[gst-devel] Video thumb nails

[Michal Benes]

Hi Pavan,

	your pipeline fails to change state to PAUSED,
gst_element_set_state(pipeline, GST_STATE_PAUSED) changes state
asynchronously. Use gst_element_get_state to wait until the state change
finishes. The problem is the queue between filesrc and decodebin (or
avidemux to be more precise). Queues work only in push-push mode (chain
mode) which is not supported by avidemux.

	Michal

Pavan Kumar Patale píše v Út 17. 10. 2006 v 17:46 +0000:
> Hi,
> 
> Thanks for the reply.  I tried applying the solution but a blank png image 
> comes up.
> Seek does not seem to be happening correctly.  Have, appended the code.  Can 
> you
> pls let me know if i am missing something in it.
> 
> Thanks,
> Pavan.
> 
> >
> >I just wanted to note that you may need to turn on these signals by
> >setting the fakesink's signal-handoffs property to true.
> >~Scott
> >
> >Michal Benes wrote:
> > >> Can anyone pls let me know if there is any support from GStreamer
> >framework
> > >> to create thumb nails for video files.
> > >
> > > Hi,
> > >
> > >     it is not difficult. Just create a pipe
> > >
> > > filesrc location=source ! decodebin ! ffmpegcolorspace ! pngenc !
> > > fakesink
> > >
> > > and connect to fakesink's preroll-handoff signal. Then put the pipeline
> > > to PAUSED state (not PLAYING) and seek to the desired position. Fakesink
> > > will give you png screenshot in preroll-handoff callback. Of course you
> > > can put videoscale before pngenc to obtain the desired resolution.
> > >
> > >     Michal
> > >
> 
> 
> #include <glib.h>
> #include <gst/gst.h>
> 
> static GstElement *pipeline = NULL;
> static GMainLoop *loop = NULL;
> static GstElement *fsink = NULL;
> static GError *error = NULL;
> 
> static void preroll_handoff_cb(GstElement * object,
>                                GstBuffer * buffer,
>                                GstPad * pad, gpointer user_data)
> {
>     g_print("Starts %s\n", __FUNCTION__);
>     FILE *fp = NULL;
>     fp = fopen("tnail.png", "wb");
>     fwrite(buffer->data, buffer->size, 1, fp);
>     fclose(fp);
>     g_print("Ends %s\n", __FUNCTION__); }
> 
> gint main(gint argc, gchar * argv[])
> {
>     gst_init(&argc, &argv);
> 
>     loop = g_main_loop_new(NULL, TRUE);
> 
>     pipeline =      gst_parse_launch ("filesrc location=1.avi ! queue ! 
> decodebin ! ffmpegcolorspace ! pngenc ! fakesink name=fsink",  &error);
> 
>     if (!pipeline) {
>         g_print("Unable to get the pipeline\n");
>         return -1;
>     }
> 
>     if (error) {
>         g_print("Error %s\n", error->message);
>         g_error_free(error);
>         error = NULL;
>         return -1;
>     }
> 
>     fsink = gst_bin_get_by_name(GST_BIN(pipeline), "fsink");
> 
>     g_object_set(G_OBJECT(fsink), "signal-handoffs", TRUE, NULL);
> 
>     g_signal_connect(G_OBJECT(fsink), "preroll-handoff",  
> preroll_handoff_cb, NULL);
> 
>     if (!gst_element_set_state(pipeline, GST_STATE_PAUSED)) {
>         g_print("Unable to set the state to paused\n");
>     }
>     if (!gst_element_seek_simple(fsink, GST_FORMAT_BYTES, 
> GST_SEEK_FLAG_ACCURATE, 0)) {
>         g_print("Unable to seek\n");
>     }
> 
>     g_print("Inside loop\n");
>     g_main_loop_run(loop);
>     return 0;
> }
> 
> 
> 
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