[gst-devel] Need help on using decodebin as media decoder

[Stefan Kost]

Fariq Izwan wrote:
> Hi good people,
>
> I'm new to gstreamer and I have a problem of using decodebin as a
> decoder to play video file. Below is my sample code that I use. The
> code below runs fine for one stream of media. But if I want to play
> both streams(audio and video), it doesn't work.
> Can anyone tell me what I did wrong here? (Please don't suggest to use
> playbin) :)
>
> Thank you.
>
> Fariq.
>
> ####Sample code####
>
> #include <gst/gst.h>
> #include <glib-2.0/glib/gprintf.h>
> #include <gstreamer-0.10/gst/gstelement.h>
> #include <glib-2.0/glib/gmessages.h>
>
> GstElement *pipeline, *audio,*video,*audioqueue,*videoqueue;
>
> static void
> cb_newpad (GstElement *decodebin,
>        GstPad     *pad,
>        gboolean    last,
>        gpointer    data)
> {
>   GstPad *audiopad,*videopad;
>
>   /* link audiopad */
>   audiopad = gst_element_get_static_pad (audio, "sink");
>   if (!GST_PAD_IS_LINKED (audiopad)) {
>       gst_pad_link (pad, audiopad);
>       g_print("audiopad has been linked");
>     g_object_unref (audiopad);
>     return;
>   }
this is not correct. You would need to check the media-type of the caps
on the provided pad. (Get the caps from the pad, the structure from the
caps and check the name of the structure (audio/video/something-else).
Depending on that you link the audio- or videobin.
Also in the above code, you leak the audiopad, if it is linked already.
The above code might work, if you check the result of gst_pad_link() and
only return if that worked, otherwise you continie and try the next pad.

Stefan

> /* link videopad */
>   videopad = gst_element_get_static_pad(video,"sink");
>   if (!GST_PAD_IS_LINKED (videopad)) {
>       gst_pad_link(pad,videopad);
>       gst_element_link(videoqueue,video);
>     g_object_unref (videopad);
>     return;
>   }
> }
>
> gint
> main (gint   argc,
>       gchar *argv[])
> {
>   GMainLoop *loop;
>   GstElement *src, *dec, *conv, *sink, *typefind,*typefind2;//*myplugin;
>   GstElement *convVid,*videosink;
>   GstPad *audiopad,*videopad;
>   GstBus *bus;
>
>   /* init GStreamer */
>   gst_init (&argc, &argv);
>   loop = g_main_loop_new (NULL, FALSE);
>
>   /* make sure we have input */
>   if (argc != 2) {
>     g_print ("Usage: %s <filename>\n", argv[0]);
>     return -1;
>   }
>
>   g_print("Playing %s \n",argv[1]);
>
>   /* setup */
>   pipeline = gst_pipeline_new ("pipeline");
>
>   bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
>   gst_bus_add_watch (bus, my_bus_callback, loop);
>   gst_object_unref (bus);
>
>   src = gst_element_factory_make ("filesrc", "source");
>   g_object_set (G_OBJECT (src), "location", argv[1], NULL);
>   typefind = gst_element_factory_make("typefind","typefinder");
>   g_signal_connect(typefind,"have-type",G_CALLBACK(typefound_cb),loop);
>   dec = gst_element_factory_make ("decodebin", "decoder");
>   g_signal_connect (dec, "new-decoded-pad", G_CALLBACK (cb_newpad), NULL);
>   //myplugin = gst_element_factory_make("myplugin","MyPlugin");
>   audioqueue = gst_element_factory_make("queue","audioqueue");
>   videoqueue = gst_element_factory_make("queue","videoqueue");
>   gst_bin_add_many (GST_BIN (pipeline), src,typefind,dec,NULL);
>   gst_element_link_many (src,typefind,dec,NULL);
>
>   /* create audio output */
>   audio = gst_bin_new ("audiobin");
>   conv = gst_element_factory_make ("audioconvert", "aconv");
>   typefind2 = gst_element_factory_make("typefind","typefinder2");
>   //g_signal_connect(typefind2,"have-type",G_CALLBACK(typefound_cb),loop);
>   audiopad = gst_element_get_static_pad (audioqueue, "sink");
>   sink = gst_element_factory_make ("osssink", "sink");
>   gst_bin_add_many (GST_BIN (audio),audioqueue,conv,typefind2, sink,
> NULL);
>   gst_element_link_many (audioqueue,conv,typefind2, sink,NULL);
>   gst_element_add_pad (audio,
>       gst_ghost_pad_new ("sink", audiopad));
>   gst_object_unref (audiopad);
>   gst_bin_add (GST_BIN (pipeline), audio);
>
>   /* create video output */
>   video = gst_bin_new("videobin");
>   convVid = gst_element_factory_make("ffmpegcolorspace","converter");
>   videopad = gst_element_get_static_pad(videoqueue,"sink");
>   videosink = gst_element_factory_make("xvimagesink","videosink");
>   gst_bin_add_many(GST_BIN(video),videoqueue,convVid,videosink,NULL);
>   gst_element_link_many(videoqueue,convVid,videosink,NULL);
>   gst_element_add_pad(video,gst_ghost_pad_new("sink",videopad));
>   gst_object_unref(videopad);
>   gst_bin_add(GST_BIN(pipeline),video);
>
>   /* run */
>   gst_element_set_state (pipeline, GST_STATE_PLAYING);
>   g_timeout_add (200, (GSourceFunc) cb_print_position, pipeline);
>   g_main_loop_run (loop);
>
>   /* cleanup */
>   gst_element_set_state (pipeline, GST_STATE_NULL);
>   gst_object_unref (GST_OBJECT (pipeline));
>
>   return 0;
> }
> ------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------
>   
> ------------------------------------------------------------------------
>
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