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Can someone please explain to me what VBR means?


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Initial post: 11 Mar 2012 19:26:50 GMT
Last edited by the author on 11 Mar 2012 19:30:55 GMT
Mandryka says:
Hi everyone.

This may be a bit technical but I am totally confused and very disappointed with the sound quality of amazon downloads. I'm wondering whether to reject 256kbps VBR (and less) completely. So here goes, here are my questions

When they say 256kbps VRR they mean that 256 kbps is a MAXIMUM , right? Not a mean? If so who decides what the actual bitrate is? Is there a standard algorithm that everyone follows? Or human beings with living ears making the judgement, on the basis of the resulting sound quality? Or on the basis of something else?

And anyway, when they implement their VBR what are they trying to do: maximise the quality or minimise the size of the file?

And do they all do it in the same way? Is itunes the same as amazon, for example? If I buy the same 256kbps VBR track from amazon and itunes, am I getting identical mp3 files?

And anyway, in terms of sound, which is better, VBR or CBR. Or does it depend on your DAC?

I should say that I listen mostly to classical, though a high end hifi, streaming with a squeezebox and using a good quality external DAC. Most of my music is FLAC files ripped from CDs.

Posted on 11 Mar 2012 22:38:01 GMT
Last edited by the author on 11 Mar 2012 22:47:58 GMT
MC Zaptone says:
I'm not sure that it matters, (although I'm sure someone better informed will correct me) the kbps are the gauge as variable rate encoding is inherent in lossless compression schemes such as FLAC and Apple Lossless although not always in Mp3.

Variable bitrate (VBR) is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate (CBR), VBR files vary the amount of output data per time segment. VBR allows a higher bitrate (and therefore more storage space) to be allocated to the more complex segments of media files while less space is allocated to less complex segments. The average of these rates can be calculated to produce an average bitrate for the file.

MP3, WMA, Vorbis, and AAC audio files can optionally be encoded in VBR.[1][2][3] Variable bit rate encoding is also commonly used on MPEG-2 video, MPEG-4 Part 2 video (Xvid, DivX, etc.), MPEG-4 Part 10/H.264 video, Theora, Dirac and other video compression formats. VBR is intrinsic to FLAC and Apple Lossless.

When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant. CBR is useful for streaming multimedia content on limited capacity channels since it is the maximum bit rate that matters, not the average, so CBR would be used to take advantage of all of the capacity. CBR would not be the optimal choice for storage as it would not allocate enough data for complex sections (resulting in degraded quality) while wasting data on simple sections.

The problem of not allocating enough data for complex sections could be solved by choosing a high bitrate (e.g., 256 kbit/s or 320 kbit/s) to ensure that there will be enough bits for the entire encoding process, though the size of the file at the end would be proportionally larger.

The above was taken from Wikipedia but seems to check out against other sources.

As usual, ultimately, it all depends on your hearing, age, perception and wallet.

Cheers
MC

In reply to an earlier post on 12 Mar 2012 13:14:15 GMT
Muten Goku says:
To be honest you wont get the result you want if you are listing to clasical music as when you create a MP3 it removes alot of information that cannot be recovered. VBR is better for compression as it varys from second to second e.g. if there is alot of sound it will use up to 256kbps but if there is near silence it may only use 10-20kbps, you are best ripping cds your self at about 320kbps CBR (Constant bit rate) as this is the best for sound but will require alot more space. but to get the best effect on clasical id use just the cd. Hope this helps

Posted on 12 Mar 2012 19:43:59 GMT
Mandryka says:
Well I'm still confused, though thanks for trying. Maybe I can just focus on one question. I'll quote from my first post:

"If I buy the same 256kbps VBR track from amazon and itunes, am I getting identical mp3 files?"

In reply to an earlier post on 12 Mar 2012 20:40:45 GMT
Musicmaster says:
yes!

Posted on 12 Mar 2012 22:02:34 GMT
zargb5 says:
I am very disappointed with anything below 320 kbps. A lot of listeners will argue till blue in the face that you couldn't tell the difference between cd 1411 kbps and 320 kbps. The compression is very clever but on a decent hi fi set up it is fairly obvious - especially so with classical music. On portable devices and pc's its very acceptable. My bug bear is that a lot of files especially classical downloads come down at around 224 kbps which is pretty poor. The amount of true high res downloads is fairly small for the uk and said e retailers can charge way over the odds for such tracks. At tte moment i'm sticking to cd quality (physical copies) until there is a better choice of higher res than cd downloads made available or just even plain old cd quality. I wish HD tracks (US based) would release to the UK.

I would disagree with the previous poster about identical files over different sites. The files have to be converted/uploaded to the compatible software of said sites using LAME or other systems. You can get distortions entering into the sound due to these processes.

In reply to an earlier post on 12 Mar 2012 22:39:29 GMT
nephran says:
Mandryka Itunes uses thems AAC files not MP3..

Posted on 12 Mar 2012 22:42:23 GMT
nephran says:
Thems classical music suffers a lot from compression systems because these systems throw away the recorded space between thems instruments..This space is vital for seperation and soundstageing..Best rip in FLAC for Classical...

Posted on 13 Mar 2012 17:33:09 GMT
Mandryka says:
Totally confused.

Posted on 16 Mar 2012 18:34:55 GMT
Last edited by the author on 16 Mar 2012 18:35:10 GMT
G. Jackson says:
When they say 256kbps VRR they mean that 256 kbps is a MAXIMUM , right? Not a mean? If so who decides what the actual bitrate is? Is there a standard algorithm that everyone follows? Or human beings with living ears making the judgement, on the basis of the resulting sound quality? Or on the basis of something else?

--------Correct. It means from 0 to a maximum of 256kbps. To explain kbps if you are not already sure, it is a measurement of data transfer, per second. e.g. 100kbps means for every second of music, 100kb (kilobytes) will be used.

And anyway, when they implement their VBR what are they trying to do: maximise the quality or minimise the size of the file?

--------They are trying to keep the quality the same as a CBR (constant byte rate) but reduce the file size at the same time.

And do they all do it in the same way? Is itunes the same as amazon, for example? If I buy the same 256kbps VBR track from amazon and itunes, am I getting identical mp3 files?

--------I don't know the answer to that. I suppose it depends on how they get their music? You could try asking them directly yourself.

And anyway, in terms of sound, which is better, VBR or CBR. Or does it depend on your DAC?

--------Some CD decks for example won't playback VBR (Denon DNS3500 for example). If the CBR rate is the same, or higher than the VBR, then it will be either the same or better, but if the VBR has a higher byte rate than the CBR, it has the potential to be better quality.

So, basically, if you have the choice, and the hard drive space, go for CBR.

Posted on 16 Mar 2012 18:58:27 GMT
Last edited by the author on 16 Mar 2012 18:59:35 GMT
Mandryka says:
That's helpful. Thanks.

When you say that "They are trying to keep the quality the same as a CBR (constant byte rate) but reduce the file size at the same time.", how do you know? You see what's at the back of my mind is that there are several different ways to convert a music file to 256kbps VBR, some of which put the emphasis on quality, some of which put the emphasis on reducing file size. We know that 256kbps VBR may or may not be the same quality as 256kbps CBR. Something must determine this.

At the back of my mind is the suspicion that VBR is an enormous swizz. And that some 256kbps VBR has very little high quality music in it because the conversion compromised sound quality for file size. But the end user is hoaxed, tricked, by the maximum value in the marketing blurb.

In reply to an earlier post on 17 Mar 2012 08:58:09 GMT
M. O'Gara says:
It's the software used to create the file that determines the method. I've never liked iTunes' compression algorithm, but maybe that just reveals my personal prejudice. I've always the Lame encoder to create my .mp3 files and I *feel* it does a better job, but I have no empirical evidence other than my own bias.

Ten years ago VBR was a very practical method for .mp3 compression, since there's a good balance between file size and sound quality. Arguably, since file storage is so cheap and bandwidth so wide (a generalisation, I know) it's no longer an issue and VBR is pretty much obsolete. There's plenty of digital vendors selling 320kb .mp3 files, and at some point it will all move lossless and .mp3 will be regarded as quaint.

You're correct since when using the Lame encoder you can choose whether to emphasise sound quality or file size, meaning that within certain parameters (determined by the encoder) there's going to be less music information in the file. The key question is whether you can actually hear any difference, or whether you *think* you can.

What you could do is take a compact disc, and encode just one song using different methods. Then listen to each one, and see if you can hear any difference. For what it's worth, I used to compress everything as 320 VBR, now I use 320 CBR - the increase in file size just doesn't make any difference any more.

Apple basically sells .mp4 files (in an .aac wrapper). The issue with buying music from iTunes is that you're pretty much locked into Apple hardware for playback (I know other players support it, but nothing like the number that play .mp3 files). Apple claim that their files sound better at the same bitrates, but again, I can't perceive the difference. I use Apple hardware and have done for almost thirty years, but I normally won't buy music from iTunes (or Amazon for that matter!) because I like to have some flexibility. Boomkat, Bleep, Zero Inch, and Beatport are my vendors of choice.

Posted on 17 Mar 2012 18:21:53 GMT
Last edited by the author on 17 Mar 2012 18:23:03 GMT
I use dbPoweramp to rip CDs, which (for MP3s) offers 4 options: Quality (VBR); Bit Rate (ABR) (in other words a VBR in which the average bit rate can be determined in advance); Bit Rate (CBR) (already discussed above) and Free Format which allows you to rip higher bit rates of MP3 which apparently can't be played by some players. It also offers a choice of Slow, Normal and Fast encoding, of which the Slow is better quality. So I use the highest available bitrate for Quality (VBR) (~240mbps) and Slow encoding. And for the most part I'm pleased with the results.

This is of course tangential to the subject discussed here, but I mention it because the Quality (VBR) setting DOES NOT claim that the quoted bitrate for a given level of quality is a maximum, merely that the file size and average bitrate cannot be accurately predicted in advance of encoding. So I can't speak for whether VBR mp3 files downloaded from Amazon are maximum or average bitrates but in other contexts VBR definitely means average. My problem with mp3 downloads here at Amazon is that in general they don't tell you ANYTHING about the bitrate so if I'm trying to decide between several versions of the same recording from different albums I can't see if one is a better bitrate than another. Let us know please, Amazon - surely it's an essential part of the information you should be giving to the consumer.

Also, regarding the difference between iTunes and other suppliers, .AAC files supposedly (I don't use iTunes) give a lower bitrate for comparable quality. While iTunes files do in theory lock you into their hardware, AAC files (provided they're not DRM-locked) can be converted to MP3 or other codecs, though I wouldn't recommend converting directly from one compressed format to another one - do it via a lossless format like .wav, though even then you will lose some quality. Or you could just not buy from iTunes...

ff

In reply to an earlier post on 18 Mar 2012 20:36:01 GMT
hi, VBR means variable bit rate.... 320 Kbps is the most acceptable rate, its near if not total cd quality, i use a programme called idfx, its an audio enhancer, google it for more details, it takes the guess work away for good sound from ipods etc.... good luck, regards sherree

Posted on 31 Mar 2012 21:36:06 BDT
The primary purpose of mp3 was to resolve a storage problem in the process reducing sound quality to a level that was acceptable to a majority of music fans; enough of them anyway to replace their previous means of listening for the smaller, more portable devices than could potentially hold several albums.

Since its introduction the 'goal posts' on what is acceptable quality have changed. Early 'techie' articles on the web claimed there was little sound quality loss when comparing 128 kbps and CD and that 192 kbps was equal to CD quality. Now there are ongoing threads with listeners demanding that Amazon offer 320 kbps because 256 kbps is no longer considered good enough.

I think G. Jackson explained the difference between CBR and VBR very well. As the former abbreviation implies you have a constant 256 kilobits per second. So why would you need the space that takes if you have sections in the music that have less than 256 kilobits of information? Hence the latter - VBR - was developed to provide better quality of sound using less space which, when portable digital music players came out, was at a premium.

I think what you are asking is which gives the best sound: CBR or VBR? That I find depends on how good a job the encoder does with the music you are trying to compress. Most times VBR is passable, especially if you listen to music on the go, e.g. commuting or at the gym. Occasionally VBR makes a complete hash of it. For instance, I've tried encoding "Save Tonight" - Eagle-Eye Cherry to VBR (320 kbps max) using both EAC/Lame and dbpoweramp and it sounds as if musicians and backing singers are sat piled up on each others laps. The spatial separation of different components has disappeared.

Storage is becoming less of an issue except perhaps for those people who like to have there entire music collection on a portable player. I keep mine stored on the PC and swop out an album or tracks as and when I've listened to it enough and want something else. It doesn't take many minutes to delete files from the player (they will still be on the PC) and upload newer stuff. To avoid possible VBR errors I tend to use 320 CBR as default.

Some portable player manufacturers, e.g. Cowan, also except FLAC compression and there is some shareware around to convert existing mp3 players to play .Flac files, if you feel brave enough (as it will invalidate manufacturer warranty). This permits the music to be compressed without loss of sound quality. It is what I listen to if working at the PC although the quality cannot exceed the limitations of the CD format.

However, there are now sites, e.g. http://www.linnrecords.com/linn-download-quality-and-file-type.aspx
that offer even better quality sound that according to some audiophiles approximates or exceeds that obtained from vinyl (minus the hisses and crackles). Of course you need high-end equipment to get the most benefit from this. And it doesn't come cheap.

If any thing/body is trying to cheat you, it will be the music companies as they always have done. You can have one piece of music produced in different formats for different customers. Blu-ray/blu-spec discs marketed to those with a discerning ear. These are replacing the once top-end SACD/HDCD discs which are gradually being made more affordable to a wider customer group. Everybody else they think will be happy with the common-or-garden mass produced CDs until such time they can persuade us to think differently. The same contemptous approach is taken with compressed and lossless downloadable formats too.

Posted on 31 Mar 2012 23:41:22 BDT
LordSputnik says:
The difference between VBR at 256 kbps and CBR at 320kbps is minimal... As for whether the number is a mean or a maximum, it depends on which program is telling you the bitrate, and whether Amazon caps the bit-rate at 256kbps. I'd expect that the two mp3 files won't be exactly the same from two different sources. Although the difference will be so small you won't hear it.

A little background about the two types:
In CBR, a lot of the audio data that's stored is useless. For example, if you have a very loud bit of track with lots of instruments, followed by a quiet flute solo, the flute solo may only require a small bitrate, but you're still using 320 kbps, so wasting file space. In VBR, the bit rate adapts for each passage of music, so sections with less going on get a lower bitrate, while sections with more going on get a higher bitrate. This means that for the same average bitrate, you get a higher quality where it matters.

VBR therefore offers more efficient encoding of the audio. I said before that the difference between 256 and 320 is minimal. CD quality audio is about 1400kbps. In both 320kbps and 256 kbps, the audio data is compressed significantly. Compared to 1400kbps, both are much smaller, and there's little relative difference between them.

So overall, there's little point using CBR over VBR, especially if you're playing it on a computer, where both types will be decoded equally well.

P.S. - I also have my CD library stored as FLACs, but it's important to convert the FLACs down to VBR MP3s before you put them on anything portable, otherwise you'll run out of space really quickly. "Foobar" is a good program that can convert FLACs to MP3s, on Windows.

Posted on 2 Apr 2012 14:10:20 BDT
Sam says:
ok simply put, clasisical music needs 320kps and ABOVE! vbr uses a very clever, complex algorithm to "decide" which bits of your music to allocate less data space to, never a good thing with real music (not electronica) as complex, low level aspects of the music will be lost - resulting in flat two dimensional sound. Spend more money on a device with large storage space and stop using vbr files, they are NEVER going to give you the sound quality you seek. Good luck with it all.

In reply to an earlier post on 2 Apr 2012 15:23:13 BDT
Last edited by the author on 2 Apr 2012 15:25:25 BDT
Hi there.

The brief answer is no, you cannot change the Amazon 256/320kbps vbr which is in truth an mp3 download. Once you have downloaded a track from them,you cannot convert the track into any other format in order to bring out the compressed 'lost' elements of the song since this has already arrived on your computer with the 'loss' already there. All downloaded items from all kinds of sources such as iTunes, Amazon, Apple etc are mp3 so it makes no difference where you take your download from. You do not get the 'full flavour' of the track.

The best way to overcome this is to purchase the cd itself. All cds come in at 1440kbps at 44khz which is the standard normal cd bitrate. I then 'rip' my own cds to the WAV lossless format at 2770kbps and 96khz and have 'tweaked' my music player software accordingly. I don't use FLAC for ripping cds as it can be quite limiting. Each cd ripped this way takes up around 1Gb of space but gives you a breadth and depth of sound far superior to standard ripping which most people do. You need a lot of space on a computer to spare but I feel its worth it.

Classical music ripped from cds deserves the WAV 2770kbps 96khz 'rip' to bring out the full flavour and nuances. If you like Herbert Von Karajans 1966 version of Debussys 'La Mer' on D.G, rip the cd twice - once in FLAC then once in WAV lossless - and enjoy listening to it twice and I'll wager you'll never go back to FLAC. If you listen through the computer, I hope you have an expensive soundcard like an Asus Xonar D2X Audio Centre and not a cheap one. This too will enhance your listening experience. I don't do streaming nor do I have an external DAC to play music with,but thats for another time.

I hope this will help you out in some way.

All the best.

Posted on 2 Apr 2012 15:35:03 BDT
Contrary to popular and misdirected belief it does not stand for Very Big Rump, despite the best efforts of the J-Lo fan club.

In reply to an earlier post on 2 Apr 2012 20:08:47 BDT
A.R. Long, I'm fascinated by your assertion that ripping CDs at 2770kbps/96khz can improve the sound. Surely you cannot find extra information in the CD over and above the 1440kbps/44khz? Is there much discernible difference between WAV at the two sampling/bit rates, as opposed to the 2770/96 WAV vs FLAC? Do you have a theory as to what is happening to make it sound better?

ff

Posted on 2 Apr 2012 20:47:54 BDT
Hello ff.

I was curious what happens when you rip a cd at almost double the bitrate and twice the 44khz. I copied several cds - mainly 1960s cds - in this fashion to hear what the discernable improvement would be if any. The basic idea was to see what would sound better through a hi-fi system - a standard rip of 1440kbps 44khz or 2770kbps 96khz. If there is a high-end on-board computer soundcard, and a 2.0 speaker system running through a wired not streamed amp, I reckoned on this type of ripping creating what hifi systems already do which is to pick up every last little nuance of lossless WAV sound and reproduce it accordingly. The huge file size on the computer has the breadth and width to justify this when I firmly believe there are noticeable differences in sound. I can detect this through my 10 year old Sennheiser HD25SP monitor 'cans'. Since I don't use FLAC I can't offer any help on this. I am of the opinion that the greater the rip and thus the greater file size which goes with it, makes the 'ripped' cd produce a small but noticeable extra clarity in sound reproduction. There may be other things at play inside the soundcard, or the media Player (in my case Winamp Pro), or the way its fed through expensive cabling and kit. I wonder if you'd like to try and see what sounds your ears detect. It would be worth an experiment to see I reckon. All the best.
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Posted on 2 Apr 2012 23:30:17 BDT
My thoughts on this:
1. Since you clearly can't be picking up extra information that wasn't on the CD in the first place, what you're hearing must have been encoded in the CD to start with.
2. I'm sure you're right that the quality of the soundcard is crucial. At the moment mine is pretty standard ...
3. ... as are my ears!
4. ... and my computer speakers. CDs sound far better over played by my Cambridge CD player and amp and ancient but excellent Monitor Audio speakers (bought second hand in 1988...)

Which is all to say that while your challenge is a very interesting one, I regretfully dont think I'm currently in a position to do anything meaningful with it. Which is a shame because I'm fascinated by what you've reported. I'm going to have to discuss this with more technically minded friends with better ears than mine.

Question: does it take notably longer to rip at this bitrate/sampling rate?

FWIW, the ripping software I use (dBpoweramp) can also offer WAV at 192 khz!

ff

Posted on 3 Apr 2012 08:52:34 BDT
Hi ff.

The answer to ripping is at my higher rate is yes,it takes significantly longer to rip but well worth it. The higher the rip quality,the more space you use on a hard-drive. A 75 min cd can take up nearly 1Gb per cd at my rate of ripping. I'd love to rip at 192 khz but for some reason my maximum is 96khz. The soundcard quality in most standard computers is ok,but not if you want higher end sound. My Dell came with such a soundcard, but I bought a high end Asus Xonar and got Dell to install it here in my home.The immediate effect on my old ancient ears was staggeringly obvious! Your ears though are the crucial arbiter of all things in this case. You'll have some really interesting discussions with your friends about this I assure you. I know I did!

I recently took delivery of a Teufel Concept B200 Active 2.0 Multimedia Speaker System direct from Germany. The amp sits underneath my screen and the speakers are angled and sit each side of the screen - perfect for listening. There are facilities for auxiliary, USB and mp3 inputs and there are seperate bass, treble and volume controls. There is also space for a mic and speakers. At almost £240 its an expensive but brilliant option and removing the need for DAC. I'd check the specs and see for yourself. I would finally suggest you cable the output of the soundcard directly to the Cambridge amp with and not stream. By using a high-end cable and RCA plugs etc,you can create a far better sound more akin to hi-fi than you will using streaming.

Happy listening.

Posted on 3 Apr 2012 10:34:52 BDT
Many thanks A.R., I've been planning to replace the PC for a while and a much better soundcard is definitely a priority. At the moment I don't connect it to the stereo (it involves a lead across the floor ... or ceiling!) Once I've got a new one I will experiment with your suggestions - though I suspect in the short term it will be restricted to a few favourites that I know are excellent recordings extremely well mastered - without which all this is a bit academic to say the least.

ff

In reply to an earlier post on 3 Apr 2012 10:57:22 BDT
It possibly reduces the error rate that happens when the laser reads the pits. This is why ripped music played back from a hard drive sounds better than that played straight from a cd.

EAC corrects all of the errors during ripping and checks your copy against a database of other folks copies to make sure it matches up, so theoretically the copy on the hard drive is as close to the digital master used for the cd as possible, therefore delivering a better sound.

I am not sure if ripping the cd to twice its original bit rate would make much difference. Ripping it at twice the sample rate could conceivably reduce errors and therefore improve things, cos its checking each bit twice, or more.
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Initial post:  11 Mar 2012
Latest post:  4 Apr 2012

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