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• How to create video by stitching together images (.png) where the serial on each image file increases by 6

  10 avril 2024, par DataStatsExplorer

  I am trying to create a video (preferably mp4) from a series of png images. However, the name of each image file increases by 6 every frame. For example, I would have depthframe_0000 as the first frame, and depthframe_0001 for the next frame.

  


  There are a few answers that have answered a similar question but I am unable to process the video when the image files are not increasing by 1.

  


  I would like to keep the fps at 5. I am using ffmpeg as the suggested in the answers above but am open to any other suggestion.

  


  The collab code that I have put together is as follows :

  


  import subprocess

# Define the frame rate and the input/output paths
output_fps = 5
input_path = "/content/drive/MyDrive/depth/depthframe_%04d.png"
output_path = "/content/drive/MyDrive/depth.mp4"

# Create a list of the frames
frames = [input_path % i for i in range(0, 2671, 6)]  # Update range as needed

# Write the list of frames to a temporary text file
with open('frames.txt', 'w') as f:
    for frame in frames:
        f.write(f"file '{frame}'\n")

# Create the command
command = [
    "ffmpeg",
    "-f", "concat",
    "-safe", "0",
    "-i", "frames.txt",
    "-c:v", "libx264",
    "-pix_fmt", "yuv420p",
    output_path
]

# Run the command
subprocess.run(command, check=True)


  


• Decoding the h.264 stream from a serial port

  18 mars, par Peter

  I would like to know if there is a reliable way to decode an H.264 NAL stream coming through a serial port using software.

  


  So far, I have managed to decode a single frame using a python script. In this script, I first write the incoming data to a file, and when the end-of-frame marker 00_00_00_01 appears, I display the frame using ffplay.

  


  import serial
import subprocess
import os
import time

ser = serial.Serial('COM3', 115200, timeout=1)
output_file = "output.264"

# Variable to store the ffplay process
ffplay_process = None

# Open the file for writing in binary mode
with open(output_file, "wb") as file:

    print("Writing bytes to output.264. Waiting for the end-of-frame marker 0x00000001.")

    buffer = bytearray()
    marker = b'\x00\x00\x00\x01'

    try:
        while True:
            if ser.in_waiting:  # If there is data in the buffer
                data = ser.read(ser.in_waiting)  # Read all available bytes
                buffer.extend(data)

                # Check if the end-of-frame marker is in the buffer
                while marker in buffer:
                    index = buffer.index(marker) + len(marker)  # Position after the marker
                    frame = buffer[:index]  # Extract the frame
                    buffer = buffer[index:]  # Keep the remaining data

                    print(f"Frame recorded: {len(frame)} bytes")
                    file.write(frame)  # Write the frame to the file
                    file.flush()  # Force writing to disk

                    # Close the ffplay window if it is already open
                    if ffplay_process and ffplay_process.poll() is None:
                        ffplay_process.terminate()
                        ffplay_process.wait()  # Wait for the process to terminate

                    # Play the recorded frame, reopening the window
                    ffplay_process = subprocess.Popen(["ffplay", "-f", "h264", "-i", output_file])

    except KeyboardInterrupt:
        print("\nRecording stopped.")
    finally:
        # Close the serial port and the ffplay process
        ser.close()


  


  However, each time a new end-of-frame marker is detected, the ffplay window closes and reopens to show the next frame. It will flicker when transferring the video. Is there a way to display the frames in the same window for seamless playback when streaming video ?

  


  Or is there a better approach or software that is more suited for this task ? I do not know where to start, so I will be glad for any hints.

  


• How to add new pages and menu items to Piwik – Introducing the Piwik Platform

  11 septembre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to create a widget). This time you’ll learn how to extend Piwik by adding new pages and menu items. For this tutorial you will need to have basic knowledge of PHP and optionally of Twig which is the template engine we use.

  What can be displayed in a page ?

  To make it short : You can display any corporate related content, key metrics, news, help pages, custom reports, contact details, information about your server, forms to manage any data and anything else.

  Getting started

  In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

  To summarize the things you have to do to get setup :

  • Install Piwik (for instance via git).
  • Activate the developer mode : ./console development:enable --full.
  • Generate a plugin : ./console generate:plugin --name="MyControllerPlugin". There should now be a folder plugins/MyControllerPlugin.
  • And activate the created plugin under Settings => Plugins.

  Let’s start creating a page

  We start by using the Piwik Console to create a new page :

  ./console generate:controller

  The command will ask you to enter the name of the plugin the controller should belong to. I will simply use the above chosen plugin name “MyControllerPlugin”. There should now be two files plugins/MyControllerPlugin/Controller.php and plugins/MyControllerPlugin/templates/index.twig which both already contain an example to get you started easily :

  Controller.php

  class Controller extends \Piwik\Plugin\Controller
  {
      public function index()
      {
          return $this->renderTemplate('index', array(
               'answerToLife' => 42
          ));
      }
  }
  Télécharger

  and templates/index.twig

  {% extends 'dashboard.twig' %}
   
  {% block content %}
      <strong>Hello world!</strong>
      <br/>
   
      The answer to life is {{ answerToLife }}
  {% endblock %}
  Télécharger

  Note : If you are generating the Controller before Piwik 2.7.0 the example will look slightly different.

  The controller action index assigns the view variable answerToLife to the view and renders the Twig template templates/index.twig. Any variable assigned this way can then be used in the view using for example {{ answerToLife }}.

  Using a Twig template to generate the content of your page is actually optional : instead feel free to generate any content as desired and return a string in your controller action.

  As the above template index.twig is extending the dashboard template the Logo as well as the top menu will automatically appear on top of your content which is defined within the block content.

  

  How to display the page within the admin

  If you would like to add the admin menu on the left you have to modify the following parts :

  • Extend \Piwik\Plugin\ControllerAdmin instead of \Piwik\Plugin\Controller in the file Controller.php. In a future version of Piwik this step will be no longer neccessary, see #6151
  • Extend the template admin.twig instead of dashboard.twig
  • Define a headline using an H2-element

  {% extends 'admin.twig' %}
   
  {% block content %}
      <h2>Hello world!</h2>
      <br/>
   
      The answer to life is {{ answerToLife }}
  {% endblock %}
  Télécharger

  Note : Often one needs to add a page to the admin to make a plugin configurable. We have a unified solution for this using the Settings API.

  

  How to display a blank page

  If you would like to generate a blank page that shows only your content the template should contain only your markup as follows :

  <strong>Hello world!</strong>
  <br/>
   
  The answer to life is {{ answerToLife }}
  Télécharger

  Predefined variables, UI components, security and accessing query parameters

  In this blog post we only cover the basics to get you started. We highly recommend to read the MVC guide on our developer pages which covers some of those advanced topics. For instance you might be wondering how to securely access $_GET or $_POST parameters, you might want to restrict the content of your page depending on a user role, and much more.

  If you would like to know how to make use of JavaScript, CSS and Less have a look at our Working with Piwik’s UI guide.

  Note : How to include existing UI components such as a site selector or a date selector will be covered in a future blog post. Also, there are default variables assigned to the view depending on the context. A list of those variables that may or may not be defined is unfortunately not available yet but we will catch up on this.

  Let’s add a menu item to make the page accessible

  So far you have created a page but you can still not access it. Therefore we need to add a menu item to one of the Piwik menus. We start by using the Piwik Console to create a menu template :

  ./console generate:menu

  The command will ask you to enter the name of the plugin the menu should belong to. I will use again the above chosen plugin name “MyControllerPlugin”. There should now be a file plugins/MyControllerPlugin/Menu.php which contains an example to get you started easily :

  Menu.php

  class Menu extends \Piwik\Plugin\Menu
  {
      public function configureUserMenu(MenuUser $menu)
      {
          // reuse an existing category. 
          $menu->addManageItem('My User Item', $this->urlForAction('showList'));
   
          // or create a custom category
          $menu->addItem('My Custom Category', 'My User Item', $this->urlForDefaultAction());
      }
  }
  Télécharger

  This is only a part of the generated template since all the examples of the different menus are similar. You can add items to four menus :

  • configureReportingMenu To add a new item to the reporting menu which includes all the reports like “Actions” and “Visitors”.
  • configureAdminMenu To add a new item to the admin menu which includes items like “User settings” and “Websites”.
  • configureTopMenu To add a new item to the top menu which includes items like “All Websites” and “Logout”.
  • configureUserMenu To add a new item to the user menu which is accessible when clicking on the username on the top right.

  In this blog post we will add a new item to the user menu and to do so we adjust the generated template like this :

  class Menu extends \Piwik\Plugin\Menu
  {
      public function configureUserMenu(MenuUser $menu)
      {
          $menu->addManageItem('My User Item', $this->urlForAction($method = 'index'), $orderId = 30);
      }
  }
  Télécharger

  That’s it. This will add a menu item named “My User Item” to the “Manage” section of the user menu. When a user chooses the menu item, the “index” method of your controller will be executed and your previously created page will be first rendered and then displayed. Optionally, you can define an order to influence the position of the menu item within the manage section. Following this example you can add an item to any menu for any action. I think you get the point !

  

  Note : In Piwik 2.6.0 and before the above example would look like this :

  class Menu extends \Piwik\Plugin\Menu
  {
      public function configureUserMenu(MenuUser $menu)
      {
          $menu->addManageItem('My User Item', array($module = 'MyControllerPlugin', $action = 'index'), $orderId = 30);
      }
  }
  Télécharger

  How to test a page

  After you have created your page you are surely wondering how to test it. A controller should be usually very simple as it is only the connector between model and view. Therefore, we do usually not create unit or integration test for controllers and for the view less than ever. Instead we would create a UI test that takes a screenshot of your page and compares it with an expected screenshot. Luckily, there is already a section UI tests in our Automated tests guide.

  Publishing your Plugin on the Marketplace

  In case you want to share your page with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin.

  Advanced features

  Isn’t it easy to create a page ? We never even created a file ! Of course, based on our API design principle “The complexity of our API should never exceed the complexity of your use case.” you can accomplish more if you want : You can make use of Vanilla JavaScript, jQuery, AngularJS, Less and CSS, you can reuse UI components, you can access query parameters and much more.

  Would you like to know more about this ? Go to our MVC (Model-View-Controller) and Working with Piwik’s UI guides in the Piwik Developer Zone.

  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.