What is required from the called party to make preview work ?

[crombeen]

Hi,

So we have Grandstream GXV3240 videophones and the R26C doorbell. We would really like to have the preview functionality working, but currently it only shows a black screen.

These Grandstream phones have a lot of video codec/protocol related options, and I don't know whether this preview feature is supposed to work with the Akuvox R26C, and how to make it work. I know you have 2 kinds of previews, one based on an image and one based on live video.

Can you elaborate what the Akuvox R26C supports, possibly with technical details to protocol standards so I can troubleshoot this at my end.

Thanks in advance.

[crombeen]

From the Grandstream videophone excellent documentation, I gathered this:

Enable Function for Incoming Call

Enables the preview feature for the incoming video calls. Defines the function for the incoming video call. If it is set to “Preview”, the phone system will pop up the PREVIEW key on the LCD screen when there is an incoming video call, and users could tap on it to check video caller without answering the incoming video call (the call will keep playing ringback on the caller side). The default setting is “None”.

Note: By pressing the preview button, the phone will send the SIP 183 message to the caller’s camera, based on SIP RFC3261; the caller’s camera should start then sending the stream to the phone. At any time, the GXV32xx user can press the "Answer" button. If done then the phone will send the SIP 200OK and call will be fully established.

So RFC3261 (SIP v2) is what we need for this.

[crombeen]

Let me also add I matched the H.264 settings for both the Grandstream GXV3240 and Akuvox R26C (wrt. Resolution, Bitrate and Payload).

The Grandstream videophone used a Payload Type of 99 while the Akuvox R26C used 105 IIRC. I tried using both on both sides. I also tried various bitrates and resolutions, both in sync, but I always get a black screen as preview.

Screenshot from 2018-04-26 18-05-28.png

Screenshot from 2018-04-26 18-06-28.png

[Akuvox_Terry]

Hello Crombeen

Just got a grandstream phone to confirm.
firstly, please help to confirm how to set preview on grandstream phone, it cannot be found on the phone.
secondly, as you wrote below, it seems it is not a standard preview protocol as ours, because we use RTSP to do video preview from outdoor station to indoor monitor. and if it is not a standard feature, we may call it private protocol, private protocol will not be widely used. if you need us to implement this customized feature, there may be some commercial condditions, please discuss with our sales first.

Thanks
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"By pressing the preview button, the phone will send the SIP 183 message to the caller’s camera, based on SIP RFC3261; the caller’s camera should start then sending the stream to the phone. At any time, the GXV32xx user can press the "Answer" button. If done then the phone will send the SIP 200OK and call will be fully established."

[crombeen]

Grandstream is not using a private protocol, and it works with other intercom systems.

You can enable preview in the phone's web interface, go to Advanced Settings, then select Call Features and then scroll down to Enable Function for Incoming Call. This needs to be set to Preview.

From that moment the phone will show the preview video as part of SIP 183 and SIP RFC3261.

[crombeen]

With the latest firmware preview is still not working together with the Grandstream GXV3240.

Can you please confirm that the Akuvox R26C supports SIP 183 messages and implements SIP RFC3261 ?

[Akuvox_Jon]

Hi sir，

Our R26C doesn't support SIP 183 messages, because we don't think it is the best way for video preview.

It can work as video preview, but that will cause some issues. Like the call actually is picked up during preview. This will affect our intercom features
like ring multi lines simultaneously.

I think there may be such and issue, if you setup a ring group for that, and press preview on one of them, others may stop ringing.

Also, many sip servers are using SIP 183 message for coloring ring back tone. That is the reason why we are using RTSP stream for video preview.

So, if grandstream ip phone doesn't support RTSP URL, I think there is no way to set video preview up.

Best Regards.