Black screen on video call, but only in SIP -> SCCP direction

[evazzoler]

Hi,
I have a Grandstream GXV3240 as SIP and a Cisco 8945 as SCCP.
All is working good except video.
When I videocall the SIP phone from the SCCP, all is good and normal (but the aspect ratio on the SCCP).
When I videocall the SCCP phone from the SIP phone, I get (not always) one frame then the screen comes black (the call remains in video mode).
The SIP phone writes ”poor network" on the display. Maybe a issue with the speed/framerate renegotiation, but that message is not so reliable...
I really don't know from where to start analyzing the problem.

[evazzoler]

I activated the sccp rtp debug and this is the cli log:

-- SEPAABBCCDDEEFF: Got Start MultiMedia Transmission ACK. Status:'Media Status: OK' (0), Remote RTP/UDP:'192.168.1.37:21560', Type:DirectRTP, PassThruPartyId:4294967260, CallID:35/CallID1:35
-- SEPAABBCCDDEEFF: Multi Media Transmission Started (State: CONNECTED[30])
[2021-03-11 19:08:15] WARNING[2927][C-0000002f]: res_rtp_asterisk.c:7506 ast_rtp_read: RTP Read too short
-- Channel SCCP/27-00000023 left 'simple_bridge' basic-bridge <7d85af4b-c58f-42fd-89d9-72c48c1eaad0>
== SCCP/27-00000023: (sccp_channel_closeAllMediaTransmitAndReceive) Stop All Media Reception and Transmission on device SEPAABBCCDDEEFF
-- SCCP/27-00000023: Close receivechannel on device SEPAABBCCDDEEFF (KeepPortOpen: NO)
-- SCCP/27-00000023: Stop mediatransmission on device SEPAABBCCDDEEFF (KeepPortOpen: NO)
-- SCCP/27-00000023: Close multimedia receive channel on device SEPAABBCCDDEEFF (KeepPortOpen: NO)
-- SCCP/27-00000023: Stop multimediatransmission on device SEPAABBCCDDEEFF (KeepPortOpen: NO)
> SEPAABBCCDDEEFF: Stopping PBX audio rtp transmission on channel SCCP/27-00000023
> SEPAABBCCDDEEFF: Stopping PBX video rtp transmission on channel SCCP/27-00000023
== SCCP/27-00000023: (sccp_channel_closeAllMediaTransmitAndReceive) Stop All Media Reception and Transmission on device SEPAABBCCDDEEFF
-- SCCP/27-00000023: (setEarlyRTP) OFF
== Extension Changed 27[ext-local] new state Idle for Notify User 60
-- Channel SIP/60-0000002c left 'simple_bridge' basic-bridge <7d85af4b-c58f-42fd-89d9-72c48c1eaad0>
== Spawn extension (macro-dial-one, s, 55) exited non-zero on 'SIP/60-0000002c' in macro 'dial-one'
== Spawn extension (macro-exten-vm, s, 26) exited non-zero on 'SIP/60-0000002c' in macro 'exten-vm'

Extension 60 is the grandstream, extension 27 the cisco.
The "WARNING[2927][C-0000002f]: res_rtp_asterisk.c:7506 ast_rtp_read: RTP Read too short" happens when I call sip from SCCP, too. In that case there are no issues with video.

Any idea about what more debug may activate?

[dkgroot]

@evazzoler Hi Enrico
Sorry that i have been so busy these last couple of days, i have just started a new job and have not had much time available. I have run some video tests in the past SCCP->SCCP and SCCP->SIP which mostly worked. You last post seems to indicate that res_rtp_asterisk.c:7506 ast_rtp_read: RTP Read too short invokes a safety measure shutting down video a little to early. I will have to make some time next weekend to see if i can find the cause for that. This will be a bit of a slow process with me only having one 8945 at my disposal.

[evazzoler]

It seems to be something linked to the screen definition. If I use a very low resolution, video will start. The strange thing is that both resolution and ratio will be different depending on the direction the call is made.
[OT] Do you think video preview is possible on a Cisco 8945 phone? I'm asking for using it in a door system. If that's not possible, maybe 8945 is not the right choice for me...

[dkgroot]

@evazzoler
At the moment we do not have much control about the resolution in use.
I don't think preview (video transmission during early rtp) is possible, i would not know how to achieve that.