Could not play back media file of amr codec with 3gp postfix

[dandan.hong@intel.com]

Test on verson 0.21 with both gstreamer and helix enabled,moblin-media could not play back the media file of amr codec with 3gp postfix .
Moblin-media version: 0.21
Gstreamer version : 0.1.10ubuntu1
Helix version : 0.22-beta1
Reproduce steps:
1.Enable helix and gst at the same time
2.Play back media encoded in amr which postfix is .3gp,for example MID_MPEG4_ARM-NB_14fps_190kbps.3gp,it can be downloaded for this link:
http://pdk_repo.sh.intel.com/pdk/media_content_test/Content/

Current result:
Could not play back this media file,and it prompts a dialog "Missing plugin Adaptive Muti Rate(AMR) decoder.Please install this plugin".But moblin-media can make a thumbnail for it.

Expected result:
Play back this media file successfully.

[Halley (halley-zhao)]

try splay and determine

[Halley (halley-zhao)]

this contents could be supported by splay and my unit test.
next, try to fix it in engine management.

[Jessica Ji (jessica-ji)]

test on 0.30 version, still can repoduce this bug. so assign to new.

[cathyshen (cathy-shen)]

can't reproduce. Please check with 0.31 version.