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Comment by IshKebab | Hacker News Reader

He is referring to modern codecs, not MP3. MP3 isn't widely used anymore.

Modern codecs don't encode noise - they remove it during decoding and then add back artificial "comfort noise" when decoding, e.g. for film grain or background noise in voice calls.

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You haven't named any lossy stream codecs that do restore white noise, so i will not consider you a reliable source of info.

> Another notable addition in this version of the AAC standard is Perceptual Noise Substitution (PNS). In that regard, the AAC profiles (AAC-LC, AAC Main and AAC-SSR profiles) are combined with perceptual noise substitution and are defined in the MPEG-4 audio standard as Audio Object Types.

https://en.wikipedia.org/wiki/Advanced_Audio_Coding

Got a source for the current usage of MP3?

What services do you know of that use MP3?

Virtually every podcast ever.

YouTube itself seems to rely more on webm for audio. That seems to be a container for Opus or Vorbis formats.

Vorbis and Opus themselves are lossy encoders (Ogg Vorbis).

Podcasts are pretty niche. Almost all codec use these days is from streaming services or video/phone calls - YouTube, Spotify, WhatsApp, etc. None of those use MP3.

What codecs do those applications use?

How do they preserve or modify white noise?

> Virtually every podcast ever.

Apple Podcasts are AAC. Spotify are Ogg Vorbis. That probably covers 90% of the market right there.

The original question was whether or not audio could be fingerprinted from white noise, or if compression would obscure that fingerprint. The original context was YouTube videos specifically.

Sufficient to support the latter assertion was that lossy compression is frequently used.

YouTube's webm does in fact use lossy compression as noted. MP3 is, I assert, still significantly used in multiple contexts, including many podcast sites. I haven't specifically surveyed those, and don't use Apple Podcasts myself (never bought into the ecosystem, though as it happens, this specific response is coming from a MacOS system). I do make heavy use of tools such as youtube-dl and mpv, and find that those do in fact frequently find and extract mp3 audio from various sources, including podcasts and IIRC Soundcloud.

Verification is as simple as:

    youtube-dl -F <URL>

The '-F' flag will list available downloadable formats.

E.g.:

   $ youtube-dl -F 'https://soundcloud.com/danyork/tdyr-362-thoughts-on-wordpress'
   [soundcloud] danyork/tdyr-362-thoughts-on-wordpress: Downloading info JSON
   [soundcloud] None: Downloading webpage
   [soundcloud] None: Downloading webpage
   [soundcloud] danyork/tdyr-362-thoughts-on-wordpress: Downloading info JSON
   [soundcloud] 637919466: Downloading JSON metadata
   [soundcloud] 637919466: Downloading JSON metadata
   [soundcloud] 637919466: Downloading JSON metadata
   [info] Available formats for 637919466:
   format code   extension  resolution note
   hls_opus_64   opus       audio only audio@ 64k
   hls_mp3_128   mp3        audio only audio@128k
   http_mp3_128  mp3        audio only audio@128k (best)

Pedants are my fourth favourite people, but only during Lent on leap years, prior to Vespers, during a blue moon.

Re: opus

'Opus (audio format) - Wikipediahttps://en.wikipedia.org › wiki › Opus_(audio_format) CELT includes both spectral replication and noise generation, similar to AAC's SBR and PNS'

Which would mean that at least some of the white noise signature of an opus-encoded audio track would be ... a compression or encoding artefact.

Does opus have a notion of bitrates similar to mp3 or ogg vorbis? If so, the white noise would vary among bitrates.

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