Learn the "patrickkfkan" in few minutes

Hi community

I add a quick look at the new comer OpenAi : Chat GPT you surely heard about, one of it’s nice application is “aide-de-camp” when understanding a programming code matter
it looks very powerfull and promising

look at that

chourmovs
explain https://github.com/patrickkfkan/volumio-ytcr/blob/master/index.js

The file you have linked to is a Node.js script called index.js, which is part of a GitHub repository for a Volumio plugin called volumio-ytcr.

The purpose of this script is to provide a way for users of the Volumio music player to stream YouTube audio content directly from within the Volumio interface. The plugin accomplishes this by utilizing a Node.js module called youtube-dl, which is a popular library for downloading videos from YouTube and other video hosting sites.

The index.js file contains the main logic for the plugin. When the plugin is installed and activated in Volumio, this script is executed to handle any requests made by the user to play YouTube audio content.

Here is a brief overview of what the script does:

First, it imports a number of Node.js modules that it will use throughout the script.

It defines a function called YoutubeAudioStream, which is used to create a stream of audio data from a YouTube video URL.

It defines another function called getStreamFromUrl, which is used to retrieve a stream of audio data from a YouTube video URL using the YoutubeAudioStream function.

It defines an event listener that listens for requests to play YouTube audio content in Volumio. When a request is received, the getStreamFromUrl function is called to retrieve the audio data stream, which is then passed to Volumio to be played back.

Overall, this script provides a convenient way for users of the Volumio music player to access and play audio content from YouTube, without having to leave the Volumio interface.

chourmovs vs
comment line by line

Sure, I’d be happy to walk you through the index.js file line by line:

// Import necessary Node.js modules
const { URL } = require('url');
const ytdl = require('ytdl-core');
const axios = require('axios');
const { spawn } = require('child_process');
const { Readable } = require('stream');
const { debug, error } = require('console');

This section imports several Node.js modules that the script will use.
URL is a built-in module that provides utilities for working with URLs.
ytdl-core is a Node.js module that provides an interface for downloading videos from YouTube.
axios is a popular HTTP client that allows us to make HTTP requests.
spawn is a function from the built-in child_process module that allows us to spawn child processes (i.e. execute commands in the shell).
Readable is a built-in class that allows us to create readable streams.
debug and error are functions from the built-in console module that allow us to print debug and error messages, respectively.

// Function to create a stream of audio data from a YouTube video URL
function YoutubeAudioStream(url) {
  const args = ['-f', 'bestaudio[ext=m4a]', '-g', url];
  const ytdl_process = spawn('youtube-dl', args);
  const stream = new Readable();
  ytdl_process.stdout.on('data', (data) => {
    stream.push(data);
  });
  ytdl_process.stderr.on('data', (data) => {
    error(`youtube-dl error: ${data}`);
  });
  ytdl_process.on('close', (code) => {
    if (code !== 0) {
      error(`youtube-dl exited with code ${code}`);
    }
    stream.push(null);
  });
  return stream;
}

This function creates a stream of audio data from a YouTube video URL using the youtube-dl command-line tool.
It takes a URL string as its input parameter.
It creates an array of arguments to pass to the youtube-dl command, which tells it to download the best audio quality available in M4A format.
It then spawns a child process to execute the youtube-dl command with the given arguments.
It creates a new Readable stream, which will be used to send the audio data back to the caller.
It listens for stdout, stderr, and close events from the youtube-dl process.
When data is received on stdout, it pushes that data to the stream.
When stderr data is received, it prints an error message.
When the youtube-dl process is closed, it checks the exit code. If it is non-zero, it prints an error message. It then signals the end of the stream by pushing null to the stream.

etc…

:grinning:

3 Likes

Amazing and funny at the same time! Thanks for posting this :wink:

I wonder what @patrickkfkan thinks about learning about him lol

and him learning I personnaly have nightmare trying to understand his music service plugin :rofl:

Sorry maybe not elegant but I fould it funny since it’s a fact that Patrick is one of the most skilled plugin provider and that plugin documentation is clearly not sufficient for understanding how things work when bridging music service with volumio
People who already tried will understand :laughing:

https://chat.openai.com/
you have to signup it’s free

patrick has just not a lot of time at the momment we are already happy that he fixed all the plugins
in his spare time. :wink:

lol
do not mistake yourself. The fact that Patrick is skilled and that volumio plugin documentation is too light were not linked in my mind.
Of course I realize the quality of his contribution. My topic title was in fact more like a tribute due to my recent browse of plugin directory :+1:

Funny indeed. The code snippets referred to aren’t even mine :slight_smile:

The particular plugin you chose (YouTube Cast Receiver, or ytcr) is not the nicest one to learn about music service plugins. It’s a ‘volatile’ plugin, i.e. one that takes control of every aspect of playback in Volumio. There is no well-documented way on how to write a volatile plugin, and I learnt from the old Spotify Connect plugin as I wrote ytcr. It’s basically a hack-as-you-go effort, so the resulting code is messy at places. If you do want to know how the ytcr plugin works, here it is:

  1. Plugin initializes an mpd-player instance which is responsible for telling Volumio’s MPD player to play / pause / resume tracks, and to also listen for such events.
  2. Plugin then starts the yt-cast-receiver module, passing the mpd-player instance to it.
  3. yt-cast-receiver is responsible for broadcasting Volumio to YouTube apps on the network, establishing connections with them, and taking commands from and sending status updates to connected YouTube app.
  4. So, for example, when you tap a video on your YouTube app, yt-cast-receiver receives notification and then tells mpd-player to play it.
  5. mpd-player plays the track (audio) and provides the updated status to the ytcr plugin, which then updates the playback state that you eventually see in Volumio UI.
  6. mpd-player also monitors MPD events, such as when playback stops it will proceed to the next track.
  7. Everytime when there’s an MPD event, or when a track is to be played, the plugin checks whether ytcr is the active plugin. This is what adds complexity / messiness to the code and also potentially reduces the plugin’s stability. Unfortunately, I do not see a way to make a volatile plugin work reliably without these checks. Fighting with Volumio’s statemachine is a frustrating process.

Now, onto my other music service plugins. They should be a lot easier to understand, despite having more files in the package. Everything basically follows the MVC design pattern. Take YouTube Music for example:

  • (M)odel: in /lib/model, you have the code for obtaining data for different entites.
  • (V)iew: this is basically Volumio UI.
  • (C)ontroller (in /lib/controller):
    • BrowseController: takes an URI (from Volumio), analyze it and pass it to one of the view-handlers for further processing. A view-handler requests data from one of the Models and converts it into data which the View (i.e. Volumio UI) can display (this is actually one of the hardest parts).
    • SearchController: like BrowseController, but takes a search query instead of URI. In the ytmusic example, the SearchController actually creates a ‘search’ URI and passes it to the BrowseController (delegation).
    • PlayController: takes an URI (from Volumio), obtains track information (like audio stream URL) from Model, then plays it using Volumio’s MPD plugin.

This structure allows for easier maintenance and versatility. Say if Google changes the album data structure returned for YouTube Music requests, I can just go to the corresponding model and make the relevant changes in the code there.

So good luck and you are welcome to ask if there are things you don’t understand.

3 Likes

Wow thank you for sharing patrick,I will keep this post in my favorite for future use.
Sorry, I’ve mixed several topics here, it’s my fault because I was trying to make humour🙂, my initial goal was primarily to share my first attempt with chatgpt that deserve it’s good reputation based on these results. I find it revolutionnary and a move forward compared to google😯. This snipet was the first I had on hands just to start a test