Jpegenc frame-encoded signal

[Lee Matthews]

Hi,

I'm trying to grab a frame from a video stream and convert it to a jpeg file.

I try to grab a frame using the following

souphttpsrc location=http://localhost:7921 is-live=true ! matroskademux ! vp8dec ! videoconvert ! jpegenc name=jpegenc ! filesink location=snapshot.jpg

According to the following webpage, there is a "frame-encoded" signal that I can use

http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-good-plugins/html/gst-plugins-good-plugins-jpegenc.html

However, using gst-inspect-1.0 jpegenc there is no mention of a  "frame-encoded" signal. 

If I try creating a "frame-encoded" callback, I get the following runtime error :

W/GLib+GLib-GObject( 3750): gsignal.c:2462: signal 'frame-encoded' is invalid for instance '0x77afa360' of type 'GstPipeline'


Can I assume that the "frame-encoded" signal no longer exists? Is there any other way of detecting that the frame has been encoded? 
Failing this, is there an element that generates an image that does produce a "frame-encoded" signal ?

Thanks
Lee