What Audio Format Does Spotify Upload Use

In 2021, the vast majority of listeners are consuming music through streaming services. And though they'll forever have their fans, the days of LPs, Tapes, CDs, and fifty-fifty MP3 downloads being the standards for music consumption are waning. As audio engineers, it'southward critical to sympathise what'south happening when nosotros upload a final version of our songs to streaming services, since this is what well-nigh listeners are likely going to be hearing.

I of the biggest players in streaming, Spotify, just updated its data on loudness normalization and file formats, and so nosotros thought this would be a adept time to go through the virtually of import parts and break downwards what it means for us as music producers and audio engineers.

Note though—platforms like Spotify aren't static; they evolve and standards are updated over time. It's on us to stay ahead of the curve and stay informed.

A brisk history of loudness normalization

When Spotify first introduced loudness normalized playback to its platform, the purpose was to create a better listening experience for users (post-obit in the footsteps of terrestrial radio and Apple's iTunes). Rather than having to suit the volume when shuffling between songs, Spotify would measure the perceptual loudness and adjust the volume for you. Overnice and like shooting fish in a barrel! But whether they knew information technology at the time or not, this accelerated awareness most loudness normalization amid producers and engineers, increasingly influencing the sound of music product overall.

In the world of digital sound, in that location is a maximum sample elevation level for a file that nosotros refer to as 0 dBFS (decibels full-scale). If your levels exceed 0 dBFS when you bounce a file, it volition be digitally clipped at a maximum of 0 dB (and probably sound pretty nasty). You tin solve this with a limiter like the Ozone Maximizer, which makes sure that no samples go in a higher place the "ceiling." At the same time we can lower the threshold, limiting the signal harder. While the acme sample level volition not increase, the perceived loudness will increment considerably. The tendency in this increase in perceived loudness is what we commonly refer to as the "Loudness War."

Historically, methods used to decide sound loudness were based entirely on aamplitude measurements and didn't consider perceived loudness. In 2006, the International Telecommunication Union (ITU) introduced the start version of their "Algorithms to mensurate audio plan loudness and truthful-superlative audio level." This included LUFS (loudness units full-calibration). I of the beginning applications was to create more consistency between the loudness of a Idiot box show and the commercial interruption, turning downwardly those super-loud commercials that would grab your attention back in the mid-2000s. Now, Spotify and other streaming services are using updated versions of the same algorithms to prepare the playback levels of each vocal and anthology.

In order to create the same consistency for music listeners, Spotify and some other streaming services "loudness normalize" songs, or set up them to the same standard level using various systems including Integrated LUFS. In 2021, Spotify adopted a level standard of -14 Integrated LUFS. What does that hateful practically for audio engineers? Using an awarding similar RX, we tin can really see what happens during this normalization procedure, which we'll do now. I'll be using my latest song called "Please, Go" as an example:

Recreating Spotify's normalization in RX

In the RX Waveform Statistics window, you can view the integrated loudness of an audio file. My vocal has an integrated loudness measurement of -11.2 LUFS. The convenient thing about loudness units is that they scale every bit with dB. To normalize my song to -14 LUFS, all I demand to do is plough the gain down past two.8 dB:

Waveform and integrated loudness for Please, Go (earlier normalization)

Waveform and integrated loudness for Please, Go (after normalization)

Nosotros can see that the song has been turned down, merely that's all that'south happening. Information technology's not like Spotify is using dynamic range compression on my song, just applying negative gain. This can be a really useful technique when mastering, because now that my song is at Spotify's loudness levels I can do an A/B comparing with any other reference song on the platform!

For demonstration, I'll show what would happen if I made a much louder master past lowering the Maximizer threshold by iii dB:

Waveform and integrated loudness for a more limited version of Please, Go (before normalization)

Without changing the peak level, I've increased the loudness of my master. The choruses now look more like rectangles without any edges poking out. Running the aforementioned simple math:

fourteen - eight.half dozen = 5.4

So Spotify will turn this new master downwardly by 5.4 dB to normalize to -xiv LUFS.

Waveform and integrated loudness for a more express version of Please, Go (after normalization)

The really interesting thing is to zoom into the waveform and compare the difficult-pushed, loud master with the original after they've both been normalized:

Comparing a brusque section of the original and more limited versions (both after normalization)

We can see that all we've done is chop off the peaks of the drums, adding distortion. In the sample-peak-normalized world of CDs, when tracks weren't normalized co-ordinate to their perceived loudness, information technology made sense to push the limiter hard. Now that we're in the age of loudness-normalized streaming, the extent to which we button the limiter is more a cistron of our creative expression than a technical requirement. Only pushing it for the sake of pushing it isn't doing our song any favors on loudness-normalized platforms!

You can hear the two versions after normalization here:

Spotify recommends that you target -14 LUFS for your song. If y'all exercise this Spotify will not apply whatever increase or subtract in gain, and your vocal volition play dorsum on Spotify at the exact same aamplitude level at which y'all bounced it.

We recommend that y'all experiment with different loudness levels, normalizing the tracks yourself with the procedure above, and and then comparison them to reference songs on Spotify.

Data compression

It can be easy to get confused about "compression" and loudness normalization. We're typically most familiar with dynamic range compression (think compressors and limiters), but the data compression that occurs in converting audio to different codecs is a bit unlike.

Codec

The most famous codec is MP3, merely Spotify opts to use a complimentary, open up-source codec called OGG Vorbis. (This is made past an organization called Xiph, who as well makes the FLAC codec.) Because OGG is a form of lossy data pinch, it necessarily involves some dynamic range compression to perform this conversion. Information compression to a lossless codec, like FLAC, would not involve the same dynamic range compression.

Fleck-rate

Depending on a user's Streaming Quality setting in their Spotify preferences, they will get a different bit-rate. Very High quality gives yous 320 kbps, High is 160 kbps, and Normal is 96 kbps. The higher the scrap-rate, the less information is lost in the filtering. Nosotros audio engineers have no control over what quality setting a listener volition utilize, but nosotros tin can at least become a sense of how our song will sound. Using RX, we can consign an OGG file and endeavor out dissimilar compression settings. For this demo, I've taken a small part of my song exported it at different OGG bit rates (and then exported back to a WAV file so they can be uploaded):

A fun matter we tin can do is to perform a null-test. If we have 1 of the compressed files and invert the waveform, then play it dorsum forth with the original, the result will exist what the data compression has removed from the audio:

Even though they audio strange, I really enjoy listening to these zero tests. Information technology's fascinating to hear what information is being removed in order to make the file smaller. While there's very little lost at the highest quality setting, there'southward quite a scrap of music being lost at normal quality. Even so, when I listen to the Normal quality version, it doesn't sound terrible to me.

Pinnacle level

When a song gets encoded into OGG Vorbis (or any other lossy codec), its meridian sample level will modify (and nigh e'er increment). You tin meet this if you lot export a WAV file into OGG using RX, import the OGG file, and check the peak levels in the Waveform Statistics view. For example, here are the sample peaks and true peaks for my song at the various bit rates we heard above:

We can see that later data compression, the pinnacle levels of my song have increased. The levels increase with the loss in quality. This means my song will exist digitally clipped at whatsoever quality setting other than Very High Quality. For this reason, Spotify recommends using a truthful acme limiter with a ceiling of no higher than -2 dB (come across the bottom of the linked page).

Track not every bit loud every bit others?

There's nothing worse than finally listening to your vocal on release mean solar day and thinking it doesn't audio proficient or doesn't sound as loud as whatever reference song you play adjacent. Since all songs are normalized to the same loudness, there shouldn't exist whatsoever loudness differences. However, Spotify calls out certain problems could crusade your song to have a college LUFS value than it should:

Your runway is only too crushed

Equally described in the first section, an extra button into the limiter may make your track excessively loud. If your song's waveform looks like a rectangle throughout, it may sound quiet compared to the loud sections of a more than dynamically-mastered vocal.

Your playback arrangement has an uneven or unreliable frequency response

It should be pretty obvious, but Spotify doesn't know and can't compensate for your personal monitoring system. If your playback system is nonlinear in some way, boosting or lacking certain frequencies, your perception of loudness in your listening environment may non consistently line upwards with the integrated LUFS value for your track.

Spotify uses this LUFS value to inform the resulting loudness normalization. So if your experience of hearing music on your organization doesn't align with the value Spotify is using, your track may be normalized in a way you weren't expecting.

Imagine you've mixed and mastered your whole song on inexpensive headphones with no high frequency extension. Yous can't tell what'south going on up there, so maybe you've cranked the highs up way too loud. The loudness algorithm is however going to register those highs and may plow your track down excessively. The same could happen if your system was defective in bass while yous were mixing.

Or imagine your speakers take a big bump in the depression mids. Any song you play with a similar frequency bump will seem louder considering your speakers are boosting information technology. Obviously the loudness algorithm doesn't know the frequency response of your speakers or headphones, so it tin can't compensate for that.

A good sanity-check for this trouble is to utilize a tool like Tonal Balance Control, which volition let you know if your track has a buildup or lack of certain frequencies in your overall tonal residue.

Edge cases

Everything I've described higher up is going to be truthful nigh of the time. Nonetheless, for the sake of completeness, in that location are a couple of edge cases to explicate:

Album playback

If you upload an album, Spotify will measure the integrated loudness of each song individually, plus perform a measurement for the entire album. When a song comes up in a playlist, Spotify volition normalize information technology based on the individual song'south loudness. When you play an album with shuffle off, Spotify volition instead utilise the integrated loudness measurement of the entire album and apply the aforementioned normalization to each song. This means that songs intentionally made to be placidity or loud relative to the rest of the album volition not lose their intended level.

Notation: At the time of writing this article, a new album normalization paradigm is being developed that would give artists more control over relative loudness inside an album. This article will be updated every bit these paradigms are released.

Other codecs

Spotify uses OGG vorbis for its mobile and desktop apps, except for the Low quality setting which uses HE-AACv2 (24kbps). The web app uses a different codec—AAC.

Volume level setting

The user tin cull to turn off normalization, though it is on by default for all users. There is also a setting to adjust the volume level for your surround, which will change the LUFS normalization level:

Loud: -11dB LUFS
Normal: -14dB LUFS
Quiet: -23dB LUFS

If your song is quieter than -14 LUFS

Before now, we've only talked about how Spotify will plow your track downwardly if it is louder than -14 LUFS. But if your track is quieter than -xiv LUFS, Spotify will actually increment the gain. Still, there's a limit to this. Spotify will not increment your runway past a true pinnacle level of -i dB. For example, if a track loudness level is -20 dB LUFS, and its True Elevation maximum is -v dB, Spotify only lifts the track up to -16 dB LUFS.

If the user has selected the "Loud" playback option, Spotify will use a limiter to raise the song to -11 LUFS, regardless of acme level. This is the only case where Spotify volition apply dynamic range compression. (Encounter the lesser of the "How we adjust loudness" section here.)

The takeaways

To take the mystery out of what will happen to a rail, it can be incredibly helpful to create your own "streaming preview" using RX. If you start with a WAV file, convert it to OGG, re-import, and and then normalize information technology with gain to -14 LUFS, this is exactly what Spotify will be playing. Now you'll never exist surprised on release twenty-four hours again. You can hear what will be lost in data compression and meet how much loudness normalization is applied. You can employ this "streaming preview" to A/B confronting other tracks on Spotify and make informed choices as y'all tweak your mix/master.

Next, yous may consider not pushing your limiter every bit hard. If streaming is your main platform, you at present know how loudness normalization volition touch your runway. You may also consider post-obit Spotify's guidelines on peak level and leaving at least two dB truthful peak headroom for the encoding process. If you're concerned that your playback system'south uneven frequency response might be hurting your loudness measurements, you may desire to apply a tool like Tonal Balance Command to place whatever problems.

We hope this has been useful and informative, and helps you lot producers and engineers get the results you expect on Spotify!

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Source: https://www.izotope.com/en/learn/how-will-my-music-sound-on-spotify.html