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MLXXX

Developing a simple petition for improved bitrates and increased spectrum allocation for DAB+ broadcasting in Australia

43 posts in this topic

20 minutes ago, alanh said:

Yes and the CD is of worse quality

Not for adult human beings. It is found that human beings in double blind tests have been unable to distinguish a 44.1kHz 16 bit stereo CD at usual recording and listening levels from a 192kHz 24 bit original source.  (Dogs might be able to tell a difference because of their higher upper frequency limit of hearing.)

Why you are trying to quibble about such matters as resampling and dither makes no sense to me when what we are discussing are low/moderate bitrate codecs. If you examine the published test results, 64kbps HE-AAC is by no means transparent for human test subjects. And yet CD quality (at usual recording and playback levels, and mastered using dither) is transparent for human test subjects.

 

23 minutes ago, alanh said:

Why are you avoiding my question.

I have given my own subjective impressions many times in the past. I will wait until I (or others) have uploaded some current examples (or linked to some new examples) before offering further subjective impressions. 

Why you are fixated on my subjective impressions I don't know, alanh. It is no secret that 64kbps HE-AAC is not transparent. There are plenty of test result graphs and tables. And I'm sure there are published subjective reports too if you were to just search for them, rather than badgering me!

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7 hours ago, alanh said:

The 44.1 kHz sample rate is so it can be locked to NTSC video which is no longer used in the USA.

Huh?

Youre crazy Al. Go do the math. 44.1KHz fits nicely into PAL 25 FPS fields, but not NTSC 29.97 FPS fields.

Or if you accept they pushed NTSC from 29.97 FPS to 30 FPS to make it work its just as true to say "The 44.1 kHz sample rate is so it can be locked to PAL video which is no longer used in the rest of the world". 44.1kHz was chosen because it could be fitted into both.

p.s. 48kHz doesnt fit in to PAL or NTSC either.

7 hours ago, alanh said:

More importantly the down sample is synchronised so exactly each alternate sample is removed. Dithering is trying to cover up the distortions created.

Go away and learn about noninteger resampling before you make yourself look more stupid.

7 hours ago, alanh said:

Why are you avoiding my question.

After taking a refresher look at the history of this subject on this stupid forum its clear MLXXX has answered your question many times before. You just refuse to beleive him or others and keep on backing up your own opinions with wild assumptions ("3.5 million listeners cant be wrong"? really?!).

Since hes answered you many time before & you just use it as another excuse to not beleive him I dont blame him for not bothering to answer you again. You want to argue with him over that? Do your own bloody spadework.

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13 hours ago, Pesto Lovin' Man said:

44.1KHz fits nicely into PAL 25 FPS fields, but not NTSC 29.97 FPS fields.

Or if you accept they pushed NTSC from 29.97 FPS to 30 FPS to make it work its just as true to say "The 44.1 kHz sample rate is so it can be locked to PAL video which is no longer used in the rest of the world". 44.1kHz was chosen because it could be fitted into both.

p.s. 48kHz doesnt fit in to PAL or NTSC either

I think there could be a problem with that.
48kHz is what is used in the television industry - certainly in Australia at the least, and if the "samples" I have which is sourced from overseas is any indication, so do they.
Here are a couple of interesting reads

http://www.tvtechnology.com/opinions/0004/digital-audio-sample-rates-the-48-khz-question/184354

https://en.wikipedia.org/wiki/Sampling_(signal_processing)   [This link needs the bracket on the end, but is doesn't seem to want to work in the translation here.]

I was talking with a tech/engineer today about this and he said 48kHz is used because it fits in with the video rate whereas 44.1 doesn't - or at least not when the system is setup to use 48.

Edited by hrh

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hrh,

The sample frequency must be at least 2.2 times the highest frequency to be sampled, but it requires a good filter prior to sampling, it is easier if it 2.5 times.

The AES standard for all audio except the CD has been 48 kHz for a very long time. The audio industry knew that TV was going digital and as a result there will not be any need for a lock to NTSC frequencies.

All HD video formats divide in whole numbers to 48 kHz. Being slightly higher frequency the filter requirements are not as tight.

Alanh

 

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MLXXX,

Has it ever occured to you the following

1. The manufacturer who made the DAB Module in your Roberts radio has gone through new 4 models of the chips used to receive the signal.

2. Manufacturers have improved the accuracy of the encoders. Even the designers of HE AAC V2 have a new model specifically designed for speech.

In both cases microprocessors have become faster and more capable.

If these low bit rates were so annoying you should be able to quote examples off you head. You have not done this so as a result the bit rates selected by our broadcasters is adequate. This is demonstrated by the fact that no one has joined your petition for increase.

The truth is that if you don't know the source you cannot detect the poor quality caused by the low bit rate.

You should apologise to Digital Radio Plus, the ABC and all the posters on this topic over the last 7 years. You cannot detect low bit rate errors on current broadcasts.

Alanh

 

Edited by alanh

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15 minutes ago, alanh said:

MLXXX,

Has it ever occured to you the following

1. The manufacturer who made the DAB Module in your Roberts radio has gone through new 4 models of the chips used to receive the signal.

2. Manufacturers have improved the accuracy of the encoders. Even the designers of HE AAC V2 have a new model specifically designed for speech.

In both cases microprocessors have become faster and more capable.

You have raised these or very similar points before, alanh. However, turning on a DAB+ radio in 2017 in a showroom and trying out a selection of services will soon reveal quite noticeable artefacts with the lower bitrate services.  If encoders in use for DAB+ broadcasts in Brisbane in 2017 are somehow more effective, it's certainly not obvious to my ears.

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13 hours ago, hrh said:

I think there could be a problem with that.
48kHz is what is used in the television industry - certainly in Australia at the least, and if the "samples" I have which is sourced from overseas is any indication, so do they.

I was talking about the digital pro audio recording systems that were around before & at the beginning of the CD era that Alan was refering too as his "reason" CD is 44.1kHz. They stored uncompressed PCM audio as a video luma signal on either NTSC (44.056kHz) or PAL (44.1kHz) recorders & couldn't fit 16 bit 48kHz asmpled audio into a NTSC or PAL video field/frame.

edit: at least the ones that were 16 bit did. There were others but they were 12/13/14/15 bit systems at differing bitrates e.g. NHK/Columbia had a 14 bit 47.25kHz system using either 2" or umatic that nearly became common.

His story is wrong or at least very misunderstood, although its a common belief thanks to dozens of websites & wikipedia that get it confused & wrong too.

Modern video studio & broadcast tape formats & digital broadcasts were developed later & are a different matter, & yes 48kHz sample rate is common. Though theres no particular reason that 48kHz fits any compressed tape/broadcast format better - its compressed so theres no strict relationship between sample rate & bitrate, its padded to fit the container if needed & usually timestamped for sync.

Edited by Pesto Lovin' Man

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MLXXX,

"However, turning on a DAB+ radio in 2017 in a showroom and trying out a selection of services will soon reveal quite noticeable artefacts with the lower bitrate services.  If encoders in use for DAB+ broadcasts in Brisbane in 2017 are somehow more effective, it's certainly not obvious to my ears. "

So when did you do this?. You still haven't stated what is the problem now.

When are you going to a broadcaster with your request to increase the data rates?

What will be your answer when they say to what is wrong with our existing broadcasts? You say go to my posts in the dtvforum in 2009 for the answer. It really sounds like a pressing problem that the broadcasters need to solve. Then you say I only have a pair of signatures for this petition and one is mine. They say that there is 3.5 million listeners and many are listening to the simulcast of their FM and AM programs.

I would like to see the expressions on both their and your faces!

The problem is that you believe there is a problem, you have never blind tested your belief to prove it is just that.

Alanh

 

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Pesto loving man.

48.000 kHz has been an Audio Engineering Society standard for a very long time. They set most audio standards.

A chief motivator for 48 kHz is that there is a whole number of samples per frame in 24, 25 and 30 frame/s TV systems along with film. So when time code is used for editing particularly separate sound and vision on a program there is no drop frames. As a result the edit decision lists have no confusion of dropped frames from the video in NTSC based systems and no drop frames in the audio. In addition because it works with 24 frame/s the movie industry has been using it extensively.

Without dropped frames, timecode is used to syncronise the recording and playback of separate sound recorders and the video recorders.

Alanh

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6 minutes ago, alanh said:

48.000 kHz has been an Audio Engineering Society standard for a very long time.

Not as long as 44.1kHz CD though which is what I was talking about in reply to your garbage statement about 44.1kHz.

Edited by Pesto Lovin' Man

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12 hours ago, alanh said:

MLXXX,

"However, turning on a DAB+ radio in 2017 in a showroom and trying out a selection of services will soon reveal quite noticeable artefacts with the lower bitrate services.  If encoders in use for DAB+ broadcasts in Brisbane in 2017 are somehow more effective, it's certainly not obvious to my ears. "

So when did you do this?. You still haven't stated what is the problem now.

There is no mystery as to the "problem". It is what it has always been with a great number of the DAB+ radio services: insufficient bitrate for the audio. Here's a picture taken today of a DAB+ radio at Myers Chernside (Brisbane northside) tuned to 4KQ Classic Hits:

20170419_144600MyersDABradio_zps0skjuqsf

 

Although nominally a 48kbps service, the actual audio bitrate of 4KQ Classic Hits currently is substantially less (about  34.6kbps, HE-AAC v2).

That is a low enough rate for encoding artefacts to be noticeable almost continually for my hearing. What did I hear when listening to the above radio today?  Well, here's a quick list of what struck me immediately:-

1.  Hi-hat cymbals sounded like a mush of high frequencies rather than a clear cymbal sound. The percussive sound of the snare drum was similarly affected.
2. A writhing, phasey quality affected the sound overall. [This is a tell-tale psychoacoustic codec artefact. You get a similar sounding artefact with low bitrate mp3.]
3. A general lack of verve. 

These and other effects were sufficiently marked as to reduce my listening enjoyment substantially. Although I don't mind the genre of the music, the audio quality of this particular DAB+ service would be too irritating for me to be comfortable listening to it for an extended period. I would move on to a higher bitrate DAB+ service, or to an FM service.

There you go, alanh. Some subjective impressions of mine formed today. However there's nothing unique in what I've reported. Nothing new. These types of artefacts have been present since the start of DAB+ broadcasting in Australia.  They have been reported on fairly extensively on this website over the years.  And of course the published literature has plenty of graphs and tables of less than ideal MUSHRA scores for low bitrate HE-AAC. 

Your apparent suggestion that there are no audible impairments is beyond my understanding. Such a suggestion conflicts with official reports of formal testing of low bitrate HE-AAC on human subjects, and it conflicts with anecdotal adverse reports on this forum from people who have tried to listen to low bitrate DAB+ radio services.

Edited by MLXXX

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MLXXX,

Finally you have gone done some listening to a new radio.Then you pick a radio with tiny speakers which does not contain a pair of tweeters which can accurately reproduce high frequencies. Those speakers are trying to reproduce lower frequencies.When are you going to listen to a radio which is not a portable or tabletop receiver which all have poor sound quality regardless of the signal source. As I have previously suggested you listen to a DAB+ car radio they generally have better speakers.

As I have already suggested that you use nationally syndicated stations so we can listen to the same programs.

6IX had similar problems a few years ago, but they moved into a new studio complex and the problems have disappeared, but the bit rate is still 48 kbit/s. You had better to complain to 4KQ.

You are yet to convince lots of people to join your petition.

Alanh

 

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9 hours ago, alanh said:

You are yet to convince lots of people to join your petition.

No such petition exists as yet, alanh, for Australia, whether put together by me or by anybody else. If and when one is drawn up and advertised, there will be the opportunity for people to subscribe to it.
 

9 hours ago, alanh said:

.Then you pick a radio with tiny speakers which does not contain a pair of tweeters which can accurately reproduce high frequencies.

 That radio at Myers Chermside is a premium standalone radio with speakers quite capable of delivering good quality, pleasant sounding, treble, as they did for me when I tried out some higher bitrate DAB+ stations.

There is no need for ruler-flat extended range speakers just to listen to a radio broadcast.  And if you did, extravagantly, connect up a very expensive audiophile system to reproduce the audio from a low bitrate DAB+ broadcast, that would not hide the artefacts. They would still be there, perhaps even a little easier to hear; perhaps even more irritating!

 

Listening to DAB+ radios in Brisbane showrooms

Most showrooms in Brisbane have too low a signal strength for DAB+ radios to work. One place I've found with a selection of DAB+ radios connected to power and capable of receiving the DAB+ signals from Mt Coot-tha is HN in the Valley. (Earlier this week I found that one of the radios there with rather better quality built-in speakers, a Panasonic SC-HC49DB, could be got to work with the help of a friend to lift the loose wire antenna into the air for you, giving you freedom to try different DAB+ services without reception cutting out!).

 

DAB+ time functionality useful for alarm clock radios

The majority of DAB+ radios on sale by the main electrical goods retailers in Australia have only mono speakers. There is a great number of alarm clock style DAB+ radios. Such radios have the convenience of being able to access the current time using the DAB+ signal. There is no need to set the time manually. It appears these radios can fully resume after a mains power outage without issues, and in particular without the need for a battery.

Edited by MLXXX

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Tonight I've been looking for website material regarding DAB+ perceived quality in Australia, beyond the many references that exist in the archives of this forum. Here are two sources of material that point out negatives:

1.  A detailed webpage from 2010 titled Digital Radio Plus: NOT - Say no to DAB+ and its minuses includes this comment:

DAB+ (on the majority of stations, as of 2010) can be described as an audio signal that has been split into a two bands, with the low (bass to mid) band sounding muffled (as if you had pillows or several sheets over the speaker), combined with an overly accentuated and crunchy high (treble) band for good measure. It may re-create some of the original sound timbre, but the results are disastrous for music such as a orchestral pieces (the stringed instruments lose most of their nuances). ABC Classic FM on DAB+ does no justice to the music.

Unless you enjoy the horrible 'tinnyness', raspy, metallic, youtube-like sounding audio compression used on DAB+ (in the current state of allocations), it would be better to stick to FM.


 

2. An informal thread on Whirlpool forum from 2012 titled DAB+ low bitrate transmitted begins:

Why is DAB transmitting at such low bit rates? the quality is no where near an FM tuner? It is completely un usable on any sort of reasonable gear unless you regard listening to the horse races an a portable am radio stuck to you ear as reasonable. Or perhaps listening to your portable on a tram with your iBuds may be better than an FM radio in the same circumstances and for that sort of use it may well be truly better especially if you only want to hear the news. As far as high quality material in your home, a few minutes is about all one can stand and then it is back to the FM tuner. Why bother? 

 

In contrast to the above, I note that there are many articles that paint a positive picture of DAB+ sound quality, especially those used by the digital radio industry in promoting DAB+.

In my searching this evening I came across an article about DAB+ (that appears to come from 2010) attributed to Steve Ahern. The website states: Steve Ahern is an international broadcast training consultant, broadcaster, author and media commentator, specialising in Radio and New Media.  The article, titled Steve Ahern explains Digital Radio, includes these words:
 

... Digital radio quality is light years better than AM, and better than FM quality, while using much less bandwidth. 

How many bits per second a station chooses to use determines the quality of its signal. The improved form of digital radio used in Australia, called DAB Plus (DAB+), can deliver twice as many stations as the original form, DAB, used in the UK, Europe and elsewhere. Many countries are now examining the possibility of upgrading to the DAB+ standard and are looking at Australia to prove that the new improved system works. So far they are concluding that it works very well.

Most stations in Australia are getting good FM quality signals at a data rate of 48 kilobits per second, one third of the bit rate used to deliver similar quality in the older system.


 

What does the last sentence mean by “FM quality signals”? Is it the quality to be expected from a car radio driven about town in a good signal strength area, the quality from a quality FM receiver in the home connected to an external antenna receiving a strong signal, or the quality to be expected from a portable FM radio using its built-in rod antenna, located in a fringe reception zone or inside a steel structured building? I think a number of us who have listened to DAB+ broadcasts in Australia would disagree that 48kbps gives anything like as good as FM quality, in circumstances where the FM radio is connected to a good antenna and receiving a healthy signal.

And what is meant by a data rate  of “48kbps” in this context? Is it simply the nominal bitrate of the particular DAB+ service, as displayed by a DAB+ radio if a listener chooses to display such information; or is it the bitrate actually devoted to the audio itself, a smaller figure known only to specialists, that takes into account the overhead of error correction, and any bitrate reserved for Program Associated Data?

I suspect many people over the years who have written that "48kbps gives FM quality" have not turned their minds to either aspect.

Nor I suspect have they actually compared for themselves reception of a high signal strength FM broadcast with reception of a "48kbps" DAB+ radio simulcast (be that the nominal rate of the DAB+ service or the actual rate of the compressed audio itself). Because if they had, they might have had real doubts that "48kbps gives FM quality".

 

A forum poll

In the next few days I'll see if I can put together some comparison files of reception of off-air FM [using good signal strength] and simulcast off-air DAB+ "at 48kbps" for the purposes of a forum poll. Should I use a DAB+ service that is at an overall data rate of 48kbps or one where the bitrate for the embedded HE-AAC audio stream is at around 48kbps?  Which interpretation would be more appropriate? 

Edited by MLXXX
Paragraph added: "A forum poll".

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MLXXX,

Get off the computer and into the real world.

Go to live concerts with real unsampled unamplified sound for example at Qpac and the QSO has a new conductor.

I note that there are many broadcast streams at 48 kbit/s and you only complain of a single faulty one. What about the others. No complaint about any of the 80 kbit/s streams.

Use your ears and not a search engine for others who copy each other and the myths keep circulating.

Lets face it your petition is a failure, your views are not held by others.

Alanh

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1 hour ago, alanh said:

Go to live concerts with real unsampled unamplified sound for example at Qpac and the QSO has a new conductor.

You have such a limited memory, alanh. I have told you in the past that I attend orchestral concerts regularly.

I also happen to be a musician and currently perform in a number of different groups.  I hear live, unamplified, symphony orchestra instruments very frequently indeed.  

 

1 hour ago, alanh said:

I note that there are many broadcast streams at 48 kbit/s and you only complain of a single faulty one. What about the others.

It isn't "faulty". Its sound quality is quite typical for a low bitrate DAB+ broadcast. I see that you describe it as 48kbps, the nominal bitrate.

 

1 hour ago, alanh said:

Lets face it your petition is a failure, your views are not held by others.

I would remind you: there is no petition at this stage. The purpose of this thread is to gather together some points that might feed into a petition. 

As for others not holding my views, what an absurd statement! There have been many contributions to this forum over the years, from a variety of members, bemoaning the poor quality of many of the DAB+ services.  And in any case, official published test results indicate audible impairment perceived by test subjects for HE-ACC stereo at bitrates well in excess of 48kbps, let alone at the audio bitrate of a nominal 48kbps service.

Edited by MLXXX

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This should keep everyone happy or unhappy

Subjective and Objective Comparative Study of DAB+ Broadcast System

DAB+ @ "96kbps" sounds better than FM but they didnt check the actual audio bitrate.

Subjective testing HE-AACv2 in all but a couple of cases showed 56kbps actual bitrate is sub-good quality & worse than 96kbps & so on.

Their objective test ViSQOLAudio wasnt a good predictor of subjective quality except maybe for some pop genres.

 

 

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9 hours ago, Pesto Lovin' Man said:

This should keep everyone happy or unhappy

Subjective and Objective Comparative Study of DAB+ Broadcast System

Thanks very much, Pesto.  When I came across that recently published paper in my searches last night I glanced at it only briefly and mistook it for a paper I'd already read!

 

The paper is unusual in that part of it compares actual simulcast broadcasts, i.e. real life broadcasting of DAB+ with real life broadcasting of FM, albeit that no details are given as to the reception conditions for the FM.

I note that the more detailed results in the paper are for test HE-AAC encodings prepared by the research team, not live broadcast encodings.

 

9 hours ago, Pesto Lovin' Man said:

Subjective testing HE-AACv2 in all but a couple of cases showed 56kbps actual bitrate is sub-good quality & worse than 96kbps & so on.

For readers not familiar with absolute character subjective ratings using a 5-step scale:

 

Rating Label
5 Excellent
4 Good
3 Fair
2 Poor
1 Bad

 

In the paper, we can see mean opinion scores on page 8 for actual HE-AAC bitrates of 64kbps, 96kbps, 128kbps and 160kbps. Perusal of the histograms reveals that use of the lowest bitrate, 64kbps, led to scores of  around 3 or "fair".  [There is no mention of broadcast processing. These appear to have been straightforward encodings using the HE-AAC codec and nothing else. I note that it is very possible the 96kbps encoding would have used AAC-LC, leaving only the 64kbps encoding to rely on HE-AAC v1, i.e. spectral band replication.]

No part of the paper explores bitrates as low as 48kbps.  At page 7 of the paper it is stated: "Currently, the digital DAB+ multiplex in Poland offers radio programs at 6 bitrates: 64, 72, 96, 104, 112, and 128 kbps.". 

 

9 hours ago, Pesto Lovin' Man said:

DAB+ @ "96kbps" sounds better than FM but they didnt check the actual audio bitrate.

I see that in Figure 1 of the paper [a 2016 paper by Gilski & Stefanski, published in 2017 in the Archives of Acoustics (The Journal of Institute of Fundamental Technological of Polish Academy of Sciences)], the lowest nominal bitrate of the simulcasting DAB+ services (the rate for the regional service) slightly exceeded 96kbps:

Figure1-2016paperbyGILSKISTEFANSKI_zpsem

We in Australia would be envious of such high nominal bitrates. (The paper does not discuss differences between the overall data rate of the service, which appears to be what is quoted in Figure 1, and the bitrate of the embedded HE-AAC audio stream.)

An aside: I am beginning to think that for my sample files for Australian DAB+ vs FM I would be justified in using nominal DAB+ bitrates rather than actual bitrates. Doing so would align with the tendency to refer to real world DAB+ broadcasts by their nominal bitrate. I think that when members of the public read a statement about DAB+ radio such as "48kbps gives comparable to FM quality" it is reasonable for them to take that to mean the bitrate information displayed on their radio,  or the rate they might see publlshed on the internet if they search.  It's quite rare to see the actual audio bitrate of a DAB+ radio service disclosed.

 

64 kbps (actual) in Australia - what could be expected?

In Australia, the bitrate of 80kbps nominal is used by the ABC for programs that consist mostly of music. That bitrate roughly translates to 64kbps for the audio depending on how much bitrate is reserved for Program Associated Data. Here is an extract from details I posted on this forum recently (at http://www.dtvforum.info/index.php?/topic/96036-digital-radio-stations-list/&do=findComment&comment=2093845) for DAB+ in Brisbane:-

9C 206.352MHz CODEC Nominal Audio Comment
BR abc&SBS RADIO   bitrate bitrate  
ABC Classic FM HE-AAC v1 80 63.8  
ABC Country HE-AAC v1 80 47.6 large PAD
ABC Jazz HE-AAC v1 80 47.6 large PAD
Double J HE-AAC v1 80 47.6 large PAD

 

It is interesting to note the following comments in the paper, which appear at page 7:

Quote

When it comes to analysing speech or singing samples, the most important issue is the clarity and transparency of the audio material, since information contained in the voice must reach the listener. According to the subjects, the sound colour was significantly worse for samples coded at lower bitrates, especially 64kbps. This impression was given regardless of the music genre.

... Furthermore, as the listeners indicated, in case of signal samples from category 3-4, spatial attributes of sound, including spaciousness, sound perspective and localization stability, were reported as annoying or even unacceptable for bitrates lower than 128kbps. This effect was less common for electronic music pieces, as it was for classical or popular music.

Edited by MLXXX

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