Prius Factus
New Member
This is my first post in this forum, so hello to everybody!
I am using Audirvana Studio for playing my local music and streaming from Qobuz. Audirvana makes it easy to see how much boost/attenuation Qobuz applies to each song to level out inter-track loudness differences (of course only if you choose to use that feature). Strangely, in some cases this replay gain seem to differ quite a lot from loudness leveling derived from industry standards (i.e. measuring the integrated loudness as defined by EBU R128 / ITU-R BS.1770 for each track and taking the difference to some reference loudness as replay gain).
I thought it might be interesting for you technically knowledgeable people to read about that in more detail, so the following is a re-post from what I wrote at the Audirvana forum.
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The latest AS version 1.11 has introduced the option to use Qobuz’s replay gain values to level loudness differences between tracks. However, with some albums/tracks there are significant differences between the gain computed by Audirvana’s built-in replay gain analysis tool and the values provided by Qobuz. Such tracks, downloaded from Qobuz and loudness-analyzed by Audirvana, result in replay gain values that can differ from Qobuz values by up to 10 dB for otherwise seemingly identical streams – that’s huge! The good news is that for music listeners preferring the most popular genres (with limited dynamic range) this is not relevant in practice. So if that is you you won't miss much if you stop reading here.
Replay gain is calculated by Audirvana in compliance with industry standards (EBU R128 / ITU-R BS.1770). Apparently Audirvana uses a reference loudness of -18 LUFS (I cross-checked with other EBU compatible analyzer software and can confirm this). Qobuz’s gain values tend to differ from this standard if music has a high dynamic range, typically with a DR value of 12 or more. Any music with DR < 10 will result in gain values practically identical to standard.
Out of curiosity I checked 10 albums with more than 100 tracks in total. It cannot be excluded with certainty that some of the analyzed local albums have been changed in Qobuz’s repository since I downloaded them, e.g. were replaced by a re-mastered version (or downloaded files could be different from their streamed version). However, I think this is rather unlikely (for reasons I will not elaborate on here).
As examples here are two pop albums, significantly compressed in line with current genre standards and in consequence with small DR indices. Audirvana and Qobuz state the same gains for these tracks.
Moving to the other end of the spectrum, classical albums often are very dynamic and typically are (almost) uncompressed. Two exemplary albums reveal DR indices up to 18. The differences between Audirvana and Qobuz are clearly significant.
The chart below summarizes this little analysis. Each dot represents one track. It is visually apparent that the bigger the DR index becomes, the more Qobuz’s loudness calculations deviate from EBU/ITU standard. This correlation is also expressed statistically in terms of R^2, i.e. the correlation coefficient for a linear regression.
(For completeness it should be mentioned that a similar but much weaker correlation exists between replay gain variance and loudness range as defined by EBU R128.)
The big question now is how Qobuz internally calculates replay gain/level matching, anyone with a clue?
I am using Audirvana Studio for playing my local music and streaming from Qobuz. Audirvana makes it easy to see how much boost/attenuation Qobuz applies to each song to level out inter-track loudness differences (of course only if you choose to use that feature). Strangely, in some cases this replay gain seem to differ quite a lot from loudness leveling derived from industry standards (i.e. measuring the integrated loudness as defined by EBU R128 / ITU-R BS.1770 for each track and taking the difference to some reference loudness as replay gain).
I thought it might be interesting for you technically knowledgeable people to read about that in more detail, so the following is a re-post from what I wrote at the Audirvana forum.
=========================
The latest AS version 1.11 has introduced the option to use Qobuz’s replay gain values to level loudness differences between tracks. However, with some albums/tracks there are significant differences between the gain computed by Audirvana’s built-in replay gain analysis tool and the values provided by Qobuz. Such tracks, downloaded from Qobuz and loudness-analyzed by Audirvana, result in replay gain values that can differ from Qobuz values by up to 10 dB for otherwise seemingly identical streams – that’s huge! The good news is that for music listeners preferring the most popular genres (with limited dynamic range) this is not relevant in practice. So if that is you you won't miss much if you stop reading here.
Replay gain is calculated by Audirvana in compliance with industry standards (EBU R128 / ITU-R BS.1770). Apparently Audirvana uses a reference loudness of -18 LUFS (I cross-checked with other EBU compatible analyzer software and can confirm this). Qobuz’s gain values tend to differ from this standard if music has a high dynamic range, typically with a DR value of 12 or more. Any music with DR < 10 will result in gain values practically identical to standard.
Out of curiosity I checked 10 albums with more than 100 tracks in total. It cannot be excluded with certainty that some of the analyzed local albums have been changed in Qobuz’s repository since I downloaded them, e.g. were replaced by a re-mastered version (or downloaded files could be different from their streamed version). However, I think this is rather unlikely (for reasons I will not elaborate on here).
As examples here are two pop albums, significantly compressed in line with current genre standards and in consequence with small DR indices. Audirvana and Qobuz state the same gains for these tracks.
Moving to the other end of the spectrum, classical albums often are very dynamic and typically are (almost) uncompressed. Two exemplary albums reveal DR indices up to 18. The differences between Audirvana and Qobuz are clearly significant.
The chart below summarizes this little analysis. Each dot represents one track. It is visually apparent that the bigger the DR index becomes, the more Qobuz’s loudness calculations deviate from EBU/ITU standard. This correlation is also expressed statistically in terms of R^2, i.e. the correlation coefficient for a linear regression.
(For completeness it should be mentioned that a similar but much weaker correlation exists between replay gain variance and loudness range as defined by EBU R128.)
The big question now is how Qobuz internally calculates replay gain/level matching, anyone with a clue?