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Checking out a new audio file type - OPUS, looking good

humblebee

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#1
So, I have been looking at finding a new audio file type because of two reasons:

1) To see what new developments can give us better audio for the same bitrate (Read : is there a successor to AAC, as it was for MP3?)

2) Can we go beyond the frustrating 320kbps limitation in bitrate? This will bring us closer to lossless audio.

3) If we can have smaller filesize, then thats a bonus.

Sometime back, I came across HE-AAC and HE+PS AAC, but sadly they were limited to low bitrates even though they had better encoding tech.

Well, today I came across OPUS (Opus Codec).
This codec has :

1) The efficiency of HE-AAC (not sure of HE+PS AAC), and in listening, I can say that I find it to be better than AAC at 256kbps. I compared iTunes downloads with files converted from original CD wav files to Opus at 256 kbps.

2) It supports bitrates upto 512 kbps. The audio quality is coming to be really close to wav here. Opus@512kbps is better than Opus@256kbps for sure.

3) File sizes are smaller than AAC. e.g. file sizes are:

Its My Life - Bon Jovi
AAC - 7.57 MB
Opus - 6.52 MB
Opus 512 - 13 MB
Flac - 31 MB
WAV - 37.7 MB

The One That Got Away - Katy Perry
AAC - 7.9 MB
Opus - 7.16 MB
Opus 512 - 13.4 MB
Flac - 26.9 MB
Wav - 38.2 MB

And the good part is that its Wikipedia page says that OPUS is supported by iPods (Hopefully iPhone) and Android devices.

As of now, the only limitation I see is that internally it upsamples the file to 48Khz. Though I didnt notice a reduction in quality but still. I will look up or try to contact the developers on this.
If we give the encoder a raw audio file instead of a wave, it can keep sample rate of 44100. This will also give smaller filesize than the current 48000 files.

So, I urge audio lovers to give this a try and post their thoughts.

Conversion tools are available from their download page.
opusenc.exe is the file.
I used the command: opusenc.exe --bitrate 512 --vbr --comp 10 input.wav output.opus

Have a good day !
 
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Thad E Ginathom

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#2
Thank you for the reminder. Time to see if my portable devices and their apps recognise opus.
Can we go beyond the frustrating 320kbps limitation in bitrate? This will bring us closer to lossless audio.
I don't think that the bitrate means anything outside of the context of the codec: the aim is to give higher quality for less bits.
the only limitation I see is that internally it upsamples the file to 48Khz
From a quick look at the site yesterday evening... it down-samples bitrates higher than 48 to 48. As it also limits to 20kHz (IIRC) you are not missing anything. If you feel you need supersonic content, I guess lossy compression is not the way to go.
 

humblebee

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#3
For those of you who are wondering as to why bother about a new format with an uncertain future, I have two things to say:

- WE make the future. We, the audio lovers, the first movers, the early adopters. It was the love for lossless audio and its adoption that has made FLAC what it is today. All this by community. The brands will follow. Where people are, they will be.

- Its one small step at a time. And then they add up. From midi to mp3. Then aac. Then this. On a bad day, compare 128kbps mp3 to 128kbps opus and it will put a smile on your face.

And regarding its use : Cloud storage and streaming of library becomes more viable now.


Two small updates regarding the codec:

It converts flac files as well. So no need to have wav files. It also converts from AIFF & Ogg files (Type opusenc.exe /?)

No need to type --vbr. Thats the default option.

So this will work:

opusenc.exe --bitrate 512 --comp 10 input.flac output.opus

@Thad:

Yeah you are right about bitrate. But what I meant was that both mp3 & aac limit us to 320 kbps which makes no sense to me.

Also regarding upsampling from 44.1 to 48, it MAY reduce quality if not implemented properly.
 
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Thad E Ginathom

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#4
I'm never too certain about the difference between up/down-sampling and sample-rate conversion --- if, indeed there is one, but with that proviso, yes, I agree. It is my (subjective and not blind-tested) experience that not all software sample-rate conversion is equal. I gave up one player because, either up or down, I thought it affected the sound.

It converts flac files as well. So no need to have wav files. It also converts from AIFF & Ogg files
It probably remains a bad idea to convert already-lossy files.

As to why-yet-another-format-?... Sure, there is always room for faster, smaller, more efficient and, in lossy formats, of course sounds better.

I guess it's also.... great science! Hats off to those Xiph guys :clapping:
 
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