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examples: Add a VideoOverlayComposition example

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Replicate the pango-cairo cairooverlay example, but
drawing into a gst::VideoOverlayComposition using the
overlaycomposition element.
This commit is contained in:
Jan Schmidt 2020-05-28 14:37:23 +10:00
parent dd226e80f8
commit 6c876a5681
2 changed files with 345 additions and 0 deletions
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6
examples/Cargo.toml
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@ -28,6 +28,7 @@ derive_more = "0.99.5"
futures = "0.3"
byte-slice-cast = "0.3"
cairo-rs = { git = "https://github.com/gtk-rs/cairo", features=["use_glib"], optional = true }
cairo-sys-rs = { git = "https://github.com/gtk-rs/cairo", features=["use_glib"], optional = true }
pango = { git = "https://github.com/gtk-rs/pango", optional = true }
pangocairo = { git = "https://github.com/gtk-rs/pangocairo", optional = true }
glutin = { version = "0.21", optional = true }
@ -49,6 +50,7 @@ gst-rtsp-server = ["gstreamer-rtsp-server", "gstreamer-rtsp", "gstreamer-sdp"]
gst-rtsp-server-record = ["gstreamer-rtsp-server-sys", "gstreamer-rtsp-server", "gstreamer-rtsp", "gio"]
v1_10 = ["gstreamer/v1_10"]
pango-cairo = ["pango", "pangocairo", "cairo-rs"]
overlay-composition = ["pango", "pangocairo", "cairo-rs", "cairo-sys-rs" ]
gl = ["gstreamer-gl", "gl_generator", "glutin"]
gl-egl = ["gstreamer-gl/egl"]
gl-x11 = ["gstreamer-gl/x11"]
@ -143,6 +145,10 @@ name = "discoverer"
name = "pango-cairo"
required-features = ["pango-cairo"]
[[bin]]
name = "overlay-composition"
required-features = ["overlay-composition"]
[[bin]]
name = "ges"
required-features = ["ges"]

339
examples/src/bin/overlay-composition.rs Normal file
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@ -0,0 +1,339 @@
// This example demonstrates how to draw an overlay on a video stream using
// cairo and the overlay composition element.
// Additionally, this example uses functionality of the pango library, which handles
// text layouting. The pangocairo crate is a nice wrapper combining both libraries
// into a nice interface.
// {videotestsrc} - {overlaycomposition} - {capsfilter} - {videoconvert} - {autovideosink}
// The capsfilter element allows us to dictate the video resolution we want for the
// videotestsrc and the overlaycomposition element.
//
// There is a small amount of unsafe code that demonstrates how to work around
// Cairo's internal refcounting of the target buffer surface
extern crate gstreamer as gst;
use gst::prelude::*;
extern crate gstreamer_video as gst_video;
use pango::prelude::*;
use std::ops;
use std::sync::{Arc, Mutex};
use anyhow::Error;
use derive_more::{Display, Error};
#[path = "../examples-common.rs"]
mod examples_common;
#[derive(Debug, Display, Error)]
#[display(fmt = "Missing element {}", _0)]
struct MissingElement(#[error(not(source))] &'static str);
#[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,
}
struct DrawingContext {
layout: glib::SendUniqueCell<LayoutWrapper>,
info: Option<gst_video::VideoInfo>,
}
#[derive(Debug)]
struct LayoutWrapper(pango::Layout);
impl ops::Deref for LayoutWrapper {
type Target = pango::Layout;
fn deref(&self) -> &pango::Layout {
&self.0
}
}
unsafe impl glib::SendUnique for LayoutWrapper {
fn is_unique(&self) -> bool {
self.0.ref_count() == 1
}
}
fn create_pipeline() -> Result<gst::Pipeline, Error> {
gst::init()?;
let pipeline = gst::Pipeline::new(None);
let src = gst::ElementFactory::make("videotestsrc", None)
.map_err(|_| MissingElement("videotestsrc"))?;
let overlay = gst::ElementFactory::make("overlaycomposition", None)
.map_err(|_| MissingElement("overlaycomposition"))?;
let capsfilter =
gst::ElementFactory::make("capsfilter", None).map_err(|_| MissingElement("capsfilter"))?;
let videoconvert = gst::ElementFactory::make("videoconvert", None)
.map_err(|_| MissingElement("videoconvert"))?;
let sink = gst::ElementFactory::make("autovideosink", None)
.map_err(|_| MissingElement("autovideosink"))?;
pipeline.add_many(&[&src, &overlay, &capsfilter, &videoconvert, &sink])?;
gst::Element::link_many(&[&src, &overlay, &capsfilter, &videoconvert, &sink])?;
// Plug in a capsfilter element that will force the videotestsrc and the overlay to work
// with images of the size 800x800, and framerate of 15 fps, since my laptop struggles
// rendering it at the default 30 fps
let caps = gst::Caps::builder("video/x-raw")
.field("width", &800i32)
.field("height", &800i32)
.field("framerate", &gst::Fraction::new(15, 1))
.build();
capsfilter.set_property("caps", &caps).unwrap();
// The videotestsrc supports multiple test patterns. In this example, we will use the
// pattern with a white ball moving around the video's center point.
src.set_property_from_str("pattern", "ball");
// The PangoFontMap represents the set of fonts available for a particular rendering system.
let fontmap = pangocairo::FontMap::new().unwrap();
// Create a new pango layouting context for the fontmap.
let context = fontmap.create_context().unwrap();
// Create a pango layout object. This object is a string of text we want to layout.
// It is wrapped in a LayoutWrapper (defined above) to be able to send it across threads.
let layout = LayoutWrapper(pango::Layout::new(&context));
// Select the text content and the font we want to use for the piece of text.
let font_desc = pango::FontDescription::from_string("Sans Bold 26");
layout.set_font_description(Some(&font_desc));
layout.set_text("GStreamer");
// The following is a context struct (containing the pango layout and the configured video info).
// We have to wrap it in an Arc (or Rc) to get reference counting, that is: to be able to have
// shared ownership of it in multiple different places (the two signal handlers here).
// We have to wrap it in a Mutex because Rust's type-system can't know that both signals are
// only ever called from a single thread (the streaming thread). It would be enough to have
// something that is Send in theory but that's not how signal handlers are generated unfortunately.
// The Mutex (or otherwise if we didn't need the Sync bound we could use a RefCell) is to implement
// interior mutability (see Rust docs). Via this we can get a mutable reference to the contained
// data which is checked at runtime for uniqueness (blocking in case of mutex, panic in case
// of refcell) instead of compile-time (like with normal references).
let drawer = Arc::new(Mutex::new(DrawingContext {
layout: glib::SendUniqueCell::new(layout).unwrap(),
info: None,
}));
let drawer_clone = drawer.clone();
// Connect to the overlaycomposition element's "draw" signal, which is emitted for
// each videoframe piped through the element. The signal handler needs to
// return a gst_video::VideoOverlayComposition to be drawn on the frame
//
// Signals connected with the connect(<name>, ...) API get their arguments
// passed as array of glib::Value. For a documentation about the actual arguments
// it is always a good idea to check the element's signals using either
// gst-inspect, or the online documentation.
//
// In this case, the signal passes the gst::Element and a gst::Sample with
// the current buffer
overlay
.connect("draw", false, move |args| {
use std::f64::consts::PI;
let drawer = &drawer_clone;
let drawer = drawer.lock().unwrap();
// Get the signal's arguments
let _overlay = args[0].get::<gst::Element>().unwrap().unwrap();
let sample = args[1].get::<gst::Sample>().unwrap().unwrap();
let buffer = sample.get_buffer().unwrap();
let timestamp = buffer.get_pts();
let info = drawer.info.as_ref().unwrap();
let layout = drawer.layout.borrow();
let angle = 2.0
* PI
* ((timestamp % (10 * gst::SECOND)).unwrap() as f64
/ (10.0 * gst::SECOND_VAL as f64));
/* Create a gst::Buffer for Cairo to draw into */
let frame_width = info.width() as usize;
let frame_height = info.height() as usize;
let stride = 4 * frame_width;
let frame_size = stride * frame_height;
/* Create an RGBA buffer, and add a video meta that the videooverlaycomposition expects */
let mut buffer = gst::Buffer::with_size(frame_size).unwrap();
gst_video::VideoMeta::add(
buffer.get_mut().unwrap(),
gst_video::VideoFrameFlags::NONE,
gst_video::VideoFormat::Bgra,
frame_width as u32,
frame_height as u32,
);
let buffer = buffer.into_mapped_buffer_writable().unwrap();
let buffer = {
let buffer_ptr = unsafe { buffer.get_buffer().as_ptr() };
let surface = cairo::ImageSurface::create_for_data(
buffer,
cairo::Format::ARgb32,
frame_width as i32,
frame_height as i32,
stride as i32,
)
.unwrap();
let cr = cairo::Context::new(&surface);
cr.save();
cr.set_operator(cairo::Operator::Clear);
cr.paint();
cr.restore();
// The image we draw (the text) will be static, but we will change the
// transformation on the drawing context, which rotates and shifts everything
// that we draw afterwards. Like this, we have no complicated calulations
// in the actual drawing below.
// Calling multiple transformation methods after each other will apply the
// new transformation on top. If you repeat the cr.rotate(angle) line below
// this a second time, everything in the canvas will rotate twice as fast.
cr.translate(
f64::from(info.width()) / 2.0,
f64::from(info.height()) / 2.0,
);
cr.rotate(angle);
// This loop will render 10 times the string "GStreamer" in a circle
for i in 0..10 {
// Cairo, like most rendering frameworks, is using a stack for transformations
// with this, we push our current transformation onto this stack - allowing us
// to make temporary changes / render something / and then returning to the
// previous transformations.
cr.save();
let angle = (360. * f64::from(i)) / 10.0;
let red = (1.0 + f64::cos((angle - 60.0) * PI / 180.0)) / 2.0;
cr.set_source_rgb(red, 0.0, 1.0 - red);
cr.rotate(angle * PI / 180.0);
// Update the text layout. This function is only updating pango's internal state.
// So e.g. that after a 90 degree rotation it knows that what was previously going
// to end up as a 200x100 rectangle would now be 100x200.
pangocairo::functions::update_layout(&cr, &**layout);
let (width, _height) = layout.get_size();
// Using width and height of the text, we can properly possition it within
// our canvas.
cr.move_to(
-(f64::from(width) / f64::from(pango::SCALE)) / 2.0,
-(f64::from(info.height())) / 2.0,
);
// After telling the layout object where to draw itself, we actually tell
// it to draw itself into our cairo context.
pangocairo::functions::show_layout(&cr, &**layout);
// Here we go one step up in our stack of transformations, removing any
// changes we did to them since the last call to cr.save();
cr.restore();
}
// Safety: The surface still owns a mutable reference to the buffer but our reference
// to the surface here is the last one. After dropping the surface the buffer would be
// freed, so we keep an additional strong reference here before dropping the surface,
// which is then returned. As such it's guaranteed that nothing is using the buffer
// anymore mutably.
drop(cr);
unsafe {
assert_eq!(
cairo_sys::cairo_surface_get_reference_count(surface.to_raw_none()),
1
);
let buffer = glib::translate::from_glib_none(buffer_ptr);
drop(surface);
buffer
}
};
/* Turn the buffer into a VideoOverlayRectangle, then place
* that into a VideoOverlayComposition and return it.
*
* A VideoOverlayComposition can take a Vec of such rectangles
* spaced around the video frame, but we're just outputting 1
* here */
let rect = gst_video::VideoOverlayRectangle::new_raw(
&buffer,
0, 0, frame_width as u32, frame_height as u32,
gst_video::VideoOverlayFormatFlags::PREMULTIPLIED_ALPHA,
);
Some(gst_video::VideoOverlayComposition::new(Some(&rect)).unwrap().to_value())
})
.unwrap();
// Add a signal handler to the overlay's "caps-changed" signal. This could e.g.
// be called when the sink that we render to does not support resizing the image
// itself - but the user just changed the window-size. The element after the overlay
// will then change its caps and we use the notification about this change to
// resize our canvas's size.
// Another possibility for when this might happen is, when our video is a network
// stream that dynamically changes resolution when enough bandwith is available.
overlay
.connect("caps-changed", false, move |args| {
let _overlay = args[0].get::<gst::Element>().unwrap().unwrap();
let caps = args[1].get::<gst::Caps>().unwrap().unwrap();
let mut drawer = drawer.lock().unwrap();
drawer.info = Some(gst_video::VideoInfo::from_caps(&caps).unwrap());
None
})
.unwrap();
Ok(pipeline)
}
fn main_loop(pipeline: gst::Pipeline) -> Result<(), Error> {
pipeline.set_state(gst::State::Playing)?;
let bus = pipeline
.get_bus()
.expect("Pipeline without bus. Shouldn't happen!");
for msg in bus.iter_timed(gst::CLOCK_TIME_NONE) {
use gst::MessageView;
match msg.view() {
MessageView::Eos(..) => break,
MessageView::Error(err) => {
pipeline.set_state(gst::State::Null)?;
return Err(ErrorMessage {
src: msg
.get_src()
.map(|s| String::from(s.get_path_string()))
.unwrap_or_else(|| String::from("None")),
error: err.get_error().to_string(),
debug: err.get_debug(),
source: err.get_error(),
}
.into());
}
_ => (),
}
}
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 main() {
// tutorials_common::run is only required to set up the application environent on macOS
// (but not necessary in normal Cocoa applications where this is set up autmatically)
examples_common::run(example_main);
}