[gst-devel] Dynamically add and remove audio sink

[Gruenke, Matt]

When you add an element to a bin, you must match its state to that of the bin.

 

I think the proper sequence is:

1.	add the element to the bin (keep in mind that a pipeline is just a special kind of bin)
2.	call gst_element_sync_state_with_parent() on the newly-added element
3.	link in the element

 

When I add a branch to a tee, I put everything on that branch in its own bin.  That way, on addition & removal, I'm just dealing with that one bin.

 

 

Matt

 

 

________________________________

From: Nagy István [mailto:nistvan.86 at gmail.com] 
Sent: Thursday, October 14, 2010 18:02
To: gstreamer-devel at lists.sourceforge.net
Subject: [gst-devel] Dynamically add and remove audio sink

 

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();

    }

 

}

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