Image Slideshow in Gstreamer

Question

I want to create a GStreamer application in which an xml file processes its contents, which provides information such as the URL of the image, its weight and the duration at which it will be displayed on the screen.

The XML file can be explicitly processed in C using libxml. But how can we create image slide shows using the GStreamer libraries. I want to use GStreamer because the hardware and SDK that I use provide native support for GStreamer.

Are there any GStreamer plugins to do the same. Or how else can be done. I know the basics of GStreamer and can write code in C for the GStreamer application.

Answer 1

Try the following C code snippet:

#include <gst/gst.h>
#include <glib.h>

char *strcpy(char *dest, const xmlChar *src)
{
    unsigned i;
    for (i=0; src[i] != '\0'; ++i)
    dest[i] = src[i];
        dest[i] = '\0';
    return dest;
}


int main (int   argc, char *argv[])

{
char *docname;
char *image1 = malloc(1000);
char *image2 = malloc(1000);

docname = "input.xml";

//parse the document
xmlDocPtr doc;
xmlNodePtr cur1, cur2, cur3;

doc = xmlParseFile(docname);

if (doc == NULL ) {
    fprintf(stderr,"Document not parsed successfully. \n");
    return -1;
}

cur1 = xmlDocGetRootElement(doc);

if (cur1 == NULL) {
    fprintf(stderr,"Empty Document\n");
    xmlFreeDoc(doc);
    return -1;
}

if (xmlStrcmp(cur1->name, (const xmlChar *) "start")) {
    fprintf(stderr,"document of the wrong type, root node is supposed to be start");
    xmlFreeDoc(doc);
    return -1;
}

int flag=0;
cur2 = cur1->xmlChildrenNode;
while (cur2 != NULL)
{
    if ((!xmlStrcmp(cur2->name, (const xmlChar *)"image")))
    {
        //parseVideo (doc, cur2);
        xmlChar *key;
        cur3 = cur2->xmlChildrenNode;
        while (cur3 != NULL) 
        {
            if ((!xmlStrcmp(cur3->name, (const xmlChar *)"filename"))) 
            {
                key = xmlNodeListGetString(doc, cur3->xmlChildrenNode, 1);
                //printf("Name of the file is: %s\n", key);
                xmlFree(key);
            }

            if ((!xmlStrcmp(cur3->name, (const xmlChar *)"src"))) 
            {
                key = xmlNodeListGetString(doc, cur3->xmlChildrenNode, 1);
                if (flag == 1)
                {
                        strcpy(image2, key);
                        printf("the image 2 is %s \n", image2);
                        flag = 2;
                }
                if(flag == 0)
                {
                        strcpy(image1, key);
                        printf("the image 1 is %s \n", image1);
                        flag = 1;
                }
                    //printf("SRC of the file is: %s\n", key);
                xmlFree(key);
            }

            if ((!xmlStrcmp(cur3->name, (const xmlChar *)"duration"))) 
            {
                key = xmlNodeListGetString(doc, cur3->xmlChildrenNode, 1);
                //printf("No. of seconds the image should be displayed is: %s\n", key);
                xmlFree(key);
            }

            if ((!xmlStrcmp(cur3->name, (const xmlChar *)"weight"))) 
            {
                key = xmlNodeListGetString(doc, cur3->xmlChildrenNode, 1);
                //printf("The weight of the image is: %s\n", key);
                xmlFree(key);
            }
        cur3 = cur3->next;
        }
    }
cur2 = cur2->next;
}

xmlFreeDoc(doc);

GstElement *pipeline, *source, *jpg_decoder, *freeze, *colorspace, *sink;

  /* Initialisation */
gst_init (&argc, &argv);

/* Create gstreamer elements */
pipeline = gst_pipeline_new ("image-player");
if(!pipeline)
{
    g_printerr ("Pipeline could not be created. Exiting.\n");
    return -1;
}

  source   = gst_element_factory_make ("filesrc",       "file-source");
  //set the location of the file to the argv[1]
  g_object_set (G_OBJECT (source), "location", image1, NULL);
if(!source)
{
    g_printerr ("File could not be created. Exiting.\n");
    return -1;
}

jpg_decoder  = gst_element_factory_make ("jpegdec", "jpg-decoder");
if(!jpg_decoder)
{
    g_printerr ("Jpg Decoder could not be created. Exiting.\n");
    return -1;
}  

freeze = gst_element_factory_make("imagefreeze", "freeze");
if(!freeze)
{
    g_printerr ("ImageFreeze could not be created. Exiting.\n");
    return -1;
}  

colorspace = gst_element_factory_make("ffmpegcolorspace", "colorspace");
if(!colorspace)
{
    g_printerr ("Colorspace could not be created. Exiting.\n");
    return -1;
}  

sink     = gst_element_factory_make ("ximagesink", "imagesink");
if(!sink)
{
    g_printerr ("Image sink could not be created. Exiting.\n");
    return -1;
}

/* file-source | jpg-decoder | image-freeze | colorspace | sink */
gst_bin_add_many (GST_BIN (pipeline), source, jpg_decoder, freeze, colorspace, sink, NULL);
gst_element_link_many (source, jpg_decoder, freeze, colorspace, sink, NULL);

/* Set the pipeline to "playing" state*/
g_print ("Now playing: %s\n", image1);
gst_element_set_state (pipeline, GST_STATE_PLAYING);

getchar();
gst_element_set_state (pipeline, GST_STATE_READY);
g_object_set (G_OBJECT (source), "location", image2, NULL);
gst_element_set_state (pipeline, GST_STATE_PLAYING);
getchar();

/* Out of the main loop, clean up nicely */
g_print ("Returned, stopping playback\n");
gst_element_set_state (pipeline, GST_STATE_NULL);

g_print ("Deleting pipeline\n");
gst_object_unref (GST_OBJECT (pipeline));

    return 0;
}

Answer 2

You need to create a pipeline with the imagefreeze element and change the location of the source when the image needs to be resized.

An example application (in Python) that shows two still images from a hard drive:

import pygst
pygst.require("0.10")
import gst

player = gst.Pipeline("player")
source = gst.element_factory_make("filesrc", "file-source")
source.set_property("location", "image1.jpeg")
jpg_decoder = gst.element_factory_make("jpegdec", "jpg-decoder")
freeze = gst.element_factory_make("imagefreeze", "freeze")
colorspace = gst.element_factory_make("ffmpegcolorspace", "colorspace")
sink = gst.element_factory_make("ximagesink", "imagesink")

player.add(source, jpg_decoder, freeze, colorspace, sink)
gst.element_link_many(source, jpg_decoder, freeze, colorspace, sink)
player.set_state(gst.STATE_PLAYING)

inp = raw_input("Press enter:")
player.set_state(gst.STATE_READY)
source.set_property("location", "image2.jpeg")
player.set_state(gst.STATE_PLAYING)
inp = raw_input("Press enter again:")