title: gstreamer flvmux and rtmp error
body: <p>I trying to stream rtmp from rasberrypi, the omx hardware encoder worked really nice, by the way, so I'm running:</p>
  
  <pre><code>gst-launch-1.0 v4l2src ! «video/x-raw,width=640,height=480,framerate=30/1» !\
   omxh264enc target-bitrate=1000000 control-rate=variable !\
   video/x-h264,profile=high ! h264parse ! queue ! \
  flvmux name=mux alsasrc device=plughw:1 ! audioresample ! \
  audio/x-raw,rate=48000,channels=1 ! queue ! voaacenc bitrate=32000 ! queue ! mux. mux. !\
   rtmpsink location='rtmp://my_rtmp_for_ustream.tv_url'
  </code></pre>
  
  <p>And there is an error:</p>
  
  <pre><code>Setting pipeline to PAUSED ...
  Pipeline is live and does not need PREROLL ...
  Setting pipeline to PLAYING ...
  New clock: GstAudioSrcClock
  ERROR: from element /GstPipeline:pipeline0/GstAlsaSrc:alsasrc0: Internal data flow error.
  Additional debug info:
  gstbasesrc.c(2812): gst_base_src_loop (): /GstPipeline:pipeline0/GstAlsaSrc:alsasrc0:
  streaming task paused, reason not-negotiated (-4)
  Execution ended after 535913298 ns.
  Setting pipeline to PAUSED ...
  Setting pipeline to READY ...
  Setting pipeline to NULL ...
  libv4l2: warning v4l2 mmap buffers still mapped on close()
  Freeing pipeline ...
  </code></pre>
  
  <p>First of all i thought that there is some alsa problems or such, but then I tried to write simple mpegts and it worked:</p>
  
  <pre><code>gst-launch-1.0 v4l2src ! «video/x-raw,width=640,height=480,framerate=30/1» ! \
  omxh264enc target-bitrate=1000000 control-rate=variable !\
   video/x-h264,profile=high ! h264parse ! queue ! \
   mpegtsmux name=mux alsasrc device=plughw:1 ! audioresample !\
   audio/x-raw,rate=48000,channels=1 ! queue ! voaacenc bitrate=32000 ! \
  queue ! mux. mux. ! filesink location=1.ts
  </code></pre>
  
  <p>But i can't just change "filesink location=1.ts" to rtmpsink location='rtmp://my_rtmp_for_ustream.tv_url' because i'll get an error:</p>
  
  <p>WARNING: erroneous pipeline: could not link mux to rtmpsink0</p>
  
  <p>So, what can I do to get it work? Thanks.</p>