We had solved the problem some time back.
Just putting it here for any body else's reference.
The problem was, if we are to use amcviddec-omxgoogleh264decoder, there are some dependent files which need to be installed besides the gstreamer application. Don't knopw exactly what they were.
Anyways, if one sees the /etc/media-codec.xml file in the android root, we will get to know all the multimedia codecs supported by one's android device. This includes the codec supported by hardware codec chips also.
For us, we tried the amcviddec-omxtiducati1videodecoder, and it worked like a charm.
Regards, Yusuf Husainy.