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

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Thu Oct 25 23:38:34 UTC 2018


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.
With Opus I noticed that the file size for 48kHz and 48 kbps compared to 96kHz Vorbis at 31kbps is about double the size 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).
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
        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
        TITLE=Sweep (0-20kHz at 96kHz) log
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:

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)

I'm attaching the Opus output (ca. 700kB) and the Vorbis output (ca. 250kB).
WARNING: Listen to it at a low volume using headphones; if you listen to it at high volume with good speakers, your house might collapse ;-) Be warned, especially as you may not hear anything the first 15 seconds.


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