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https://gitlab.freedesktop.org/gstreamer/gstreamer-rs.git
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134 lines
5.1 KiB
Rust
134 lines
5.1 KiB
Rust
// This example demonstrates how to use GStreamer's query functionality.
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// These are a way to query information from either elements or pads.
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// Such information could for example be the current position within
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// the stream (i.e. the playing time). Queries can traverse the pipeline
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// (both up and downstream). This functionality is essential, since most
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// queries can only answered by specific elements in a pipeline (such as the
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// stream's duration, which often can only be answered by the demuxer).
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// Since gstreamer has many elements that itself contain other elements that
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// we don't know of, we can simply send a query for the duration into the
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// pipeline and the query is passed along until an element feels capable
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// of answering.
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// For convenience, the API has a set of pre-defined queries, but also
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// allows custom queries (which can be defined and used by your own elements).
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use gst::prelude::*;
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use std::convert::TryInto;
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use std::env;
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#[path = "../examples-common.rs"]
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mod examples_common;
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fn example_main() {
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// Get a string containing the passed pipeline launch syntax
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let pipeline_str = env::args().collect::<Vec<String>>()[1..].join(" ");
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gst::init().unwrap();
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let main_loop = glib::MainLoop::new(None, false);
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// Let GStreamer create a pipeline from the parsed launch syntax on the cli.
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let pipeline = gst::parse_launch(&pipeline_str).unwrap();
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let bus = pipeline.get_bus().unwrap();
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pipeline
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.set_state(gst::State::Playing)
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.expect("Unable to set the pipeline to the `Playing` state");
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// Need to move a new reference into the closure.
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// !!ATTENTION!!:
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// It might seem appealing to use pipeline.clone() here, because that greatly
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// simplifies the code within the callback. What this actually dose, however, is creating
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// a memory leak. The clone of a pipeline is a new strong reference on the pipeline.
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// Storing this strong reference of the pipeline within the callback (we are moving it in!),
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// which is in turn stored in another strong reference on the pipeline is creating a
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// reference cycle.
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// DO NOT USE pipeline.clone() TO USE THE PIPELINE WITHIN A CALLBACK
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let pipeline_weak = pipeline.downgrade();
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// Add a timeout to the main loop. This closure will be executed
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// in an interval of 1 second.
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let timeout_id = glib::timeout_add_seconds(1, move || {
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// Here we temporarily retrieve a strong reference on the pipeline from the weak one
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// we moved into this callback.
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let pipeline = match pipeline_weak.upgrade() {
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Some(pipeline) => pipeline,
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None => return glib::Continue(true),
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};
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//let pos = pipeline.query_position(gst::Format::Time).unwrap_or(-1);
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//let dur = pipeline.query_duration(gst::Format::Time).unwrap_or(-1);
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let pos: gst::ClockTime = {
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// Create a new position query and send it to the pipeline.
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// This will traverse all elements in the pipeline, until one feels
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// capable of answering the query.
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let mut q = gst::query::Position::new(gst::Format::Time);
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if pipeline.query(&mut q) {
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Some(q.get_result())
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} else {
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None
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}
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}
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.and_then(|pos| pos.try_into().ok())
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.unwrap();
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let dur: gst::ClockTime = {
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// Create a new duration query and send it to the pipeline.
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// This will traverse all elements in the pipeline, until one feels
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// capable of answering the query.
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let mut q = gst::query::Duration::new(gst::Format::Time);
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if pipeline.query(&mut q) {
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Some(q.get_result())
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} else {
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None
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}
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}
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.and_then(|dur| dur.try_into().ok())
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.unwrap();
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println!("{} / {}", pos, dur);
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glib::Continue(true)
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});
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// Need to move a new reference into the closure.
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let main_loop_clone = main_loop.clone();
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//bus.add_signal_watch();
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//bus.connect_message(None, move |_, msg| {
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bus.add_watch(move |_, msg| {
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use gst::MessageView;
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let main_loop = &main_loop_clone;
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match msg.view() {
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MessageView::Eos(..) => main_loop.quit(),
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MessageView::Error(err) => {
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println!(
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"Error from {:?}: {} ({:?})",
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err.get_src().map(|s| s.get_path_string()),
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err.get_error(),
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err.get_debug()
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);
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main_loop.quit();
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}
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_ => (),
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};
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glib::Continue(true)
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})
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.expect("Failed to add bus watch");
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main_loop.run();
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pipeline
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.set_state(gst::State::Null)
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.expect("Unable to set the pipeline to the `Null` state");
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bus.remove_watch().unwrap();
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glib::source_remove(timeout_id);
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}
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fn main() {
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// tutorials_common::run is only required to set up the application environent on macOS
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// (but not necessary in normal Cocoa applications where this is set up autmatically)
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examples_common::run(example_main);
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}
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