Bus Message Structure

[Brian Duffy]

Hello,

I am trying to use CMU's PocketSphinx plugin for Gstreamer from Vala and I am running into a problem getting access to the message structure in my bus callback function (app_message). For some reason when I use the get_structure method to return the structure of the message and then call a method on that structure such as get_name() or get_string(), I get a critical Gstreamer error :

(cmu:26958): GStreamer-CRITICAL **: gst_structure_get_string: assertion `structure != NULL' failed

I just can't figure out why my message structure would be null. Any ideas? Here is my code ...

using Gst;

class Sphinx : GLib.Object {

// experimenting with gstreamer pocketsphinx

private Gst.Pipeline pipeline;

private Gst.Element vader;

dynamic Gst.Element asr;

private Gst.Bus bus;

private Gst.Structure msg;

private Gst.Structure my_struct;

private Gst.Structure my_struct2;

private Gst.Message message;

private MainLoop loop; 

public Sphinx() {

string a = """pulsesrc device="alsa_input.usb-AKM_AK5370-00-AK5370.analog-mono" ! audioconvert !""";

string b = """ audioresample ! vader name=vad auto-threshold=true ! pocketsphinx name=asr ! fakesink""";

string pipeDef = a + b;

try {

pipeline = (Pipeline)Gst.parse_launch(pipeDef);

} catch (Error e) {

stdout.printf("Error: %s\n", e.message);

}

bus = pipeline.get_bus();

                bus.add_signal_watch();

bus.message.connect(app_message);

asr = pipeline.get_by_name("asr");

asr.set_property("lm", "4038.lm");

                asr.set_property("dict", "4038.dic");

asr.partial_result.connect(asrPartialResult);

asr.result.connect(asrResult);

asr.set_property("configured", true);

bus = pipeline.get_bus();

                bus.add_signal_watch();

bus.message.connect(app_message);

pipeline.set_state(Gst.State.PLAYING);

loop = new MainLoop ();

loop.run();

}

private void asrPartialResult(Gst.Element asr, string text, string uttid) {

              my_struct = new Gst.Structure.empty("partial_result");

              my_struct.set_value("hyp", text);

              my_struct.set_value("uttid", uttid);

              asr.post_message(new Gst.Message.application(asr, my_struct));

}

private void asrResult(Gst.Element asr, string text, string uttid) {

//stdout.printf("%s", "inside asrResult");

               my_struct2 = new Gst.Structure.empty("result");

               my_struct2.set_value("hyp", text);

               my_struct2.set_value("uttid", uttid);

               asr.post_message(new Gst.Message.application(asr, my_struct2));

}

private void app_message(Gst.Bus bus, Gst.Message p_msg) {

// trying to get the string that PocketSphinx converts my voice to here

// but I keep getting : GStreamer-CRITICAL **: gst_structure_get_string: assertion `structure != NULL' failed

string msg_string = p_msg.get_structure().get_string("hyp");

/* // Not using any of this for now

if (msgType == null) {

stdout.printf("%s", "null");

}else{

stdout.printf("%s", "not null");

}

*/

//stdout.printf("%s", msgType);

//if (p_msg.type == MessageType.APPLICATION) {

// stdout.printf("%s", "booyah");

//}

/*

if (msg["hyp"]) {

stdout.printf("%s", "true");

}else{

stdout.printf("%s", "false");

}

*/

/*

if (msgType == "partial_result") {

//partialResult(msg["hyp"], msg["uttid"]);

}else if (msgType == "result") {

//finalResult(msg["hyp"], msg["uttid"]);

//pipeline.set_state(Gst.State.PAUSED);

}

*/

//return true;

}

private void partialResult(GLib.Value hyp, GLib.Value uttid) {

stdout.printf("%s", (string)hyp);

}

private void finalResult(GLib.Value hyp, GLib.Value uttid) {

stdout.printf("%s", (string)hyp);

}

}

int main (string[] args) {

    

Gst.init(ref args);

var sphinx = new Sphinx();

return 0;

}

--
Duff

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