LibMISB - Examples - GStreamer Application

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Testing library

This library has an example that you can execute. This example is a metadata converter that can encode or decode metadata. If you want to encode, the input file must respect one of the formats developed (for this first version, only could use JSON format) and will return a binary file with metadata encoded. On the other hand, if you want to decode the program receives a binary file and converts it to the format file selected (for this first version, only could use JSON format).

The executable is located on /misb-library/examples/misb/ or if you want to compile and execute the example file out of the project. The path of the example is located on /misb-library/examples/misb/misb-converter.cpp. To compile the example we suggest you follow the next Makefile:

FLAGS:=`pkg-config --cflags --libs misb-0.0`
misb-converter: misb-converter.cpp
	g++ -o misb-converter misb-converter.cpp $(FLAGS)

Encode command

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To perform the encoding, the following command is executed. Where the --encode flag indicates that encoding is to be performed. The -i flag indicates the input file, where the metadata must be raw without encoding. On the other hand, the -o flag indicates the output file, which contains the encoded bytes in a binary file. The --verbose flag shows the KLV bytes encoded on the terminal.

./misb-converter --verbose --encode -i misb_ST0601_sample.json -o klv.bin

Decode command

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To perform the decoding, the following command is executed. Where the --decode flag indicates that decoding is to be performed. The -i flag indicates the input file, where the metadata must be encoded. The -o flag indicates the output file, which contains the metadata decoded.

./misb-converter --decode -i klv.bin -o output.json

Reference application

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In the following example, we show you how to use Gstreamer In-Band metadata to add a KLV packet (generated by LibMISB) into a Transport Stream. Based on GStreamer In-Band Metadata for MPEG Transport Stream - Examples - C - C++

/* Copyright (C) 2022 RidgeRun, LLC (http://www.ridgerun.com)
 * All Rights Reserved.
 *
 * The contents of this software are proprietary and confidential to RidgeRun,
 * LLC.  No part of this program may be photocopied, reproduced or translated
 * into another programming language without prior written consent of
 * RidgeRun, LLC.  The user is free to modify the source code after obtaining
 * a software license from RidgeRun.  All source code changes must be provided
 * back to RidgeRun without any encumbrance.
 */

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

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define PIPELINE_DESCRIPTION                                                   \
  "metasrc name=meta ! meta/x-klv,stream_type=21 ! mpegtsmux name=mux ! "      \
  "filesink name=sink location=./metadata_misb_library.ts videotestsrc "      \
  "is-live=true ! video/x-raw,width=640,height=480,framerate=30/1 ! queue ! "  \
  "x264enc ! mux."

#define METADATA_PERIOD_SECS 1
#define FILE_LOCATION "./metadata_misb_library.ts"

static guint8 klv_metadata[61];


const char* filename = "klv.bin";

typedef struct _GstMetaDemo GstMetaDemo;
struct _GstMetaDemo {
  GstElement *pipeline;
  GstElement *metasrc;
  GstElement *filesink;
  GMainLoop *main_loop;
};

static gboolean create_pipeline(GstMetaDemo *metademo);
static void start_pipeline(GstMetaDemo *metademo);
static void stop_pipeline(GstMetaDemo *metademo);
static void release_resources(GstMetaDemo *metademo);
static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data);
static gboolean handle_signal(gpointer data);

int main(int argc, char *argv[]) {
struct stat sb;

  FILE* in_file = fopen(filename, "rb");
    if (!in_file) {
        perror("fopen");
        exit(EXIT_FAILURE);
    }

    
    if (stat(filename, &sb) == -1) {
        perror("stat");
        exit(EXIT_FAILURE);
    }

    fread(klv_metadata, sizeof(klv_metadata), 1, in_file);

    for(uint i = 0; i<sizeof(klv_metadata); i++)
        printf("%u ", klv_metadata[i]);
    printf("\n");
    fclose(in_file);

  GstMetaDemo *metademo = g_malloc(sizeof(GstMetaDemo));
  if(!metademo){
    g_print("Could not create demo\n");
    return 1;
  }

  g_unix_signal_add(SIGINT, (GSourceFunc)handle_signal, metademo);

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

  if (!create_pipeline(metademo)) {
    g_free(metademo);
    return 1;
  }

  /* Set the pipeline to "playing" state*/
  g_print("Playing pipeline\n");
  start_pipeline(metademo);

  /* Iterate */
  g_print("Running...\n");
  g_main_loop_run(metademo->main_loop);

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

  return 0;
}

static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data) {
  GMainLoop *loop = (GMainLoop *)data;

  switch (GST_MESSAGE_TYPE(msg)) {

  case GST_MESSAGE_EOS:
    g_print("End of stream\n");
    g_main_loop_quit(loop);
    break;

  case GST_MESSAGE_ERROR: {
    gchar *debug;
    GError *error;

    gst_message_parse_error(msg, &error, &debug);
    g_free(debug);

    g_printerr("Error: %s\n", error->message);
    g_error_free(error);

    g_main_loop_quit(loop);
    break;
  }
  default:
    break;
  }

  return TRUE;
}

static gboolean create_pipeline(GstMetaDemo *metademo) {

  GMainLoop *loop;

  GstElement *pipeline = NULL;
  GstElement *metasrc = NULL;
  GstElement *filesink = NULL;
  GstBus *bus = NULL;
  GByteArray *barray = NULL;
  guint8 *array_copy = NULL;
  guint metalen = 0;
  GError *error = NULL;

  if (!metademo) {
    return FALSE;
  }

  loop = g_main_loop_new(NULL, FALSE);

  pipeline = gst_parse_launch(PIPELINE_DESCRIPTION, &error);

  if (error) {
    g_printerr("Unable to build pipeline (%s)\n", error->message);
    g_clear_error(&error);
    return FALSE;
  }

  metasrc = gst_bin_get_by_name(GST_BIN(pipeline), "meta");
  if (!metasrc) {
    g_printerr("Could not get metadata element\n");
    return FALSE;
  }

  filesink = gst_bin_get_by_name(GST_BIN(pipeline), "sink");
  if (!filesink) {
    g_printerr("Could not get filesink element\n");
    return FALSE;
  }

  /*Prepare metadata*/

  /*We need to copy the array since the GByteArray will be the new owner and free it for us*/
  metalen = sizeof(klv_metadata);
  array_copy = g_malloc (metalen);
  memcpy (array_copy, klv_metadata, metalen);
  
  barray = g_byte_array_new_take(array_copy, metalen);
  g_object_set(metasrc, "metadata-binary", barray, NULL);
  g_boxed_free(G_TYPE_BYTE_ARRAY, barray);

  g_object_set(G_OBJECT(metasrc), "period", METADATA_PERIOD_SECS, NULL);
  g_object_set(G_OBJECT(filesink), "location", FILE_LOCATION, NULL);

  /* we add a message handler */
  bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
  gst_bus_add_watch(bus, bus_call, loop);
  gst_object_unref(bus);

  metademo->pipeline = pipeline;
  metademo->main_loop = loop;
  metademo->metasrc = metasrc;
  metademo->filesink = filesink;

  return TRUE;
}

static void start_pipeline(GstMetaDemo *metademo) {
  gst_element_set_state(metademo->pipeline, GST_STATE_PLAYING);
}
static void stop_pipeline(GstMetaDemo *metademo) {
  gst_element_set_state(metademo->pipeline, GST_STATE_NULL);
}

static void release_resources(GstMetaDemo *metademo) {
  if (!metademo) {
    return;
  }

  stop_pipeline(metademo);

  if (metademo->pipeline) {
    gst_object_unref(metademo->pipeline);
    metademo->pipeline = NULL;
  }

  if (metademo->metasrc) {
    gst_object_unref(metademo->metasrc);
    metademo->metasrc = NULL;
  }

  if (metademo->filesink) {
    gst_object_unref(metademo->filesink);
    metademo->filesink = NULL;
  }

  if (metademo->main_loop) {
    g_main_loop_unref(metademo->main_loop);
    metademo->main_loop = NULL;
  }
}

static gboolean handle_signal(gpointer data) {
  GstMetaDemo *metademo = (GstMetaDemo *)data;

  g_main_loop_quit(metademo->main_loop);

  return TRUE;
}

Building the application

In order to build the appication, copy the example into a file called main.c and build using the following command:

gcc -Wall main.c -o main `pkg-config --cflags --libs gstreamer-1.0`

After this you will end up with a binary called main.

Running the application

Execute the application with the following command:

./main

This will create a file called 'metadata_misb_library.ts in the same directory where the application is running.

Stop the application with Ctrl + C.