I sent a BubbleUPnP log to Bubblesoft and this is what they had to say:
The log shows that:
- BubbleUPnP instructs MC to play a track
- MC requests immediately the stream
- but it takes forever (tens of seconds) for MC to report it is in the PLAYING state, thus that playback has started.
The result is that when the renderer is configured for gapless playback, the second track will begin to play but Bubble still shows the info for the first track, and the Play/Pause icon is in the "start Play" state. After some delay (typically 25 seconds or longer), Bubble will toggle the control into the "Pause playback" state (which means it has finally heard from MC that playback has started). After the second track finishes, there will be a long pause, and then the first track will start to play again.
When gapless is turned off, it's easier to see what's going on. After the track ends there will be a long pause before the next track starts to play. I've seen pauses for one minute or longer.
If I restart MC this behaviour stops, for a while at least. I haven't been able to determine what causes it to go bad again, although my typical usage suggests it could have something to do with using JRemote to control playback on "Player".
Incidentally, this is what your utility has to say about the JRiver renderer:
Device Description Url=http://192.168.86.33:52103/DeviceDescription.xml
HTTP Server Header=Windows, UPnP/1.0 DLNADOC/1.50, JRiver/26, JRiver Internet Reader/2.0 (compatible; Windows-Media-Player/10)
Description=JRiver DLNA Renderer
Friendly Name=NUC
Manufacturer Name=JRiver, Inc.
Manufacturer Url=http://192.168.86.33:52103/https://www.jriver.com
Model Name=Media Center
Model Number=26.0.12
Presentation Url=http://192.168.86.33:52199/Panel/
Serial Number=c0-3f-d5-68-09-07
UPnP Device Type=urn:schemas-upnp-org:device:MediaRenderer:1
UPnP Media Renderer version=1
Unique Device Name=uuid:20e68194-0d9b-475e-9f9d-e154c6168b78
X_DLNADOC Element=DMR-1.50
Service Url for ConnectionManager=http://192.168.86.33:52103/ConnectionManager/scpd.xml
Service Url for AVTransport=http://192.168.86.33:52103/AVTransport/scpd.xml
Service Url for RenderingControl=http://192.168.86.33:52103/RenderingControl/scpd.xml
Common Renderer Type=JRiver Media Center
AVT:GetDeviceCapabilities action=Supported
AVT:GetMediaInfo action=Supported
AVT:GetPositionInfo action=Supported
AVT:GetTransportInfo action=Supported
AVT:GetTransportSettings action=Supported
AVT:SetNextAVTransportURI (gapless play)=Supported
AVT:SyncPlay (synchronous play)=NOT Supported
RC:GetVolume action=Supported
RC:SetVolume action=Supported
AVT:Event Subscription=Missing Notification
RC:Event Subscription=Succeeded
HTTP User Agent (client)=Mozilla/5.0 (compatible; MSIE 11.0; Windows NT 6.3; WOW64; JRiver Internet Reader/2.0) UPnP/1.0
Play test file result=Play success => Start Ok / Stop Ok / Muted / Subscribe error