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<h1 id="tutorial-5-build-application-using-gstreamer-api">Tutorial 5. Build application using GStreamer API</h1>
<p>The <code>gst-launch</code> tool is convenient, but it is recommended to use it simply to test pipeline description.<br>
In this tutorial, let's learn how to create an application. (Full example source code can be found <a href="https://github.com/nnstreamer/nnstreamer-example/blob/main/native/example_object_detection_tensorflow_lite/nnstreamer_example_object_detection_tflite.cc">here</a>).<br>
Creating a pipeline application is simple. You can use <code>gst_parse_launch ()</code> which is GStreamer API instead of <code>gst-launch</code> tool.<br>
Refer to <a href="how-to-run-examples.html">here</a> for building nnstreamer-example.</p>
<p>This is a part of the code explanation. The code lines below are essential for operating a pipeline application. The omitted codes are error handling and additional.</p>
<p>Part of <strong>nnstreamer_example_object_detection_tflite.cc</strong></p>
<pre><code>int
main (int argc, char ** argv)
{
...
/* Init gstreamer */
gst_init (&argc, &argv);
/* Same pipeline description as tutorial 2 */
str_pipeline =
g_strdup_printf
("v4l2src name=src ! videoconvert ! videoscale ! video/x-raw,format=RGB,width=640,height=480,framerate=30/1 ! tee name=t "
"t. ! queue leaky=2 max-size-buffers=2 ! videoscale ! video/x-raw,format=RGB,width=300,height=300 ! tensor_converter ! "
"tensor_transform mode=arithmetic option=typecast:float32,add:-127.5,div:127.5 ! "
"tensor_filter framework=tensorflow-lite model=%s ! "
"tensor_decoder mode=bounding_boxes option1=mobilenet-ssd option2=%s option3=%s option4=640:480 option5=300:300 !"
"compositor name=mix sink_0::zorder=2 sink_1::zorder=1 ! videoconvert ! ximagesink "
"t. ! queue leaky=2 max-size-buffers=10 ! mix. ",
g_app.tflite_info.model_path, g_app.tflite_info.label_path, g_app.tflite_info.box_prior_path);
...
/* Create a new pipeline */
g_app.pipeline = gst_parse_launch (str_pipeline, NULL);
...
/* Start pipeline. Setting pipeline to the PLAYING state. */
gst_element_set_state (g_app.pipeline, GST_STATE_PLAYING);
...
/* Pipeline is running */
...
/* Stop and release the resources */
gst_element_set_state (g_app.pipeline, GST_STATE_NULL);
gst_object_unref (g_app.pipeline);
...
}
</code></pre>
<p>Then let's run the application.</p>
<pre><code># If you built tutorial 5 yourself, go to the path you specified, and if you installed it using apt, go to /usr/lib/nnstreamer/bin.
$ cd /usr/lib/nnstreamer/bin
$ ./nnstreamer_example_object_detection_tflite
</code></pre>
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