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examples: Simplify cairo compositor example a bit and improve/add comments.

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This commit is contained in:
Sebastian Dröge 2022-03-23 10:27:08 +02:00
parent 21dbe86c8e
commit 208e1ef7a4
1 changed files with 105 additions and 74 deletions
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179
examples/src/bin/cairo_compositor.rs
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@ -5,12 +5,11 @@ use gst::prelude::*;
use gst_base::prelude::*;
use anyhow::{Context, Error};
use derive_more::{Display, Error};
#[path = "../examples-common.rs"]
mod examples_common;
// Our custom compositor element is defined in this module
// Our custom compositor element is defined in this module.
mod cairo_compositor {
use super::*;
use gst_base::subclass::prelude::*;
@ -19,13 +18,13 @@ mod cairo_compositor {
use once_cell::sync::Lazy;
// In the imp submodule we include the actual implementation
// In the imp submodule we include the actual implementation of the compositor.
mod imp {
use super::*;
use std::sync::Mutex;
// Settings of the compositor
// Settings of the compositor.
#[derive(Clone)]
struct Settings {
background_color: u32,
@ -39,7 +38,7 @@ mod cairo_compositor {
}
}
// This is the private data of our pad
// This is the private data of our compositor.
#[derive(Default)]
pub struct CairoCompositor {
settings: Mutex<Settings>,
@ -47,7 +46,7 @@ mod cairo_compositor {
// This trait registers our type with the GObject object system and
// provides the entry points for creating a new instance and setting
// up the class data
// up the class data.
#[glib::object_subclass]
impl ObjectSubclass for CairoCompositor {
const NAME: &'static str = "CairoCompositor";
@ -55,14 +54,17 @@ mod cairo_compositor {
type ParentType = gst_video::VideoAggregator;
}
// Implementation of glib::Object virtual methods
// Implementation of glib::Object virtual methods.
impl ObjectImpl for CairoCompositor {
// Specfication of the compositor properties.
// In this case a single property for configuring the background color of the
// composition.
fn properties() -> &'static [glib::ParamSpec] {
static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
vec![glib::ParamSpecUInt::new(
"background-color",
"Background Color",
"Background color as AARRGGBB",
"Background color as 0xRRGGBB",
0,
u32::MAX,
Settings::default().background_color,
@ -73,6 +75,7 @@ mod cairo_compositor {
&*PROPERTIES
}
// Called by the application whenever the value of a property should be changed.
fn set_property(
&self,
_obj: &Self::Type,
@ -90,6 +93,7 @@ mod cairo_compositor {
};
}
// Called by the application whenever the value of a property should be retrieved.
fn property(
&self,
_obj: &Self::Type,
@ -105,13 +109,13 @@ mod cairo_compositor {
}
}
// Implementation of gst::Object virtual methods
// Implementation of gst::Object virtual methods.
impl GstObjectImpl for CairoCompositor {}
// Implementation of gst::Element virtual methods
// Implementation of gst::Element virtual methods.
impl ElementImpl for CairoCompositor {
// The element specific metadata. This information is what is visible from
// gst-inspect-1.0 and can also be programatically retrieved from the gst::Registry
// gst-inspect-1.0 and can also be programmatically retrieved from the gst::Registry
// after initial registration without having to load the plugin in memory.
fn metadata() -> Option<&'static gst::subclass::ElementMetadata> {
static ELEMENT_METADATA: Lazy<gst::subclass::ElementMetadata> = Lazy::new(|| {
@ -137,6 +141,7 @@ mod cairo_compositor {
.field("format", gst_video::VideoFormat::Bgrx.to_str())
.field("width", gst::IntRange::<i32>::new(1, i32::MAX))
.field("height", gst::IntRange::<i32>::new(1, i32::MAX))
.field("pixel-aspect-ratio", gst::Fraction::new(1, 1))
.field(
"framerate",
gst::FractionRange::new(
@ -148,17 +153,19 @@ mod cairo_compositor {
vec![
// The src pad template must be named "src" for aggregator
// and always be there
gst::PadTemplate::with_gtype(
// and always be there.
gst::PadTemplate::new(
"src",
gst::PadDirection::Src,
gst::PadPresence::Always,
&caps,
super::CairoCompositorPad::static_type(),
)
.unwrap(),
// The sink pad template must be named "sink_%u" by default for aggregator
// and be requested by the application
// and be requested by the application.
//
// Also declare here that it should be a pad with our custom compositor pad
// type that is defined further below.
gst::PadTemplate::with_gtype(
"sink_%u",
gst::PadDirection::Sink,
@ -174,8 +181,9 @@ mod cairo_compositor {
}
}
// Implementation of gst_base::Aggregator virtual methods
// Implementation of gst_base::Aggregator virtual methods.
impl AggregatorImpl for CairoCompositor {
// Called whenever a query arrives at the given sink pad of the compositor.
fn sink_query(
&self,
aggregator: &Self::Type,
@ -214,17 +222,24 @@ mod cairo_compositor {
}
}
// Implementation of gst_video::VideoAggregator virtual methods
// Implementation of gst_video::VideoAggregator virtual methods.
impl VideoAggregatorImpl for CairoCompositor {
// Called by videoaggregator whenever the output format should be determined.
fn find_best_format(
&self,
_element: &Self::Type,
_downstream_caps: &gst::Caps,
) -> Option<(gst_video::VideoInfo, bool)> {
// Let videoaggregator select whatever format downstream wants
// Let videoaggregator select whatever format downstream wants.
//
// By default videoaggregator doesn't allow a different format than the input
// format.
None
}
// Called whenever a new output frame should be produced. At this point, each pad has
// either no frame queued up at all or the frame that should be used for this output
// time.
fn aggregate_frames(
&self,
element: &Self::Type,
@ -233,21 +248,28 @@ mod cairo_compositor {
) -> Result<gst::FlowSuccess, gst::FlowError> {
let pads = element.sink_pads();
// Map the output frame writable.
let out_info = element.video_info().unwrap();
let mut out_frame =
gst_video::VideoFrameRef::from_buffer_ref_writable(outbuf, &out_info).unwrap();
// And then create a cairo context for drawing on the output frame.
with_frame(&mut out_frame, |ctx| {
let settings = self.settings.lock().unwrap().clone();
// First of all, clear the background.
let bg = (
((settings.background_color >> 16) & 0xff) as f64 / 255.0,
((settings.background_color >> 8) & 0xff) as f64 / 255.0,
((settings.background_color >> 0) & 0xff) as f64 / 255.0,
);
ctx.set_operator(cairo::Operator::Source);
ctx.set_source_rgb(bg.0, bg.1, bg.2);
ctx.paint().unwrap();
ctx.set_operator(cairo::Operator::Over);
// Then for each pad (in zorder), draw it according to the current settings.
for pad in pads {
let pad = pad.downcast_ref::<CairoCompositorPad>().unwrap();
@ -286,6 +308,8 @@ mod cairo_compositor {
}
}
// Creates a cairo context around the given video frame and then calls the closure to operate
// on the cairo context. Ensures that no references to the video frame stay inside cairo.
fn with_frame<F: FnOnce(&cairo::Context)>(
frame: &mut gst_video::VideoFrameRef<&mut gst::BufferRef>,
func: F,
@ -315,6 +339,8 @@ mod cairo_compositor {
}
}
// Paints the frame with the given alpha on the cairo context at the current origin.
// Ensures that no references to the video frame stay inside cairo.
fn paint_frame(
ctx: &cairo::Context,
frame: &gst_video::VideoFrameRef<&gst::BufferRef>,
@ -348,24 +374,27 @@ mod cairo_compositor {
}
// This here defines the public interface of our element and implements
// the corresponding traits so that it behaves like any other gst::Element
// the corresponding traits so that it behaves like any other gst::Element.
glib::wrapper! {
pub struct CairoCompositor(ObjectSubclass<imp::CairoCompositor>) @extends gst_video::VideoAggregator, gst_base::Aggregator, gst::Element, gst::Object;
}
impl CairoCompositor {
// Creates a new instance of our compositor with the given name
// Creates a new instance of our compositor with the given name.
pub fn new(name: Option<&str>) -> Self {
glib::Object::new(&[("name", &name)]).expect("Failed to create cairo compositor")
}
}
// In the imp submodule we include the implementation of the pad subclass
// In the imp submodule we include the implementation of the pad subclass.
//
// This doesn't implement any additional logic but only provides properties for configuring the
// appearance of the stream corresponding to this pad and the storage of the property values.
mod imp_pad {
use super::*;
use std::sync::Mutex;
// Settings of our pad
// Settings of our pad.
#[derive(Clone)]
pub(super) struct Settings {
pub(super) alpha: f64,
@ -387,7 +416,7 @@ mod cairo_compositor {
}
}
// This is the private data of our pad
// This is the private data of our pad.
#[derive(Default)]
pub struct CairoCompositorPad {
pub(super) settings: Mutex<Settings>,
@ -395,7 +424,7 @@ mod cairo_compositor {
// This trait registers our type with the GObject object system and
// provides the entry points for creating a new instance and setting
// up the class data
// up the class data.
#[glib::object_subclass]
impl ObjectSubclass for CairoCompositorPad {
const NAME: &'static str = "CairoCompositorPad";
@ -403,8 +432,11 @@ mod cairo_compositor {
type ParentType = gst_video::VideoAggregatorPad;
}
// Implementation of glib::Object virtual methods
// Implementation of glib::Object virtual methods.
impl ObjectImpl for CairoCompositorPad {
// Specfication of the compositor pad properties.
// In this case there are various properties for defining the position and otherwise
// the appearance of the stream corresponding to this pad.
fn properties() -> &'static [glib::ParamSpec] {
static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
vec![
@ -459,6 +491,7 @@ mod cairo_compositor {
PROPERTIES.as_ref()
}
// Called by the application whenever the value of a property should be changed.
fn set_property(
&self,
_obj: &Self::Type,
@ -488,6 +521,7 @@ mod cairo_compositor {
};
}
// Called by the application whenever the value of a property should be retrieved.
fn property(
&self,
_obj: &Self::Type,
@ -507,39 +541,30 @@ mod cairo_compositor {
}
}
// Implementation of gst::Object virtual methods
// Implementation of gst::Object virtual methods.
impl GstObjectImpl for CairoCompositorPad {}
// Implementation of gst::Pad virtual methods
// Implementation of gst::Pad virtual methods.
impl PadImpl for CairoCompositorPad {}
// Implementation of gst_base::AggregatorPad virtual methods
// Implementation of gst_base::AggregatorPad virtual methods.
impl AggregatorPadImpl for CairoCompositorPad {}
// Implementation of gst_video::VideoAggregatorPad virtual methods
// Implementation of gst_video::VideoAggregatorPad virtual methods.
impl VideoAggregatorPadImpl for CairoCompositorPad {}
}
// This here defines the public interface of our element and implements
// the corresponding traits so that it behaves like any other gst::Element
// the corresponding traits so that it behaves like any other gst::Pad.
glib::wrapper! {
pub struct CairoCompositorPad(ObjectSubclass<imp_pad::CairoCompositorPad>) @extends gst_video::VideoAggregatorPad, gst_base::AggregatorPad, gst::Pad, gst::Object;
}
}
#[derive(Debug, Display, Error)]
#[display(fmt = "Received error from {}: {} (debug: {:?})", src, error, debug)]
struct ErrorMessage {
src: String,
error: String,
debug: Option<String>,
source: glib::Error,
}
fn create_pipeline() -> Result<gst::Pipeline, Error> {
gst::init()?;
// Create our pipeline with the compositor and two input streams
// Create our pipeline with the compositor and two input streams.
let pipeline = gst::Pipeline::new(None);
let src1 = gst::ElementFactory::make("videotestsrc", None).context("Creating videotestsrc")?;
let src2 = gst::ElementFactory::make("videotestsrc", None).context("Creating videotestsrc")?;
@ -550,9 +575,7 @@ fn create_pipeline() -> Result<gst::Pipeline, Error> {
pipeline.add_many(&[&src1, &src2, comp.upcast_ref(), &conv, &sink])?;
src1.set_property_from_str("pattern", "ball");
src2.set_property_from_str("pattern", "smpte");
// Link everything together.
src1.link_filtered(
&comp,
&gst::Caps::builder("video/x-raw")
@ -579,6 +602,9 @@ fn create_pipeline() -> Result<gst::Pipeline, Error> {
.context("Linking converter")?;
conv.link(&sink).context("Linking sink")?;
src1.set_property_from_str("pattern", "ball");
src2.set_property_from_str("pattern", "smpte");
comp.set_property("background-color", 0xff_33_33_33u32);
// Change positions etc of both inputs based on a timer
@ -593,7 +619,7 @@ fn create_pipeline() -> Result<gst::Pipeline, Error> {
comp.set_emit_signals(true);
comp.connect_samples_selected(move |_agg, _seg, pts, _dts, _dur, _info| {
// Position and rotation period is 10s
// Position and rotation period is 10s.
let pos = (pts.unwrap().nseconds() % gst::ClockTime::from_seconds(10).nseconds()) as f64
/ gst::ClockTime::from_seconds(10).nseconds() as f64;
@ -612,18 +638,19 @@ fn create_pipeline() -> Result<gst::Pipeline, Error> {
sink_0.set_property("rotate", pos * 360.0);
sink_1.set_property("rotate", 360.0 - pos * 360.0);
// Alpha period is 2s
// Alpha period is 2s.
let pos = (pts.unwrap().nseconds() % gst::ClockTime::from_seconds(2).nseconds()) as f64
/ gst::ClockTime::from_seconds(2).nseconds() as f64;
if pos < 0.5 {
sink_0.set_property("alpha", 2.0 * pos);
sink_1.set_property("alpha", 1.0 - 2.0 * pos);
} else {
sink_0.set_property("alpha", 1.0 - 2.0 * (pos - 0.5));
sink_1.set_property("alpha", 2.0 * (pos - 0.5));
}
sink_0.set_property(
"alpha",
(1.0 + f64::sin(2.0 * std::f64::consts::PI * pos)) / 2.0,
);
sink_1.set_property(
"alpha",
(1.0 + f64::cos(2.0 * std::f64::consts::PI * pos)) / 2.0,
);
// Scale period is 20s
// Scale period is 20s.
let pos = (pts.unwrap().nseconds() % gst::ClockTime::from_seconds(20).nseconds()) as f64
/ gst::ClockTime::from_seconds(20).nseconds() as f64;
sink_0.set_property("scale", pos);
@ -633,55 +660,59 @@ fn create_pipeline() -> Result<gst::Pipeline, Error> {
Ok(pipeline)
}
// Start the pipeline and collect messages from the bus until an error or EOS.
fn main_loop(pipeline: gst::Pipeline) -> Result<(), Error> {
pipeline.set_state(gst::State::Playing)?;
let bus = pipeline
.bus()
.expect("Pipeline without bus. Shouldn't happen!");
let mut bus_stream = bus.stream();
let main_loop = glib::MainLoop::new(None, false);
bus.add_watch({
let main_loop = main_loop.clone();
move |_bus, msg| {
let main_context = glib::MainContext::default();
// Storage for any error so we can report it later.
let mut error = None;
main_context.block_on(async {
use futures::prelude::*;
while let Some(msg) = bus_stream.next().await {
use gst::MessageView;
match msg.view() {
MessageView::Eos(..) => main_loop.quit(),
MessageView::Eos(..) => break,
MessageView::Error(err) => {
println!(
error = Some(anyhow::anyhow!(
"Error from {:?}: {} ({:?})",
err.src().map(|s| s.path_string()),
err.error(),
err.debug()
);
));
main_loop.quit();
break;
}
_ => (),
}
glib::Continue(true)
}
})
.unwrap();
});
main_loop.run();
// In case of error, report to the caller.
if let Some(error) = error {
let _ = pipeline.set_state(gst::State::Null);
return Err(error);
}
pipeline.set_state(gst::State::Null)?;
Ok(())
}
fn example_main() {
match create_pipeline().and_then(main_loop) {
Ok(r) => r,
Err(e) => eprintln!("Error! {}", e),
}
fn example_main() -> Result<(), Error> {
create_pipeline().and_then(main_loop)
}
fn main() {
fn main() -> Result<(), Error> {
// tutorials_common::run is only required to set up the application environment on macOS
// (but not necessary in normal Cocoa applications where this is set up automatically)
examples_common::run(example_main);
// (but not necessary in normal Cocoa applications where this is set up automatically).
examples_common::run(example_main)
}