#[repr(transparent)]
pub struct BaseSrc { /* private fields */ }
Expand description

This is a generic base class for source elements. The following types of sources are supported:

  • random access sources like files
  • seekable sources
  • live sources

The source can be configured to operate in any gst::Format with the BaseSrcExt::set_format() method. The currently set format determines the format of the internal gst::Segment and any gst::EventType::Segment events. The default format for BaseSrc is gst::Format::Bytes.

BaseSrc always supports push mode scheduling. If the following conditions are met, it also supports pull mode scheduling:

If all the conditions are met for operating in pull mode, BaseSrc is automatically seekable in push mode as well. The following conditions must be met to make the element seekable in push mode when the format is not gst::Format::Bytes:

  • GstBaseSrcClass::is_seekable returns true.
  • GstBaseSrcClass::query can convert all supported seek formats to the internal format as set with BaseSrcExt::set_format().
  • GstBaseSrcClass::do_seek is implemented, performs the seek and returns true.

When the element does not meet the requirements to operate in pull mode, the offset and length in the GstBaseSrcClass::create method should be ignored. It is recommended to subclass PushSrc instead, in this situation. If the element can operate in pull mode but only with specific offsets and lengths, it is allowed to generate an error when the wrong values are passed to the GstBaseSrcClass::create function.

BaseSrc has support for live sources. Live sources are sources that when paused discard data, such as audio or video capture devices. A typical live source also produces data at a fixed rate and thus provides a clock to publish this rate. Use BaseSrcExt::set_live() to activate the live source mode.

A live source does not produce data in the PAUSED state. This means that the GstBaseSrcClass::create method will not be called in PAUSED but only in PLAYING. To signal the pipeline that the element will not produce data, the return value from the READY to PAUSED state will be gst::StateChangeReturn::NoPreroll.

A typical live source will timestamp the buffers it creates with the current running time of the pipeline. This is one reason why a live source can only produce data in the PLAYING state, when the clock is actually distributed and running.

Live sources that synchronize and block on the clock (an audio source, for example) can use BaseSrcExt::wait_playing() when the GstBaseSrcClass::create function was interrupted by a state change to PAUSED.

The GstBaseSrcClass::get_times method can be used to implement pseudo-live sources. It only makes sense to implement the GstBaseSrcClass::get_times function if the source is a live source. The GstBaseSrcClass::get_times function should return timestamps starting from 0, as if it were a non-live source. The base class will make sure that the timestamps are transformed into the current running_time. The base source will then wait for the calculated running_time before pushing out the buffer.

For live sources, the base class will by default report a latency of 0. For pseudo live sources, the base class will by default measure the difference between the first buffer timestamp and the start time of get_times and will report this value as the latency. Subclasses should override the query function when this behaviour is not acceptable.

There is only support in BaseSrc for exactly one source pad, which should be named “src”. A source implementation (subclass of BaseSrc) should install a pad template in its class_init function, like so:

⚠️ The following code is in C ⚠️

static void
my_element_class_init (GstMyElementClass *klass)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
  // srctemplate should be a #GstStaticPadTemplate with direction
  // %GST_PAD_SRC and name "src"
  gst_element_class_add_static_pad_template (gstelement_class, &srctemplate);

  gst_element_class_set_static_metadata (gstelement_class,
     "Source name",
     "Source",
     "My Source element",
     "The author <my.sink@my.email>");
}

Controlled shutdown of live sources in applications

Applications that record from a live source may want to stop recording in a controlled way, so that the recording is stopped, but the data already in the pipeline is processed to the end (remember that many live sources would go on recording forever otherwise). For that to happen the application needs to make the source stop recording and send an EOS event down the pipeline. The application would then wait for an EOS message posted on the pipeline’s bus to know when all data has been processed and the pipeline can safely be stopped.

An application may send an EOS event to a source element to make it perform the EOS logic (send EOS event downstream or post a GST_MESSAGE_SEGMENT_DONE on the bus). This can typically be done with the ElementExtManual::send_event() function on the element or its parent bin.

After the EOS has been sent to the element, the application should wait for an EOS message to be posted on the pipeline’s bus. Once this EOS message is received, it may safely shut down the entire pipeline.

This is an Abstract Base Class, you cannot instantiate it.

Implements

BaseSrcExt, gst::prelude::ElementExt, gst::prelude::ObjectExt, trait@glib::ObjectExt, BaseSrcExtManual

Implementations

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

Override the virtual methods of this class for the given subclass and do other class initialization. Read more

Instance specific initialization. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Returns the type identifier of Self.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Upcasts an object to a superclass or interface T. Read more

Upcasts an object to a reference of its superclass or interface T. Read more

Tries to downcast to a subclass or interface implementor T. Read more

Tries to downcast to a reference of its subclass or interface implementor T. Read more

Tries to cast to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more

Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more

Casts to T unconditionally. Read more

Casts to &T unconditionally. Read more

Abort the state change of the element. This function is used by elements that do asynchronous state changes and find out something is wrong. Read more

Adds a pad (link point) to self. pad’s parent will be set to self; see GstObjectExt::set_parent() for refcounting information. Read more

Perform transition on self. Read more

Commit the state change of the element and proceed to the next pending state if any. This function is used by elements that do asynchronous state changes. The core will normally call this method automatically when an element returned StateChangeReturn::Success from the state change function. Read more

This is supported on crate feature v1_14 only.
This is supported on crate feature v1_14 only.
This is supported on crate feature v1_14 only.

Performs a query on the given element. Read more

Sends an event to an element. If the element doesn’t implement an event handler, the event will be pushed on a random linked sink pad for downstream events or a random linked source pad for upstream events. Read more

This is supported on crate feature v1_10 only.
This is supported on crate feature v1_10 only.
This is supported on crate feature v1_10 only.
This is supported on crate feature v1_10 only.
This is supported on crate feature v1_10 only.
This is supported on crate feature v1_10 only.

Performs the conversion.

Attach the ControlBinding to the object. If there already was a ControlBinding for this property it will be replaced. Read more

A default error function that uses g_printerr() to display the error message and the optional debug string.. Read more

Gets the corresponding ControlBinding for the property. This should be unreferenced again after use. Read more

Obtain the control-rate for this self. Audio processing Element objects will use this rate to sub-divide their processing loop and call sync_values() in between. The length of the processing segment should be up to control-rate nanoseconds. Read more

Returns a copy of the name of self. Caller should g_free() the return value after usage. For a nameless object, this returns None, which you can safely g_free() as well. Read more

Returns the parent of self. This function increases the refcount of the parent object so you should gst_object_unref() it after usage. Read more

Generates a string describing the path of self in the object hierarchy. Only useful (or used) for debugging. Read more

Gets the value for the given controlled property at the requested time. Read more

Performs the conversion.

Returns true if the object is an instance of (can be cast to) T.

Returns the type of the object.

Returns the ObjectClass of the object. Read more

Returns the class of the object.

Returns the class of the object in the given type T. Read more

Returns the interface T of the object. Read more

Similar to Self::set_property but fails instead of panicking.

Sets the property property_name of the object to value value. Read more

Similar to Self::set_property but fails instead of panicking.

Sets the property property_name of the object to value value. Read more

Similar to Self::set_properties but fails instead of panicking.

Sets multiple properties of the object at once. Read more

Similar to Self::set_properties_from_value but fails instead of panicking.

Sets multiple properties of the object at once. Read more

Similar to Self::property but fails instead of panicking.

Gets the property property_name of the object and cast it to the type V. Read more

Similar to Self::property_value but fails instead of panicking.

Gets the property property_name of the object. Read more

Check if the object has a property property_name of the given type_. Read more

Get the type of the property property_name of this object. Read more

Get the ParamSpec of the property property_name of this object.

Return all ParamSpec of the properties of this object.

Freeze all property notifications until the return guard object is dropped. Read more

Set arbitrary data on this object with the given key. Read more

Return previously set arbitrary data of this object with the given key. Read more

Retrieve previously set arbitrary data of this object with the given key. Read more

Set arbitrary data on this object with the given key. Read more

Return previously set arbitrary data of this object with the given key. Read more

Retrieve previously set arbitrary data of this object with the given key. Read more

Block a given signal handler. Read more

Unblock a given signal handler.

Stop emission of the currently emitted signal.

Stop emission of the currently emitted signal by the (possibly detailed) signal name.

Similar to Self::connect but fails instead of panicking.

Connect to the signal signal_name on this object. Read more

Similar to Self::connect_id but fails instead of panicking.

Connect to the signal signal_id on this object. Read more

Similar to Self::connect_local but fails instead of panicking.

Connect to the signal signal_name on this object. Read more

Similar to Self::connect_local_id but fails instead of panicking.

Connect to the signal signal_id on this object. Read more

Similar to Self::connect_unsafe but fails instead of panicking.

Connect to the signal signal_name on this object. Read more

Similar to Self::connect_unsafe_id but fails instead of panicking.

Similar to Self::connect_closure but fails instead of panicking.

Connect a closure to the signal signal_name on this object. Read more

Similar to Self::connect_closure_id but fails instead of panicking.

Connect a closure to the signal signal_id on this object. Read more

Limits the lifetime of closure to the lifetime of the object. When the object’s reference count drops to zero, the closure will be invalidated. An invalidated closure will ignore any calls to Closure::invoke. Read more

Connect to the signal signal_id on this object. Read more

Similar to Self::emit but fails instead of panicking.

Emit signal by signal id. Read more

Similar to Self::emit_with_values but fails instead of panicking.

Same as Self::emit but takes Value for the arguments.

Similar to Self::emit_by_name but fails instead of panicking.

Emit signal by its name. Read more

Similar to Self::emit_by_name_with_values but fails instead of panicking.

Emit signal by its name. Read more

Similar to Self::emit_by_name_with_details but fails instead of panicking.

Emit signal by its name with details. Read more

Similar to Self::emit_by_name_with_details_and_values but fails instead of panicking.

Emit signal by its name with details. Read more

Similar to Self::emit_with_details but fails instead of panicking.

Emit signal by signal id with details. Read more

Similar to Self::emit_with_details_and_values but fails instead of panicking.

Emit signal by signal id with details. Read more

Disconnect a previously connected signal handler.

Connect to the notify signal of the object. Read more

Connect to the notify signal of the object. Read more

Connect to the notify signal of the object. Read more

Notify that the given property has changed its value. Read more

Notify that the given property has changed its value. Read more

Downgrade this object to a weak reference.

Bind property source_property on this object to the target_property on the target object. Read more

Returns the strong reference count of this object.

Ensures that the type has been registered with the type system.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

Returns a SendValue clone of self.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.