Re: [Banshee-List] Banshee and radio FM player

[Alp Toker <alp atoker com>]

Salvatore Benedetto wrote:
> Hi,
>
> would it be possible, and useful, to develop a plugin that allows to use 
> banshee
> as a radio FM player by using the video4linux API?
>
> As far as I know there are no many radio FM player around.

A couple of weeks ago I wrote C# bindings for v4l2 and ALSA to make use 
of the FM radio chip in the Nokia 800. (The bindings cover everything 
you need to tune a radio, and might be able to do more but they aren't 
yet complete for general use.) The interface is standard so the code 
will work with any Linux-supported tuner device.

Both are split into a low level API and high level .NET-style API. There 
are examples in the git repositories and it's all pretty easy to use:

Radio radio = new Radio ("/dev/radio0");
radio.IsMuted = false;
radio.Frequency = 95.8f; //Capital FM

The API was stream-of-thought, so I might rename this class to Tuner, or 
make Radio a subclass of Tuner based on the result of a TunerType query 
(which can be Radio, AnalogTv or DigitalTv) etc. I'm figuring out as I 
go how to provide a fun and powerful API so your thoughts would be welcome.

For integration into Banshee, it probably makes sense to enumerate tuner 
devices with hal-sharp (which is already included in the code base). 
Once you discover the device node, pass the path to the Radio constructor.

Tuners are often patched or looped back into Line-in, and this is where 
alsa-sharp comes in. You need access to ALSA to un-mute and set the 
volume of line in, and if you want to record the stream you need to use 
the enumerated value type in that API to set the recording source.

HCtl ctl = new HCtl ("default");
foreach (HCtlElem elem in ctl.Elements)
	//do stuff

alsa-sharp currently lacks GLib main loop integration, so if another 
application changes the volume, a Gtk# volume widget will not move to 
reflect the new value (unless it polls or uses a thread, neither of 
which are valid approaches). This is easy to implement -- will push the 
changes soon.

I'm designing these APIs so they can be used as standalone libraries or 
pipelined in the style of GStreamer. If there are bad interactions with 
Banshee's media framework and alsa-sharp being in the same process for 
example, the libraries can be turned into D-Bus services with some five 
lines of code each so tuners and controls can be manipulated 
out-of-process, over the network etc.

This means that whatever code you write to support radio tuners in 
Banshee will be trivially modified to remote control some other tuner on 
the network. This is only interesting because I assume there are now 
more N800s out there than actual FM radio tuner cards.

The code is at http://www.ndesk.org/