Monday, March 31, 2008

How to write a wxPython video player with Gstreamer

wxPython ships by default with the wx.MediaCtrl for very basic playback of music or videos. As I would like to do more advanced video manipulation, I was curious if I could use Gstreamer directly in wxPython to create my own pipelines. It was surprisingly easy.
For those who don't know Gstreamer, I quote the website (http://www.gstreamer.org):
GStreamer is a library that allows the construction of graphs of media-handling components, ranging from simple playback to complex audio (mixing) and video (non-linear editing) processing. Applications can take advantage of advances in codec and filter technology transparently.


There are python bindings for it, of which the documentation can be found on http://pygstdocs.berlios.de
I would also suggest to read these introductions to gstreamer & python:

I translated the video player example 2.2 of the tutorial from pyGtk to wxPython:
http://pygstdocs.berlios.de/pygst-tutorial/playbin.html

It should be straightforward to use this as a base for implementing your own pipelines. I work on Ubuntu, where I could install everything straight from the standard repositories.

Here is the source code:
#!/usr/bin/env python
#Example 2.2 http://pygstdocs.berlios.de/pygst-tutorial/playbin.html

import sys, os
import wx
import pygst
pygst.require("0.10")
import gst

import gobject
gobject.threads_init()

class WX_Main(wx.App):

def OnInit(self):
window = wx.Frame(None)
window.SetTitle("Video-Player")
window.SetSize((500, 400))
window.Bind(wx.EVT_CLOSE,self.destroy)
vbox = wx.BoxSizer(wx.VERTICAL)
hbox = wx.BoxSizer(wx.HORIZONTAL)
self.entry = wx.TextCtrl(window)
hbox.Add(self.entry, 1, wx.ALL|wx.ALIGN_CENTER_VERTICAL, 4)
self.button = wx.Button(window,label="Start")
hbox.Add(self.button, 0, wx.ALL|wx.ALIGN_CENTER_VERTICAL, 4)
self.button.Bind(wx.EVT_BUTTON, self.start_stop)
vbox.Add(hbox, 0, wx.EXPAND, 0)
self.movie_window = wx.Panel(window)
vbox.Add(self.movie_window,1,wx.ALL|wx.EXPAND,4)
window.SetSizer(vbox)
window.Layout()
window.Show()
self.SetTopWindow(window)

self.player = gst.element_factory_make("playbin", "player")
bus = self.player.get_bus()
bus.add_signal_watch()
bus.enable_sync_message_emission()
bus.connect('message', self.on_message)
bus.connect('sync-message::element', self.on_sync_message)

return True

def start_stop(self, event):
if self.button.GetLabel() == "Start":
filepath = self.entry.GetValue()
if os.path.exists(filepath):
self.button.SetLabel("Stop")
self.player.set_property('uri',"file://" + filepath)
self.player.set_state(gst.STATE_PLAYING)
else:
self.player.set_state(gst.STATE_NULL)
self.button.SetLabel("Start")

def on_message(self, bus, message):
t = message.type
if t == gst.MESSAGE_EOS:
self.player.set_state(gst.STATE_NULL)
self.button.SetLabel("Start")
elif t == gst.MESSAGE_ERROR:
self.player.set_state(gst.STATE_NULL)
self.button.SetLabel("Start")

def on_sync_message(self, bus, message):
if message.structure is None:
return
message_name = message.structure.get_name()
if message_name == 'prepare-xwindow-id':
imagesink = message.src
imagesink.set_property('force-aspect-ratio', True)
imagesink.set_xwindow_id(self.movie_window.GetHandle())

def destroy(self,event):
#Stop the player pipeline to prevent a X Window System error
self.player.set_state(gst.STATE_NULL)
event.Skip()

app = WX_Main()
app.MainLoop()

Tuesday, March 25, 2008

SPE packaged for Mac OS X

Krzysztof Olczyk did a wonderful job by packaging SPE for Mac OS X. You can download it here:
http://olczyk.krzysztof.googlepages.com/SPE.dmg

He commented:
You can install now SPE in your Macintosh in a way you do with native applcation.
Simply mount the DMG and drag the SPE to Applications folder.

Another advantage is, that now SPE will have its own icon in dock, like any application in Mac.

Have fun.

I will release soon SPE 0.8.4.e with some important bug fixes and I hope Krzysztof Olczyk will update the package for the Mac.

Please test the package and let Krystof know how it works.

Thanks Krystof!
Stani
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