[opus] Opus vs AAC (endurance test)

[Gregory Maxwell]

Opus is specifically designed to survive tandeming but you need to keep the
frames aligned and not mess with the gain, which your tools probably do not
do.

On Thu, Nov 16, 2017 at 10:58 PM, encrupted anonymous <
sergeinakamoto at gmail.com> wrote:

> using iTunes i've noticed that AAC is
> very good at re-encoding own lossy sound.
> let's test Opus!
>
> neroaacenc.exe -q 0.75 -if 000.wav -of 001.m4a
> neroaacdec.exe -if 001.m4a -of aac001.wav
> wavdiff.exe 000.wav aac001.wav
> Comparing 000.wav - aac001.wav...
> Max diff: -17.3867dB
> RMS diff: -33.0851dB
> Mean diff: -32.4582dB
>
> opusenc.exe --bitrate 512 "000.wav" 001.opus
> opusdec.exe 001.opus opus001.wav
> wavdiff 000.wav opus001.wav
> Comparing 000.wav - opus001.wav...
> Max diff: -22.5646dB
> RMS diff: -39.0425dB
> Mean diff: -38.7372dB
>
> Opus @482kbps is much better than AAC @288kbps.
> now let's see what happens after 10 passes
>
> Comparing 000.wav - aac010.wav...
> Max diff: -16.1286dB
> RMS diff: -32.3361dB
> Mean diff: -31.715dB
>
> AAC stepped back just a little
>
> Comparing 000.wav - opus010.wav...
> Max diff: -7.61385dB
> RMS diff: -20.3666dB
> Mean diff: -20.1286dB
>
> Opus made complete disaster, but HF looks
> good (so it isn't an error in frames
> synchronisation of wavdiff program).
>
> And no, i'm not going to do ABX test at high
> bitrates because i'm not wavdiff.exe, and i'm
> not going to do ABX tests at low bitrates
> because i don not use them.
>
> FLAC is good, but MIDI is better. Lossy codecs
> "reverse-engeneering" audio back to MIDI, that's
> what they do :)
>
>
>
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