[Bug 699786] New: mpegtsmux: memory leak when using prepare_func

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=699786
  GStreamer | gst-plugins-bad | 1.x

           Summary: mpegtsmux: memory leak when using prepare_func
    Classification: Platform
           Product: GStreamer
           Version: 1.x
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: greg at gsr-tek.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=243438)
 View: https://bugzilla.gnome.org/attachment.cgi?id=243438
 Review: https://bugzilla.gnome.org/review?bug=699786&attachment=243438

Proposed fix

In the mpegtsmux collect pads clip function (mpegtsmux_clip_inc_running_time),
it is possible that a "prepare" function is necessary to modify the incoming
buffer when it arrives on a pad (AC3 audio uses this prepare_func).  The
prepare returns a newly alloc'd GstBuffer based on the incoming buffer data. 
The call is made like this:

  if (pad_data->prepare_func) {
    MpegTsMux *mux = (MpegTsMux *) user_data;

    buf = pad_data->prepare_func (buf, pad_data, mux);
    if (buf)
      gst_buffer_replace (outbuf, buf);
  }

Since the clip function is supposed to return the buffer in an output parameter
and not as a return value, the buffer returned from the prepare_func is passed
to gst_buffer_replace.  gst_buffer_replace serves the purpose of allowing the
new buffer to returned in a function parameter, but I think is has the
unintended side-effect of reffing the buffer one more time.

My proposed patch will just add a call to gst_buffer_unref after
gst_buffer_replace.  The other possible solution is to not use
gst_buffer_replace at all and just do "*outbuf = buf".  I'm not sure if the
atomicity of gst_buffer_replace is really necessary.

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