Gstreamer Editing Services. Playing real video file. GESAsset element (translation from Python to C)

Question

I'm trying to play video file using GES. I found python bindings example cut parts of a video using gstreamer/Python (gnonlin?) and I want to translate it to C language.

This is the excerpt of the python code which I want to translate to C:

asset = GES.UriClipAsset.request_sync(source_uri)
timeline = GES.Timeline.new_audio_video()
layer = timeline.append_layer()

start_on_timeline = 0
start_position_asset = 10 * 60 * Gst.SECOND
duration = 5 * Gst.SECOND
# GES.TrackType.UNKNOWN => add every kind of stream to the timeline
clip = layer.add_asset(asset, start_on_timeline, start_position_asset,
    duration, GES.TrackType.UNKNOWN)

What I have translated to the C code so far:

gint start_on_timeline = 0;
gint start_position_asset = 10 * 60 * GST_SECOND;
gint duration = 5 * GST_SECOND;
GESTimeline *timeline2;
GESLayer *layer2;
gchar *uri = gst_filename_to_uri (argv[1], NULL);
GError **error;
GESUriClipAsset *asset = ges_uri_clip_asset_request_sync(uri,error);
timeline2 = ges_timeline_new_audio_video();
if (!ges_timeline_add_layer (timeline2, layer2))
    return -1;
ges_layer_add_asset(layer2, asset, start_on_timeline, start_position_asset, duration, GES_TRACK_TYPE_UNKNOWN);

The problem is that function ges_layer_add_asset accepts type GESAsset asset , and I have type GESUriClipAsset asset.

In GES documentation page http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer-editing-services/html/GESUriClipAsset.html#ges-uri-clip-asset-request-sync there doesn't seem to be any alternatives to the ges_uri_clip_asset_request_sync (const gchar *uri, GError **error) function. Is there any way how can I construct GESAsset from video file uri? Maybe there are other ways how can I play video file using GES?

Answer 1

I needed to cast GESUriClipAsset to GESAsset using GES_ASSET(asset).

What is more here is the C example of playing file in GES, when the program argument is the address to video file (might leak memory) (most of the code is taken from test1.c):

#include <ges/ges.h>

int main (int argc, gchar ** argv)
{
  GESAsset *src_asset;
  GESPipeline *pipeline;
  GESTimeline *timeline;
  GESClip *source;
  GESLayer *layer;
  GMainLoop *mainloop;
  GError **error;
  gchar *uri;
  GESUriClipAsset *asset;
  /* Initialize GStreamer (this will parse environment variables and commandline
   * arguments. */
  gst_init (&argc, &argv);

  /* Initialize the GStreamer Editing Services */
  ges_init ();

  /* Setup of a A/V timeline */

  /* This is our main GESTimeline */
  timeline = ges_timeline_new_audio_video ();

  /* We are only going to be doing one layer of clips */
  layer = ges_layer_new ();

  /* Add the tracks and the layer to the timeline */
  if (!ges_timeline_add_layer (timeline, layer))
    return -1;

  /* We create a simple asset able to extract GESTestClip */
  uri = gst_filename_to_uri (argv[1], NULL);
  asset = ges_uri_clip_asset_request_sync(uri,error);
  src_asset = GES_ASSET(asset);

  /* Add sources to our layer */
  ges_layer_add_asset (layer, src_asset, 0, 0, 4*GST_SECOND,
      GES_TRACK_TYPE_UNKNOWN);

  /* In order to view our timeline, let's grab a convenience pipeline to put
   * our timeline in. */
  pipeline = ges_pipeline_new ();

  /* Add the timeline to that pipeline */
  if (!ges_pipeline_set_timeline (pipeline, timeline))
    return -1;

  /* The following is standard usage of a GStreamer pipeline (note how you haven't
   * had to care about GStreamer so far ?).
   *
   * We set the pipeline to playing ... */
  gst_element_set_state (GST_ELEMENT (pipeline), GST_STATE_PLAYING);

  /* .. and we start a GMainLoop. GES **REQUIRES** a GMainLoop to be running in
   * order to function properly ! */
  mainloop = g_main_loop_new (NULL, FALSE);

  /* Simple code to have the mainloop shutdown after 4s */
  g_timeout_add_seconds (4, (GSourceFunc) g_main_loop_quit, mainloop);
  g_main_loop_run (mainloop);

  return 0;
}