MLT++ library
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3.4 KiB

MLT++
-----

This mlt sub-project provides a C++ wrapping for the MLT library.

INSTALLATION
------------

./configure [ --prefix=path ]
make
make install

USAGE
-----

Use the following definitions in a Makefile to compile and link with mlt++:

CXXFLAGS=`mlt-config -Wall`
LDFLAGS=-lmlt++

Include files for the classes can either be explicitly included, ie:

#include <mlt++/MltProducer.h>
etc

Or you can include all using:

#include <mlt++/Mlt.h>

All definitions are placed in an Mlt namespace, and adhere closely to the C
naming convention. Mappings always follow the pattern:

Factory methods:

mlt_factory_init ==> Mlt::Factory::init
mlt_factory_producer ==> Mlt::Factory::producer
mlt_factory_filter ==> Mlt::Factory::filter
mlt_factory_transition ==> Mlt::Factory::transition
mlt_factory_consumer ==> Mlt::Factory::consumer
mlt_factory_close ==> Mlt::Factory::close

NB: Factory usage for service construction is optional.

Types:

mlt_properties ==> Mlt::Properties
mlt_frame ==> Mlt::Frame
mlt_service ==> Mlt::Service
mlt_producer ==> Mlt::Producer
mlt_filter ==> Mlt::Filter
mlt_transition ==> Mlt::Transition
mlt_consumer ==> Mlt::Consumer

Methods:

mlt_type_method ==> Mlt::Type.method
ie: mlt_playlist_append ==> Mlt::Playlist.append

Parent methods are available directly on children.

Additionally, you can specify:

using namespace Mlt;

To avoid the enforced use of the Mlt:: prefix.

Enumerators and macros are reused directly from the C library.

CLASS HIERARCHY
---------------

The currently mapped objects are shown in the following hierarchy:

Factory
Properties
Frame
Service
Consumer
Field
Filter
Multitrack
Producer
Playlist
Tractor
Transition

An additional set of classes allow apps to behave as, and communicate with,
client/server components - these components provide MLT with unique
possibilties for process to process or system to system communications.

Miracle
Response

SPECIAL CASES
-------------

Care should be taken with wrapper objects.

Taking, as an example, the C function that returns the immediate consumer of
a service:

mlt_service mlt_service_consumer( mlt_service );

This maps to:

Mlt::Service *Mlt::Service.consumer( );

Note that you get an object back - it is never the original c++ object, but
a wrapping object. This is done to keep consistency with the C api which may
instantiate C instances - therefore it cannot be assumed that a C++ object
exists for all mlt service instances.

As such, it is mandatory that you delete these objects. The original will
not be affected. However, all other modifications (to properties or its
state of connection) will be reflected in the original object.

This approach excludes the use of RTTI to determine the real type of the
object - this can only be done by parsing the objects properties.

Objects may be invalid - always use the is_valid method to check validity
before use.

LIMITATIONS
-----------

The mechanisms for the definition of new services are deliberately
excluded from the C++ wrappings - this is done to ensure that service
networks constructed can be serialised and used by existing applications
which are based on the C API (such as miracle).

SWIG
----

Experimental swig bindings based on mlt++ are provided.