Dahua VTO4202F-P-S2 <-> Asterisk <-> Dahua VTH5422H kein video

[dahdah]

Hallo,
entschuldigen Sie Bitte, mein Deutsch ist noch nicht so gut, deswegen schreibe ich auf Englisch und Sie können mir gerne auf Deutsch antworten.
Falls jemand helfen will aber kein Englisch spricht bitte sagen Sie und Ich will alles uberzetzen (oder mindestens probieren

So what I have tried till now:
1. Using the Dahua built in SIP server the devices can connect to one another audio/video/door lock work.
2. Using asterisk 20 (built by me) and PJSIP - no video.
3. Using asterisk 18 (built by me) and chan_sip - no video.
4. Using asterisk16 from the rpi distro and chan_sip - no video.

What is my config?

VTO (video doorbell) is 8001, one VTH (monitor) is 102.
On the VTH I have configured the VTO so that I can get video/audio before answering the call.
If I disable the VTO config on the VTH I gen only audio call from the VTO (but after some time it stops as no video can be connected "Network abnormal. Video connect timeout!").
Reading the forums here I learned that this "video" preview is Dahua native implementation and has nothing to do with SIP.
After answering the call the VTH shall switch to normal SIP (e.g. show video from the VTO via sip/rtp)

Network:
Both devices are on the same POE switch (e.g. in the same LAN)
8001 has IP 192.168.178.180
102 has IP 191.168.178.41
Asterisk in running on Raspberry pi 192.168.178.47

What happens?
When I call from VTO to VTH initially the VTO video is shown, then when I answer there is audio and no video and after some seconds I get message on the VTH
"Network abnormal. Video connect timeout!" which then breaks the call.
The same happens when I call the VTO from the VTH using 8001 extension.

What is my sip.conf
sip.conf

[general]
language=de
bindport = 5060
bindaddr = 0.0.0.0
externrefresh=30
transport=udp
localnet=192.168.178.1/255.255.0.0
directmedia=yes
videosupport=yes
[8001]
host=dynamic
username=Door Bell
type=friend
secret=8001
context=outgoing
canreinvite=yes
videosupport=yes
directmedia=yes
qualify=yes
disallow=all
allow=ulaw
allow=h264

[102]
videosupport=yes
directmedia=yes
type=friend
username=102
secret=102
context=outgoing
dtmfmode=info
host=dynamic
canreinvite=yes
qualify=yes
allow=ulaw
allow=h264

What is my extensions.conf

[general]
static=yes
writeprotect=no
[outgoing]
exten => 102,1,Dial(SIP/102,30)
[default]
include => outgoing

What is my SIP log?
See debug_log_dahua2.zip

Do I have something in mind? Well on the VTO when configuring the SIP server I had no menu "Asterisk" but only a menu "Dahua/Dss Express/Third Party".
I have selected "Third Party" and have given the Asterisk user/pass and I have set "SIP Domain" to asterisk (SIP Server Username and SIP Server Password are left empty).
Looks like for whatever reason the VTH cannot get the video stream from the VTO but by looking on the log I found nothing find anything obvious.
So there is logic on this VTH that dislikes the way Asterisk serves the video but I have no idea what it might be.
Perhaps we can compare with someone that has this setup working? Or even better - someone can tell me that I am missing a config somewhere?


Danke vorab!