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Topic: I want to know few things about Opus. Please help me out! (Read 1470 times) previous topic - next topic
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I want to know few things about Opus. Please help me out!

I've been using Apple AAC/QAAC 192kbps (TVBR) for the last few years and now i want to try out something new. I've converted some of my FLAC music into Opus 128 kbps (VBR) and I'm blown away by the audio quality.

But I want to clear some things. Please help me.
1. A lot of people on the Internet say that Opus should not be used for music. It's made for Voice data and telephony applications.
2. Opus Upsamples CD sample rate 44.1 Khz to 48 KHZ which is not Ideal and Could affect audio quality.

Are they right about all these things I've mentioned?

I only have 1 TB of internal hard drive and 2.1 speakers and i want to store more and more music in my hard drive. I guess Opus at 128 kbps (VBR) could really help me store a lot of music at very good quality.

I need your expert opinions and suggestions!

...and sorry for my english it's not that good.

Re: I want to know few things about Opus. Please help me out!

Reply #1
Quote
1. A lot of people on the Internet say that Opus should not be used for music. It's made for Voice data and telephony applications.

It is true that Opus excels at encoding voice, especially at lower bitrates, but as you yourself noted, if it gives superb results for music at low bitrates, what difference does it make? To get a bit more technical, Opus uses the linear predictive coding SILK algorithm for speech-oriented applications, and a CELT algorithm for both music and speech encoding, and uses both these modes, either combining them or using one or the other to get the best result, so it really is suited for both applications.

Quote
2. Opus Upsamples CD sample rate 44.1 Khz to 48 KHZ which is not Ideal and Could affect audio quality.

This really shouldn't be an issue. Chances are, you'll hear compression artefacts before the ones due to resampling. This thread is useful, as well as this from the Opus developers.

The gist is, you won't notice the resampling, and if the fact that it resamples bothers you, you shouldn't be using a lossy codec in the first place. Seriously, I wouldn't worry about it. I've tried to ABX a lot of music I have against a 96kbps Opus encode, and I can't ever distinguish the lossless original from the Opus file.
Lossless: flac --best --verify
Lossy: opusenc --bitrate 160

Re: I want to know few things about Opus. Please help me out!

Reply #2
I've been using Apple AAC/QAAC 192kbps (TVBR) for the last few years and now i want to try out something new. I've converted some of my FLAC music into Opus 128 kbps (VBR) and I'm blown away by the audio quality.

Ill say this... with Apple AAC(QAAC) (i.e. AAC-LC) or Opus you likely don't need to use anything else besides one of the following three settings given the information around here....

-96kbps = quality sound but at a efficient bit rate.
-128kbps = you can't go wrong with this and maintains a decent level of efficiency while still retaining a high percentage of the sound quality for the more sound quality conscious types.
-160kbps = sound quality is of higher important but still want some level of efficiency. any higher than this and efficiency is largely out the window.

beyond 160kbps is a bit overkill as I would say anything higher than 160kbps (maybe 192kbps TOPS) is a waste of storage space.

but with Opus I think you will be happy with 96kbps. even 64kbps is pretty good especially for the bit rate (Opus definitely has the edge over AAC-LC at about 64kbps and lower). but unless someone is really trying to cram a lot of songs into the least amount of storage space I would probably not use lower than 64kbps even though 48kbps is pretty good especially for the bit rate. hell, even 32kbps is quite good for such a low bit rate although I would rather just use 48kbps+ as you clean up the sound a fair amount for a minimal increase to the file size. so I guess for those trying to cram the most songs into the least amount of storage space and don't mind sacrificing the sound quality a bit... you will likely prefer 48kbps or 64kbps with Opus.

p.s. with MP3... I would probably not use lower than LAME v5 (130kbps) as that seems to be similar sound quality to Opus/AAC @ 96kbps. even for those who try to push MP3 as low as possible in bit rates.... I would suggest going no lower than LAME v7 (100kbps) as I feel going any lower than that point the sound quality hit starts to become more obvious. I would say a rough equivalent to LAME v7 (100kbs) in terms of Apple AAC-LC would be 64kbps (q27 TVBR). so you can see how Opus starts to stand out over these two as the bit rates get lower-and-lower.

I've tried to ABX a lot of music I have against a 96kbps Opus encode, and I can't ever distinguish the lossless original from the Opus file.

Yeah, I doubt I could either (especially on most equipment). that's why I figure for most people Opus @ 96kbps is plenty as after this point efficiency starts to drop off and bit rates beyond 128kbps are largely unnecessary with modern encoders like Opus/Apple AAC (although with MP3 I see LAME v5 (130kbps) as the minimum as that's about the equivalent to 96kbps Opus/Apple AAC).

I am curious if those who can ABX Opus @ 96kbps need rather expensive headphones or not? ; because I would imagine most people probably don't have headphones better than around $30 or so and from what I have heard unless you start shelling out $100+ (maybe even more) there ain't that much of a difference in headphones within the reasonably priced ranges (say something in the ball park of $50-ish and less).

or put it this way.... take a pair of random headphones or speakers and play a random song with Opus @ 96kbps... you won't complain about sound quality.
For music (especially on-the-go)...
-I suggest Opus @ 96kbps (or... 64kbps minimum, 128kbps maximum). *preferred choice*
-I suggest AAC(Apple) @ 96kbps (q45 TVBR) or 128kbps (q64 TVBR). *secondary choice*
-I use Foobar2000 (/w Encoders Pack etc) to convert FLAC to Opus/AAC(Apple).

Re: I want to know few things about Opus. Please help me out!

Reply #3
p.s. with MP3... I would probably not use lower than LAME v5 (130kbps) as that seems to be similar sound quality to Opus/AAC @ 96kbps.
It's not the case. Both Opus, AAC 96k outperform MP3 128k
We have performed a whole test to verify that.
https://listening-test.coresv.net/results.htm
https://listening-test.coresv.net/s/scores_by_tracks_closeup_en.png

An equivalent of MP3 128k is Opus 80k (not 96k).

Re: I want to know few things about Opus. Please help me out!

Reply #4
I've been using Apple AAC/QAAC 192kbps (TVBR) for the last few years and now i want to try out something new. I've converted some of my FLAC music into Opus 128 kbps (VBR) and I'm blown away by the audio quality.

-96kbps = quality sound but at a efficient bit rate.
-128kbps = you can't go wrong with this and maintains a decent level of efficiency while still retaining a high percentage of the sound quality for the more sound quality conscious types.
-160kbps = sound quality is of higher important but still want some level of efficiency. any higher than this and efficiency is largely out the window.

Thank you so much for this explanation. I think 128 kbps will be good for me.

Re: I want to know few things about Opus. Please help me out!

Reply #5
Apart from sound quality check whether your specific use case  throws up any issues. Being a newer codec there may be some issues you need to be aware of before you make the switch. Although I use opus pretty much exclusively now, I had compatibility  issues with some media servers, and I had to  rework some tagging before I was 100% satisfied.

Re: I want to know few things about Opus. Please help me out!

Reply #6
An equivalent of MP3 128k is Opus 80k (not 96k).

Hell, that makes Opus even better.

p.s. how would Opus @ 96kbps compare to MP3's next highest setting of LAME v4 (165kbps)? ; are these roughly comparable? ; from a hunch I would guess they would not be much apart either way especially with more recent versions of Opus.

Thank you so much for this explanation. I think 128 kbps will be good for me.

No problem.

or I can even post direct info from the wiki around here about those three bit rates on Opus...

96kbps = "approaching transparency"
128kbps = "Very close to transparency"
160-192kbps = "Transparent with very low chance of artifacts (a few killer samples still detectable)."

so that basically plays inline with my comments in my previous post and why I think 128kbps (give or take 32kbps) is the sweet spot for many as you can't go wrong with sound quality on any of those settings.

plus, looking at the link IgorC posted, which is a older version of Opus, you can see Opus @ 96kbps scored very well and this was July 2014 and apparently there have been some decent progress since then.
For music (especially on-the-go)...
-I suggest Opus @ 96kbps (or... 64kbps minimum, 128kbps maximum). *preferred choice*
-I suggest AAC(Apple) @ 96kbps (q45 TVBR) or 128kbps (q64 TVBR). *secondary choice*
-I use Foobar2000 (/w Encoders Pack etc) to convert FLAC to Opus/AAC(Apple).

Re: I want to know few things about Opus. Please help me out!

Reply #7
p.s. how would Opus @ 96kbps compare to MP3's next highest setting of LAME v4 (165kbps)? ; are these roughly comparable? ;
I'm not sure. It's up to listener, hardware, conditions...

Re: I want to know few things about Opus. Please help me out!

Reply #8
I am curious if those who can ABX Opus @ 96kbps need rather expensive headphones or not? ; because I would imagine most people probably don't have headphones better than around $30 or so and from what I have heard unless you start shelling out $100+ (maybe even more) there ain't that much of a difference in headphones within the reasonably priced ranges (say something in the ball park of $50-ish and less).

or put it this way.... take a pair of random headphones or speakers and play a random song with Opus @ 96kbps... you won't complain about sound quality.

It took me a really long time to ABX Opus @96kbps but I was able to in the end. The main problem was that I was expecting the typical issues with lower bitrates from other codecs like distortions and frequency balding but there wasn't any of that. Instead what I noticed was that the stereo field over 12Khz gets mostly centred so transient-like instruments and sounds that have hard pans to either side will mostly be centred. That was really tricky to detect and I got really lucky with the track I noticed that something was off and it took a lot of thinking to understand what was not what I was expecting. But after that jumping to 128kbps it's completely transparent to me, the issue above gets fixed.

Re: I want to know few things about Opus. Please help me out!

Reply #9
I am curious if those who can ABX Opus @ 96kbps need rather expensive headphones or not? ; because I would imagine most people probably don't have headphones better than around $30 or so and from what I have heard unless you start shelling out $100+ (maybe even more) there ain't that much of a difference in headphones within the reasonably priced ranges (say something in the ball park of $50-ish and less).

or put it this way.... take a pair of random headphones or speakers and play a random song with Opus @ 96kbps... you won't complain about sound quality.

It took me a really long time to ABX Opus @96kbps but I was able to in the end. The main problem was that I was expecting the typical issues with lower bitrates from other codecs like distortions and frequency balding but there wasn't any of that. Instead what I noticed was that the stereo field over 12Khz gets mostly centred so transient-like instruments and sounds that have hard pans to either side will mostly be centred. That was really tricky to detect and I got really lucky with the track I noticed that something was off and it took a lot of thinking to understand what was not what I was expecting. But after that jumping to 128kbps it's completely transparent to me, the issue above gets fixed.

That's interesting. I may try this someday with some Beatles (stereo) songs I have, since they really like to hard-pan some of their stuff.
Lossless: flac --best --verify
Lossy: opusenc --bitrate 160

Re: I want to know few things about Opus. Please help me out!

Reply #10
p.s. how would Opus @ 96kbps compare to MP3's next highest setting of LAME v4 (165kbps)? ; are these roughly comparable? ;
Now I'm remembering this test it's to expect  Opus/AAC 96/100k performing on par with MP3 -V4 ~160k.

Re: I want to know few things about Opus. Please help me out!

Reply #11
That's interesting. I may try this someday with some Beatles (stereo) songs I have, since they really like to hard-pan some of their stuff.
It won't work with real instrument based music. You need something that has a synth that is based on white noise or some kind of square wave that it has applied a high pass filter and it pans from one side to the other. There is no natural sound that meets this criteria and this case is so rare even on electronic music that it went under the radar for me for so long.

Re: I want to know few things about Opus. Please help me out!

Reply #12
That's interesting. I may try this someday with some Beatles (stereo) songs I have, since they really like to hard-pan some of their stuff.
It won't work with real instrument based music. You need something that has a synth that is based on white noise or some kind of square wave that it has applied a high pass filter and it pans from one side to the other. There is no natural sound that meets this criteria and this case is so rare even on electronic music that it went under the radar for me for so long.

I see. Hm, I wonder if I can whip up a test sample in Audacity using white noise then.
Lossless: flac --best --verify
Lossy: opusenc --bitrate 160

Re: I want to know few things about Opus. Please help me out!

Reply #13
It took me a really long time to ABX Opus @96kbps but I was able to in the end. The main problem was that I was expecting the typical issues with lower bitrates from other codecs like distortions and frequency balding but there wasn't any of that. Instead what I noticed was that the stereo field over 12Khz gets mostly centred so transient-like instruments and sounds that have hard pans to either side will mostly be centred. That was really tricky to detect and I got really lucky with the track I noticed that something was off and it took a lot of thinking to understand what was not what I was expecting. But after that jumping to 128kbps it's completely transparent to me, the issue above gets fixed.

I doubt it would bother me as I generally prefer music to be in both speakers more evenly instead of shifting back and fourth etc between the left and right speakers. still, I imagine that's some good info for some people and they might prefer the 128kbps option instead since it more accurately matches the way the lossless audio is meant to be.

also, since you said it took a very long time to ABX Opus @ 96kbps that gives me even further confidence that one can't go wrong with 96kbps (or higher) as if one is focusing quite hard to ABX 96kbps then it's obviously a strong performer in the sound quality dept.

p.s. but come to think of it... one weird thing I noticed with Opus v1.2.1 or the v1.3 RC (the one the Opus developer posted almost two months ago now) is on a lossless Korean speech file IgorC posted there was a volume change in the left speaker between the lossless file and the lossy files which made it easy for me to ABX on the volume change alone.... https://hydrogenaud.io/index.php/topic,116059.msg958101.html#msg958101 ; the bottom part of my post there explains things.

Now I'm remembering this test it's to expect  Opus/AAC 96/100k performing on par with MP3 -V4 ~160k.

Okay, thanks for the info as that seems to further confirm how obsolete MP3 is in comparison to Opus/AAC as MP3 needs not far from twice the bit rate of Opus/AAC for a similar level of sound quality.

so if one has a standard with Opus/AAC @ 96kbps as a minimum that would pretty much require MP3 @ v4 (165kbps) and if one was going to use MP3 @ v4 (165kbps) they would be better off using Opus/AAC at either 96kbps or if they don't mind using the 160kbps range they would be better off using Opus/AAC as that would basically make the sound quality fully transparent or real close to it. with that said... I realize this assumes Opus/AAC is a option on their device as if MP3 is all they got then this won't matter.

that's basically why I think in terms of lossy formats the only two worth using at this point in time are.... Opus or AAC(Apple/QAAC) because that covers the highest possible sound quality at the lowest possible bit rates (i.e. Opus) and wide enough compatibility between the two formats (i.e. AAC for when Opus is not a option).
For music (especially on-the-go)...
-I suggest Opus @ 96kbps (or... 64kbps minimum, 128kbps maximum). *preferred choice*
-I suggest AAC(Apple) @ 96kbps (q45 TVBR) or 128kbps (q64 TVBR). *secondary choice*
-I use Foobar2000 (/w Encoders Pack etc) to convert FLAC to Opus/AAC(Apple).

Re: I want to know few things about Opus. Please help me out!

Reply #14
1. A lot of people on the Internet say that Opus should not be used for music. It's made for Voice data and telephony applications.
Opus is two parts: SILK is made for voice, CELT is made for music. When it really comes down to it, CELT is so good that it does speech quite well too, but either way, Opus is the highest-quality low-delay codec ever developed, and still manages to be the highest quality archival format.

Re: I want to know few things about Opus. Please help me out!

Reply #15
1. A lot of people on the Internet say that Opus should not be used for music. It's made for Voice data and telephony applications.
Opus is two parts: SILK is made for voice, CELT is made for music. When it really comes down to it, CELT is so good that it does speech quite well too, but either way, Opus is the highest-quality low-delay codec ever developed, and still manages to be the highest quality archival format.

(Bold emphasis mine).

I'm intrigued by the part I made bold; generally, by "archival" one means a file format that isn't used much for the purposes of listening, but to keep around stored somewhere in case, say, another lossy encode is required. This is usually, thus, a lossless format such as FLAC, and not a lossy encode. Or am I misunderstanding something?
Lossless: flac --best --verify
Lossy: opusenc --bitrate 160

Re: I want to know few things about Opus. Please help me out!

Reply #16
Opus is two parts: SILK is made for voice, CELT is made for music. When it really comes down to it, CELT is so good that it does speech quite well too, but either way, Opus is the highest-quality low-delay codec ever developed, and still manages to be the highest quality archival format.
I'm intrigued by the part I made bold; generally, by "archival" one means a file format that isn't used much for the purposes of listening, but to keep around stored somewhere in case, say, another lossy encode is required. This is usually, thus, a lossless format such as FLAC, and not a lossy encode. Or am I misunderstanding something?
Here "archival" only means in a way that's not interactive. Your music player counts as "archival" in that sense because you're not trying to listen to audio you've encoded only a few milliseconds before. It's a generally easier task than interactive applications (e.g. videoconference) because there's no constraints of the size of the chunks you process and how much you look at the "surrounding audio" to process a chunk.

 

Re: I want to know few things about Opus. Please help me out!

Reply #17
Opus is two parts: SILK is made for voice, CELT is made for music. When it really comes down to it, CELT is so good that it does speech quite well too, but either way, Opus is the highest-quality low-delay codec ever developed, and still manages to be the highest quality archival format.
I'm intrigued by the part I made bold; generally, by "archival" one means a file format that isn't used much for the purposes of listening, but to keep around stored somewhere in case, say, another lossy encode is required. This is usually, thus, a lossless format such as FLAC, and not a lossy encode. Or am I misunderstanding something?
Here "archival" only means in a way that's not interactive. Your music player counts as "archival" in that sense because you're not trying to listen to audio you've encoded only a few milliseconds before. It's a generally easier task than interactive applications (e.g. videoconference) because there's no constraints of the size of the chunks you process and how much you look at the "surrounding audio" to process a chunk.

Ah, that's interesting, so indeed I was misunderstanding. Thanks for the explanation!
Lossless: flac --best --verify
Lossy: opusenc --bitrate 160

 
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