Opus encoder blends both audio channels in each audio channel in low bitrates
In low bitrate encoding of a stereo file (WAV), the Opus codec seems to blend both audio channel in each audio channel. From my initial testing it seems that the border is around ~38-40kbps and the lower the bitrate is, the more significant this seems. This may be a problem in recording of two speakers, where each of the speaker represent one of the audio channel.
Steps:
-
Install opus-tools 0.1.9-1 (e.g. sudo apt-get install opus-tools)
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Encode stereo file by running opusenc --bitrate 24 --hard-cbr --framesize 60
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Play the file and listen to each of the channels separately
Expected:
- both channels will retain only their audio footage
Environment:
-
Ubuntu MATE 15.04 running on Dell Latitude E5430
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WAV info (file available at: [https://drive.google.com/folderview?id=0B_W_T_CohbhsfnNaOGZkb0NzekhKeDZDV2FnbFJTeUV4QzdBaDFPalpGQUdIVkJoTUpIVEk&usp=sharing]):
$ mediainfo ~/Desktop/1352389720037_5516_5517_31870.wav
General
Complete name : /home/pavel/Desktop/1352389720037_5516_5517_31870.wav
Format : Wave
File size : 2.81 MiB
Duration : 1mn 32s
Overall bit rate mode : Constant
Overall bit rate : 256 Kbps
Audio
Format : PCM
Format settings, Endianness : Little
Format settings, Sign : Signed
Codec ID : 1
Duration : 1mn 32s
Bit rate mode : Constant
Bit rate : 256 Kbps
Channel(s) : 2 channels
Sampling rate : 8 000 Hz
Bit depth : 16 bits
Stream size : 2.81 MiB (100%)
- Opus codec:
$ dpkg -l | grep opus
ii libopus0:amd64 1.1-0ubuntu2 amd64 Opus codec runtime library
ii opus-tools 0.1.9-1 amd64 Opus codec command line tools