It’s been a while since I last blogged about Rygel. Many things have happened since, mainly in features and documentation.
Exchangeable media engines: We’ve loosened the dependency on GStreamer a bit. While it is still our first-class transcoding and general media handling library, it is now possible to substitute it with other media processing libraries. A simple example is included in the source.
Change tracking. This is a feature introduced in the UPnP content directory specification version 3. It allows clients to, well, track the changes that happen on the server in detail for synchronization purposes. It’s implemented in the framework and as a demonstration in the MediaExport plug-in.
GStreamer 1.0 support. As the rest of GNOME, we transitioned to GStreamer 1.0.
Playlist support. Rygel now generates playlists for containers on-the-fly and the renderer framework supports automatic playback of them. The only format that’s supported currently is one of the two formats defined by DLNA, DIDL_S, which is just the same format that is used by UPnP AV to describe the media content on a server.
Playspeed support. A renderer now can announce that it supports different speeds and directions than normal forward playback.
There was another split-up into a renderer framework library and a specific implementation of a renderer using GStreamer which again may be used in your own programs. This is mainly due to the aforementioned change in media backend flexibility.
Otherwise we’re working on making the API easier to use from C and other languages through introspection.
There’s been a lot of effort into extending our sparse documentation. It is currently concentrating on the APIsideofthings but will be extended to a higher level as well soon.
There is an example now that implements a DLNA renderer which is running in full-screen
There are several examples for the most common init systems to run Rygel as a system service if wanted
We get a lot of reports of UPnP AV clients not working properly with Rygel. It either isn’t seen by the client at all or does not show any content.
The reason is usually the same. People are not following the specs. Rygel seems to be one of the few UPnP-AV/DLNA server out there that implements a higher version of the UPnP-AV specification than :1. A lot of clients are explicitly testing for this version, ignoring higher versions although the UPnP standard states that higher version services need to be backward-compatible. (cf. UDA 1.1, section 1.2.2, last paragraph on page 10). Of course we can work around that – and we do, but the list of exceptions is getting longer and longer and to be honest I’m starting to get really annoyed of those fixes.
I expect that there will be more and more devices with higher versions now that DLNA has added features that require higher versions of the specification than :1. So pretty please get your clients fixed. And if you don’t want to, then don’t make it extra complicated to work around your bug. But really, fix it.
And please have a working support email address so I can complain directly. About every client author I tried to contact has bounced – and the rest ignored me.
librygel-core: This has been a long-standing TODO item. It was necessary to allow in-process use of the DLNA and UPnP knowledge coded in Rygel, allowing the creation of librygel-renderer (see below). On top of this there are other benefits
It will allow a Rygel version running on Windows without ugly libtool hacks for the plug-ins.
It simplifies the reuse of other parts of Rygel’s code, such as the transcoding HTTP server, in programs like Korva.
the new librygel-renderer: In essence this is the playbin plugin with a bit of API on top that simplifies the code necessary to create a renderer. It offers either a playbin element you can use in your code or wraps around an existing playbin.
In future we can extend this family of libraries by “librygel-browse” for remote content access and “librygel-control” for remote control.
To demonstrate librygel-renderer’s capabilities of converting an arbitrary media player based on GStreamer’s GstPlaybin2 into a proper UPnP/DLNA renderer, I have added librygel-renderer support to Totem. You can see the result in the following demo:
The first part of the video (using Sintel) shows how changes in local file playback are being reflected on the UPnP side. In the second part, I set a remote video (Big Buck Bunny) and control totem solely via UPnP, where play, pause, stop, controlling volume, seeking and getting the current playback position is working quite well.
This simple conversion is not a complete DLNA Player. It would need UPnP/DLNA server browsing capabilities for this, as stated in the proposal (In general. Totem can access these servers via its Grilo plug-in).
Of course, with Totem being a complex, mature piece of software, some things don’t work yet:
Volume changes in Totem aren’t reflected via UPnP
It is not possible to initiate a remote play-back until Totem has an item in its playlist
The announced media format support is nowhere near what Totem actually supports
There’s one draw-back that I realized while implementing this. My initial idea to sit on top of a GStreamer playbin2 might be flawed for already existing and mature software such as Totem. There might be much more code-paths dealing with control that happen outside of a playbin. We have an alternative for that as well and that would be implementing one of Rygel’s interfaces by the consuming party. The UPnP and DLNA compatibility that is already in the current code would need to be transferred to this, which is, of course, more work than just attaching to a playbin.
Why should I prefer this above the already available MPRIS Rygel plug-in? There might be several reasons.
You don’t want a whole separate Rygel process running just for adding UPnP renderer capabilities to your media player.
You aim for some kind of UPnP or DLNA certification – The additional layer of indirection can make that really hard while the presented approach is nearly ready.
So are we going to abandon Rygel’s MPRIS renderer plugin now? No. Because we can’t expect every media player in the world a) use GStreamer and b) want to link against Rygel. MPRIS gives us a quick, ready-made access to a vast amount of players out there and the compatibility it offers is (most of the time) just enough for casual home use.
Currently TweakUp only speaks English. I’ve modified the source and setup a Transifex instance to change that in a future release. Since the only two languages I can express myself in without sounding too stupid are English and German, my translation skills are a bit limited. So if anyone is interested in contributing a translation, feel free.
As I mentioned on several places already, due to the aim of getting the N9 DLNA-certified we had to introduce some restrictions. One of the most annoying limitation from an end user point of view is that you can’t share arbitrary videos or music which you may have put on your device. Another, though minor, issue is that it’s not possible to change the name shown in UPnP or DLNA clients on the network.
While it is possible to change all this by editing the configuration file, it is somewhat inconvenient to do this on the device. That’s why I’ve written a small application called TweakUp which allows all these settings (and a few more, see the screenshot) to be changed more comfortably. It is available in the Nokia Store and on this website. It has been signed with my public key 6BA1DF74.
Today we have reached step two of what we aimed for when using Rygel on the N9. This morning I got notified that it has been certified by DLNA as a M-DMS device. After a very long struggle (more than two years) with the sometimes nearly insane requirements DLNA imposes on a project, the weird tooling and the testing process, after all the effort that multiple people have thrown into this goal, by the end of last month, it looked like we were not going to make it. The reasons were very, very stupid and didn’t have to do anything at all with Rygel. Getting the news today was a great relief, a huge reward and a very fitting finish for working on this project.
A big thank you to Zeeshan and all the other people involved in making this happen.