infinite/streaming sources within some pads of a videomixer

[Matt Pekar]

I'm experimenting with the videomixer and videomixer2 elements, and having
very good luck with them when using live streams.  I want to add file-based
streams into the mix, and have them either repeat or disappear upon
completion.

Repeating a single stream is relatively easy.  We can listen for the EOS
event on the bus callback and seek to the beginning when the event arrives:

=====================================================================
gboolean bus_cb (GstBus *bus, GstMessage *message, gpointer data) {
...
switch (GST_MESSAGE_TYPE (message)) {
...
case GST_MESSAGE_EOS:
 if (!gst_element_seek_simple (GST_ELEMENT(pipeline), GST_FORMAT_TIME,
GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT, 1)) {
 g_warning ("Failed to Return to Beginning of Stream\n");
 }
 break;
...
=====================================================================

Works fine, but the "src" in the "message" variable seems to originate from
the pipeline, and not any of the elements linked to the filesrc.  So with
this approach I seem to be tied to seeking on the entire pipeline instead
of a subelement.

The next approach I tried was to create a new element "infinitestream".  I
figured maybe I could trap the EOS event in this element and seek to the
beginning for just a filesrc, like so:

gst-launch videomixer2 name=mix sink_0::zorder=1 sink_1::zorder=0 !
ffmpegcolorspace ! video/x-raw-rgb ! ximagesink sync=false filesrc
location=videofile.mp4 ! decodebin2 ! identity sync=true ! infinitestream !
ffmpegcolorspace ! video/x-raw-yuv ! mix. videotestsrc pattern=snow
is-live=TRUE ! mix.

This comes close, with the stream successfully repeating and playing at the
correct rate, but the live pads in the mixer become frozen.

Here is the relevant code in "infinitestream":

=====================================================================
static void
gst_infinite_stream_class_init (GstInfiniteStreamClass * klass)
{
...
  GST_BASE_TRANSFORM_CLASS (klass)->event =
      GST_DEBUG_FUNCPTR (gst_infinitestream_sink_eventfunc);
...
}

...

static gboolean
gst_infinitestream_sink_eventfunc (GstBaseTransform * trans, GstEvent *
event) {
  if(event->type != GST_EVENT_EOS) {
return TRUE;
  }

   if (!gst_element_seek_simple (GST_ELEMENT(trans), GST_FORMAT_TIME,
GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT, 1)) {
    g_warning ("Infinite Loop Failed to Return to Beginning of Stream\n");
  }

  return FALSE;
}
=====================================================================

Could anyone comment on this approach?  Is there anything I can do
out-of-the-box to implement this behavior, or would a change to the
gstreamer source be necessary?  I'd be happy to investigate such a change
if anyone can point me in the right direction.
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