[opus] Possible bug in Opus 1.3 (opus-tools-0.2-opus-1.3)?

[Jan Stary]

(Please wrap your lines.)

On Oct 26 01:38:34, Ulrich.Windl at rz.uni-regensburg.de wrote:
> Playing with Opus 1.3 I converted a tone sweep with a sample rate of 96kHz (just for fun). Before I had converted that from WAV to FLAC, and to Vorbis without problems.

Can you please post the original wav?

I am not sure what Audacity means by a logarithmisch sweep.
Is that a fixed number of Hertz per second (SoX calls that linear)?
Or a fixed number of semitones per second (SoX calls that exponantional)?

(The ogg comment says 5s=10Hz, 10s=20Hz, 15s=39Hz, 20s=78Hz, 25s=156Hz,
30s=312Hz, 35s=625Hz, 40s=1.25kHz, 45s=2.5kHz, 50s=5kHz, 55s=10kHz, 60s=20kHz
so it seems the frequency rises logarithmically.)

$ sox -c 1 -r 96k -b 16 -n /tmp/sweep.wav synth 60 sin create 1-20 gain -3

> With Opus I noticed that the file size for 48kHz and 48 kbps
> compared to 96kHz Vorbis at 31kbps is about double the size

Your opusenc line says "--bitrate 56 --vbr",
so where does the 48 come from?

Anyway:

$ flac sweep.wav
$ oggenc sweep.wav
$ opusenc sweep.wav sweep.opus
$ ls -l sweep.*
-rw-r--r--  1 hans  wheel   2635692 Nov  1 08:49 sweep.flac
-rw-r--r--  1 hans  wheel    215185 Nov  1 08:49 sweep.ogg 
-rw-r--r--  1 hans  wheel    660815 Nov  1 08:49 sweep.opus
-rw-r--r--  1 hans  wheel  11520044 Nov  1 08:49 sweep.wav

So for me it is actualy about three times the size of an ogg
(and about 6% the size of the original wav).

I am not sure why you are using 96kHz in the original,
but doing the same with a 48kHz original wav results in

-rw-r--r--  1 hans  wheel  1468106 Nov  1 08:51 sweep.flac
-rw-r--r--  1 hans  wheel   113787 Nov  1 08:51 sweep.ogg
-rw-r--r--  1 hans  wheel   611386 Nov  1 08:51 sweep.opus
-rw-r--r--  1 hans  wheel  5760044 Nov  1 08:51 sweep.wav

All of them approximately halve, but opus does not.
Is that expected?

> and it sounds even worse (than Vorbis)
> (there is a lot of noise in the lower frequencies
> when a low frequency tone is being played).

Are you sure your speakers/headphones can even reproduce
such low frequencies accurately? I doubt it.

> Here is what opusinfo outputs:
> 
> Processing file "D:\Work\Ulrich\Musik\Vega\Opus\Audacity\Test-Sweeps\02 Sweep (0
> -20kHz at 96kHz) log.opus"...
> 
> New logical stream (#1, serial: 000028fd): type opus
> Encoded with libopus 1.3, libopusenc 0.2.1
> User comments section follows...
>         ENCODER=opusenc from opus-tools 0.2-3-gf5f571b
>         ENCODER_OPTIONS=--bitrate 56 --vbr --comp 5
>         ALBUM=Test-Sweeps
>         ARTIST=Audacity
>         COMMENT=60s logarithmic sweep (0-20kHz): 5s=10Hz, 10s=20Hz, 15s=39Hz, 20
> s=78Hz, 25s=156Hz, 30s=312Hz, 35s=625Hz, 40s=1.25kHz, 45s=2.5kHz, 50s=5kHz, 55s=
> 10kHz, 60s=20kHz
>         COMMENTS=60s logarithmisch
>         DATE=2016
>         TITLE=Sweep (0-20kHz at 96kHz) log
>         TRACKNUMBER=2
> Opus stream 1:
>         Pre-skip: 312
>         Playback gain: 0 dB
>         Channels: 1
>         Original sample rate: 96000 Hz
>         Packet duration:   20.0ms (max),   20.0ms (avg),   20.0ms (min)
>         Page duration:   1000.0ms (max),  983.9ms (avg),   20.0ms (min)
>         Total data length: 637535 bytes (overhead: 1.07%)
>         Playback length: 1m:00.000s
>         Average bitrate: 85 kbit/s, w/o overhead: 84.09 kbit/s
> Logical stream 1 ended
> 
> 
> Here is the encoding output for a manual test:

Wait, so there are two opus files at play here?
How exactly did you create each? Is this the 48kHz one?
Post the files you are describing.

	Jan


> C:\Program Files (x86)\foobar2000\codecs\opus-tools-0.2-opus-1.3>opusenc.exe --b
> itrate 56 --vbr "D:\Work\Ulrich\Musik\Vega\FLAC\Audacity\Test-Sweeps\02 Sweep (0
> -20kHz at 96kHz) log.flac" "D:\Work\Ulrich\Musik\test.opus"
> Encoding using libopus 1.3 (audio)
> -----------------------------------------------------
>    Input: 96 kHz, 1 channel
>   Output: 1 channel (1 uncoupled)
>           20ms packets, 56 kbit/s VBR
>  Preskip: 312
> 
> Encoding complete
> -----------------------------------------------------
>        Encoded: 1 minute and 0.02 seconds
>        Runtime: 1 second
>                 (60.02x realtime)
>          Wrote: 749625 bytes, 3001 packets, 63 pages
>        Bitrate: 98.9456 kbit/s (without overhead)
>  Instant rates: 44 to 122.4 kbit/s
>                 (110 to 306 bytes per packet)
>       Overhead: 0.972% (container+metadata)
>