[gst-devel] Dynamically add and remove audio sink

[Nagy István]

Hello everyone!

I'm very new to GStreamer, i'm experimenting with the framework since a
week. My current goal would be to write a radio scheduler application which
can handle audio playback required for a web radio, stream the result with
different encoders and optionally do audio output on a local audio hardware.
I did some tests about how can i plugin different sources to an Adder so i
can use the pipeline as an audio mixer. After finding the pad
blocking capability of GStreamer, i could add and remove audio sources into
the pipeline without stopping it.
http://stackoverflow.com/questions/3899666/adding-and-removing-audio-sources-to-from-gstreamer-pipeline-on-the-go
I
want to do this with the audio outputs as well, i like to add and remove
different audio sinks while the pipeline is running.

I've added a Tee after the Adder so i can split up sources to many outputs.
If i fire up the pipeline with an autoaudiosink (with it's own queue),
playback works fine. If i add a fakesink to the Tee's output on the go
(requesting a new src request pad an linking it with an another queue in the
middle), one of my audio sources pauses the pipeline with a

basesrc gstbasesrc.c:2447:gst_base_src_loop:<Buzzer1> pausing after
gst_pad_push() = wrong-state

error message in the debug output.

I've tried to put a block on the Adder's source output while adding the new
audio sink, but it wouldn't help me.

Here is the code i'm working with), it's the Java rewrite of the
StackOverflow Python script what i linked above. I don't know what to try
next. If i put the pipeline together with two sinks before the first start,
everything works fine.

package test;

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.gstreamer.Element;
import org.gstreamer.ElementFactory;
import org.gstreamer.Gst;
import org.gstreamer.Pad;
import org.gstreamer.Pipeline;
import org.gstreamer.State;
public class Main {

    public static void main(String[] args) {
        Gst.init("RadioBeans", args);
        Pipeline pipe = new Pipeline("Scheduler");

        Element mixer = ElementFactory.make("adder", "Mixer");
        pipe.add(mixer);

        Element tee = ElementFactory.make("tee", "Splitter");
        pipe.add(tee);

        mixer.link(tee);

        Element audioSink =
ElementFactory.make("autoaudiosink","AudioOutput");
        pipe.add(audioSink);
        Element audioQueue = ElementFactory.make("queue","AudioQueue");
        pipe.add(audioQueue);
        tee.link(audioQueue);
        audioQueue.link(audioSink);

        Pad mixerLine1=mixer.getRequestPad("sink%d");
        Pad mixerLine2=mixer.getRequestPad("sink%d");

        Element buzzer1 = ElementFactory.make("audiotestsrc", "Buzzer1");
        pipe.add(buzzer1);
        buzzer1.set("freq", 1000);
        Pad buzzer1src=buzzer1.getSrcPads().get(0);
        buzzer1src.link(mixerLine1);

        Element buzzer2 = ElementFactory.make("audiotestsrc", "Buzzer2");
        pipe.add(buzzer2);
        buzzer2.set("freq", 500);
        Pad buzzer2src=buzzer2.getSrcPads().get(0);
        buzzer2src.link(mixerLine2);

        pipe.play();

        try {
          System.in.read();
        } catch (IOException ex) {
          Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null,
ex);
        }

        Element fakeOutput = ElementFactory.make("fakesink", "FakeOutput");
        pipe.add(fakeOutput);
        Element fakeQueue = ElementFactory.make("queue","FakeQueue");
        pipe.add(fakeQueue);
        fakeQueue.link(fakeOutput);
        tee.link(fakeQueue);

        pipe.play();

        System.out.println("Added fakesink");

        try {
          System.in.read();
        } catch (IOException ex) {
          Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null,
ex);
        }

        buzzer1src.setBlocked(true);
        buzzer1.setState(State.NULL);
        buzzer1src.unlink(mixerLine1);
        mixer.releaseRequestPad(mixerLine1);

        System.out.println("Released buzzer1");

        try {
          System.in.read();
        } catch (IOException ex) {
          Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null,
ex);
        }

        System.out.println("Stopping.");

        pipe.stop();
    }

}
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/gstreamer-devel/attachments/20101015/ec59a3ea/attachment.htm>