Add basic-tutorial-3 from the GStreamer tutorials

https://cgit.freedesktop.org/gstreamer/gst-docs/tree/examples/tutorials/basic-tutorial-3.c

Fixes https://github.com/sdroege/gstreamer-rs/pull/38

tutorials/src/bin/basic-tutorial-3.rs

@@ -0,0 +1,117 @@
+extern crate gstreamer as gst;
+
+use gst::prelude::*;
+
+fn main() {
+    // Initialize GStreamer
+    gst::init().unwrap();
+
+    // Create the elements
+    let source = gst::ElementFactory::make("uridecodebin", "source")
+        .expect("Could not create uridecodebin element.");
+    let convert = gst::ElementFactory::make("audioconvert", "convert")
+        .expect("Could not create convert element.");
+    let sink =
+        gst::ElementFactory::make("autoaudiosink", "sink").expect("Could not create sink element.");
+
+    // Create the empty pipeline
+    let pipeline = gst::Pipeline::new("test-pipeline");
+
+    // Build the pipeline Note that we are NOT linking the source at this
+    // point. We will do it later.
+    pipeline.add_many(&[&source, &convert, &sink]).unwrap();
+    convert.link(&sink).expect("Elements could not be linked.");
+
+    // Set the URI to play
+    let uri = "https://www.freedesktop.org/software/gstreamer-sdk/data/media/sintel_trailer-480p.webm";
+    source
+        .set_property("uri", &uri)
+        .expect("Can't set uri property on uridecodebin");
+
+    // Connect the pad-added signal
+    let pipeline_clone = pipeline.clone();
+    let convert_clone = convert.clone();
+    source.connect_pad_added(move |_, src_pad| {
+        let pipeline = &pipeline_clone;
+        let convert = &convert_clone;
+
+        println!(
+            "Received new pad {} from {}",
+            src_pad.get_name(),
+            pipeline.get_name()
+        );
+
+        let sink_pad = convert
+            .get_static_pad("sink")
+            .expect("Failed to get static sink pad from convert");
+        if sink_pad.is_linked() {
+            println!("We are already linked. Ignoring.");
+            return;
+        }
+
+        let new_pad_caps = src_pad
+            .get_current_caps()
+            .expect("Failed to get caps of new pad.");
+        let new_pad_struct = new_pad_caps
+            .get_structure(0)
+            .expect("Failed to get first structure of caps.");
+        let new_pad_type = new_pad_struct.get_name();
+
+        let is_audio = new_pad_type.starts_with("audio/x-raw");
+        if !is_audio {
+            println!(
+                "It has type {} which is not raw audio. Ignoring.",
+                new_pad_type
+            );
+            return;
+        }
+
+        let ret = src_pad.link(&sink_pad);
+        if ret != gst::PadLinkReturn::Ok {
+            println!("Type is {} but link failed.", new_pad_type);
+        } else {
+            println!("Link succeeded (type {}).", new_pad_type);
+        }
+    });
+
+    // Start playing
+    let ret = pipeline.set_state(gst::State::Playing);
+    assert_ne!(
+        ret,
+        gst::StateChangeReturn::Failure,
+        "Unable to set the pipeline to the Playing state."
+    );
+
+    // Wait until error or EOS
+    let bus = pipeline.get_bus().unwrap();
+    while let Some(msg) = bus.timed_pop(gst::CLOCK_TIME_NONE) {
+        use gst::MessageView;
+        match msg.view() {
+            MessageView::Error(err) => {
+                eprintln!(
+                    "Error received from element {}: {}",
+                    msg.get_src().get_path_string(),
+                    err.get_error()
+                );
+                eprintln!("Debugging information: {:?}", err.get_debug());
+                break;
+            }
+            MessageView::StateChanged(s) => if msg.get_src() == pipeline {
+                println!(
+                    "Pipeline state changed from {:?} to {:?}",
+                    s.get_old(),
+                    s.get_current()
+                );
+            },
+            MessageView::Eos(..) => break,
+            _ => (),
+        }
+    }
+
+    let ret = pipeline.set_state(gst::State::Null);
+    assert_ne!(
+        ret,
+        gst::StateChangeReturn::Failure,
+        "Unable to set the pipeline to the Null state."
+    );
+}