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 <span id="projectnumber">0.2.9</span>
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<div class="textblock"><h1><a class="anchor" id="sec_overview"></a>
Overview</h1>
<p>Media streams are used to exchange data with the PipeWire server. A stream is a wrapper around a proxy for a pw_client_node with just one port.</p>
<p>Streams can be used to:</p>
<ul>
<li>Consume a stream from PipeWire. This is a PW_DIRECTION_INPUT stream. </li>
<li>Produce a stream to PipeWire. This is a PW_DIRECTION_OUTPUT stream</li>
</ul>
<p>You can connect the stream port to a specific server port or let PipeWire choose a port for you.</p>
<p>For more complicated nodes such as filters or ports with multiple inputs and/or outputs you will need to create a <a class="el" href="classpw__node.html" title="PipeWire node class.">pw_node</a> yourself and export it with <a class="el" href="remote_8c.html#ad16e4bdd4e2d45ef70366adf85c3ab61">pw_remote_export</a>.</p>
<h1><a class="anchor" id="sec_create"></a>
Create</h1>
<p>Make a new stream with <a class="el" href="classpw__stream.html#a6f1606e27cc3bd9c522b92c9469a6f2f">pw_stream_new()</a>. You will need to specify a name for the stream and extra properties. You can use <a class="el" href="classpw__pipewire.html#a841dbb7608dc9cdda4a320d33fbbd39a">pw_fill_stream_properties()</a> to get a basic set of properties for the stream.</p>
<p>Once the stream is created, the state_changed event should be used to track the state of the stream.</p>
<h1><a class="anchor" id="sec_connect"></a>
Connect</h1>
<p>The stream is initially unconnected. To connect the stream, use <a class="el" href="classpw__stream.html#a0e12176f13e654e64e7f5689e7a6dd54">pw_stream_connect()</a>. Pass the desired direction as an argument.</p>
<h2><a class="anchor" id="ssec_stream_target"></a>
Stream target</h2>
<p>To make the newly connected stream automatically connect to an existing PipeWire node, use the <a class="el" href="stream_8h.html#a058907c2dffbb8fb5ede8a53d7604106ab648fa0c0c7adf6aa3139eddc3a9cd7c">PW_STREAM_FLAG_AUTOCONNECT</a> and the port_path argument while connecting.</p>
<h2><a class="anchor" id="ssec_stream_formats"></a>
Stream formats</h2>
<p>An array of possible formats that this stream can consume or provide must be specified.</p>
<h1><a class="anchor" id="sec_format"></a>
Format negotiation</h1>
<p>After connecting the stream, it will transition to the <a class="el" href="stream_8h.html#a9ceaca6fc9acd9a1af080258d763fb82a6d38d0ac9310b1822fcc98add8e4a8d2">PW_STREAM_STATE_CONFIGURE</a> state. In this state the format will be negotiated by the PipeWire server.</p>
<p>Once the format has been selected, the format_changed event is emited with the configured format as a parameter.</p>
<p>The client should now prepare itself to deal with the format and complete the negotiation procedure with a call to <a class="el" href="classpw__stream.html#abcd423c15a39666ea50abef5ff7a75bd">pw_stream_finish_format()</a>.</p>
<p>As arguments to <a class="el" href="classpw__stream.html#abcd423c15a39666ea50abef5ff7a75bd">pw_stream_finish_format()</a> an array of spa_param structures must be given. They contain parameters such as buffer size, number of buffers, required metadata and other parameters for the media buffers.</p>
<h1><a class="anchor" id="sec_buffers"></a>
Buffer negotiation</h1>
<p>After completing the format negotiation, PipeWire will allocate and notify the stream of the buffers that will be used to exchange data between client and server.</p>
<p>With the add_buffer event, a stream will be notified of a new buffer that can be used for data transport. You can attach user_data to these buffers.</p>
<p>Afer the buffers are negotiated, the stream will transition to the <a class="el" href="stream_8h.html#a9ceaca6fc9acd9a1af080258d763fb82a0537b5f9f722fb2faf7822cd09370825">PW_STREAM_STATE_PAUSED</a> state.</p>
<h1><a class="anchor" id="sec_streaming"></a>
Streaming</h1>
<p>From the <a class="el" href="stream_8h.html#a9ceaca6fc9acd9a1af080258d763fb82a0537b5f9f722fb2faf7822cd09370825">PW_STREAM_STATE_PAUSED</a> state, the stream can be set to the <a class="el" href="stream_8h.html#a9ceaca6fc9acd9a1af080258d763fb82af3c3b39039810d40a7c9e1ae3c6c905d">PW_STREAM_STATE_STREAMING</a> state by the PipeWire server when data transport is started.</p>
<p>Depending on how the stream was connected it will need to Produce or Consume data for/from PipeWire as explained in the following subsections.</p>
<h2><a class="anchor" id="ssec_consume"></a>
Consume data</h2>
<p>The process event is emited for each new buffer that can can be consumed.</p>
<p><a class="el" href="stream_8h.html#ab2ef0e28a1e91816f8015ef9814d18f7">pw_stream_dequeue_buffer()</a> should be used to get the data and metadata of the buffer.</p>
<p>When the buffer is no longer in use, call <a class="el" href="stream_8h.html#abe1c593f34080ea9c8c6231abe4e7386">pw_stream_queue_buffer()</a> to let PipeWire reuse the buffer.</p>
<h2><a class="anchor" id="ssec_produce"></a>
Produce data</h2>
<p><a class="el" href="stream_8h.html#ab2ef0e28a1e91816f8015ef9814d18f7">pw_stream_dequeue_buffer()</a> gives an empty buffer that can be filled.</p>
<p>Filled buffers should be queued with <a class="el" href="stream_8h.html#abe1c593f34080ea9c8c6231abe4e7386">pw_stream_queue_buffer()</a>.</p>
<p>The process event is emited when PipeWire has emptied a buffer that can now be refilled.</p>
<h1><a class="anchor" id="sec_stream_disconnect"></a>
Disconnect</h1>
<p>Use <a class="el" href="classpw__stream.html#aa727d7a41acb9d0ec574f93f01328d30">pw_stream_disconnect()</a> to disconnect a stream after use. </p>
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