| Hello all
My name is Corentin and I'm working on
a web multimedia project based on Django frameworkand Gstreamer, and
I want to add a scene change detection fonctionality to my project.
To do this i need to acces to the video
data so I take a (long..) look at Gstreamer manual and made this
code. It's made with the Hello world code to read a ogg audio file
(Chapter 10 in the manual), I easily turned to play ogg video file
and with the code from the example of data probing (Chapter 18 in the
manual)
so here is my code :
#include <gst/gst.h>
/*
* Global objects are usually a bad
thing. For the purpose of this
* example, we will use them, however.
*/
GstElement *pipeline, *source, *parser,
*decoder, *csp, *filter, *sink;
static gboolean
bus_call (GstBus *bus,
GstMessage *msg,
gpointer data)
{
GMainLoop *loop = (GMainLoop *) data;
switch (GST_MESSAGE_TYPE (msg)) {
case GST_MESSAGE_EOS:
g_print ("End-of-streamn");
g_main_loop_quit (loop);
break;
case GST_MESSAGE_ERROR: {
gchar *debug;
GError *err;
gst_message_parse_error (msg,
&err, &debug);
g_free (debug);
g_print ("Error: %sn",
err->message);
g_error_free (err);
g_main_loop_quit (loop);
break;
}
default:
break;
}
return TRUE;
}
// this fonction deals with the pixels
(it should invert the video)
static gboolean
cb_have_data (GstPad *pad,
GstBuffer *buffer,
gpointer u_data)
{
g_print ("Youpi, you are in the
loop of the frame n");
gint x, y;
guint16 *data = (guint16 *)
GST_BUFFER_DATA (buffer), t;
// invert data
for (y = 0; y < 288; y++) {
for (x = 0; x < 384 / 2; x++) {
t = data[384 - 1 - x];
data[384 - 1 - x] = data[x];
data[x] = t;
}
data += 384;
}
return TRUE;
}
// add a pad
static void
new_pad (GstElement *element,
GstPad *pad,
gpointer data)
{
GstPad *sinkpad; /* We can now link this pad with the
audio decoder */
g_print ("Dynamic pad created,
linking parser/decodern");
sinkpad = gst_element_get_pad
(decoder, "sink");
gst_pad_link (pad, sinkpad);
gst_object_unref (sinkpad);
}
int
main (int argc,
char *argv[])
{
GMainLoop *loop;
GstBus *bus;
GstCaps *filtercaps;
GstPad *pad2;
/* initialize GStreamer */
gst_init (&argc, &argv);
loop = g_main_loop_new (NULL, FALSE);
/* check input arguments */
if (argc != 2) {
g_print ("Usage: %s
<Ogg/Vorbis filename>n", argv[0]);
return -1;
}
/* create elements */
pipeline = gst_pipeline_new
("player");
source = gst_element_factory_make
(";filesrc", "file-source");
parser = gst_element_factory_make
(";oggdemux", "ogg-parser";);
decoder = gst_element_factory_make
(";theoradec", "theora-decoder");
filter = gst_element_factory_make
(";capsfilter", "filter");
csp = gst_element_factory_make
(";ffmpegcolorspace";, "csp");
g_assert (filter != NULL); /* should
always exist */
sink = gst_element_factory_make
(";ximagesink", "sink");
if (!pipeline || !source || !parser
|| !decoder || !csp || !filter ||!sink) {
g_print ("One element could
not be createdn");
return -1;
}
/* set filename property on the file
source. Also add a message
* handler. */
g_object_set (G_OBJECT (source),
"location", argv[1], NULL);
bus = gst_pipeline_get_bus
(GST_PIPELINE (pipeline));
gst_bus_add_watch (bus, bus_call,
loop);
gst_object_unref (bus);
/* put all elements in a bin */
gst_bin_add_many (GST_BIN (pipeline),
source, parser, decoder,
csp,filter, sink, NULL);
/* link together - note that we
cannot link the parser and
* decoder yet, becuse the parser
uses dynamic pads. For that,
* we set a pad-added signal handler.
*/
gst_element_link (source, parser);
gst_element_link_many (decoder, csp ,
filter, sink, NULL);
g_signal_connect (parser,
"pad-added", G_CALLBACK (new_pad), NULL);
// create the filter caps vvith the video caracteristics
filtercaps = gst_caps_new_simple
("video/x-raw-rgb",
"width", G_TYPE_INT,
288,
"height", G_TYPE_INT,
208,
"framerate",
GST_TYPE_FRACTION, 30, 1,
//";bpp", G_TYPE_INT,
16,
//"depth", G_TYPE_INT,
16,
// "endianness";,
G_TYPE_INT, G_BYTE_ORDER,
NULL);
g_print ("try to set the caps on
the filtern");
g_object_set (G_OBJECT (filter),
"caps", filtercaps, NULL);
gst_caps_unref (filtercaps);
g_print ("try to get the
padn");
pad2 = gst_element_get_pad
(csp,"csp");
if ( pad2 == NULL )
{
g_print ("could not get the
padn");
}
//pad2 = gst_element_get_pad (csp,
"csp";);
//add the probe
g_print ("n setting the probe";);
gst_pad_add_buffer_probe (pad2,
G_CALLBACK (cb_have_data), NULL);
g_print ("nprobe addedn");
gst_object_unref (pad2);
/* Now set to playing and iterate. */
g_print ("Setting to
PLAYINGn");
gst_element_set_state (pipeline,
GST_STATE_PLAYING);
g_print ("Runningn");
g_main_loop_run (loop);
/* clean up nicely */
g_print ("Returned, stopping
playbackn");
gst_element_set_state (pipeline,
GST_STATE_NULL);
g_print ("Deleting pipelinen");
gst_object_unref (GST_OBJECT
(pipeline)); return 0;
}
To my mind the error comes from getting
the pad. I take a look about this and I tried all the functions :
gst_element_get_static_pad() &
gst_element_get_request_pad().
The fact is I set the filter after the
csp (ffmpegcolorspace) because it think this is here I will find the video data.
I tried to set the filter before but
nothing changed.
I can't find my error.
If anyone of you knows where I'm wrong
it would be very nice to tell me because i'm getting mad.
You 'll find the little video I use to
test my code at :
http://corentino.fr/dl/vid.ogg
you'll need it, because some video properties are set in hard, if you try my code ! : )
Thank you by advance,
Sincerly
Corentin
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