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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<a href="#GstBaseTransform.synopsis" class="shortcut">Top</a>
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<a href="#GstBaseTransform.description" class="shortcut">Description</a>
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<a href="#GstBaseTransform.object-hierarchy" class="shortcut">Object Hierarchy</a>
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<a href="#GstBaseTransform.properties" class="shortcut">Properties</a>
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<div class="refentry">
<a name="GstBaseTransform"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="GstBaseTransform.top_of_page"></a>GstBaseTransform</span></h2>
<p>GstBaseTransform — Base class for simple transform filters</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<a name="GstBaseTransform.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include <gst/base/gstbasetransform.h>
struct <a class="link" href="GstBaseTransform.html#GstBaseTransform-struct" title="struct GstBaseTransform">GstBaseTransform</a>;
struct <a class="link" href="GstBaseTransform.html#GstBaseTransformClass" title="struct GstBaseTransformClass">GstBaseTransformClass</a>;
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> <a class="link" href="GstBaseTransform.html#gst-base-transform-is-passthrough" title="gst_base_transform_is_passthrough ()">gst_base_transform_is_passthrough</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBaseTransform.html#gst-base-transform-set-passthrough" title="gst_base_transform_set_passthrough ()">gst_base_transform_set_passthrough</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> passthrough</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> <a class="link" href="GstBaseTransform.html#gst-base-transform-is-in-place" title="gst_base_transform_is_in_place ()">gst_base_transform_is_in_place</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBaseTransform.html#gst-base-transform-set-in-place" title="gst_base_transform_set_in_place ()">gst_base_transform_set_in_place</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> in_place</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> <a class="link" href="GstBaseTransform.html#gst-base-transform-is-qos-enabled" title="gst_base_transform_is_qos_enabled ()">gst_base_transform_is_qos_enabled</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBaseTransform.html#gst-base-transform-set-qos-enabled" title="gst_base_transform_set_qos_enabled ()">gst_base_transform_set_qos_enabled</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> enabled</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBaseTransform.html#gst-base-transform-update-qos" title="gst_base_transform_update_qos ()">gst_base_transform_update_qos</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> proportion</code></em>,
<em class="parameter"><code><a href="../gstreamer-1.0/GstClock.html#GstClockTimeDiff"><span class="type">GstClockTimeDiff</span></a> diff</code></em>,
<em class="parameter"><code><a href="../gstreamer-1.0/GstClock.html#GstClockTime"><span class="type">GstClockTime</span></a> timestamp</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBaseTransform.html#gst-base-transform-set-gap-aware" title="gst_base_transform_set_gap_aware ()">gst_base_transform_set_gap_aware</a> (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> gap_aware</code></em>);
#define <a class="link" href="GstBaseTransform.html#GST-BASE-TRANSFORM-SINK-NAME:CAPS" title="GST_BASE_TRANSFORM_SINK_NAME">GST_BASE_TRANSFORM_SINK_NAME</a>
#define <a class="link" href="GstBaseTransform.html#GST-BASE-TRANSFORM-SRC-NAME:CAPS" title="GST_BASE_TRANSFORM_SRC_NAME">GST_BASE_TRANSFORM_SRC_NAME</a>
#define <a class="link" href="GstBaseTransform.html#GST-BASE-TRANSFORM-SINK-PAD:CAPS" title="GST_BASE_TRANSFORM_SINK_PAD()">GST_BASE_TRANSFORM_SINK_PAD</a> (obj)
#define <a class="link" href="GstBaseTransform.html#GST-BASE-TRANSFORM-SRC-PAD:CAPS" title="GST_BASE_TRANSFORM_SRC_PAD()">GST_BASE_TRANSFORM_SRC_PAD</a> (obj)
#define <a class="link" href="GstBaseTransform.html#GST-BASE-TRANSFORM-FLOW-DROPPED:CAPS" title="GST_BASE_TRANSFORM_FLOW_DROPPED">GST_BASE_TRANSFORM_FLOW_DROPPED</a>
</pre>
</div>
<div class="refsect1">
<a name="GstBaseTransform.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="synopsis">
<a href="http://library.gnome.org/devel/gobject/unstable/gobject-The-Base-Object-Type.html#GObject">GObject</a>
+----<a href="http://library.gnome.org/devel/gobject/unstable/gobject-The-Base-Object-Type.html#GInitiallyUnowned">GInitiallyUnowned</a>
+----<a href="../gstreamer-1.0/GstObject.html">GstObject</a>
+----<a href="../gstreamer-1.0/GstElement.html">GstElement</a>
+----GstBaseTransform
</pre>
</div>
<div class="refsect1">
<a name="GstBaseTransform.properties"></a><h2>Properties</h2>
<pre class="synopsis">
"<a class="link" href="GstBaseTransform.html#GstBaseTransform--qos" title='The "qos" property'>qos</a>" <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> : Read / Write
</pre>
</div>
<div class="refsect1">
<a name="GstBaseTransform.description"></a><h2>Description</h2>
<p>
This base class is for filter elements that process data.
</p>
<p>
It provides for:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem"><p>one sinkpad and one srcpad</p></li>
<li class="listitem"><p>
Possible formats on sink and source pad implemented
with custom transform_caps function. By default uses
same format on sink and source.
</p></li>
<li class="listitem"><p>Handles state changes</p></li>
<li class="listitem"><p>Does flushing</p></li>
<li class="listitem"><p>Push mode</p></li>
<li class="listitem"><p>
Pull mode if the sub-class transform can operate on arbitrary data
</p></li>
</ul></div>
<p>
</p>
<p>
</p>
<div class="refsect2">
<a name="idp8766032"></a><h3>Use Cases</h3>
<p>
</p>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
<div class="itemizedlist">
<p class="title"><b>Passthrough mode</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem"><p>
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.
</p></li>
<li class="listitem"><p>
On the GstBaseTransformClass is the passthrough_on_same_caps variable
which will automatically set/unset passthrough based on whether the
element negotiates the same caps on both pads.
</p></li>
<li class="listitem"><p>
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)
</p></li>
</ul>
</div>
<div class="itemizedlist">
<p class="title"><b>Example elements</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem">Level</li>
<li class="listitem">Videoscale, audioconvert, ffmpegcolorspace, audioresample in
certain modes.</li>
</ul>
</div>
</li>
<li class="listitem">
<div class="itemizedlist">
<p class="title"><b>Modifications in-place - input buffer and output buffer are the
same thing.</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem"><p>
The element must implement a transform_ip function.
</p></li>
<li class="listitem"><p>
Output buffer size must <= input buffer size
</p></li>
<li class="listitem"><p>
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.
</p></li>
<li class="listitem"><p>
Incoming writable buffers will be passed to the transform_ip function
immediately. </p></li>
<li class="listitem"><p>
only implementing transform_ip and not transform implies always_in_place
= TRUE
</p></li>
</ul>
</div>
<div class="itemizedlist">
<p class="title"><b>Example elements</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem">Volume</li>
<li class="listitem">Audioconvert in certain modes (signed/unsigned
conversion)</li>
<li class="listitem">ffmpegcolorspace in certain modes (endianness
swapping)</li>
</ul>
</div>
</li>
<li class="listitem">
<div class="itemizedlist">
<p class="title"><b>Modifications only to the caps/metadata of a buffer</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem"><p>
The element does not require writable data, but non-writable buffers
should be subbuffered so that the meta-information can be replaced.
</p></li>
<li class="listitem"><p>
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
</p></li>
</ul>
</div>
<div class="itemizedlist">
<p class="title"><b>Example elements</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem">Capsfilter when setting caps on outgoing buffers that have
none.</li>
<li class="listitem">identity when it is going to re-timestamp buffers by
datarate.</li>
</ul>
</div>
</li>
<li class="listitem">
<div class="itemizedlist">
<p class="title"><b>Normal mode</b></p>
<ul class="itemizedlist" type="disc">
<li class="listitem"><p>
always_in_place flag is not set, or there is no transform_ip function
</p></li>
<li class="listitem"><p>
Element will receive an input buffer and output buffer to operate on.
</p></li>
<li class="listitem"><p>
Output buffer is allocated by calling the prepare_output_buffer function.
</p></li>
</ul>
</div>
<div class="itemizedlist">
<p class="title"><b>Example elements</b></p>
<ul class="itemizedlist" type="disc"><li class="listitem">Videoscale, ffmpegcolorspace, audioconvert when doing
scaling/conversions</li></ul>
</div>
</li>
<li class="listitem">
<div class="itemizedlist">
<p class="title"><b>Special output buffer allocations</b></p>
<ul class="itemizedlist" type="disc"><li class="listitem"><p>
Elements which need to do special allocation of their output buffers
other than what gst_buffer_pad_alloc allows should implement a
prepare_output_buffer method, which calls the parent implementation and
passes the newly allocated buffer.
</p></li></ul>
</div>
<div class="itemizedlist">
<p class="title"><b>Example elements</b></p>
<ul class="itemizedlist" type="disc"><li class="listitem">efence</li></ul>
</div>
</li>
</ol></div>
<p>
</p>
</div>
<p>
</p>
<hr>
<div class="refsect2">
<a name="idp10669744"></a><h3>Sub-class settable flags on GstBaseTransform</h3>
<p>
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
<p>
</p>
<div class="itemizedlist">
<p class="title"><b>passthrough</b></p>
<ul class="itemizedlist" type="circle">
<li class="listitem"><p>
Implies that in the current configuration, the sub-class is not
interested in modifying the buffers.
</p></li>
<li class="listitem"><p>
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.
</p></li>
</ul>
</div>
<p>
</p>
</li>
<li class="listitem">
<p>
</p>
<div class="itemizedlist">
<p class="title"><b>always_in_place</b></p>
<ul class="itemizedlist" type="circle">
<li class="listitem"><p>
Determines whether a non-writable buffer will be copied before passing
to the transform_ip function.
</p></li>
<li class="listitem"><p>
Implied TRUE if no transform function is implemented.
</p></li>
<li class="listitem"><p>
Implied FALSE if ONLY transform function is implemented.
</p></li>
</ul>
</div>
<p>
</p>
</li>
</ul></div>
<p>
</p>
</div>
<p>
</p>
</div>
<div class="refsect1">
<a name="GstBaseTransform.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="GstBaseTransform-struct"></a><h3>struct GstBaseTransform</h3>
<pre class="programlisting">struct GstBaseTransform;</pre>
<p>
The opaque <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> data structure.
</p>
</div>
<hr>
<div class="refsect2">
<a name="GstBaseTransformClass"></a><h3>struct GstBaseTransformClass</h3>
<pre class="programlisting">struct GstBaseTransformClass {
GstElementClass parent_class;
gboolean passthrough_on_same_caps;
gboolean transform_ip_on_passthrough;
/* virtual methods for subclasses */
GstCaps* (*transform_caps) (GstBaseTransform *trans,
GstPadDirection direction,
GstCaps *caps, GstCaps *filter);
GstCaps* (*fixate_caps) (GstBaseTransform *trans,
GstPadDirection direction, GstCaps *caps,
GstCaps *othercaps);
gboolean (*accept_caps) (GstBaseTransform *trans, GstPadDirection direction,
GstCaps *caps);
gboolean (*set_caps) (GstBaseTransform *trans, GstCaps *incaps,
GstCaps *outcaps);
gboolean (*query) (GstBaseTransform *trans, GstPadDirection direction,
GstQuery *query);
/* decide allocation query for output buffers */
gboolean (*decide_allocation) (GstBaseTransform *trans, GstQuery *query);
gboolean (*filter_meta) (GstBaseTransform *trans, GstQuery *query, GType api);
/* propose allocation query parameters for input buffers */
gboolean (*propose_allocation) (GstBaseTransform *trans, GstQuery *decide_query,
GstQuery *query);
/* transform size */
gboolean (*transform_size) (GstBaseTransform *trans,
GstPadDirection direction,
GstCaps *caps, gsize size,
GstCaps *othercaps, gsize *othersize);
gboolean (*get_unit_size) (GstBaseTransform *trans, GstCaps *caps,
gsize *size);
/* states */
gboolean (*start) (GstBaseTransform *trans);
gboolean (*stop) (GstBaseTransform *trans);
/* sink and src pad event handlers */
gboolean (*sink_event) (GstBaseTransform *trans, GstEvent *event);
gboolean (*src_event) (GstBaseTransform *trans, GstEvent *event);
GstFlowReturn (*prepare_output_buffer) (GstBaseTransform * trans,
GstBuffer *input, GstBuffer **outbuf);
/* metadata */
gboolean (*copy_metadata) (GstBaseTransform *trans, GstBuffer *input,
GstBuffer *outbuf);
gboolean (*transform_meta) (GstBaseTransform *trans, GstBuffer *outbuf,
GstMeta *meta, GstBuffer *inbuf);
void (*before_transform) (GstBaseTransform *trans, GstBuffer *buffer);
/* transform */
GstFlowReturn (*transform) (GstBaseTransform *trans, GstBuffer *inbuf,
GstBuffer *outbuf);
GstFlowReturn (*transform_ip) (GstBaseTransform *trans, GstBuffer *buf);
};
</pre>
<p>
Subclasses can override any of the available virtual methods or not, as
needed. At minimum either <em class="parameter"><code>transform</code></em> or <em class="parameter"><code>transform_ip</code></em> need to be overridden.
If the element can overwrite the input data with the results (data is of the
same type and quantity) it should provide <em class="parameter"><code>transform_ip</code></em>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><a href="../gstreamer-1.0/GstElement.html#GstElementClass"><span class="type">GstElementClass</span></a> <em class="structfield"><code><a name="GstBaseTransformClass.parent-class"></a>parent_class</code></em>;</span></p></td>
<td>Element parent class</td>
</tr>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> <em class="structfield"><code><a name="GstBaseTransformClass.passthrough-on-same-caps"></a>passthrough_on_same_caps</code></em>;</span></p></td>
<td>If set to <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a>, passthrough mode will be
automatically enabled if the caps are the same.
Set to <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> by default.</td>
</tr>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> <em class="structfield"><code><a name="GstBaseTransformClass.transform-ip-on-passthrough"></a>transform_ip_on_passthrough</code></em>;</span></p></td>
<td>If set to <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a>, <em class="parameter"><code>transform_ip</code></em> will be called in
passthrough mode. The passed buffer might not be
writable. When <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a>, neither <em class="parameter"><code>transform</code></em> nor
<em class="parameter"><code>transform_ip</code></em> will be called in passthrough mode.
Set to <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> by default.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.transform-caps"></a>transform_caps</code></em> ()</span></p></td>
<td>Optional. Given the pad in this direction and the given
caps, what caps are allowed on the other pad in this
element ?</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.fixate-caps"></a>fixate_caps</code></em> ()</span></p></td>
<td>Optional. Given the pad in this direction and the given
caps, fixate the caps on the other pad. The function takes
ownership of <em class="parameter"><code>othercaps</code></em> and returns a fixated version of
<em class="parameter"><code>othercaps</code></em>. <em class="parameter"><code>othercaps</code></em> is not guaranteed to be writable.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.accept-caps"></a>accept_caps</code></em> ()</span></p></td>
<td>Optional. Since 0.10.30
Subclasses can override this method to check if <em class="parameter"><code>caps</code></em> can be
handled by the element. The default implementation might not be
the most optimal way to check this in all cases.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.set-caps"></a>set_caps</code></em> ()</span></p></td>
<td>allows the subclass to be notified of the actual caps set.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.query"></a>query</code></em> ()</span></p></td>
<td>Optional Since 0.10.36
Handle a requested query. Subclasses that implement this
should must chain up to the parent if they didn't handle the
query</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.decide-allocation"></a>decide_allocation</code></em> ()</span></p></td>
<td>Setup the allocation parameters for allocating output
buffers. The passed in query contains the result of the
downstream allocation query. This function is only called
when not operating in passthrough mode. The default
implementation will remove all memory dependent metadata.
If there is ia <em class="parameter"><code>filter_meta</code></em> method implementation, it will
be called for all metadata API in the downstream query,
otherwise the metadata API is removed.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.filter-meta"></a>filter_meta</code></em> ()</span></p></td>
<td>Return TRUE if the metadata API should be proposed in the
upstream allocation query. The default implementation is NULL
and will cause all metadata to be removed.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.propose-allocation"></a>propose_allocation</code></em> ()</span></p></td>
<td>Propose buffer allocation parameters for upstream elements.
This function must be implemented if the element reads or
writes the buffer content. The query that was passed to
the decide_allocation is passed in this method (or NULL
when the element is in passthrough mode). The default
implementation will pass the query downstream when in
passthrough mode and will copy all the filtered metadata
API in non-passthrough mode.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.transform-size"></a>transform_size</code></em> ()</span></p></td>
<td>Optional. Given the size of a buffer in the given direction
with the given caps, calculate the size in bytes of a buffer
on the other pad with the given other caps.
The default implementation uses get_unit_size and keeps
the number of units the same.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.get-unit-size"></a>get_unit_size</code></em> ()</span></p></td>
<td>Required if the transform is not in-place.
get the size in bytes of one unit for the given caps.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.start"></a>start</code></em> ()</span></p></td>
<td>Optional.
Called when the element starts processing.
Allows opening external resources.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.stop"></a>stop</code></em> ()</span></p></td>
<td>Optional.
Called when the element stops processing.
Allows closing external resources.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.sink-event"></a>sink_event</code></em> ()</span></p></td>
<td>Optional.
Event handler on the sink pad. The default implementation
handles the event and forwards it downstream.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.src-event"></a>src_event</code></em> ()</span></p></td>
<td>Optional.
Event handler on the source pad. The default implementation
handles the event and forwards it upstream.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.prepare-output-buffer"></a>prepare_output_buffer</code></em> ()</span></p></td>
<td>Optional.
Subclasses can override this to do their own
allocation of output buffers. Elements that only do
analysis can return a subbuffer or even just
return a reference to the input buffer (if in
passthrough mode). The default implementation will
use the negotiated allocator or bufferpool and
transform_size to allocate an output buffer or it
will return the input buffer in passthrough mode.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.copy-metadata"></a>copy_metadata</code></em> ()</span></p></td>
<td>Optional.
Copy the metadata from the input buffer to the output buffer.
The default implementation will copy the flags, timestamps and
offsets of the buffer.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.transform-meta"></a>transform_meta</code></em> ()</span></p></td>
<td>Optional. Transform the metadata on the input buffer to the
output buffer. By default this method is NULL and no
metadata is copied. subclasses can implement this method and
return TRUE if the metadata is to be copied.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.before-transform"></a>before_transform</code></em> ()</span></p></td>
<td>Optional. Since 0.10.22
This method is called right before the base class will
start processing. Dynamic properties or other delayed
configuration could be performed in this method.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.transform"></a>transform</code></em> ()</span></p></td>
<td>Required if the element does not operate in-place.
Transforms one incoming buffer to one outgoing buffer.
The function is allowed to change size/timestamp/duration
of the outgoing buffer.</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="GstBaseTransformClass.transform-ip"></a>transform_ip</code></em> ()</span></p></td>
<td>Required if the element operates in-place.
Transform the incoming buffer in-place.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-is-passthrough"></a><h3>gst_base_transform_is_passthrough ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> gst_base_transform_is_passthrough (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>);</pre>
<p>
See if <em class="parameter"><code>trans</code></em> is configured as a passthrough transform.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>the <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> to query</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>TRUE is the transform is configured in passthrough mode.
MT safe.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-set-passthrough"></a><h3>gst_base_transform_set_passthrough ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_base_transform_set_passthrough (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> passthrough</code></em>);</pre>
<p>
Set passthrough mode for this filter by default. This is mostly
useful for filters that do not care about negotiation.
</p>
<p>
Always TRUE for filters which don't implement either a transform
or transform_ip method.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>the <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> to set</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>passthrough</code></em> :</span></p></td>
<td>boolean indicating passthrough mode.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-is-in-place"></a><h3>gst_base_transform_is_in_place ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> gst_base_transform_is_in_place (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>);</pre>
<p>
See if <em class="parameter"><code>trans</code></em> is configured as a in_place transform.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>the <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> to query</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>TRUE is the transform is configured in in_place mode.
MT safe.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-set-in-place"></a><h3>gst_base_transform_set_in_place ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_base_transform_set_in_place (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> in_place</code></em>);</pre>
<p>
Determines whether a non-writable buffer will be copied before passing
to the transform_ip function.
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">Always TRUE if no transform function is implemented.</li>
<li class="listitem">Always FALSE if ONLY transform function is implemented.</li>
</ul></div>
<p>
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>the <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> to modify</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>in_place</code></em> :</span></p></td>
<td>Boolean value indicating that we would like to operate
on in_place buffers.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-is-qos-enabled"></a><h3>gst_base_transform_is_qos_enabled ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> gst_base_transform_is_qos_enabled (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>);</pre>
<p>
Queries if the transform will handle QoS.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>a <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>TRUE if QoS is enabled.
MT safe.</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 0.10.5</p>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-set-qos-enabled"></a><h3>gst_base_transform_set_qos_enabled ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_base_transform_set_qos_enabled (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> enabled</code></em>);</pre>
<p>
Enable or disable QoS handling in the transform.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>a <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>enabled</code></em> :</span></p></td>
<td>new state</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 0.10.5</p>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-update-qos"></a><h3>gst_base_transform_update_qos ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_base_transform_update_qos (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> proportion</code></em>,
<em class="parameter"><code><a href="../gstreamer-1.0/GstClock.html#GstClockTimeDiff"><span class="type">GstClockTimeDiff</span></a> diff</code></em>,
<em class="parameter"><code><a href="../gstreamer-1.0/GstClock.html#GstClockTime"><span class="type">GstClockTime</span></a> timestamp</code></em>);</pre>
<p>
Set the QoS parameters in the transform. This function is called internally
when a QOS event is received but subclasses can provide custom information
when needed.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>a <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>proportion</code></em> :</span></p></td>
<td>the proportion</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>diff</code></em> :</span></p></td>
<td>the diff against the clock</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>timestamp</code></em> :</span></p></td>
<td>the timestamp of the buffer generating the QoS expressed in
running_time.</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 0.10.5</p>
</div>
<hr>
<div class="refsect2">
<a name="gst-base-transform-set-gap-aware"></a><h3>gst_base_transform_set_gap_aware ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_base_transform_set_gap_aware (<em class="parameter"><code><a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a> *trans</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> gap_aware</code></em>);</pre>
<p>
If <em class="parameter"><code>gap_aware</code></em> is <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> (the default), output buffers will have the
<a href="../gstreamer-1.0/gstreamer-GstBuffer.html#GST-BUFFER-FLAG-GAP:CAPS"><code class="literal">GST_BUFFER_FLAG_GAP</code></a> flag unset.
</p>
<p>
If set to <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a>, the element must handle output buffers with this flag set
correctly, i.e. it can assume that the buffer contains neutral data but must
unset the flag if the output is no neutral data.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>trans</code></em> :</span></p></td>
<td>a <a class="link" href="GstBaseTransform.html" title="GstBaseTransform"><span class="type">GstBaseTransform</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>gap_aware</code></em> :</span></p></td>
<td>New state</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 0.10.16</p>
</div>
<hr>
<div class="refsect2">
<a name="GST-BASE-TRANSFORM-SINK-NAME:CAPS"></a><h3>GST_BASE_TRANSFORM_SINK_NAME</h3>
<pre class="programlisting">#define GST_BASE_TRANSFORM_SINK_NAME "sink"
</pre>
<p>
The name of the templates for the sink pad.
</p>
</div>
<hr>
<div class="refsect2">
<a name="GST-BASE-TRANSFORM-SRC-NAME:CAPS"></a><h3>GST_BASE_TRANSFORM_SRC_NAME</h3>
<pre class="programlisting">#define GST_BASE_TRANSFORM_SRC_NAME "src"
</pre>
<p>
The name of the templates for the source pad.
</p>
</div>
<hr>
<div class="refsect2">
<a name="GST-BASE-TRANSFORM-SINK-PAD:CAPS"></a><h3>GST_BASE_TRANSFORM_SINK_PAD()</h3>
<pre class="programlisting">#define GST_BASE_TRANSFORM_SINK_PAD(obj) (GST_BASE_TRANSFORM_CAST (obj)->sinkpad)
</pre>
<p>
Gives the pointer to the sink <a href="../gstreamer-1.0/GstPad.html"><span class="type">GstPad</span></a> object of the element.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>obj</code></em> :</span></p></td>
<td>base transform instance</td>
</tr></tbody>
</table></div>
<p class="since">Since 0.10.4</p>
</div>
<hr>
<div class="refsect2">
<a name="GST-BASE-TRANSFORM-SRC-PAD:CAPS"></a><h3>GST_BASE_TRANSFORM_SRC_PAD()</h3>
<pre class="programlisting">#define GST_BASE_TRANSFORM_SRC_PAD(obj) (GST_BASE_TRANSFORM_CAST (obj)->srcpad)
</pre>
<p>
Gives the pointer to the source <a href="../gstreamer-1.0/GstPad.html"><span class="type">GstPad</span></a> object of the element.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>obj</code></em> :</span></p></td>
<td>base transform instance</td>
</tr></tbody>
</table></div>
<p class="since">Since 0.10.4</p>
</div>
<hr>
<div class="refsect2">
<a name="GST-BASE-TRANSFORM-FLOW-DROPPED:CAPS"></a><h3>GST_BASE_TRANSFORM_FLOW_DROPPED</h3>
<pre class="programlisting">#define GST_BASE_TRANSFORM_FLOW_DROPPED GST_FLOW_CUSTOM_SUCCESS
</pre>
<p>
A <a href="../gstreamer-1.0/GstPad.html#GstFlowReturn"><span class="type">GstFlowReturn</span></a> that can be returned from transform and transform_ip to
indicate that no output buffer was generated.
</p>
<p class="since">Since 0.10.13</p>
</div>
</div>
<div class="refsect1">
<a name="GstBaseTransform.property-details"></a><h2>Property Details</h2>
<div class="refsect2">
<a name="GstBaseTransform--qos"></a><h3>The <code class="literal">"qos"</code> property</h3>
<pre class="programlisting"> "qos" <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> : Read / Write</pre>
<p>Handle Quality-of-Service events.</p>
<p>Default value: FALSE</p>
</div>
</div>
<div class="refsect1">
<a name="GstBaseTransform.see-also"></a><h2>See Also</h2>
<a class="link" href="GstBaseSrc.html" title="GstBaseSrc"><span class="type">GstBaseSrc</span></a>, <a class="link" href="GstBaseSink.html" title="GstBaseSink"><span class="type">GstBaseSink</span></a>
</div>
</div>
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