youtube-leecher

Here we go! youtube-leecher has just landed on SourceForge and now it's available for download here.

But what's youtube-leecher actually? Well, youtube-leecher is a simple yet powerful Ruby program to download all YouTube videos found inside video containers.

So now what's a "video container"?
From youtube-leecher perspective, a video container can be basically a HTML page or a text file that contain references to YouTube videos.

Now, let's imagine you are surfing the Net and then you come up to a page that contains a lot of YouTube videos you are interested in. Let's say the page you are visiting is a video container. Now what if you need to download them all?

I know there are a lot of YouTube video downloaders all around, but in situations like those described above, well... downloading each video separately can be just time-consuming. So here started my work.

The idea was to have a tool that, given a list of video containers, could display the basic info about each video found and then proceed to download. Therefore, I developed youtube-leecher, devoting some hours of spare time to it. I worked on it mainly during the night, from 10pm to 2am, when a lot of silence boosts my focusing. After about a week, the first promising results came out.

It was an interesting experience for some reasons I'm going to tell you: first off, Ruby. Ruby is a concise and powerful language. It's funny to solve problems using it. It gives you... excitement.
Another reason that caught me was I discovered the way to download a YouTube video, given its ID. (If you don't know it, downloading a YouTube video is not just a matter of right-clicking on it and choosing the option "save as", like for an image).
Finally, I found the way to query YouTube using Data API to obtain basic info about a video. Now it's the time to share these info with you.

Let's start from downloading a YouTube video.

Just suppose you want to download a video whose ID is video_id. Firstly, you need to access to the web page that allows you to watch the video. This page corresponds to URL:

http://www.youtube.com/watch?v=video_id

Then you have to look inside the Javascript code of that page searching for the definition of object swfArgs (var swfArgs = ...). As you will see, this object has several members. The most important for our purposes are: l, sk, fmt_map, t. Take notice of the value assigned to each of them inside the Javascript object definition statement. (In the following, we will refer to them in boldface). To download the video, all you need to do is calling a URL composed this way:

http://www.youtube.com/get_video?video_id=video_id&l=l&sk=sk&fmt_map=fmt_map&t=t

If a parameter value is set to null, just don't express the corresponding pair parameter name=parameter value inside the URL: so, if for instance fmt_map is null, don't write the part fmt_map=fmt_map.

Note that the aforementioned URL allows you to get a video in flv (Flash) format. Sometimes the mp4 version of it is available too. Currently the program doesn't allow you to download videos in this format, but just for your information, to get a video as mp4 (when available) just append to URL the parameter fmt=18.

What about getting info on a specified YouTube video?

It’s very easy: given a video whose id is video_id, just call the following URL:

http://gdata.youtube.com/feeds/api/videos?vq=video_id

As the reference documentation for Data API says, this URL will provide you with a RSS that contains all the info about videos that satisfy the query condition (in our case just a video: the one with with id = video_id)

Beware of videos whose ids start with the character – (dash). Calling the previous URL as stated before doesn’t work. To have info about these videos, you have to call the Data API URL without providing the first character (the dash).

Now... what's about the program?

Let's imagine you have downloaded it right now and you want to get all YouTube videos from http://www.xy.com. All you need to do is writing:

youtube-leecher http://www.xy.com

Of course, you can specify several options, such as the directory where to place downloaded videos, or the video naming, just to name a few.

... I don't want to bore you anymore. If you are interested in, you'll find all these info inside the full package.