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Spotify - normalization vs dynamic range compression

Discussion in 'audio' started by steve_1979, Dec 26, 2014.

  1. steve_1979

    steve_1979 pfm Member

    Have you ever wondered what the 'Set the same volume level for all tracks' option in Spotify is really doing?
    No probably not, but I have.

    [​IMG]

    Googling didn't help to find an answer to this question because some people say that it works by normalization and others say that it works by reducing the dynamic range of the tracks that would originally have had a high dynamic range.

    I hoped that it would only normalize* the volume to make all of the tracks seem equally loud. If this was done the full dynamic range (and thus the sound quality) of each track would be kept intact and it would simply balance the volume levels by reducing the volume of the tracks that have already had their dynamic range compressed.

    So I decided to put it to the test myself by using the dynamic range meter in Foobar and comparing a track played via Spotify twice. Once with the 'Set the same volume level for all tracks' turned on and once with it turned off.

    The one on the left is the result with it turned on and the one on the right is with it turned off.

    [​IMG]

    A very disappointing result Spotify! They're reducing the dynamic range (and thus sound quality) of their music. :(

    This may not seem like a big issue to most people but I think that Spotify have missed a chance here to put an end to the loudness wars once and for all. A bold statement you may think? Well think about it this way. Spotify and other streaming services have become the most popular way to listen to music right? Well, if they were to make all of the tracks play at the same volume by implementing normalization of the tracks this would allow their full dynamic range (and thus sound quality) to be kept intact.

    All of the music would still play at the same average volume level like it already does. The only difference would be that the sound quality inadequacies of the dynamically compressed tracks would be obvious to hear when compared to music that has more dynamic range.

    As we all know the loudness wars were started by record companies wanting their music to jump out at you by reducing its dynamic range to make it seem louder. However if everything was played at the same average volume by applying normalization this tactic would no longer work. Quite the opposite, they would now be motivated to make their music stand out by improving the sound quality instead by allowing music to be made with its full dynamic range still intact.

    Spotify could still keep the existing dynamic range compression option available for people who want to use it because it can come in useful when listening to music in a loud environment. But they should also give a normalization option for people who want to listen to music that offers the best possible sound quality with a full dynamic range.

    If enough people read this and spread the word to push Spotify (and other streaming services) to normalize the volume levels rather than dynamically compressing them we could put an end to the loudness war.

    What do you think?

    * http://en.wikipedia.org/wiki/Audio_normalization
     
  2. darrenyeats

    darrenyeats pfm Member

    I have low level of trust for how these things are implemented in general. I just switch that stuff off everywhere.

    Search for 'replaygain'.
     
  3. steve_1979

    steve_1979 pfm Member

  4. whatsnext

    whatsnext Naimless

    No I haven't wondered. I leave it unticked and enjoy what Spotify offers without thinking about it to the extent you have. You are unlikely to change anything let alone the world. If you don't like Spotify try another of the streaming services, many of which are higher quality. Even if their subscription base falls I doubt tSpotify will blame ticking that box for their ills. It was something to think about on Boxing day though.
     
  5. demotivated

    demotivated pfm Member

    I'm no fan of normalisation either. A loud track is supposed to be louder than a quiet track
     
  6. Julf

    Julf Evil brother of Mark V Shaney

    Actually, yes. Appreciate you taking the effort to check! Too bad they don't make the two entirely different normalization modes separate selectable options.
     
  7. SteveS1

    SteveS1 I heard that, pardon?

    Same as 'sound check' in iTunes isn't it? To be avoided.
     
  8. Zombie

    Zombie pfm Member

    Isn't it just adjusting all tracks to the same level so you don't have to adjust with your own volume control?
     
  9. narabdela

    narabdela who?

    er,no. That's dealt with in post #1.
     
  10. SteveS1

    SteveS1 I heard that, pardon?

    No. That's Steve's point. The level of dynamic range is adjusted.
     
  11. Julf

    Julf Evil brother of Mark V Shaney

    It is my understanding that the "sound check" feature in itunes only adjusts the relative volume of individual tracks compared to each other (so does the same as replaygain-compatible software). Seems Spotify does more than that - it actually adjusts the dynamic level of the track itself, changing the actual waveform.
     
  12. darrenyeats

    darrenyeats pfm Member

    Julf, the wikipedia entry on ReplayGain lists "peak normalisation" under 'Alternatives' ...
     
  13. Julf

    Julf Evil brother of Mark V Shaney

    Yes, it is discussed as an inferior alternative.

    Replaygain is a standard for measuring relative loudness, and storing that information in the metadata tags of the music file (without changing the actual music in any way). That information can then be used by a compatible player to adjust the overall gain for the track.
     
  14. darrenyeats

    darrenyeats pfm Member

    I took it to mean that ReplayGain does something other than normalising peaks (i.e. some form of dynamic compression), at least if the track has a wide dynamic range, they mention -14db as the target.
     
  15. Julf

    Julf Evil brother of Mark V Shaney

    It is a target level, not a target dynamic range. ReplayGain doesn't compress individual tracks.

    (in any case, ReplayGain as a measurement/adjustment standard has been superseded by ITU-R BS.1770 and EBU R128. What remains is the metadata tag.
     
  16. darrenyeats

    darrenyeats pfm Member

    I wasn't quite sure what the -14db was, hence me ambiguously writing 'target'! If as you say no compression occurs, then I infer this 'target' could be missed for the tracks with widest dynamic range.

    I didn't know it was superseded, thanks.
     
  17. steve_1979

    steve_1979 pfm Member

    Exactly how is dynamic range calculated?

    This question has arisen before but was never satisfactorily answered. I don't know exactly how the dynamic range is measured/calculated by either Foobar or the DR database (the DR database seems to use the same or a very similar system to Foobar).

    Most tracks have around 10dB of dynamic range give or take a few dB either way. Obviously there's more then 10dB dynamic range between the quietest wave peak and the loudest. If the maximum dB was around 10dB the music would be too quiet to hear at all.

    I guess that the way that dynamic range is measured by both Foobar and the DR database must be some sort of average dynamic range between peaks when measured out over a set period of time (1 second maybe?). Again I guess that this is done for each set period of time (one second?) for the whole of the track and the resulting DR figure is calculated from all of the one second long averages.

    If anyone can confirm whether that is correct or explain how it is calculated I'd be very interested to know the answer.
     
  18. Julf

    Julf Evil brother of Mark V Shaney

    As a general principle, yes, kind of along those lines, but slightly more sophisticated algorithms.

    EBU R128

    ITU-RT BS.1770
     
  19. steve_1979

    steve_1979 pfm Member

    Thanks Julf. :)
     
  20. Julf

    Julf Evil brother of Mark V Shaney

    The Hydrogen Audio knowledgebase actually has a pretty good writeup on replaygain, including a discussion of avoiding peak clipping.
     

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