# GStreamer SDK documentation : QtGStreamer vs C GStreamer This page last changed on May 24, 2013 by xartigas. QtGStreamer is designed to mirror the C GStreamer API as closely as possible. There are, of course, minor differences. They are documented here. # Common Functions
C GStreamer QtGStreamer
gst_element_factory_make() QGst::ElementFactory::make(const QString &factoryName, const char *elementName=NULL)
gst_parse_bin_from_description() QGst::Bin::fromDescription(const QString &description, BinFromDescriptionOption ghostUnlinkedPads=Ghost)
gst_caps_from_string()

QGst::Caps::fromString(const QString &string)

g_signal_connect() QGlib::connect(GObject* instance, const char *detailedSignal, T *receiver, R(T::*)(Args...) slot, ConnectFlags flags)
# Naming Convention QtGStreamer follows a strict naming policy to help make cross referencing easier: ### Namespaces The "G" namespace (`GObject`, `GValue`, etc...) is referred to as "QGlib". The "Gst" namespace (`GstObject`, `GstElement`, etc...) is referred to as "QGst". ### Class Names Class names should be the same as their G\* equivalents, with the namespace prefix removed. For example, "`GstObject`" becomes "`QGst::Object`", "`GParamSpec`" becomes "`QGlib::ParamSpec`", etc... ### Method Names In general the method names should be the same as the GStreamer ones, with the g\[st\]\_\ prefix removed and converted to camel case. For example, ``` theme: Default; brush: cpp; gutter: false gboolean gst_caps_is_emtpy(const GstCaps *caps); ``` becomes: ``` theme: Default; brush: cpp; gutter: false namespace QGst { class Caps { bool isEmpty() const; } } ``` There are cases where this may not be followed: 1. **Properties**. Most property getters have a "get" prefix, for example, `gst_object_get_name()`. In QtGStreamer the "get" prefix is omitted, so this becomes just `name()`. 2. **Overloaded members**. In C there is no possibility to have two methods with the same name, so overloaded members usually have some extra suffix, like "\_full". For example, `g_object_set_data()` and `g_object_set_data_full()`. In C++ we just add a method with the same name, or put optional parameters in the existing method. 3. **Other cases where the glib/gstreamer method name doesn't make much sense**. For example, `gst_element_is_locked_state()`. That doesn't make sense in english, as "sate" is the subject and should go before the verb "is". So, it becomes `stateIsLocked()`. # Reference Counting Reference counting is handled the same way as Qt does. There is no need to call `g_object_ref()`` and g_object_unref()`. # Access to GStreamer Elements QtGStreamer provides access to the underlying C objects, in case you need them. This is accessible with a simple cast: ``` theme: Default; brush: cpp; gutter: false ElementPtr qgstElement = QGst::ElementFactory::make("playbin2"); GstElement* gstElement = GST_ELEMENT(qgstElement); ``` Document generated by Confluence on Oct 08, 2015 10:27