How Does Opus Sample rate Work

[jamespoo]

ive been testing out audio bitrates and codecs and found opus to be the best at this bitrate my ears cant tell the difference when compered to 320kbps mp3/aac
i just have 1 problem when i rip a cd to opus meda info in media player classic shows the khz as 44.1khz same as what the original cd is but vlc player and the app on my phone both say the audio is 48khz

General
Complete name : G:\All Time Low\Nothing Personal\04 All Time Low - Lost In Stereo.opus
Format : Ogg
File size : 3.98 MiB
Duration : 3 min 47 s
Overall bit rate : 133 kb/s
Album : Nothing Personal
Album/Performer : All Time Low
Part : 1
Part/Total : 1
Track name : Lost In Stereo
Track name/Position : 4
Track name/Total : 12
Performer : All Time Low
Label : Hopeless Records
Genre : Pop / Rock
Recorded date : 2009
Writing application : Opus 1.3.1
ISRC : USHR20947004
ENCODER_OPTIONS : --bitrate 120
Style : Pop Rock / Power Pop / Punk / Pop Punk
Catalog # : 710
Source : CD (Lossless)
Encoded By : dBpoweramp Release 17.4
Encoder Settings : -bitrate="120"
AccurateRipResult : AccurateRip: Accurate (confidence 2) [3D071E1E]
AccurateRipDiscID : 012-00120512-00a952af-8f099f0c-4

Audio
ID : 1888 (0x760)
Format : Opus
Duration : 3 min 47 s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 44.1 kHz
Compression mode : Lossy
Writing library : libopus 1.3-26-ge85ed772, libopusenc 0.2.1-2-g9cb17c6

so im confused is media info wrong or has it really converted the 44.1khz to 48khz and will there be any problems so far the 2 cds i ripped sound fine without problems

[davexnet]

It says sampling rate 44.1 in the report above

[jamespoo]

It says sampling rate 44.1 in the report above

yes but all other programs say it 48khz

[Cornucopia]

Assuming you did NOT do any SRC (sample rate conversion), ALL CD rips would be 44.1kHz, and so would any compressed version from them. So, I must deduce that those other apps are wrong.
MediaInfo does not do any SRC, it just shows you what the metadata is in the file. Would love to see some of these other apps that are reporting otherwise.

Scott

[El Heggunte]

ive been testing out audio bitrates and codecs and found opus to be the best at this bitrate my ears cant tell the difference when compered to 320kbps mp3/aac
i just have 1 problem when i rip a cd to opus meda info in media player classic shows the khz as 44.1khz same as what the original cd is but vlc player and the app on my phone both say the audio is 48khz.

From Wikipedia's article about the Opus audio format:

Opus allows the following bandwidths during encoding. Opus compression does not depend on the input sample rate; timestamps are measured in 48 kHz units even if the full bandwidth is not used. Likewise, the output sample rate may be freely chosen. For example, audio can be input at 16 kHz yet be set to encode only narrowband audio.

Abbreviation          Audio bandwidth    Effective sample rate

NB (narrowband)        4 kHz               8 kHz
MB (medium-band)       6 kHz              12 kHz
WB (wideband)          8 kHz              16 kHz
SWB (super-wideband)  12 kHz              24 kHz
FB (fullband)         20 kHz              48 kHz

[Cornucopia]

Wow.

This was news to me.

Reading those docs, it appears Opus applies SRC both on encode and (usually) on decode, And there are also built in lags for that src as well as for packet resiliency, and a few other codec-switching-trick functions.

This may be cool for some of those features, but the audiophile in me says F**k No! I have so far rarely used the codec family, mainly because I have few hardware devices that support it, but it seriously gives me pause about using it again. I don't want any app applying SRC that isn't fully under my control.


Scott