YouTube signature descrambling fails when using "do" reserved keyword

Error message

Added attachment:

VLC error after attempt to open youtube music video.JPG

VLC fails to decode the Opus audio track here:

[000061c000068880] avcodec decoder debug: using ffmpeg Lavc58.91.100
[000061c000068880] avcodec decoder debug: CPU flags: 0x000fd3db
[opus @ 0x6190000b4a80] Extradata version 97 is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.                      
[opus @ 0x6190000b4a80] If you want to help, upload a sample of this file to https://streams.videolan.org/upload/ and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)                                                          
[000061c000068880] avcodec decoder error: cannot start codec (opus)
[00007fcea8952b20] main generic debug: no audio decoder modules matched with name any

Thanks for your report. The current descrambling algorithm is:

Nx=function(a){a=a.split("");Mx["do"](a,17);Mx.FH(a,61);Mx.xK(a,3);Mx["do"](a,12);Mx.xK(a,1);Mx.FH(a,37);Mx["do"](a,47);Mx.FH(a,6);return a.join("")};

This is a known rare limitation of the youtube.lua script that I think I've observed before: one of the object members just so randomly happened to get assigned do as name, which is a reserved keyword and triggers these syntactic quirks in the JavaScript minifier that the script fails to parse.

I expect that it'll sort itself out when the next iteration of the algorithm is rolled out in the coming days. I recommend not worrying, and just a bit of patience.

Replying to [comment:2 Rémi Denis-Courmont]:

VLC fails to decode the Opus audio track here: {{{ [000061c000068880] avcodec decoder debug: using ffmpeg Lavc58.91.100 [000061c000068880] avcodec decoder debug: CPU flags: 0x000fd3db [opus @ 0x6190000b4a80] Extradata version 97 is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[opus @ 0x6190000b4a80] If you want to help, upload a sample of this file to https://streams.videolan.org/upload/ and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)
[000061c000068880] avcodec decoder error: cannot start codec (opus) [00007fcea8952b20] main generic debug: no audio decoder modules matched with name any }}}

OK nevermind, that's an unrelated limitation in my system's FFmpeg because I forgot to build the Opus plugin. With the the !YoutubeDL plugin and the libopus decoder, the URL works just fine.

changed title from Youtube MUSIC videos don't open in VLC to YouTube signature descrambling fails when using "do" reserved keyword

As predicted, this sorted itself out a couple days after the report.

Lua patterns are seriously limited by the lack of alternative matching, so I'm not convinced that it's worth the risk and complexity to modify and relax the current code to support this corner case. Well, maybe I'll try it next time this manifests.

For reference, the corresponding descrambling helper code was:

var Mx={FH:function(a){a.reverse()},
"do":function(a,b){var c=a[0];a[0]=a[b%a.length];a[b%a.length]=c},
xK:function(a,b){a.splice(0,b)}};

added 1 deleted label

changed milestone to %Bugs paradize

mentioned in issue #25495 (closed)

YouTube signature descrambling fails when using "do" reserved keyword

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