A simple program to create a GStreamer or GStreamer Editing Services pipeline

README.md

GStreamer Editing Services Pipeline debug

Usage:

main <path-to-file> <\"gst\" or \"ges\"> <playback-rate> <start-position-in-seconds>

• <path-to-file>: The file path to the media file to play.
• <\"gst\" or \"ges\">: Whether to create just a GStreamer pipeline, or a GStreamer Editing Services pipeline.
• <playback-rate>: The playback rate. 1.0 for playback at normal speed.
• <start-position-in-seconds>: Where to seek to before playing the media file. 0 to play from the beginning.

main.cpp

#include <cstdlib>
#include <iostream>
#include <thread>
#include <ges/ges.h>
#include <gst/app/gstappsink.h>

bool setAndWaitForPipelineState(GstElement *pipeline, GstState targetState) {
  GstStateChangeReturn ret = gst_element_set_state(pipeline, targetState);
  GstState result = GST_STATE_NULL;
  GstState pendingState = GST_STATE_NULL;
  if (ret == GST_STATE_CHANGE_ASYNC) {
    double timeout = 10.0;
    double step = 0.1;
    while (result != targetState && timeout > 0) {
      gst_element_get_state(pipeline,
                            &result, &pendingState, GST_SECOND * step);
      timeout -= step;
    }
    
    if (timeout <= 0) {
      std::cout << "Failed to set pipeline state "
      << gst_element_state_get_name(targetState);
      std::cout.flush();
      return false;
    }
  }
  return true;
}

void seek(GstElement *pipeline, gdouble const playback_rate, gint64 const start_position) {
  auto flags =
  static_cast<GstSeekFlags>(GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE | GST_SEEK_FLAG_TRICKMODE);
  
  while (gst_element_seek(pipeline, playback_rate, GST_FORMAT_TIME, flags,
                          GST_SEEK_TYPE_SET, start_position, GST_SEEK_TYPE_NONE,
                          GST_CLOCK_TIME_NONE) == FALSE) {
    std::cout << "Seek failed, will try again...";
    std::this_thread::sleep_for(std::chrono::milliseconds(10));
    std::cout.flush();
  }
}

void launch_gstreamer_pipeline(std::string const file_path, gdouble const playback_rate, gint64 const start_position) {
  GError *err = nullptr;
  std::string description = "filesrc location=" + file_path + " ! decodebin name=dmux \
    dmux. ! queue ! videoconvert ! autovideosink \
    dmux. ! queue ! audioconvert ! autoaudiosink";
  GstElement *pipeline = gst_parse_launch(description.c_str(), &err);
  
  setAndWaitForPipelineState(GST_ELEMENT(pipeline), GST_STATE_PLAYING);
  
  seek(pipeline, playback_rate, start_position);
}

void launch_ges_pipeline(std::string const file_path, gdouble const playback_rate, gint64 const start_position) {
  // Setup GES pipeline
  ges_init();
  GESPipeline *pipeline = ges_pipeline_new();
  GstElement *pipelineElement = GST_ELEMENT(pipeline);
  GESTimeline *timeline = ges_timeline_new_audio_video ();
  GESLayer *layer = ges_layer_new ();
  ges_timeline_add_layer(timeline, layer);
  
  // Load file as a clip & add to timeline
  std::string uri_string = "file://" + file_path;
  GESUriClip *clip = ges_uri_clip_new(uri_string.c_str());
  ges_layer_add_clip(layer, GES_CLIP(clip));
  ges_pipeline_set_timeline(pipeline, timeline);
  
  // Setup audio & video sinks
  GstElement *audioSink = gst_element_factory_make("autoaudiosink", "audio-sink");
  ges_pipeline_preview_set_audio_sink(pipeline, audioSink);
  
  GstElement *videoSink = gst_element_factory_make("autovideosink", "video-sink");
  ges_pipeline_preview_set_video_sink(pipeline, videoSink);
  
  setAndWaitForPipelineState(pipelineElement, GST_STATE_PAUSED);
  setAndWaitForPipelineState(pipelineElement, GST_STATE_PLAYING);
  
  seek(pipelineElement, playback_rate, start_position);
}

int main(int argc, char **argv) {
  if(argc < 5) {
    std::cout << "Usage: " << argv[0] << " <path-to-file> <\"gst\" or \"ges\"> <playback-rate> <start-position-in-seconds>\n";
    return 1;
  }
  
  std::string const file_path = argv[1];
  std::string const pipeline_type = argv[2];
  std::string const playback_rate_arg = argv[3];
  std::string const start_position_arg = argv[4];
  
  gdouble const playback_rate = std::stod(playback_rate_arg);
  gint64 const start_position = std::stol(start_position_arg) * GST_SECOND;
  
  gst_init(&argc, &argv);
  GMainLoop *mainloop;
  
  if (pipeline_type == "gst") {
    std::thread pipelineThread(launch_gstreamer_pipeline, file_path, playback_rate, start_position);
    pipelineThread.detach();
  } else if (pipeline_type == "ges") {
    std::thread pipelineThread(launch_ges_pipeline, file_path, playback_rate, start_position);
    pipelineThread.detach();
  } else {
    std::cout << "Second argument must be either \"gst\" or \"ges\"";
    return 1;
  }
  
  // Start a GMainLoop. GES **REQUIRES** a GMainLoop to be running in
  // order to function properly!
  mainloop = g_main_loop_new(nullptr, FALSE);
  g_main_loop_run(mainloop);
  
  return 0;
}