from git installed newest versions and for a H.264 streaming camera (Logitec C920). It complains that it misses a plugin, but I did gst-inspect-1.0 on all of the element mention below and they all exist.

I did the following:

#: gst-launch-1.0 -v v4l2src device=/dev/video0 ! 'video/x-h264,width=800,height=448,framerate=(fraction)30/1' ! h264parse ! decodebin ! fpsdisplaysink fps-update-interval=5000 sync=false

Result:

Setting pipeline to PAUSED ...
libEGL warning: failed to create a pipe screen for i965
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0/GstAutoVideoSink:fps-display-video_sink/GstEglGlesSink:fps-display-video_sink-actual-sink-eglgles: sync = false
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
/GstPipeline:pipeline0/GstV4l2Src:v4l2src0.GstPad:src: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:src: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstH264Parse:h264parse0.GstPad:sink: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:sink: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstH264Parse:h264parse0.GstPad:src: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
/GstPipeline:pipeline0/GstDecodeBin:decodebin0.GstGhostPad:sink.GstProxyPad:proxypad0: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstTypeFindElement:typefind.GstPad:src: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstTypeFindElement:typefind.GstPad:sink: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
/GstPipeline:pipeline0/GstDecodeBin:decodebin0.GstGhostPad:sink: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstH264Parse:h264parse1.GstPad:sink: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstH264Parse:h264parse1.GstPad:src: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
Missing element: H.264 decoder
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstCapsFilter:capsfilter1.GstPad:src: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
ERROR: from element /GstPipeline:pipeline0/GstDecodeBin:decodebin0: Your GStreamer installation is missing a plug-in.
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstCapsFilter:capsfilter1.GstPad:sink: caps = "video/x-h264\,\ width\=\(int\)800\,\ height\=\(int\)448\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ parsed\=\(boolean\)true\,\ stream-format\=\(string\)byte-stream\,\ alignment\=\(string\)au"
Additional debug info:
gstdecodebin2.c(3908): gst_decode_bin_expose (): /GstPipeline:pipeline0/GstDecodeBin:decodebin0:
no suitable plugins found
Execution ended after 0:00:00.370118979
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...