example appsrc for gstreamer 1.0 with own mainloop & external buffers

gst-appsrc.c

// example appsrc for gstreamer 1.0 with own mainloop & external buffers. based on example from gstreamer docs.
// public domain, 2015 by Florian Echtler <floe@butterbrot.org>. compile with:
// gcc --std=c99 -Wall $(pkg-config --cflags gstreamer-1.0) -o gst-appsrc gst-appsrc.c $(pkg-config --libs gstreamer-1.0) -lgstapp-1.0

#include <gst/gst.h>
#include <gst/app/gstappsrc.h>

#include <stdint.h>

int want = 1;

uint16_t b_white[384*288];
uint16_t b_black[384*288];

static void prepare_buffer(GstAppSrc* appsrc) {

  static gboolean white = FALSE;
  static GstClockTime timestamp = 0;
  GstBuffer *buffer;
  guint size;
  GstFlowReturn ret;

  if (!want) return;
  want = 0;

  size = 384 * 288 * 2;

  buffer = gst_buffer_new_wrapped_full( 0, (gpointer)(white?b_white:b_black), size, 0, size, NULL, NULL );

  white = !white;

  GST_BUFFER_PTS (buffer) = timestamp;
  GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale_int (1, GST_SECOND, 4);

  timestamp += GST_BUFFER_DURATION (buffer);

  ret = gst_app_src_push_buffer(appsrc, buffer);

  if (ret != GST_FLOW_OK) {
    /* something wrong, stop pushing */
    // g_main_loop_quit (loop);
  }
}

static void cb_need_data (GstElement *appsrc, guint unused_size, gpointer user_data) {
  //prepare_buffer((GstAppSrc*)appsrc);
  want = 1;
}

gint main (gint argc, gchar *argv[]) {

  GstElement *pipeline, *appsrc, *conv, *videosink;

  for (int i = 0; i < 384*288; i++) { b_black[i] = 0; b_white[i] = 0xFFFF; }

  /* init GStreamer */
  gst_init (&argc, &argv);

  /* setup pipeline */
  pipeline = gst_pipeline_new ("pipeline");
  appsrc = gst_element_factory_make ("appsrc", "source");
  conv = gst_element_factory_make ("videoconvert", "conv");
  videosink = gst_element_factory_make ("xvimagesink", "videosink");

  /* setup */
  g_object_set (G_OBJECT (appsrc), "caps",
  		gst_caps_new_simple ("video/x-raw",
				     "format", G_TYPE_STRING, "RGB16",
				     "width", G_TYPE_INT, 384,
				     "height", G_TYPE_INT, 288,
				     "framerate", GST_TYPE_FRACTION, 0, 1,
				     NULL), NULL);
  gst_bin_add_many (GST_BIN (pipeline), appsrc, conv, videosink, NULL);
  gst_element_link_many (appsrc, conv, videosink, NULL);

  /* setup appsrc */
  g_object_set (G_OBJECT (appsrc),
		"stream-type", 0, // GST_APP_STREAM_TYPE_STREAM
		"format", GST_FORMAT_TIME,
    "is-live", TRUE,
    NULL);
  g_signal_connect (appsrc, "need-data", G_CALLBACK (cb_need_data), NULL);

  /* play */
  gst_element_set_state (pipeline, GST_STATE_PLAYING);
  
  while (1) {
    prepare_buffer((GstAppSrc*)appsrc);
    g_main_context_iteration(g_main_context_default(),FALSE);
  }

  /* clean up */
  gst_element_set_state (pipeline, GST_STATE_NULL);
  gst_object_unref (GST_OBJECT (pipeline));

  return 0;
}

@floe, how come the buffer has a size of (width + 1) * height and not just width * height?

@blakat360 - good question, I would suppose that's just an old off-by-one error...

EDIT: tested and yes, no need for the extra width pixel, works fine with the correct width. Fixed.

@floe can you take a look at this? I've adapted your example but can't seem to flash between single-channel images (e.g. red/blue). If I use the RGB format it insists I pass a size of WIDTH * HEIGHT * CHANNELS + HEIGHT, Hence, I thought that your larger buffer related to that.

I'm not sure why this is the case that the docs seem to suggest it should just be straight RGB with no padding.

EDIT: My bad, if the width is a multiple of 3 it works.