Convert a video to another format

[kususe]

I apologize. I'm a newbie in this subject and I'm learning. 
My idea is to code a script to display a video, adding some infos on the
screen and, while it's playing I'd like to convert my original webm video to
avi. 
So, what I got until now is just the first phase: I've the webmvideo, I
demux it, I add text/time on the screen and send it out on a window. 

So, the pipeline I implemented in the code is:

gst-launch-0.10 filesrc location=video.webm ! matroskademux ! queuev !
mpeg2dec ! textoverlay text="zzz" ! timeoverlay ! ffmpegcolorspace !
autovideosink ! queuea ! vorbisdec ! audioconvert ! autoaudiosink

And, using the code (I'm using python): 

gst.element_link_many(filesrc,self.demuxer)
gst.element_link_many(self.queuev,
self.video_decoder,textoverlay,timeoverlay,colorspace,autovideosink) 
gst.element_link_many(self.queuea, self.audio_decoder,
audioconv,autoaudiosink) 

Now, I'd like to convert, while it's playing or at least without displaying
the video itself, to convert the "encode" the output in another format,
which is avi. 
So, what I think is something like this:

                            queuev- decodervideo - textoverlay -timeoverlay
-ffmpegcolorspace - x264enc -> 
filesrc - demuxer -                                                                                                                       
avimux - filesink v.avi
                           queuea - decoderaudio - audioconvert - lame
-------------------------------------------------->

so, in the code I implemented: 
gst.element_link_many(filesrc,demuxer)
gst.element_link_many(self.queuev, self.video_decoder,colorspace,x264enc) 
gst.element_link_many(self.queuea, self.audio_decoder, audioconv,lame) 
gst.element_link_many(avimux,filesink)

but I got

I get an error: Error: GStreamer ha incontrato un errore generico di stream.
> gstbasesrc.c(2582): gst_base_src_loop ():
> /GstPipeline:player/GstFileSrc:file-source:
> streaming task paused, reason not-linked (-1) 

is the code correct?? 
Should I implemented the pipeline like I set up?
so, suggestions?? I hobe have been clear.

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