Flaws in recent Opus codec? Options

[145dBSPL]

Hi everybody,

this is my first post here, even if i read this forum for a quite long time already.

Recently i did some testing on the Opus codec an found a strange behaviour.
I encoded a file with the official 0.1.5 binaries and had a look the frequency response.
Knowing that judging quality with this is useless, i discovered a ~1000Hz /-3dB drop
around 16 kHz which is not present e.g. in Ogg encoded files.

This lead me to encode/decode a linear sweep for comparison and this finally showed
a really messed up response for the Opus encoded sweep in the HF region.
I am not quite sure if it is encoder or decoder related.
For decoding i used the official opusdec and the foobar built-in one.

Opus music sample:


Oggvorbis music sample:


Opus linear sweep:


Oggvorbis linear sweep:


What do you think? Could someone try to replicate or has this been
noticed already?

Thank you.
Cheers!

[145dBSPL]

Hi Dynamic,

thank you.

Yes, i forgot to mention the settings.
Opus 0.1.5 and Oggenc2.87 (libVorbis v1.3.3) with following switches
<opusenc --bitrate 128> and <oggenc -q 4> is what i used.
So nothing special.

Both decoders showed the same behavior.
Foobar decoder was used finally.

Sweep was generated as a 10 seconds .wav with 16 bit / 44,1 kHz and -10dB gain.

Regards

This post has been edited by 145dBSPL: Oct 13 2012, 17:50