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posted by Fnord666 on Friday July 19 2019, @05:08PM   Printer-friendly
from the interesting dept.

Over the years I have viewed many a video on YouTube. I quickly noticed an "ID" string that appeared in each video URL. Here's an example: https://www.youtube.com/watch?v=ShvnDSgjfXw -- see that string "ShvnDSgjfXw"? What characters are permitted? How long is it?

Along the way, I came upon an amazingly useful utility: youtube-dl. I accidentally discovered that it will happily download a YouTube video given just the Video ID. (Don't let the name of the utility mislead you; it seems to work fine with Instagram, Twitter, Sound Cloud... it's amazing!)

Now with my curiosity suitably piqued, I started a genuine search for what the parameters were that defined a valid YouTube Video ID. This question on "Web Applications Stack Exchange" was most helpful. Especially this response.

It appears that the Video ID (and the Channel ID) are modified base64 encodings of 64-bit (and 128-bit) integers. The primary change is that the base64 encoding produces two characters that are verboten in URLs. A generated "/" is replaced with "-" and a generated "+" is replaced with a "_".

There is no official documentation claiming that the ID lengths are guaranteed to always be 11 or 22 characters long, but empirical evidence suggests that is the current, de-facto standard.

There is even mention of " the maximally-constrained regular expression (RegEx) for the videoId" being:

[0-9A-Za-z_-]{10}[048AEIMQUYcgkosw]

Things get even more interesting if you are using Windows. Under NTFS, file names default to be case-preserving, but case-insensitive. Say I create a file called "Foo.txt" and then get a directory listing. Sure enough, I see: "Foo.txt" displayed. The fun comes if I do "DIR foo.txt" or "DIR FOO.TXT" or any other variation... they all find the same file: "Foo.txt"; this is counter to Unix where filenames are case-sensitive and each of those variations would be treated as separate and distinct files. Though it is possible to make an NTFS volume case-sensitive, it is not for the faint of heart!

One could, therefore, reverse-engineer the integer that produced the Video ID and use that in addition (or for the adventuresome: instead of) the Video ID.

The whole discussion was well-worth the read and highly recommended for anyone who would like more information on where it came from and how it came about.


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  • (Score: 2) by DavePolaschek on Saturday July 20 2019, @03:06AM (1 child)

    by DavePolaschek (6129) on Saturday July 20 2019, @03:06AM (#869267) Homepage Journal

    If only I could figure out how to properly quote 💩 when passing it into iname...

    Starting Score:    1  point
    Karma-Bonus Modifier   +1  

    Total Score:   2  
  • (Score: 1) by jrbrtsn on Tuesday July 23 2019, @11:32AM

    by jrbrtsn (6338) Subscriber Badge on Tuesday July 23 2019, @11:32AM (#870286)
    Magic bullet is this: any character preceded by \ (backslash), including a space character, is not considered to be special by the shell, and therefore passes to the invoked command unmodified. Supposing I have a file named: siLly's File nAme
    I could find it by issuing the command: find ~ -iname silly\'s\ file\ name
    To make life easier for the GUI crowd, you could write a GUI program that takes the contents of a text box, escapes potentially special characters, then passes the resulting string to the find command.