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Most audio codecs by now use perceptual noise substitution, which potentially substitutes in identical noise (I think it just EQs it?).

by cma 6y ago

DreamScatter 6y ago
no, the mp3 codec actually deletes humanly inaudible portions of the frequency spectrum to reduce storage, this data isn't recoverd or replaced or referred when played back again, it's lost information. what is removed is based on human perception limits for audio
- IshKebab 6y ago
  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.
  - orestarod 6y ago
    Got a source for the current usage of MP3?
    - chrisseaton 6y ago
      What services do you know of that use MP3?
      - dredmorbius 6y ago
        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).
        chrisseaton 6y ago
        > Virtually every podcast ever. Apple Podcasts are AAC. Spotify are Ogg Vorbis. That probably covers 90% of the market right there.
        dredmorbius 6y ago
        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.
        cma 6y ago
        Re: opus 'Opus (audio format) - Wikipediahttps://en.wikipedia.org https://en.wikipedia.org › wiki › Opus_(audio_format) CELT includes both spectral replication and noise generation, similar to AAC's SBR and PNS'
  - DreamScatter 6y ago
    You haven't named any lossy stream codecs that do restore white noise, so i will not consider you a reliable source of info.
    - cma 6y ago
      > 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 https://en.wikipedia.org/wiki/Advanced_Audio_Coding

Most audio codecs by now use perceptual noise substitution, which potentially substitutes in identical noise (I think it just EQs it?).

by cma 6y ago

Most audio codecs by now use perceptual noise substitution, which potentially substitutes in identical noise (I think it just EQs it?).

DreamScatter 6y ago

no, the mp3 codec actually deletes humanly inaudible portions of the frequency spectrum to reduce storage, this data isn't recoverd or replaced or referred when played back again, it's lost information. what is removed is based on human perception limits for audio

IshKebab 6y ago
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.
- orestarod 6y ago
  Got a source for the current usage of MP3?
  - chrisseaton 6y ago
    What services do you know of that use MP3?
    - dredmorbius 6y ago
      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).
      - chrisseaton 6y ago
        > Virtually every podcast ever. Apple Podcasts are AAC. Spotify are Ogg Vorbis. That probably covers 90% of the market right there.
        dredmorbius 6y ago
        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.
        cma 6y ago
        Re: opus 'Opus (audio format) - Wikipediahttps://en.wikipedia.org https://en.wikipedia.org › wiki › Opus_(audio_format) CELT includes both spectral replication and noise generation, similar to AAC's SBR and PNS'
- DreamScatter 6y ago
  You haven't named any lossy stream codecs that do restore white noise, so i will not consider you a reliable source of info.
  - cma 6y ago
    > 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 https://en.wikipedia.org/wiki/Advanced_Audio_Coding