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55 lines
2 KiB
XML
55 lines
2 KiB
XML
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<chapter id="chapter-metadata">
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<title>Metadata</title>
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<para>
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&GStreamer; makes a clear distinction between two types of metadata, and
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has support for both types. The first is stream tags, which describe the
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content of a stream in a non-technical way. Examples include the author
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of a song, the title of that very same song or the album it is a part of.
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The other type of metadata is stream-info, which is a somewhat technical
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description of the properties of a stream. This can include video size,
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audio samplerate, codecs used and so on. Tags are handled using the
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&GStreamer; tagging system. Stream-info can be retrieved from a
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<classname>GstPad</classname>.
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</para>
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<sect1 id="section-streaminfo">
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<title>Stream information</title>
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<para>
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Stream information can most easily be read by reading them from a
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<classname>GstPad</classname>. This has already been discussed before
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in <xref linkend="section-caps-metadata"/>. Therefore, we will skip
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it here.
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</para>
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</sect1>
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<sect1 id="section-tags-read">
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<title>Tag reading</title>
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<para>
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Tag reading is remarkably simple in &GStreamer; Every element supports
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the <quote>found-tag</quote> signal, which will be fired each the time
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the element reads tags from the stream. A <classname>GstBin</classname>
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will conveniently forward tags found by its childs. Therefore, in most
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applications, you will only need to connect to the
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<quote>found-tag</quote> signal on the top-most bin in your pipeline,
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and you will automatically retrieve all tags from the stream.
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</para>
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<para>
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Note, however, that the <quote>found-tag</quote> might be fired
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multiple times and by multiple elements in the pipeline. It is the
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application's responsibility to put all those tags together and
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display them to the user in a nice, coherent way.
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</para>
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</sect1>
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<sect1 id="section-tags-write">
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<title>Tag writing</title>
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<para>
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WRITEME
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</para>
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</sect1>
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</chapter>
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