start/stop recording from live preview+stream

[rashmi]

I have a pipeline 
v4l2src-->queue-->filtercaps--
                              \
                               -->tee-->queue-->TIDmaivideosink(DVI output)
                                      |
                                     
|-->queue-->dmaienc_h264-->rtph264pay-->udpsink(streaming)

and i wish to initiate and stop recording to this pipeline.
Recording has turned out to be more tedious .There are 4 approaches I have
tried out for this:
1)First Approach 
On start recording command
 A recording bin is created with a event probe attached to it using :
gst_pad_add_probe (pipedata.vsrcpad,
GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM,G_CALLBACK(drop_eos_probe),pipeline,
NULL);
|----------------------------------------------------------|
|recording bin                                             |
|                                                          |
|   queue-->dmaienc_h264-->qtmux-->filesink                |
|                                                          |
|                                                          |
|----------------------------------------------------------|
 
and it is attached to the tee by requesting a pad from it when the start
command is received.
On the stop command(send 5 over socket) the bin is unlinked and removed from
the pipeline.
The following are the steps involved in it:
1)call a stop encoding function
2)send EOS to the recording bin  .
4)In the event probe callback function unlink the pads and remove the event
probe
5)the recording bin is removed from the pipeline.
6)the recording bin is set to null and unref.

>From what I read at the site:
https:/-add/developer.pidgin.im/ticket/13237 
A recommended solution is to use event probes.However the above code ended
up with errors in compiling due to undefined references to probing flags set
up in gst_pad_add_probe()function.
according to https://developer.gnome.org/gstreamer/unstable/GstPad.html
the gst pad events hav eto be explicitly enabled.

2)Second Approach:
  tried using gst_pad_set_blocked_async()
here on start recording:
1)create the recording bin
2)get static pad to recording bin
3)set its state to playing
4)add recording bin to pipeline
5)get request pad to tee
6)link it to recording bin

In this approach 
On the stop command 
The following are the steps involved in it:
1)block the tee pad connected to bin using gst_pad_set_blocked_async()
2)inside the callback function unlink the tee pad connected to the recording
bin ghost pad.
3)send EOS to the recording bin  .
4)unblock the requested tee pad and release it.
5)the recording bin is removed from the pipeline.
6)the recording bin is set to null and unref.

The problem with this approach is that the recording works initially for a
few times .Eventually however the recording hangs at
gst_pad_set_blocked_async() not calling the blocking callback function as
expected and the recording bin  fails to get the EOS. Sometimes the
application crashes with a memory backtrace message(log attched with mail).

3)Third Solution:

As an alternative approach I have also tried not to unref the bins at the
end and add the same bin to the pipeline the next time recording/capture
command is received. With this approach I find the
gst_pad_set_blocked_async() function not calling the callback function and
the threads remain deadlocked.

4) fouth approach
to the tee element fakesink is attached initially and on user command to
start recording fakesink is replaced by the recording bin .


I have also read that blocking a tee element is not necessary and we can
directly link and unlink elements to tee without affecting the running
pipeline.Not blocking the tee however has resulted in freezing the entire
pipeline after a definite no. of times.

I would be grateful if somebody takes time to go through this.Kindly let me
know which of these approaches are more feasible.I need to capture images
too.
If the first approach is suitable,then how can  I go about removing the
compile time errors.



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