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24
Listening Tests / A Session In The Abyss: xHE-AAC vs OPUS at 12, 24 and 32 kbps (voice & music)
Last post by guruboolez -
Introduction

I made several listening tests in my life and at various bitrates (from 48 kbps lately to 190 kbps many years ago). But I never thought I would make one at 12 kbps.

Just to put this little value into perspective: at 12 kbps one hour of music only takes 5.40 Mb—which is usually the size of a single track at 128 kbps. Hotel California full album: 3.97 Mb. Back in Black: 3.82 Mb. Thriller: 3.86 Mb. One full album is half the space needed by a JPG shot done with my cheap smartphone! For older people who knew CD-R burning: 130 hours of music could be stored on a 700 Mb CD-R… Every file is insanely small! And for streaming purpose, EDGE poor network is still enough to stream music without issue (in a tunnel, on mountain…).


But why doing this test?
First, to get some comparison data at unexplored regions and fill some gaps. I am really curious to check how modern audio codecs are dealing with such huge bitrate starvation. When a new video or pictures format appears it’s immediately tested at ultra low bitrate—but audio isn’t. If you take a look on the next graph, you won’t see any popular format below 40 kbps:

(credit: opus-codec.org)

Now that a modern opponent to OPUS is easily available (Exhale first, now Fraunhofer's encoder with EZ Audio Converter) an interesting duel is at least possible.


Second reason: For the sake of curiosity I recently forced myself to listen to ~35 kbps xHE-AAC on my phone, streamed over bluetooth in my car or earbuds and the result was far from disaster. In fact, it was a bit better than acceptable. I even listened to these ultra-low bitrate encoded albums many times during two weeks. This was a real big surprise. Because I’m not fond of low bitrates: 20 years ago I discovered --r3mix, then became a LAME --alt-presets pilgrim and finally turned into a MPC priest. I spent afternoons and weeks on ABX softwares just to get significant scores on castanets samples… It would be an understatement to say that I was totally neurotic about sound quality. Fortunately I’m clearly more tolerant today. So these low bitrate performances are something I wanted to investigate, for practical usage. If I can put on my phone a lot of stuff I rarely listen to without ruining the storage capacity it’s definitely something I should try (it’s less expensive than streaming subscription and even much more reliable—I often get off cellular networks while wandering in the forest or in nature).
Low bitrate encodings is also a very reasonable choice for audiobooks and even movies ripping (Netflix made recently the switch to xHE-AAC to improve quality and efficiency). That’s why 20 samples of voice are included here.



Challengers: The choice of formats/encoder is limited to the most recent ones: OPUS (2012) and USAC/xHE-AAC (2012?). Both are unified formats for voice and music coding. As Exhale open-source xHE-AAC doesn’t handle such low bitrate, only Fraunhofer’s xHE-AAC (included in EZ-CDA Converter) encoder is able to compete here.
Opus : last version on official website (1.31, executable). VBR is used (auto detection between voice and music).
xHE-AAC : version by Fraunhofer included in EZ CD Audio Converter 9.3.1. The Fraunhofer (FhG) encoder was updated with 9.3.2—but I missed the update so it’s not tested here. I used VBR preset 0 (24 kbps) and CBR for 12 and 32 kbps.

BITRATE: Average bitrate for a large CD collection

Opus 12Opus 24Opus 32FhG 12FhG VBR 0FhG 32
12,0 kbps25,7 kbps34,0 kbps12,0 kbps24,0 kbps32,0 kbps
(+0 %)(+7.8 %)(+6.25 %)(+0 %)(+0 %)(+0 %)
VBRVBRVBRCBRVBRCBR
The full bitrate table is available here.

SAMPLES: 60 samples in 6 groups:

music: billboard 2010-2020 greatest hits. Standard range for each: 01.00.000 to 01.20.000. 10 samples, best-sellings music. Difficulty: average.
music: classical: 10 musical samples from a larger collection. Classical music. Criteria selection: favorite moments. Difficulty: below average.
music: HA.io: 10 samples submitted by Hydrogenaudio’s members. Many of them were chosen because they revealed some issues with encoders of the past (usually LAME MP3). Difficulty: above average.
music: problem: 10 samples shared on HA.io that revealed strong encoding issues with encoders of the past. Mostly issues like pre-echo or additional noise on transients. Difficulty: hard to very hard
voice: audiobooks: 12 samples from audiobooks. 6 male, 6 female. 8 different languages. Criteria selection: random or favorite part. Difficulty: easy.
voice-movies: stereo samples of famous soundtrack (dialog, with or without music and/or ambient noise). 48 KHz, 16 and 24 bit. Criteria selection: cult dialog, favorite moment, or random. Difficulty: easy.

All samples are available here:
https://www.dropbox.com/sh/zjephy3g54j4gur/AACjGhM9tabl26n7s4ihYl2Ra?dl=0

SOFTWARE & HARDWARE:  I used Java ABC/HR. All files were normalised. Two first seconds of each encoding were discarded from evaluation. An AKG Q701 was plugged on the headphone jack of my computer (I was unable to run my DAC on ABC/HR).



RESULTS:


On the graph I put the overall score for all 60 samples on the middle of each column, the result for the 40 musical samples on the left and the result of the 20 samples of voice on the right.


  • At 12 kbps Opus is totally lost on music; it performs significantly better on voice but quality is not truly convincing. The overall result is very poor: sound is muffled, mono-ish, and there is often a bad amount of noise/grain. xHE-AAC sounds differently but much better: lowpass is not as strong, stereo is here but often weird (like out of phase). There’s a hollow and synthetic sound image on many samples. Music is not good to my taste but it’s not catastrophic either. Voice samples (especially movies) are almost acceptable.
    ► 12 kbps has nothing enjoyable but it sounds much better with xHE-AAC than with Opus.
  • At 24 kbps Opus is making a big step forward. Sound is not muffled anymore and the stereo image is quite excellent. The problem is a layer of  strong and harsh sibilant artifacts that didn’t exist at 12 kbps. In many cases there’s still an aggressive amount of grain/noise. Music at 24 kbps is still poor (score < 2.0); audiobooks and movies are now acceptable though irritating (score < 2.50). xHE-AAC has much less issue with stereo here and sound is much less synthetic. Music is not stellar but is quite acceptable now (score : 2.77). And voice has minor issues and is good (3.43 on average, and even 3.70 for movies! Hello Netflix!).
    ► 24 kbps is now usable with xHE-AAC (average score: 2.99) and is quite enjoyable with voice recording. OPUS is not really usable on music and its score is still lower than USAC CBR 12 kbps! On voice OPUS 24 kbps VBR reaches the same score than USAC CBR 12. In other words OPUS is far less efficient than xHE-AAC at 12 and 24 kbps.
  • At 32 kbps Opus is still not very pleasing with music (score: 2.38) but on voice it’s now more than simply usable (3.19). xHE-AAC makes quite a good job on music (3.21) and is almost stellar on voice (especially movies: score = 4.0, hello again Netflix).
    ► xHE-AAC outperforms OPUS at 32 kbps (in fact 34 kbps) and really plays in a different league.
  • 96 kbps USAC (here with Exhale) is excellent in comparison and in absolute terms (probably a bit overrated here as it's included as high anchor)

To finish I just want to remind that this evaluation is personal. OPUS and xHE-AAC have very different kind of distortions and judging one less annoying to a different one if very subjective :)

As always thanks to kamedo2 for its useful tool!
25
General Audio / Re: Codec / Encoder terminology
Last post by Markuza97 -
Answers above are very technical.
I hope this is somewhat easier for you to understand.
(This is not 100% technically correct, but it is the easiest way for him to understand)

Your sound card only accepts uncompressed PCM.
Uncompressed PCM is huge. It wastes a ton of space, we want to compress it.

Format is a written standard that defines what compression technologies/techniques you can use.
Example: Format says you can only have 2 channels with sampling rate up to 48 kHz.

In order to create a file that complies to that standard, you will need encoder.
That encoder is limited to 2 channels and 48 kHz.
If your encoder can create 6 channel 192 kHz file, then your encoder doesn't comply to that format.

Encoder will create stream.
Stream is useless for us. We are missing some crucial information like number of channels, sampling rate...

We want to put it inside container.
Container, just like the name says, contains something, in this case stream.
But, container also includes header and that header will give us all the information (mentioned above) we need to "play" that file.

Okay, so we have our file, how do we actually play it?
Now you will need decoder.
Decoder will "decompress" your file into uncompressed PCM so you can play it!
27
General Audio / Re: Codec / Encoder terminology
Last post by Porcus -
So, is "container" the same as "file format" or is the "file format" contained in a "container"?
Rather, a "container" is a type of file format structured to say "I am a box and I contain the following:"
(By "type" here I just mean how humans designed them to work - not how it looks under electron microscope to your hard drive.)
A text file is not a container file. It is not designed to say that "Here is a list of content, content has this property, and now I am done with describing this, so the actual content that you want to put in here, will follow this colon:"
Nitpickers can tell you about byte-order marks and the like, but essentially to you as an end-user: a text file has the text data, and that's it.

On the other extreme, archive formats like .zip are not designed to have anything but what you put into them by way of other means, and they can take whatever is organized as a file. But apart from the restriction - to files - you don't get much info out of someone saying "a .zip file". (Contrast that to "an mp4 file".)
And to make use of the data, you need something that can open the .zip ("open" is imprecise: "open and understand" is clear enough?) - and something that make use of what is inside the box. Your software must know the container and it must know how to read the content.
Same with Matroska; if you put a PCM stream into a Matroska and try to play it by something that does not know the Matroska file format - no luck. And if you get by some obsolete audio format your player cannot handle, and put it into a Matroska container - after all your player can open Matroska - you are in for a disappointment.

But if you can read a text file you can read a text file. Well I am simplifying, but you get it.
28
Support - (fb2k) / My foobar has been crashing for the past few months.
Last post by ProTofik -
Hello,

I have been using foobar2000 as my default music player for probably more than 10 years now, and I listen to music for hours every day. I never had any issues until few months ago.

My foobar started crashing when listening to music few months ago. The timing seems random, sometimes few minutes into listening to music, sometimes after few hours, sometimes it goes fine for 2-3 days without any problem. I send crash report every time.

I'm on latest version v1.6.5. All my addons are up to date as well, as have always been the case over the past many years. I've used beta trouble-shooter on foobar website which recommend that I remove one plugin, which I did but crashes still occur.

Not really sure how to begin the troubleshooting process. Does foobar create any crash log anywhere I could analyse?

Normally I would start with reverting any recently introduced changes to my system, but it's a moving beast so who knows where to start. I haven't added any new addons. I probably upgraded foobar to latest version as I do every few months. I install Windows Updates, drivers updates, etc...
29
3rd Party Plugins - (fb2k) / Re: foo_youtube
Last post by Fidde -
thank you Mojo. I see a lot of investigation and experimental work :) and proberly some fugh-ups lol.

Just tryied (bad spelling, sorry) you'r suggestion. It worked perfect, but gave me another question:
Is it taking the sound/video directly from youtube?


Okey.. sorry, now i need help. To see the video, I doo what suggestet, and then I getting this fault-prompt:
LAV Splitter: not found
LAV Video: not found
30
General Audio / Re: Codec / Encoder terminology
Last post by guruboolez -
A container is more a storage bag: you can put several files in different formats into one single container.
Matroska and MP4 are both containers. Into one single container, you can put:
• different audio files (stereo + multichannel for example; or also original soundtrack + dubbed soundtrack + commentary; lossless and lossy…)
• one or more video file
• subtitles (image or text)
• metadata
• additional files (jpeg…)

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