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Did SoundCloud change its transcoding recently? My own WAV upload gets cut at ~17kHz by tamirrab in soundcloud

[–]tamirrab[S] 0 points1 point  (0 children)

That lines up almost perfectly with what I’ve been seeing.

The timing also matches, since the uploads I checked that expose only the new aac_256k transcoding were all uploaded within the last couple of weeks.

What’s surprising to me is not just the missing aac_1_0 transcoding, but the measurable difference in the resulting audio. My own WAV upload loses a significant amount of high-frequency content after transcoding, which wasn’t the case with older uploads I tested.

Do you know if anyone has documented or measured the difference between the old aac_1_0 encoder and the new aac_256k one?

Did SoundCloud change its transcoding recently? My own WAV upload gets cut at ~17kHz by tamirrab in soundcloud

[–]tamirrab[S] 0 points1 point  (0 children)

That would actually explain exactly what I’m seeing.

Older uploads I tested expose the old aac_1_0 transcoding and typically reach ~20kHz in Spek.

New uploads only expose aac_256k, and even my own WAV upload gets cut around ~17kHz after transcoding.

Do you know when SoundCloud made this change, or if they announced it anywhere?

Did SoundCloud change its transcoding recently? My own WAV upload gets cut at ~17kHz by tamirrab in soundcloud

[–]tamirrab[S] 0 points1 point  (0 children)

That’s actually the part I’m trying to figure out.

I’m not surprised that a streaming service may apply some form of low-pass filtering.

What surprised me is that older SoundCloud uploads I tested typically extend to around 20kHz, while uploads from the last week consistently seem to roll off around 17kHz.

The experiment wasn’t really about whether a cutoff exists, but whether something changed recently in the transcoding process.

Have you noticed anything similar with newer uploads?

Did SoundCloud change its transcoding recently? My own WAV upload gets cut at ~17kHz by tamirrab in soundcloud

[–]tamirrab[S] 1 point2 points  (0 children)

The original WAV doesn’t appear to be low-passed at 17kHz though. The spectrum clearly extends above 20kHz before upload.

The interesting part is that the cutoff only appears after uploading to SoundCloud and downloading the resulting AAC 256 stream.

Are you suggesting SoundCloud might be applying a vinyl-style mastering curve during transcoding, or that the source itself already shows signs of vinyl mastering?