Sophie: libgstreamer0.7-devel-0.7.4-2mdk i586

libgstreamer0.7-devel-0.7.4-2mdk.i586.rpm

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><H1
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><A
NAME="section-programs-gst-launch"
>33.2. <B
CLASS="command"
>gst-launch</B
></A
></H1
><P
> 
      This is a tool that will construct pipelines based on a command-line
      syntax.
    </P
><P
> 
      A simple commandline looks like:

    <PRE
CLASS="screen"
>&#13;gst-launch filesrc location=hello.mp3 ! mad ! osssink
    </PRE
>

      A more complex pipeline looks like:

    <PRE
CLASS="screen"
>&#13;gst-launch filesrc location=redpill.vob ! mpegdemux name=demux \
 demux.audio_00! { ac3parse ! a52dec ! osssink } \
 demux.video_00! { mpeg2dec ! xvideosink }
    </PRE
>

    </P
><P
>&#13;      You can also use the parser in you own
      code. <SPAN
CLASS="application"
>GStreamer</SPAN
> provides a function
      gst_parse_launch () that you can use to construct a pipeline.
      The following program lets you create an MP3 pipeline using the
      gst_parse_launch () function:
    </P
><PRE
CLASS="programlisting"
>&#13;#include &#60;gst/gst.h&#62;

int
main (int argc, char *argv[])
{
  GstElement *pipeline;
  GstElement *filesrc;
  GError *error = NULL;

  gst_init (&#38;argc, &#38;argv);

  if (argc != 2) {
    g_print ("usage: %s &#60;filename&#62;\n", argv[0]);
    return -1;
  }

  pipeline = gst_parse_launch ("filesrc name=my_filesrc ! mad ! osssink", &#38;error);
  if (!pipeline) {
    g_print ("Parse error: %s\n", error-&#62;message);
    exit (1);
  }
  
  filesrc = gst_bin_get_by_name (GST_BIN (pipeline), "my_filesrc");
  g_object_set (G_OBJECT (filesrc), "location", argv[1], NULL);

  gst_element_set_state (pipeline, GST_STATE_PLAYING);

  while (gst_bin_iterate (GST_BIN (pipeline)));

  gst_element_set_state (pipeline, GST_STATE_NULL);

  return 0;
}
    </PRE
><P
>&#13;      Note how we can retrieve the filesrc element from the constructed bin using the
      element name.
    </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN1210"
>33.2.1. Grammar Reference</A
></H2
><P
>&#13;        The <B
CLASS="command"
>gst-launch</B
> syntax is processed by a flex/bison parser. This section
        is intended to provide a full specification of the grammar; any deviations from this
        specification is considered a bug.
      </P
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN1214"
>33.2.1.1. Elements</A
></H3
><PRE
CLASS="screen"
>&#13;          ... mad ...
        </PRE
><P
>&#13;          A bare identifier (a string beginning with a letter and containing
          only letters, numbers, dashes, underscores, percent signs, or colons)
          will create an element from a given element factory. In this example,
          an instance of the "mad" MP3 decoding plugin will be created.
        </P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN1218"
>33.2.1.2. Links</A
></H3
><PRE
CLASS="screen"
>&#13;          ... !sink ...
        </PRE
><P
>&#13;          An exclamation point, optionally having a qualified pad name (an the name of the pad,
          optionally preceded by the name of the element) on both sides, will link two pads. If
          the source pad is not specified, a source pad from the immediately preceding element
          will be automatically chosen. If the sink pad is not specified, a sink pad from the next
          element to be constructed will be chosen. An attempt will be made to find compatible
          pads. Pad names may be preceded by an element name, as in
          <SAMP
CLASS="computeroutput"
>my_element_name.sink_pad</SAMP
>.
        </P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN1223"
>33.2.1.3. Properties</A
></H3
><PRE
CLASS="screen"
>&#13;          ... location="http://gstreamer.net" ...
        </PRE
><P
>&#13;          The name of a property, optionally qualified with an element name, and a value,
          separated by an equals sign, will set a property on an element. If the element is not
          specified, the previous element is assumed. Strings can optionally be enclosed in
          quotation marks. Characters in strings may be escaped with the backtick
          (<VAR
CLASS="literal"
>\</VAR
>). If the right-hand side is all digits, it is considered to be an
          integer. If it is all digits and a decimal point, it is a double. If it is "true",
          "false", "TRUE", or "FALSE" it is considered to be boolean. Otherwise, it is parsed as a
          string. The type of the property is determined later on in the parsing, and the value is
          converted to the target type. This conversion is not guaranteed to work, it relies on
          the g_value_convert routines. No error message will be displayed on an invalid
          conversion, due to limitations in the value convert API.
        </P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN1228"
>33.2.1.4. Bins, Threads, and Pipelines</A
></H3
><PRE
CLASS="screen"
>&#13;          ( ... )
        </PRE
><P
>&#13;          A pipeline description between parentheses is placed into a bin. The open paren may be
          preceded by a type name, as in <SAMP
CLASS="computeroutput"
>jackbin.( ... )</SAMP
> to make
          a bin of a specified type. Square brackets make pipelines, and curly braces make
          threads. The default toplevel bin type is a pipeline, although putting the whole
          description within parentheses or braces can override this default.
        </P
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