[Hiki] update - tut-gst-queues (ruby-gnome2-doc-cvs) - Ruby-GNOME2

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REMOTE_ADDR = 195.207.101.112
REMOTE_HOST = 
        URL = http://ruby-gnome2.sourceforge.jp/en/?tut-gst-queues
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  = Queues
+ {{link("tut-gst-threads", nil, "tut-gst", nil)}}

  A Gst::Queue is a filter element. Queues can be used to link two elements in such way that the data can be buffered.

  A buffer that is sinked to a Queue will not automatically be pushed to the next linked element but will be buffered. It will be pushed to the next element as soon as a Gst::Pad#pull is called on the queue's source pad.

  Queues are mostly used in conjunction with a Gst::Thread to provide an external link for the thread elements. You could have one thread feeding buffers into a Gst::Queue and another thread repeadedly calling Gst::Pad#pull on the queue to feed its internal elements.

  Below is a figure of a two-threaded decoder. We have one thread (the main execution thread) reading the data from a file, and another thread decoding the data. 

  {{image_left("queue.png")}}
  {{br}}

  The standard GStreamer queue implementation has some properties that can be changed using their accessors methods. To set the maximum number of buffers that can be queued to 30, do:

    queue.max_level = 30

  The following MP3 player shows you how to create the above pipeline using a thread and a queue.

    require 'gst'

    Gst.init
    unless ARGV.size == 1
        $stderr.puts "Usage: "{__FILE__} <mp3 filename>"
        exit 1
    end

    playing = true

    # create a new thread to hold the elements
    thread = Gst::Thread.new

    # create a new bin to hold the elements
    bin = Gst::Bin.new

    # create a disk reader
    filesrc = Gst::ElementFactory.make("filesrc")
    filesrc.location = ARGV.first
    filesrc.signal_connect("eos") do
        puts "have eos, quitting..."
        playing = false
    end

    # a decoder
    decoder = Gst::ElementFactory.make("mad")

    # and an audio sink
    audiosink = Gst::ElementFactory.make("osssink")

    # create our queue
    queue = Gst::ElementFactory.make("queue")

    # add objects to the main bin
    thread.add(decode, audiosink)
    bin.add(filesrc, queue, thread)

    # link elements
    filesrc >> queue >> decode >> audiosink

    # start playing
    bin.play

    while playing do
        bin.iterate
    end

    bin.stop

Ruby-GNOME2

[ruby-gnome2-doc-cvs] [Hiki] update - tut-gst-queues