Monthly Archives: February 2011

Bye bye Sourceforge

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GStreamer was originally hosted on Sourceforge when the project started up 10 years ago. As time went by we migrated most of our stuff over to freedesktop.org, except our bugzilla which ended up on gnome.org.

The one thing that stayed on Sourceforge was our mailing lists, until today that is. Thanks to the hard work of Tim-Philipp Müller all our lists are now migrated to freedesktop.org. There are a few advantages we see with this move, one being getting nicer archives, another being not needing to maintain an administrator list on SF anymore and finally I guess it makes the mailing lists feel a bit more authentic that they are on freedesktop.org, just like the website.

All this of course means that in the coming Months the 10 year old SF project will get gradually shut down, and maybe we end up deleting it completely. So a thanks to SF for the last 10 years of hosting :) Feels strangely nostalgic for some reason :)

And if anyone wonders if we will move bugzilla too, I don’t think that is in the cards anytime soon. Many of the most popular GStreamer applications, like Totem, Banshee, PiTiVi and so on use the GNOME bugzilla and the option to easily re-assign GStreamer bugs to GStreamer is atm more valuable than what we perceive the value of having everything on freedesktop.

Fixing the US patent system

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Just saw the White House putting out this page asking for input on innovation. I recommend every US citizen reading this making sure to fill out the form explaining how the current US patent regime is not helping innovation, but hindering it. How the patent system, due to the volume and low quality of patents granted, and the unbalanced and painful process of getting them revoked, has turned the patent system into a mafia style protection racket where it costs more to fight the extortion than to just pay up. There is a great article on techdirt on this.

encodebin and python

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So I went down to FOSDEM this weekend. One of the things I was able to do while there was sit down with Edward Hervey and figure out how to use the new encodebin element with Transmageddon. The goal of the new encodebin element is to make encoding a much easier task with GStreamer, where you basically pass it a GStreamer caps value for your container format and audio and video streams, and encodebin figures out which elements it needs to create output with those caps. I have a minimal example below:

import sys
import os
import gobject; gobject.threads_init()
import gst
import pygst
import glib
import gst.pbutils
import gtk

class Transcoder:
   def __init__(self):
       # create GStreamer pipeline object
       self.pipeline = gst.Pipeline("TranscodingPipeline")
       self.pipeline.set_state(gst.STATE_PAUSED)

       self.uridecoder = gst.element_factory_make("uridecodebin", "uridecoder") 
       self.uridecoder.set_property("uri", "file:///home/cschalle/Videos/gravity.mpg")
       self.uridecoder.connect("pad-added", self.OnDynamicPad)
       self.pipeline.add(self.uridecoder)

       self.containerprofile = gst.pbutils.EncodingContainerProfile ("ogg", None , gst.Caps("application/ogg"), None)
       self.videoprofile = gst.pbutils.EncodingVideoProfile (gst.Caps("video/x-dirac"), None, gst.caps_new_any(), 0)
       self.audioprofile = gst.pbutils.EncodingAudioProfile (gst.Caps("audio/x-vorbis"), None, gst.caps_new_any(), 0)
       self.containerprofile.add_profile(self.videoprofile)
       self.containerprofile.add_profile(self.audioprofile)

       self.ebin = gst.element_factory_make ("encodebin", None)
       self.ebin.set_property("profile", self.containerprofile)
       self.pipeline.add(self.ebin)

       print "self.ebin is " + str(self.ebin)
       self.ebin.set_state(gst.STATE_PAUSED)
       self.uridecoder.set_state(gst.STATE_PAUSED)
       self.filesink = gst.element_factory_make("filesink", None)
       self.filesink.set_property("location", "/tmp/test.ogg")
       self.pipeline.add(self.filesink)
       self.filesink.set_state(gst.STATE_PAUSED)
       self.ebin.link(self.filesink)

       self.pipeline.set_state(gst.STATE_PLAYING)

   def OnDynamicPad(self, uridecodebin, src_pad):
       c = src_pad.get_caps().to_string()
       print c
       sinkpad = self.ebin.emit("request-pad", src_pad.get_caps())
       print "action signal returned", sinkpad
       src_pad.link(sinkpad)

if __name__ == "__main__":
	hwg = Transcoder()
	gtk.main()

The most important thing to notice about this code is the creation of the profiles, the adding of the audio and video profile to the container profile and then finally the setting of that profile onto the encodebin element. In my example I have extremely simple caps statements, basically just the codecs names, but you could add further things here like video height and width, framerate, audio bitrate, audio channels and so on, and encodebin would be able to give you the correct output.

We did find a couple of Python binding bugs though, which Edward fixed promptly, so if you want to try this code now, you need to grab gstreamer-python from git master.