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Topic: Opus killer sample at 315 kbps found in the wild?? (Read 2288 times) previous topic - next topic
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Opus killer sample at 315 kbps found in the wild??

I'm having as hard a time believing the title of this post as you are.

While messing around with different codecs at lower bitrates, I noticed a rather annoying "wind rushing noise" during the first few seconds of a 64 kbps CD-sourced encoding of Björk's "Thunderbolt." I was already a little surprised by this, since 64 kbps Opus is rarely annoying to me, but I was shocked to find I seem to be able to pick it out all the way up to 315 kbps (but not at 320).

To make sure this artifact wasn't a result of resampling from 44.1 kHz to 48 kHz, I first resampled the CD rip to a 48 kHz FLAC, then encoded to Opus with ffmpeg and did an ABX test against the 48 kHz FLAC.

Even a 128 kbps MP3 seems to be closer to transparent on these few seconds of audio than 140 kbps Opus. What's going on here? Is there something wrong with my methodology?

Attached are a 16/48 FLAC of a 5-second sample, this sample transcoded to Opus at 64 kbps (obvious artifact) and 315 kbps (audible artifact), and an ABX test log between thunderbolt.flac and thunderbolt315.opus.

Re: Opus killer sample at 315 kbps found in the wild??

Reply #1
I can't hear a problem. That's the advantage of the $30 speakers  ;D 

But if I was you I'll try with --downmix-mono and see if it persistent.


Re: Opus killer sample at 315 kbps found in the wild??

Reply #2
After a second I hear, with my cheap desk speakers, something like 4 repetitions of very lowpass filtered crackle, but that's only in the opus-64. In the flac and 315 it's there once.