Internal data flow error in Multipart(De)Mux's official document example

[k l]

In the official documents for MultipartMux [1] and Multipartdemux [2],
there are two sample pipelines as below. It's fine when I run the first
pipeline to encode. But when running the sencond pipeline to decode, it
gave me the following error.

Any hint? I'm running:

  Linux ubuntu 3.8.0-19-generic #29-Ubuntu SMP Wed Apr 17 18:19:42 UTC 2013
i686 athlon i686 GNU/Linux
  Distributor ID: Ubuntu
  Description:    Ubuntu 13.04
  Release:        13.04
  Codename:       raring


Encoding video to to jpeg multipart:

  $ gst-launch-1.0 videotestsrc ! video/x-raw, framerate='(fraction)'5/1 !
jpegenc ! multipartmux ! filesink location=/tmp/test.multipart

Decoding video from jpeg multipart:

  $ gst-launch-1.0 filesrc location=/tmp/test.multipart ! multipartdemux !
jpegdec ! videoconvert ! ximagesink


Error Message for the above demux pipeline:
------------------
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
ERROR: from element /GstPipeline:pipeline0/GstFileSrc:filesrc0: Internal
data flow error.
Additional debug info:
gstbasesrc.c(2809): gst_base_src_loop ():
/GstPipeline:pipeline0/GstFileSrc:filesrc0:
streaming task paused, reason not-negotiated (-4)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...


References
===========
[1] multipartmux:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-good-plugins/html/gst-plugins-good-plugins-multipartmux.html#GstMultipartMux

[2] multipartdemux:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-good-plugins/html/gst-plugins-good-plugins-multipartdemux.html
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