integrate gstreamer in discrete event simulation

[Maxime Louvel]

Hi everyone,

this is my first post on this list, I hope I'll make things right.
If no please tell me.

So, I want to integrate Gstreamer in a discrete event simulation
environment (Omnet++).
I want to integrate network delay into a streaming application.
My idea is to execute the gstreamer pipelines (server and client) on a
local PC.
Here are the pipelines corresponding to my application :

Server:
gst-launch -v -e videotestsrc ! video/x-raw-yuv, framerate=25/1, width=640,
height=480 ! ffmpegcolorspace ! x264enc  byte-stream=true bitrate=2048 !
rtph264pay ! udpsink port=5000 host=127.0.0.1

Client:
 gst-launch -v -e udpsrc caps="application/x-rtp, media=(string)video,
clock-rate=(int)90000, encoding-name=(string)H264, payload=(int)96"
port=5000 ! rtph264depay ! capsfilter caps="video/x-h264,width=(int)640,
height=(int)480, framerate=(fraction)25/1" ! qtmux ! filesink
location=/tmp/video.mp4


Then I added probes on the udpsink pad to get the data that are going to be
sent on the local socket.
This triggers network event in my simulation environment,
On the receiver pipeline, I want to add the network delay to the timestamp
of the received packet.
I also want to simulate packet loss.
I've done that by adding a probe on the udpsrc pad.

here is the code I used :
...
pad = gst_element_get_pad (udpsrc, "src");
gst_pad_add_buffer_probe (pad, G_CALLBACK (c_udp_src_pad), NULL);
gst_object_unref (pad);
...

static gboolean c_udp_src_pad(GstPad *pad, GstBuffer *buffer, gpointer
u_data)
{
   gboolean ret;
   gst_element_set_state (pipeline, GST_STATE_PAUSED);
   If (corresponding omnet packet is lost){
      ret=FALSE;
   }
   else{
      buffer->timestamp= buffer->timestamp + net_delay;
      ret = TRUE;
   }
   gst_element_set_state (pipeline, GST_STATE_PLAYING);
   return ret;
}

What I expect to have is :
 - the lost packets removed from the client pipeline
 - the network delay taken into account in the client pipeline.

My questions are :

1/ Is my approach correct ?

2/ Is is OK to PAUSE / START the pipeline as I do ?

3/ I think I read somewhere that probes should not block, is that true for
my case (for the source element) ? If yes I might have a problem then since
the client pipeline have sometime to wait for the network simulation. Do
think I should write a plug-in to do what I want and to generate the
pipeline clock ?

thank you very much

Max

-- 
Maxime Louvel
web page : https://sites.google.com/site/mlouvel/
linkedin : http://fr.linkedin.com/in/mlouvel
address : 5400-B ridge oak drive
               Austin, Texas, 78731
               USA
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