Text test source element

[iron_guitarist1987]

Hello,

I'm trying to create the simplest text source element that outputs the same string over and over again. I tried doing something with the audiotestsrc, but I know is wrong. Below is what I have so far. Any ideas?

thanks



/* GStreamer
 * Copyright (C) 2005 Stefan Kost <[e-mail]>
 *
 * 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
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
/**
 * SECTION:element-texttestsrc
 *
 * Texttestsrc can be used to generate basic strings.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>
#include <string.h>
#include <gst/controller/gstcontroller.h>

#include "texttestsrc.h"


GST_DEBUG_CATEGORY_STATIC (text_test_src_debug);
#define GST_CAT_DEFAULT text_test_src_debug


enum
{
  PROP_0,
  PROP_LAST
};


static GstStaticPadTemplate gst_text_test_src_src_template =
    GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("text/plain")
    );


GST_BOILERPLATE (GstTexttestsrc, gst_text_test_src, GstBaseSrc,
    GST_TYPE_BASE_SRC);

#define GST_TYPE_TEXT_TEST_SRC_WAVE (gst_audiostestsrc_wave_get_type())



static void gst_text_test_src_set_property (GObject * object,
    guint prop_id, const GValue * value, GParamSpec * pspec);
static void gst_text_test_src_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec);


static GstFlowReturn gst_text_test_src_create (GstBaseSrc * basesrc,
    guint64 offset, guint length, GstBuffer ** buffer);


static void
gst_text_test_src_base_init (gpointer g_class)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);

  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&gst_text_test_src_src_template));
  gst_element_class_set_details_simple (element_class,
      "Audio test source", "Source/Audio",
      "Creates audio test signals of given frequency and volume",
      "Stefan Kost <[e-mail]>");
}

static void
gst_text_test_src_class_init (GstTexttestsrcClass * klass)
{
  GObjectClass *gobject_class;
  GstBaseSrcClass *gstbasesrc_class;

  gobject_class = (GObjectClass *) klass;
  gstbasesrc_class = (GstBaseSrcClass *) klass;

  gobject_class->set_property = gst_text_test_src_set_property;
  gobject_class->get_property = gst_text_test_src_get_property;


  gstbasesrc_class->create = GST_DEBUG_FUNCPTR (gst_text_test_src_create);
}

static void
gst_text_test_src_init (GstTexttestsrc * src, GstTexttestsrcClass * g_class)
{
  GstPad *pad = GST_BASE_SRC_PAD (src);


  /* we operate in time */
  gst_base_src_set_format (GST_BASE_SRC (src), GST_FORMAT_TIME);
  gst_base_src_set_blocksize (GST_BASE_SRC (src), -1);
}

static gboolean
gst_text_test_src_stop (GstBaseSrc * basesrc)
{
  return TRUE;
}


static GstFlowReturn
gst_text_test_src_create (GstBaseSrc * basesrc, guint64 offset,
    guint length, GstBuffer ** buffer)
{
  GstFlowReturn res;
  GstTexttestsrc *src;
  src = GST_TEXT_TEST_SRC (basesrc);

  *buffer = "This is my test string";

  return GST_FLOW_OK;
}

static void
gst_text_test_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstTexttestsrc *src = GST_TEXT_TEST_SRC (object);

  switch (prop_id) {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_text_test_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstTexttestsrc *src = GST_TEXT_TEST_SRC (object);

  switch (prop_id) {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static gboolean
plugin_init (GstPlugin * plugin)
{
  /* initialize gst controller library */
  gst_controller_init (NULL, NULL);

  GST_DEBUG_CATEGORY_INIT (text_test_src_debug, "texttestsrc", 0,
      "Text Test Source");

  return gst_element_register (plugin, "texttestsrc",
      GST_RANK_NONE, GST_TYPE_TEXT_TEST_SRC);
}

GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "texttestsrc",
    "Creates test string",
    plugin_init, VERSION, "LGPL", GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN);

[Josh Doe]

On Thu, Jun 14, 2012 at 10:44 AM, iron_guitarist1987
<[hidden email]> wrote:
> I'm trying to create the simplest text source element that outputs the same
> string over and over again. I tried doing something with the audiotestsrc,
> but I know is wrong. Below is what I have so far. Any ideas?

I recommend you go through the plugin writers guide first:
http://gstreamer.freedesktop.org/data/doc/gstreamer/0.10.36/pwg/html/index.html

The first problem I see is in _create, you can't just assign a static
string to the *buffer pointer. After going through the tutorials look
at the docs such as:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/gstreamer-GstBuffer.html
http://gstreamer.freedesktop.org/data/doc/gstreamer/0.10.36/gstreamer-libs/html/GstBaseSrc.html
http://developer.gnome.org/glib/2.32/glib-String-Utility-Functions.html#g-strdup

You need to allocate a new buffer, set the data (see g_strdup), size,
etc using GST_BUFFER_*.

-Josh
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[iron_guitarist1987]

Does this look better?

static GstFlowReturn
gst_text_test_src_create (GstBaseSrc * basesrc, guint64 offset,
    guint length, GstBuffer ** buffer)
{
  GstFlowReturn res;
  GstTexttestsrc *src;
  src = GST_TEXT_TEST_SRC (basesrc);
  GstBuffer *buf;
 
  buf = gst_buffer_new_and_alloc (sizeof("test"));
  buf = g_strdup("test string");
 
  *buffer = buf;

  return GST_FLOW_OK;
}

When I run it I get:

$ gst-launch texttestsrc ! georeg_test ! fakesink
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Caught SIGSEGV accessing address 0x74736574
Spinning.  Please run 'gdb gst-launch 14052' to continue debugging, Ctrl-C to quit, or Ctrl-\ to dump core.

[Josh Doe]

On Thu, Jun 14, 2012 at 11:51 AM, iron_guitarist1987
<[hidden email]> wrote:

> Does this look better?
>
> static GstFlowReturn
> gst_text_test_src_create (GstBaseSrc * basesrc, guint64 offset,
>    guint length, GstBuffer ** buffer)
> {
>  GstFlowReturn res;
>  GstTexttestsrc *src;
>  src = GST_TEXT_TEST_SRC (basesrc);
>  GstBuffer *buf;
>
>  buf = gst_buffer_new_and_alloc (sizeof("test"));
>  buf = g_strdup("test string");
>
>  *buffer = buf;
>
>  return GST_FLOW_OK;
> }

I'd recommend taking a second look at some more tutorials on C.
GstBuffer is an object (glorified struct) that holds many pieces of
information, not just a pointer to memory. You need to tell the buffer
where the memory is (GST_BUFFER_DATA), the size (GST_BUFFER_SIZE), and
the pointer to free (GST_BUFFER_MALLOCDATA, typically the same as
GST_BUFFER_DATA). Since you're using new_and_alloc you don't dup the
string, but copy it into the existing memory.
-Josh
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[iron_guitarist1987]

Sorry for being so naive, but I am still new to gstreamer, and the development guide isn't as thorough as I would like it to be.

static GstFlowReturn
gst_text_test_src_create (GstBaseSrc * basesrc, guint64 offset,
    guint length, GstBuffer ** buffer)
{
  GstFlowReturn res;
  GstTexttestsrc *src;
  src = GST_TEXT_TEST_SRC (basesrc);
  GstBuffer *buf;
  char *data = "test string";
 
  buf = gst_buffer_new_and_alloc (sizeof(data));
  buf->data = data;
 
  buffer = buf;

  return GST_FLOW_OK;
}


I get:

$ gst-launch -v videotestsrc pattern=1 ! georeg name=s ! ffmpegcolorspace ! ximagesink texttestsrc ! s.
Setting pipeline to PAUSED ...
ERROR: Pipeline doesn't want to pause.
ERROR: from element /GstPipeline:pipeline0/GstTexttestsrc:texttestsrc0: Could not negotiate format
Additional debug info:
gstbasesrc.c(2787): gst_base_src_start (): /GstPipeline:pipeline0/GstTexttestsrc:texttestsrc0:
Check your filtered caps, if any
Setting pipeline to NULL ...
Freeing pipeline ...


georeg has an "any" and a text/plain sinkpads

[Josh Doe]

On Thu, Jun 14, 2012 at 2:11 PM, iron_guitarist1987
<[hidden email]> wrote:
> Sorry for being so naive, but I am still new to gstreamer, and the
> development guide isn't as thorough as I would like it to be.

True, it could use improvement. You also need to set the caps on the
buffer, and it's better style to
use the GST_BUFFER_* macros instead of accessing members directly. I'm
not familiar with the georeg element, so I don't know what it's doing,
the problem could lie with either element. I just noticed you have the
type MACRO incorrectly set to be the audiotestsrc. Is this supposed to
be a live source? I suggest you spend a day or two thoroughly reading
the existing docs (PWG from beginning to end, then API docs of
GstBaseSrc, Element, Buffer, etc.) and look at existing plugins.

-Josh
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[Stefan Sauer]

On 06/14/2012 04:44 PM, iron_guitarist1987 wrote:

Hello,

I'm trying to create the simplest text source element that outputs the same
string over and over again. I tried doing something with the audiotestsrc,
but I know is wrong. Below is what I have so far. Any ideas?

https://bugzilla.gnome.org/show_bug.cgi?id=657684

Stefan

thanks



/* GStreamer
 * Copyright (C) 2005 Stefan Kost [hidden email]
 *
 * 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
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
/**
 * SECTION:element-texttestsrc
 *
 * Texttestsrc can be used to generate basic strings. 
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>
#include <string.h>
#include <gst/controller/gstcontroller.h>

#include "texttestsrc.h"


GST_DEBUG_CATEGORY_STATIC (text_test_src_debug);
#define GST_CAT_DEFAULT text_test_src_debug


enum
{
  PROP_0,
  PROP_LAST
};


static GstStaticPadTemplate gst_text_test_src_src_template =
    GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("text/plain")
    );


GST_BOILERPLATE (GstTexttestsrc, gst_text_test_src, GstBaseSrc,
    GST_TYPE_BASE_SRC);

#define GST_TYPE_TEXT_TEST_SRC_WAVE (gst_audiostestsrc_wave_get_type())



static void gst_text_test_src_set_property (GObject * object,
    guint prop_id, const GValue * value, GParamSpec * pspec);
static void gst_text_test_src_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec);


static GstFlowReturn gst_text_test_src_create (GstBaseSrc * basesrc,
    guint64 offset, guint length, GstBuffer ** buffer);


static void
gst_text_test_src_base_init (gpointer g_class)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);

  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&gst_text_test_src_src_template));
  gst_element_class_set_details_simple (element_class,
      "Audio test source", "Source/Audio",
      "Creates audio test signals of given frequency and volume",
      "Stefan Kost [hidden email]");
}

static void
gst_text_test_src_class_init (GstTexttestsrcClass * klass)
{
  GObjectClass *gobject_class;
  GstBaseSrcClass *gstbasesrc_class;

  gobject_class = (GObjectClass *) klass;
  gstbasesrc_class = (GstBaseSrcClass *) klass;

  gobject_class->set_property = gst_text_test_src_set_property;
  gobject_class->get_property = gst_text_test_src_get_property;


  gstbasesrc_class->create = GST_DEBUG_FUNCPTR (gst_text_test_src_create);
}

static void
gst_text_test_src_init (GstTexttestsrc * src, GstTexttestsrcClass * g_class)
{
  GstPad *pad = GST_BASE_SRC_PAD (src);


  /* we operate in time */
  gst_base_src_set_format (GST_BASE_SRC (src), GST_FORMAT_TIME);
  gst_base_src_set_blocksize (GST_BASE_SRC (src), -1);
}

static gboolean
gst_text_test_src_stop (GstBaseSrc * basesrc)
{
  return TRUE;
}


static GstFlowReturn
gst_text_test_src_create (GstBaseSrc * basesrc, guint64 offset,
    guint length, GstBuffer ** buffer)
{
  GstFlowReturn res;
  GstTexttestsrc *src;
  src = GST_TEXT_TEST_SRC (basesrc);

  *buffer = "This is my test string";

  return GST_FLOW_OK;
}

static void
gst_text_test_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstTexttestsrc *src = GST_TEXT_TEST_SRC (object);

  switch (prop_id) {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_text_test_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstTexttestsrc *src = GST_TEXT_TEST_SRC (object);

  switch (prop_id) {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static gboolean
plugin_init (GstPlugin * plugin)
{
  /* initialize gst controller library */
  gst_controller_init (NULL, NULL);

  GST_DEBUG_CATEGORY_INIT (text_test_src_debug, "texttestsrc", 0,
      "Text Test Source");

  return gst_element_register (plugin, "texttestsrc",
      GST_RANK_NONE, GST_TYPE_TEXT_TEST_SRC);
}

GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "texttestsrc",
    "Creates test string",
    plugin_init, VERSION, "LGPL", GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN);


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