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/* GStreamer
* appsrc-ra.c: example for using appsrc in random-access mode.
* Copyright (C) 2008 Wim Taymans <>
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* Library General Public License for more details.
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
#include "config.h"
#include <gst/gst.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
GST_DEBUG_CATEGORY (appsrc_playbin_debug);
#define GST_CAT_DEFAULT appsrc_playbin_debug
* an example application of using appsrc in random-access mode. When the
* appsrc requests data with the need-data signal, we retrieve a buffer of the
* requested size and push it to appsrc.
* This is a good example how one would deal with a local file resource.
* Appsrc in random-access mode needs seeking support and we must thus connect
* to the seek signal to perform any seeks when requested.
* In random-access mode we must set the size of the source material.
typedef struct _App App;
struct _App
GstElement *playbin;
GstElement *appsrc;
GMainLoop *loop;
GMappedFile *file;
guint8 *data;
gsize length;
guint64 offset;
App s_app;
/* This method is called by the need-data signal callback, we feed data into the
* appsrc with the requested size.
static void
feed_data (GstElement * appsrc, guint size, App * app)
GstBuffer *buffer;
GstFlowReturn ret;
if (app->offset >= app->length) {
/* we are EOS, send end-of-stream */
g_signal_emit_by_name (app->appsrc, "end-of-stream", &ret);
/* read the amount of data, we are allowed to return less if we are EOS */
buffer = gst_buffer_new ();
if (app->offset + size > app->length)
size = app->length - app->offset;
gst_buffer_append_memory (buffer,
gst_memory_new_wrapped (GST_MEMORY_FLAG_READONLY,
app->data, app->length, app->offset, size, NULL, NULL));
/* we need to set an offset for random access */
GST_BUFFER_OFFSET (buffer) = app->offset;
GST_BUFFER_OFFSET_END (buffer) = app->offset + size;
GST_DEBUG ("feed buffer %p, offset %" G_GUINT64_FORMAT "-%u", buffer,
app->offset, size);
g_signal_emit_by_name (app->appsrc, "push-buffer", buffer, &ret);
gst_buffer_unref (buffer);
app->offset += size;
/* called when appsrc wants us to return data from a new position with the next
* call to push-buffer. */
static gboolean
seek_data (GstElement * appsrc, guint64 position, App * app)
GST_DEBUG ("seek to offset %" G_GUINT64_FORMAT, position);
app->offset = position;
return TRUE;
/* this callback is called when playbin has constructed a source object to read
* from. Since we provided the appsrc:// uri to playbin, this will be the
* appsrc that we must handle. We set up some signals to push data into appsrc
* and one to perform a seek. */
static void
found_source (GObject * object, GObject * orig, GParamSpec * pspec, App * app)
/* get a handle to the appsrc */
g_object_get (orig, pspec->name, &app->appsrc, NULL);
GST_DEBUG ("got appsrc %p", app->appsrc);
/* we can set the length in appsrc. This allows some elements to estimate the
* total duration of the stream. It's a good idea to set the property when you
* can but it's not required. */
g_object_set (app->appsrc, "size", (gint64) app->length, NULL);
gst_util_set_object_arg (G_OBJECT (app->appsrc), "stream-type",
/* configure the appsrc, we will push a buffer to appsrc when it needs more
* data */
g_signal_connect (app->appsrc, "need-data", G_CALLBACK (feed_data), app);
g_signal_connect (app->appsrc, "seek-data", G_CALLBACK (seek_data), app);
static gboolean
bus_message (GstBus * bus, GstMessage * message, App * app)
GST_DEBUG ("got message %s",
gst_message_type_get_name (GST_MESSAGE_TYPE (message)));
switch (GST_MESSAGE_TYPE (message)) {
g_error ("received error");
g_main_loop_quit (app->loop);
g_main_loop_quit (app->loop);
return TRUE;
main (int argc, char *argv[])
App *app = &s_app;
GError *error = NULL;
GstBus *bus;
gst_init (&argc, &argv);
GST_DEBUG_CATEGORY_INIT (appsrc_playbin_debug, "appsrc-playbin", 0,
"appsrc playbin example");
if (argc < 2) {
g_print ("usage: %s <filename>\n", argv[0]);
return -1;
/* try to open the file as an mmapped file */
app->file = g_mapped_file_new (argv[1], FALSE, &error);
if (error) {
g_print ("failed to open file: %s\n", error->message);
g_error_free (error);
return -2;
/* get some vitals, this will be used to read data from the mmapped file and
* feed it to appsrc. */
app->length = g_mapped_file_get_length (app->file);
app->data = (guint8 *) g_mapped_file_get_contents (app->file);
app->offset = 0;
/* create a mainloop to get messages */
app->loop = g_main_loop_new (NULL, TRUE);
app->playbin = gst_element_factory_make ("playbin", NULL);
g_assert (app->playbin);
bus = gst_pipeline_get_bus (GST_PIPELINE (app->playbin));
/* add watch for messages */
gst_bus_add_watch (bus, (GstBusFunc) bus_message, app);
/* set to read from appsrc */
g_object_set (app->playbin, "uri", "appsrc://", NULL);
/* get notification when the source is created so that we get a handle to it
* and can configure it */
g_signal_connect (app->playbin, "deep-notify::source",
(GCallback) found_source, app);
/* go to playing and wait in a mainloop. */
gst_element_set_state (app->playbin, GST_STATE_PLAYING);
/* this mainloop is stopped when we receive an error or EOS */
g_main_loop_run (app->loop);
GST_DEBUG ("stopping");
gst_element_set_state (app->playbin, GST_STATE_NULL);
/* free the file */
g_mapped_file_unref (app->file);
gst_object_unref (bus);
g_main_loop_unref (app->loop);
return 0;