements to the jv2driver since the recomended path was to use the 
>mmeserver instead of the jv2driver on DEC workstations.
>
>So we scraped the old gateway and are now attempting to build a new one
>using a DEC AlphaStation 255/233, with AV321 cards, and DEC's mmeserver.  
>
>The problem is that vic does not support the video out port on the
>AV321 card so instead we decided just to display the vic window on
>the screen and convert the screen to NTSC using a VGA to NTSC converter.
>This resulted in an image that we could feed back to the Codec, but
>we are not very happy with the quality of that image.
>
>If anyone on the list has any other ideas on how to get a better video 
>stream from the mbone I would welcome them.  Apparently, vic supports the 
>video out on one of the SGI frame capture cards, but from what I've heard, 
>the performance on the card is not very good.
>
>Craig Tenney
>[email-masked]
>
---------------------------
Soghra Zamani
e-mail: [email-masked]
Tel: +44 (0)171 753 3214
---------------------------

---

From: Craig Tenney <[email-masked]>
Date: Wed, 12 Feb 97 10:18:29 -0800

Soghra,

> devices yet as we are in the process of purchasing one.

First, I will admit that I am not an audio expert, but the codec we
are using has a audio line out which I plug into the audio line in on my
DEC AlphaStation.  You could have troubles if the codec only has 
a speaker out, and the workstation only has a mic in, then I think you 
would need something to do the conversion.

For video, I just plug the video out on the codec to the video in on the 
AV321 card on the DEC AlphaStation.

Craig Tenney
[email-masked]