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added gst-launch grammar reference
Original commit message from CVS: added gst-launch grammar reference
This commit is contained in:
Andy Wingo
parent
a64e400a97
commit
b3d5bbd72c
3 changed files with 136 additions and 4 deletions
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@ -16,7 +16,7 @@
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<title><command>gst-launch</command></title>
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<para>
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This is a tool that will construct pipelines based on a command-line
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syntax. FIXME: need a more extensive grammar reference
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syntax.
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</para>
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<para>
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A simple commandline looks like:
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@ -79,6 +79,73 @@ main (int argc, char *argv[])
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Note how we can retrieve the filesrc element from the constructed bin using the
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element name.
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</para>
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<sect2>
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<title>Grammar Reference</title>
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<para>
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The <command>gst-launch</command> syntax is processed by a flex/bison parser. This section
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is intended to provide a full specification of the grammar; any deviations from this
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specification is considered a bug.
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</para>
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<sect3>
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<title>Elements</title>
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<screen>
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... mad ...
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</screen>
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<para>
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A bare identifier (a string beginning with a letter and containing only letters,
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numbers, dashes, underscores, percent signs, or colons) will create an element from a
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given elementfactory. In this example, an instance of the "mad" mp3 decoding plugin will
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be created.
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</para>
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</sect3>
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<sect3>
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<title>Connections</title>
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<screen>
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... !sink ...
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</screen>
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<para>
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An exclamation point, optionally having a qualified pad name (an the name of the pad,
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optionally preceded by the name of the element) on both sides, will connect two pads. If
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the source pad is not specified, a source pad from the immediately preceding element
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will be automatically chosen. If the sink pad is not specified, a sink pad from the next
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element to be constructed will be chosen. An attempt will be made to find compatible
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pads. Pad names may be preceded by an element name, as in
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<computeroutput>my_element_name.sink_pad</computeroutput>.
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</para>
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</sect3>
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<sect3>
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<title>Properties</title>
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<screen>
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... location="http://gstreamer.net" ...
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</screen>
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<para>
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The name of a property, optionally qualified with an element name, and a value,
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separated by an equals sign, will set a property on an element. If the element is not
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specified, the previous element is assumed. Strings can optionally be enclosed in
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quotation marks. Characters in strings may be escaped with the backtick
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(<literal>\</literal>). If the right-hand side is all digits, it is considered to be an
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integer. If it is all digits and a decimal point, it is a double. If it is "true",
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"false", "TRUE", or "FALSE" it is considered to be boolean. Otherwise, it is parsed as a
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string. The type of the property is determined later on in the parsing, and the value is
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converted to the target type. This conversion is not guaranteed to work, it relies on
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the g_value_convert routines. No error message will be displayed on an invalid
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conversion, due to limitations in the value convert API.
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</para>
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</sect3>
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<sect3>
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<title>Bins, Threads, and Pipelines</title>
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<screen>
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( ... )
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</screen>
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<para>
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A pipeline description between parentheses is placed into a bin. The open paren may be
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preceded by a type name, as in <computeroutput>jackbin.( ... )</computeroutput> to make
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a bin of a specified type. Square brackets make pipelines, and curly braces make
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threads. The default toplevel bin type is a pipeline, although putting the whole
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description within parentheses or braces can override this default.
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</para>
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</sect3>
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</sect2>
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</sect1>
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<sect1>
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@ -16,7 +16,7 @@
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<title><command>gst-launch</command></title>
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<para>
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This is a tool that will construct pipelines based on a command-line
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syntax. FIXME: need a more extensive grammar reference
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syntax.
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</para>
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<para>
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A simple commandline looks like:
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@ -79,6 +79,73 @@ main (int argc, char *argv[])
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Note how we can retrieve the filesrc element from the constructed bin using the
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element name.
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</para>
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<sect2>
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<title>Grammar Reference</title>
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<para>
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The <command>gst-launch</command> syntax is processed by a flex/bison parser. This section
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is intended to provide a full specification of the grammar; any deviations from this
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specification is considered a bug.
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</para>
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<sect3>
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<title>Elements</title>
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<screen>
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... mad ...
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</screen>
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<para>
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A bare identifier (a string beginning with a letter and containing only letters,
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numbers, dashes, underscores, percent signs, or colons) will create an element from a
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given elementfactory. In this example, an instance of the "mad" mp3 decoding plugin will
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be created.
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</para>
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</sect3>
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<sect3>
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<title>Connections</title>
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<screen>
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... !sink ...
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</screen>
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<para>
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An exclamation point, optionally having a qualified pad name (an the name of the pad,
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optionally preceded by the name of the element) on both sides, will connect two pads. If
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the source pad is not specified, a source pad from the immediately preceding element
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will be automatically chosen. If the sink pad is not specified, a sink pad from the next
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element to be constructed will be chosen. An attempt will be made to find compatible
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pads. Pad names may be preceded by an element name, as in
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<computeroutput>my_element_name.sink_pad</computeroutput>.
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</para>
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</sect3>
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<sect3>
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<title>Properties</title>
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<screen>
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... location="http://gstreamer.net" ...
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</screen>
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<para>
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The name of a property, optionally qualified with an element name, and a value,
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separated by an equals sign, will set a property on an element. If the element is not
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specified, the previous element is assumed. Strings can optionally be enclosed in
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quotation marks. Characters in strings may be escaped with the backtick
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(<literal>\</literal>). If the right-hand side is all digits, it is considered to be an
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integer. If it is all digits and a decimal point, it is a double. If it is "true",
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"false", "TRUE", or "FALSE" it is considered to be boolean. Otherwise, it is parsed as a
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string. The type of the property is determined later on in the parsing, and the value is
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converted to the target type. This conversion is not guaranteed to work, it relies on
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the g_value_convert routines. No error message will be displayed on an invalid
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conversion, due to limitations in the value convert API.
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</para>
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</sect3>
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<sect3>
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<title>Bins, Threads, and Pipelines</title>
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<screen>
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( ... )
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</screen>
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<para>
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A pipeline description between parentheses is placed into a bin. The open paren may be
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preceded by a type name, as in <computeroutput>jackbin.( ... )</computeroutput> to make
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a bin of a specified type. Square brackets make pipelines, and curly braces make
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threads. The default toplevel bin type is a pipeline, although putting the whole
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description within parentheses or braces can override this default.
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</para>
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</sect3>
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</sect2>
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</sect1>
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<sect1>
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@ -56,8 +56,6 @@
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</para>
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<informaltable pgwide="1" frame="none" role="enum">
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<tgroup cols="2">
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<colspec colwidth="2*" />
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<colspec colwidth="8*" />
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<tbody>
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<row>
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<entry><literal>GST_STATE_NULL</literal></entry>
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