Gaplessness....

[Cebolla]

(05-07-2019 17:12)soundhound Wrote:  I looked intently into gapless playback and come to the conclusion
my SONY NS510 Upnp renderer just doesn't do SetNextAVTransportURI,
required for Upnp galess playback.

so I turned to OhMedia for which I have seen various claims of implementing
gapless in an alternate way to Upnp.
Presumably this would have been by running a stream to the renderer.
I understand lossless formats in particular are straightforward to
place back-to-back on a stream. MP3 (and others) not so much, at least without
specialised software up to the task (JRiver Media Centre? didn't work for me)

I turned then to BubbleUPnpServer which can proxy a standard Upnp renderer
as an OhMedia one. And it has an option for gapless playback. Yay!
Yet it doesn't work for me (and the warning documentation link about not working with all renderers gives no clue what it _does_ do).

You appear to have misunderstood how OpenHome (aka UPnP with Linn extensions) streaming works, what (if any) involvement the UPnP media server has with the renderer implementing gapless playback and what the BubbleUPnP Server's association with OpenHome is.


OpenHome renderers exist separately to standard UPnP renderers and use a different incompatible mechanism for providing audio file streaming, which includes the implementation of gapless playback. The main difference is that with OpenHome streaming it's the renderer that owns the current playlist; whereas with standard UPnP streaming it's the control point that owns the current playlist.

Hence the reason why an OpenHome renderer should be able to easily implement gapless playback support on its own, as it does not require the OpenHome control point to tell it what track to fetch next from the UPnP media server every time, during playback of the current playlist. Compare that to the standard UPnP renderer, which requires the SetNextAVTransportURI UPnP AVTransport action to be sent from the UPnP control point every time (and in time) to play the next track in the playlist, in order to implement gapless.

Some streamers support both OpenHome and standard UPnP streaming, so contain both a standard UPnP renderer and an OpenHome renderer, but the majority only support standard UPnP streaming and therefore only have a standard UPnP renderer - such as your Sony NS510 streamer.


The UPnP media server, such as MinimServer, has a more passive role in all of this and delivers to the renderer the audio files that the renderer has requested, as discrete separate streams. All the UPnP media server needs to do in order for standard UPnP renderers and OpenHome renderers to play gaplessly, is allow more than at least one audio file to be streamed from it at the same time (still as separate streams) by the requesting renderer.
Note, the UPnP media server does not get any knowledge of the current playlist, so it would not be able to know which audio files to, as you said, "place back to back" on a long single stream (presumably to help implement gapless playback), even if it could!


The BubbleUPnP Server's Create an OpenHome renderer function is there to allow standard UPnP renderers to be controlled by OpenHome control points, so provides a bridge between the two incompatible streaming technologies. Its main jobs are to:

- Maintain the current playlist for the 'OpenHome renderer' created for the associated standard UPnP renderer;

- Provide connectivity and proxying for the TIDAL & Qobuz online streaming services as supported by OpenHome;

- Translate any received OpenHome control point commands into standard UPnP control point commands (UPnP AVTransport actions) and send them out to the associated standard UPnP renderer. This includes translating one received 'play current playlist' OpenHome control point command into several (depending on the number of tracks in the playlist) SetNextAVTransportURI actions and, at the appropriate times, sending them to the associated UPnP renderer. Of course, this can only work if the associated UPnP renderer supports the SetNextAVTransportURI action in the first place!

The tick box for gapless support by the BubbleUPnP Server is only enabled if the associated UPnP renderer advertises support for the SetNextAVTransportURI action and is otherwise greyed out. The reason why the user has to manually set gapless playback support is that some UPnP renderers claiming SetNextAVTransportURI action support have been found to be faulty, leading to playback problems if the action is sent.