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Topic: Test of 4 audio codecs on very very low bitrates - up to 32/36 kbps (Read 315 times) previous topic - next topic
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Test of 4 audio codecs on very very low bitrates - up to 32/36 kbps

I pushed the limits of 4 audio codecs by encoding to very very low bitrates, using CBR and VBR.

Bitrates tested: from 12 to 32 (CBR) / 36 (VBR) kbps.
Music: Poptimistic by VERBA music (the person who generated the song) - generated with Suno 3.5 (now we are using AI-generated music). Clipped to 29 seconds to follow TOS.

Encoders:
HE-AACv2 - Nero AAC Encoder 1.5.4.0
Speex - Speexenc 1.2.1
Vorbis - Lavc61.5.103 libvorbis from FFmpeg 2024-04-25-git-cae0f2bc55-full_build-www.gyan.dev
Opus - opusenc from opus-tools 0.2-34-g98f3ddc (using libopus 1.5.2-22-g7db26934)
Note that Opus is the only codec tested with 12 kbps.

Results:
HE-AACv2 sounds the best at 24 and 32 kbps. Clear sound and full frequency range.
Opus has glitchliness. Not the greatest.
Speex is worse than Opus. But 24 kbps is the greatest so far.
Vorbis is even worse than Speex. Doesn't even support 48 kHz for those bitrates.

Preference:
HE-AACv2 (best) > Opus > Speex > Vorbis (worst)

Attached ZIP file with sample encoded with 4 codecs at different bitrates (plus original file).

Re: Test of 4 audio codecs on very very low bitrates - up to 32/36 kbps

Reply #1 –
About Speex... I can't describe with few words how terrible is it except for lower bitrates and speech. And it's not really good for stereo content, it will sounds quite poor and more like mono, and will cause clipping for anything too loud.

Vorbis doesn't really have CBR, and force it to get close to a constant bitrate will only decrease quality.

And... I just won't bother to listen the files. I don't have the time or patience right now.

Re: Test of 4 audio codecs on very very low bitrates - up to 32/36 kbps

Reply #2 –
Quote from: a.ok.in on
About Speex... I can't describe with few words how terrible is it except for lower bitrates and speech. And it's not really good for stereo content, it will sounds quite poor and more like mono, and will cause clipping for anything too loud.
Despite Speex is "poor" expect for speech, Speex encodes music better than Vorbis does.
Quote from: a.ok.in on
Vorbis doesn't really have CBR, and force it to get close to a constant bitrate will only decrease quality.
Yeah, you're right. Unlike MP3, Vorbis doesn't have TRUE CBR, only a more ABR-like CBR.
Quote from: a.ok.in on
And... I just won't bother to listen the files. I don't have the time or patience right now.
Ok. You can do it later!
 

Re: Test of 4 audio codecs on very very low bitrates - up to 32/36 kbps

Reply #3 –
It appears that this wasn't a blind test and you didn't rate the encodes, just ordered them. A single sample, single listener test is already not enough data to make substantial conclusions from, but a non blind test means even this one data point is simply not usable data. See TOS#8. Ether MUSHRA or ABC/HR are usable blind testing methodologies.