Hi.

Im trying to make gstreamer to work with an external application through named pipes. Named pipes are like files in many aspects, but opening a named pipe reading is blocked until it is also opened somhow for writing. And likewise when openeing for writing.

This is how I set it up using CVS from yesterday (in this example 'cat' is the external application) 

$ ls -l >myfile1
$ mkfifo raw_pipe encoded_pipe
$ cat <raw_pipe >encoded_pipe &
$ gst-launch -v filesrc location=myfile1 \
    ! queue \
    ! filesink location=raw_pipe \
    filesrc location=encoded_pipe \
    ! queue \
    ! filesink  location=myfile2
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock

What you can observer is that a) not all data is copied from myfile1 to myfile2 and b) gst-launch never exits.

This is what I conclude :

When the first filesrc detects EOF, it sends an EOS downstream but thats all. The first filsink receives the EOS event and probably flushes its buffers, but keeps its fd to raw_pipe open so far.

The 'cat' process reading from raw_pipe never gets an EOF because Gstreamer keeps its fd on raw_pipe open. Subsequently 'cat' never closes its fd to encoded_pipe and since it is opened in a BLOCKING rather than a NONBLOCKING mode, 'cat' probably even keeps some data back in its internal buffers.

Now since cat never closes encoded_pipe for writing, Gstreamer never receives an EOF on it second filesrc reading encoded_pipe. Subsequently Gstreamer can not close its open fd's and it can not terminate. 

You can't exactly say it is a bug in filesink, but it limits the usability of Gstreamer together with named pipes.

If the event handling of EOS in gstfilesink.c line xxx is changed from
----------------------
  case GST_EVENT_EOS:
        if (fflush (filesink->file))
          goto flush_failed;
        break;
----------------------
to
----------------------
  case GST_EVENT_EOS:
        if (fflush (filesink->file))
          goto flush_failed;
        if (!filesink->seekable) gst_file_sink_close_file (filesink);
      break;
----------------------
then non seekable files (like named pipes) are closed upon EOS and subsequently signalling EOF to external sources reading the named pipes.

Closing a fd is the only way to signal EOF across a named pipe.

Kind regards

Peter Maersk-Moller