mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-11-14 13:21:28 +00:00
108 lines
3.1 KiB
Markdown
108 lines
3.1 KiB
Markdown
# QtGStreamer vs C GStreamer
|
||
|
||
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
|
||
|
||
<table>
|
||
<colgroup>
|
||
<col width="50%" />
|
||
<col width="50%" />
|
||
</colgroup>
|
||
<thead>
|
||
<tr class="header">
|
||
<th>C GStreamer</th>
|
||
<th>QtGStreamer</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="odd">
|
||
<td><code>gst_element_factory_make()</code></td>
|
||
<td><code>QGst::ElementFactory::make(const QString &factoryName, const char *elementName=NULL)</code></td>
|
||
</tr>
|
||
<tr class="even">
|
||
<td><code>gst_parse_bin_from_description()</code></td>
|
||
<td><code>QGst::Bin::fromDescription(const QString &description, BinFromDescriptionOption ghostUnlinkedPads=Ghost)</code></td>
|
||
</tr>
|
||
<tr class="odd">
|
||
<td><code>gst_caps_from_string()</code></td>
|
||
<td><p><code>QGst::Caps::fromString(const QString &string)</code></p></td>
|
||
</tr>
|
||
<tr class="even">
|
||
<td><code>g_signal_connect()</code></td>
|
||
<td><code>QGlib::connect(GObject* instance, const char *detailedSignal, T *receiver, R(T::*)(Args...) slot, ConnectFlags flags)</code></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
|
||
# 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\[st\]\_\<class\> prefix removed and converted to camel case.
|
||
|
||
For example,
|
||
|
||
``` c
|
||
gboolean gst_caps_is_emtpy(const GstCaps *caps);
|
||
```
|
||
|
||
becomes:
|
||
|
||
``` c
|
||
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:
|
||
|
||
``` c
|
||
ElementPtr qgstElement = QGst::ElementFactory::make("playbin");
|
||
GstElement* gstElement = GST_ELEMENT(qgstElement);
|
||
```
|