Tl;dr: change the little song previews on the site to Opus 32kb/s, it's a great codec at low bitrates and it can do fullband stereo at this bitrate.

We all know that those little previews in the website are of low quality, and it really doesn't fit the new look and feel. I suggest making the little previews in Opus format, so that we get a really close approximation of what we'll get at a very low bitrate.

For the purpose of demonstration, I'll be showing a spectogram of Camellia - δ-for the DELTA, a very complex song that you probably already know.

Original .flac, extracted from the PLANET SHAPER album, song nº 6


Opus, encoded at vbr 32kb/s stereo


Opus, encoded at vbr 32kb/s mono


Mp3, encoded at abr 32kb/s stereo


Mp3, encoded at abr 32kb/s mono


Quick graph compating perceived quality between popular codecs(a bit outdated, after version 1.2 Opus can do a bit more than that)


Taking advantage of band folding, tonality estimation and a lot of other modern techniques, Opus can achieve very high frequencies at low bitrates, up to the point that a 128kb/s Opus is transparent compared to the original uncompressed audio.

About its implementation(aside from already being open source), Opus encoders and decoders are available on ffmpeg, the bass library and an official encoder libopus(which is the reccomended and the one I used on these tests). Chrome, Firefox, Edge and even recent Windows, Linux and Mac already brought updates to support native playback, so there woudn't be a major browser incompatibility problem.

In https://people.xiph.org/~jm/opus/opus-1.2/ there are some comparisons between Mp3 and Opus at different bitrates (32, 48, 64, 96) and umcompressed for reference. Note the difference between Mp3 ad Opus at 32kb/s is huge!

I searched the forums about Opus, and it seems some people really want to switch from all of osu's Mp3 to Opus. Mp3 is 23 years old and Opus is a new, flexible and modern all-purpose codec that is already in use on major platforms like Youtube, Discord, Whatsapp and some recent webm files encoded with vp9. I understand why and I support it, but if the game doesn't have any major problems with its audio, maybe we shouldn't change it. But the site sure does have a big problem with audio quality.

Here are some links for those who want to learn more about Opus:

1. https://www.opus-codec.org/comparison/
2. https://www.opus-codec.org/examples/
3. https://people.xiph.org/~xiphmont/demo/celt/demo.html
4. https://people.xiph.org/~xiphmont/demo/opus/demo3.shtml
5. https://people.xiph.org/~jm/opus/opus-1.2/

Here are some listening tests

1. http://listening-test.coresv.net/results.htm
2. http://listening-tests.hydrogenaud.io/igorc/results.html

Here is some links if you want to test it for yourself

1. opus-tools(you can alternatively use ffmpeg, i guess it's the same version atm): https://opus-codec.org/downloads/
2. reccomended settings: https://wiki.xiph.org/Opus_Recommended_Settings

Here is a nice slide if you still didn't got what the hell are we talking about: https://www.opus-codec.org/static/presentations/opus_ccbe2013.pdf

And here is a super important FAQ about the codec: https://wiki.xiph.org/OpusFAQ

Ps.: for those who will say Opus is a voice codec, it works on 2 modes: CELT and hybrid (CELT + SILK), and it changes between them as necessary, demonstrated at https://people.xiph.org/~xiphmont/demo/opus/demo3.shtml

Ps2.: I used Mp3 on the examples for 2 reasons: it's a popular format and I don't know which codec is really being used on the previews. Based on my tests it sounded pretty similar, so i went with it.

Ps3.: Hey devs, remember that Opus is an all-purpose codec, it can also do great at 128kb/s for the music in the game(at this bitrate, it is already considered transparent(https://en.wikipedia.org/wiki/Transparency_(data_compression))), saving a lot of space both on the servers and on the clients!

abraker wrote:

https://osu.ppy.sh/forum/t/199444
t/446368

rip long post

abraker wrote:

https://osu.ppy.sh/forum/t/199444
https://osu.ppy.sh/forum/t/446368

I've already read those posts, but they are about the music ingame, not the previews on the site itself(and they're old, I didn't wanted to revive old posts to make a different point).

I really belive that with all the changes osu is getting trough(including the fact that the site will be accessible ingame on osu lazer), those old audio previews should really get a refresh, not necessarily on all maps but at least the newest ones if possible.

Age of request does not matter for requests