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

This base class is for filter elements that process data. Elements that are suitable for implementation using BaseTransform are ones where the size and caps of the output is known entirely from the input caps and buffer sizes. These include elements that directly transform one buffer into another, modify the contents of a buffer in-place, as well as elements that collate multiple input buffers into one output buffer, or that expand one input buffer into multiple output buffers. See below for more concrete use cases.

It provides for:

  • one sinkpad and one srcpad

  • Possible formats on sink and source pad implemented with custom transform_caps function. By default uses same format on sink and source.

  • Handles state changes

  • Does flushing

  • Push mode

  • Pull mode if the sub-class transform can operate on arbitrary data

Use Cases

Passthrough mode

  • Element has no interest in modifying the buffer. It may want to inspect it, in which case the element should have a transform_ip function. If there is no transform_ip function in passthrough mode, the buffer is pushed intact.

  • The GstBaseTransformClass.passthrough_on_same_caps variable will automatically set/unset passthrough based on whether the element negotiates the same caps on both pads.

  • GstBaseTransformClass.passthrough_on_same_caps on an element that doesn’t implement a transform_caps function is useful for elements that only inspect data (such as level)

  • Example elements

  • Level

  • Videoscale, audioconvert, videoconvert, audioresample in certain modes.

Modifications in-place - input buffer and output buffer are the same thing.

  • The element must implement a transform_ip function.

  • Output buffer size must <= input buffer size

  • If the always_in_place flag is set, non-writable buffers will be copied and passed to the transform_ip function, otherwise a new buffer will be created and the transform function called.

  • Incoming writable buffers will be passed to the transform_ip function immediately.

  • only implementing transform_ip and not transform implies always_in_place = true

  • Example elements:

  • Volume

  • Audioconvert in certain modes (signed/unsigned conversion)

  • videoconvert in certain modes (endianness swapping)

Modifications only to the caps/metadata of a buffer

  • The element does not require writable data, but non-writable buffers should be subbuffered so that the meta-information can be replaced.

  • Elements wishing to operate in this mode should replace the prepare_output_buffer method to create subbuffers of the input buffer and set always_in_place to true

  • Example elements

  • Capsfilter when setting caps on outgoing buffers that have none.

  • identity when it is going to re-timestamp buffers by datarate.

Normal mode

  • always_in_place flag is not set, or there is no transform_ip function
  • Element will receive an input buffer and output buffer to operate on.
  • Output buffer is allocated by calling the prepare_output_buffer function.
  • Example elements:
  • Videoscale, videoconvert, audioconvert when doing scaling/conversions

Special output buffer allocations

  • Elements which need to do special allocation of their output buffers beyond allocating output buffers via the negotiated allocator or buffer pool should implement the prepare_output_buffer method.

  • Example elements:

  • efence

Sub-class settable flags on GstBaseTransform

  • passthrough

  • Implies that in the current configuration, the sub-class is not interested in modifying the buffers.

  • Elements which are always in passthrough mode whenever the same caps has been negotiated on both pads can set the class variable passthrough_on_same_caps to have this behaviour automatically.

  • always_in_place

  • Determines whether a non-writable buffer will be copied before passing to the transform_ip function.

  • Implied true if no transform function is implemented.

  • Implied false if ONLY transform function is implemented.

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

Implements

BaseTransformExt, gst::prelude::ElementExt, gst::prelude::ObjectExt, trait@glib::ObjectExt, BaseTransformExtManual

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 !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
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
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

Returns the argument unchanged.

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

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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
Sets the property property_name of the object to value value. Read more
Sets the property property_name of the object to value value. Read more
Sets multiple properties of the object at once. Read more
Sets multiple properties of the object at once. Read more
Gets the property property_name of the object and cast it to the type V. Read more
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.
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect a closure to the signal signal_name on this object. Read more
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 invoke_with_values, or invoke when using Rust closures. Read more
Emit signal by signal id. Read more
Same as Self::emit but takes Value for the arguments.
Emit signal by its name. Read more
Emit signal by its name. Read more
Emit signal by its name with details. Read more
Emit signal by its name with details. Read more
Emit signal by signal id with details. Read more
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.
Add a callback to be notified when the Object is disposed.
Add a callback to be notified when the Object is disposed. Read more
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.
Runs the dispose mechanism of the object. Read more
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
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.