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Are the YouTube's 40 kHz videos real? Does YouTube allow such high frequency sound videos without compressing them?

Specifically this video.

Thank you.

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    With youtube-dl, no options set, I get an mkv file whose audiostream is at a 48 kHz sample rate, so no 40 kHz audio for sure.
    – audionuma
    Jun 16, 2023 at 12:30
  • But that's not the source file the audio stream was transcoded from, unless I'm not understanding what that software does. Jun 16, 2023 at 13:17
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    YouTube has 16 different video transcodes & 5 audio transcodes of that track. Using JDownloader I can see [& get] all versions. Highest is an opus file which i can't really read with anything I have here (hate opus files, PITA on a Mac), standard 1080p mp4 movie has AAC at 44.1. Basically I see no transcode that can play a 40kHz sine. None of this has anything to do with compression in an audio sense, only in a data sense. Comments are turned off so no-one can even tell him his file is useless, though 329 idiots seems to like it:\
    – Tetsujin
    Jun 16, 2023 at 14:51
  • @Tetsujin That Mac refuses to support open standards makes you hate open standards? They actually support the codec, just not the container. A video-stream-free WEBM with Opus-encoded audio plays fine on a Mac.
    – user107063
    Jun 20, 2023 at 10:22
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    That wasn't really the main thrust of my comment, merely an aside. I find them irritating, like I find flac irritating. I don't really give a monkey's whether it's an open standard or not.
    – Tetsujin
    Jun 20, 2023 at 10:37

1 Answer 1

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The audio sample rates YouTube seems to use are 48000 and 44100 Hz (for Opus and AAC). Only one of these formats (AAC) would even be able to be used with a higher sample rate (Opus specification says it's always 48kHz)

Since the maximum frequency able to be encoded is half of the sample rate, there is no way such a video could be real.

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