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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: 0) by Anonymous Coward on Saturday July 20 2019, @06:01PM

    by Anonymous Coward on Saturday July 20 2019, @06:01PM (#869432)

    Why would they *not* put it in? They are shipping the linux kernel in the next version https://www.theverge.com/2019/5/6/18534687/microsoft-windows-10-linux-kernel-feature [theverge.com]

    It is not that big of leap of logic that windows users can native mount ext4 and all of the other linux style file systems.

    NTFS should have had many major fixes (and it has). But it is showing its age. It was designed in a time where HD space cost a bit more than it does now. The central MFT is one of the stumbling blocks. Where as the place anywhere inode style OS's seem to be working better. Both come at a cost. For the time NTFS came out it was the best there was for the price.

    The NT driver system is not some special magic sauce that only MS has access to. https://www.paragon-drivers.com/en/lfswin/ [paragon-drivers.com] https://sourceforge.net/projects/ext2fsd/ [sourceforge.net] They have an option here buy/build.

    They will probably want a way to do it such that they do not have to open source windows (yet). Which I suspect they will eventually do anyway. The problem they have is the amount of 3rd party software they bought and plugged into windows. For example their defragment library is a 3rd party program. They will have to either re-negotiate those bits or strip them out if they want that. For example the last line of this https://devblogs.microsoft.com/oldnewthing/20121218-00/?p=5803 [microsoft.com] https://devblogs.microsoft.com/oldnewthing/20181221-00/?p=100535 [microsoft.com] and that is just an ad on game! They are doing some bits where they can https://github.com/microsoft/calculator [github.com]