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255 lines
10 KiB
Rust
255 lines
10 KiB
Rust
// Copyright (C) 2018 Sebastian Dröge <sebastian@centricular.com>
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//
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// SPDX-License-Identifier: MIT OR Apache-2.0
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use gst::glib;
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use gst::prelude::*;
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use gst::subclass::prelude::*;
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use gst::glib::once_cell::sync::Lazy;
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// This module contains the private implementation details of our element
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static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
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gst::DebugCategory::new(
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"rsidentity",
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gst::DebugColorFlags::empty(),
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Some("Identity Element"),
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)
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});
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// Struct containing all the element data
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pub struct Identity {
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srcpad: gst::Pad,
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sinkpad: gst::Pad,
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}
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impl Identity {
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// Called whenever a new buffer is passed to our sink pad. Here buffers should be processed and
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// whenever some output buffer is available have to push it out of the source pad.
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// Here we just pass through all buffers directly
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//
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// See the documentation of gst::Buffer and gst::BufferRef to see what can be done with
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// buffers.
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fn sink_chain(
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&self,
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pad: &gst::Pad,
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buffer: gst::Buffer,
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) -> Result<gst::FlowSuccess, gst::FlowError> {
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gst::log!(CAT, obj: pad, "Handling buffer {:?}", buffer);
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self.srcpad.push(buffer)
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}
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// Called whenever an event arrives on the sink pad. It has to be handled accordingly and in
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// most cases has to be either passed to Pad::event_default() on this pad for default handling,
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// or Pad::push_event() on all pads with the opposite direction for direct forwarding.
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// Here we just pass through all events directly to the source pad.
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//
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// See the documentation of gst::Event and gst::EventRef to see what can be done with
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// events, and especially the gst::EventView type for inspecting events.
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fn sink_event(&self, pad: &gst::Pad, event: gst::Event) -> bool {
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gst::log!(CAT, obj: pad, "Handling event {:?}", event);
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self.srcpad.push_event(event)
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}
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// Called whenever a query is sent to the sink pad. It has to be answered if the element can
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// handle it, potentially by forwarding the query first to the peer pads of the pads with the
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// opposite direction, or false has to be returned. Default handling can be achieved with
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// Pad::query_default() on this pad and forwarding with Pad::peer_query() on the pads with the
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// opposite direction.
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// Here we just forward all queries directly to the source pad's peers.
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//
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// See the documentation of gst::Query and gst::QueryRef to see what can be done with
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// queries, and especially the gst::QueryView type for inspecting and modifying queries.
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fn sink_query(&self, pad: &gst::Pad, query: &mut gst::QueryRef) -> bool {
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gst::log!(CAT, obj: pad, "Handling query {:?}", query);
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self.srcpad.peer_query(query)
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}
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// Called whenever an event arrives on the source pad. It has to be handled accordingly and in
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// most cases has to be either passed to Pad::event_default() on the same pad for default
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// handling, or Pad::push_event() on all pads with the opposite direction for direct
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// forwarding.
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// Here we just pass through all events directly to the sink pad.
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//
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// See the documentation of gst::Event and gst::EventRef to see what can be done with
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// events, and especially the gst::EventView type for inspecting events.
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fn src_event(&self, pad: &gst::Pad, event: gst::Event) -> bool {
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gst::log!(CAT, obj: pad, "Handling event {:?}", event);
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self.sinkpad.push_event(event)
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}
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// Called whenever a query is sent to the source pad. It has to be answered if the element can
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// handle it, potentially by forwarding the query first to the peer pads of the pads with the
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// opposite direction, or false has to be returned. Default handling can be achieved with
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// Pad::query_default() on this pad and forwarding with Pad::peer_query() on the pads with the
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// opposite direction.
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// Here we just forward all queries directly to the sink pad's peers.
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//
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// See the documentation of gst::Query and gst::QueryRef to see what can be done with
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// queries, and especially the gst::QueryView type for inspecting and modifying queries.
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fn src_query(&self, pad: &gst::Pad, query: &mut gst::QueryRef) -> bool {
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gst::log!(CAT, obj: pad, "Handling query {:?}", query);
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self.sinkpad.peer_query(query)
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}
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}
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// This trait registers our type with the GObject object system and
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// provides the entry points for creating a new instance and setting
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// up the class data
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#[glib::object_subclass]
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impl ObjectSubclass for Identity {
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const NAME: &'static str = "GstRsIdentity";
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type Type = super::Identity;
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type ParentType = gst::Element;
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// Called when a new instance is to be created. We need to return an instance
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// of our struct here and also get the class struct passed in case it's needed
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fn with_class(klass: &Self::Class) -> Self {
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// Create our two pads from the templates that were registered with
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// the class and set all the functions on them.
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//
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// Each function is wrapped in catch_panic_pad_function(), which will
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// - Catch panics from the pad functions and instead of aborting the process
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// it will simply convert them into an error message and poison the element
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// instance
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// - Extract our Identity struct from the object instance and pass it to us
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//
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// Details about what each function is good for is next to each function definition
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let templ = klass.pad_template("sink").unwrap();
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let sinkpad = gst::Pad::builder_from_template(&templ)
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.chain_function(|pad, parent, buffer| {
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Identity::catch_panic_pad_function(
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parent,
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|| Err(gst::FlowError::Error),
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|identity| identity.sink_chain(pad, buffer),
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)
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})
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.event_function(|pad, parent, event| {
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Identity::catch_panic_pad_function(
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parent,
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|| false,
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|identity| identity.sink_event(pad, event),
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)
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})
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.query_function(|pad, parent, query| {
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Identity::catch_panic_pad_function(
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parent,
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|| false,
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|identity| identity.sink_query(pad, query),
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)
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})
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.build();
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let templ = klass.pad_template("src").unwrap();
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let srcpad = gst::Pad::builder_from_template(&templ)
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.event_function(|pad, parent, event| {
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Identity::catch_panic_pad_function(
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parent,
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|| false,
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|identity| identity.src_event(pad, event),
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)
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})
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.query_function(|pad, parent, query| {
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Identity::catch_panic_pad_function(
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parent,
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|| false,
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|identity| identity.src_query(pad, query),
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)
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})
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.build();
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// Return an instance of our struct and also include our debug category here.
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// The debug category will be used later whenever we need to put something
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// into the debug logs
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Self { srcpad, sinkpad }
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}
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}
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// Implementation of glib::Object virtual methods
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impl ObjectImpl for Identity {
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// Called right after construction of a new instance
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fn constructed(&self) {
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// Call the parent class' ::constructed() implementation first
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self.parent_constructed();
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// Here we actually add the pads we created in Identity::new() to the
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// element so that GStreamer is aware of their existence.
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let obj = self.obj();
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obj.add_pad(&self.sinkpad).unwrap();
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obj.add_pad(&self.srcpad).unwrap();
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}
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}
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impl GstObjectImpl for Identity {}
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// Implementation of gst::Element virtual methods
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impl ElementImpl for Identity {
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// Set the element specific metadata. This information is what
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// is visible from gst-inspect-1.0 and can also be programmatically
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// retrieved from the gst::Registry after initial registration
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// without having to load the plugin in memory.
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fn metadata() -> Option<&'static gst::subclass::ElementMetadata> {
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static ELEMENT_METADATA: Lazy<gst::subclass::ElementMetadata> = Lazy::new(|| {
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gst::subclass::ElementMetadata::new(
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"Identity",
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"Generic",
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"Does nothing with the data",
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"Sebastian Dröge <sebastian@centricular.com>",
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)
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});
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Some(&*ELEMENT_METADATA)
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}
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// Create and add pad templates for our sink and source pad. These
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// are later used for actually creating the pads and beforehand
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// already provide information to GStreamer about all possible
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// pads that could exist for this type.
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//
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// Actual instances can create pads based on those pad templates
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fn pad_templates() -> &'static [gst::PadTemplate] {
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static PAD_TEMPLATES: Lazy<Vec<gst::PadTemplate>> = Lazy::new(|| {
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// Our element can accept any possible caps on both pads
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let caps = gst::Caps::new_any();
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let src_pad_template = gst::PadTemplate::new(
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"src",
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gst::PadDirection::Src,
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gst::PadPresence::Always,
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&caps,
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)
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.unwrap();
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let sink_pad_template = gst::PadTemplate::new(
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"sink",
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gst::PadDirection::Sink,
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gst::PadPresence::Always,
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&caps,
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)
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.unwrap();
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vec![src_pad_template, sink_pad_template]
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});
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PAD_TEMPLATES.as_ref()
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}
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// Called whenever the state of the element should be changed. This allows for
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// starting up the element, allocating/deallocating resources or shutting down
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// the element again.
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fn change_state(
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&self,
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transition: gst::StateChange,
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) -> Result<gst::StateChangeSuccess, gst::StateChangeError> {
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gst::trace!(CAT, imp: self, "Changing state {:?}", transition);
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// Call the parent class' implementation of ::change_state()
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self.parent_change_state(transition)
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}
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}
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