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Topic: MP3 decoders test : MAD isn't so good! (for me...) (Read 93070 times) previous topic - next topic
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MP3 decoders test : MAD isn't so good! (for me...)

Reply #25 –
The foobar decoder may have been based on mpglib, it has been improved quite a bit since.

The dithering/noiseshaping code is from me, based on SSRC and suggestions from KikeG.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #26 –
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I wonder why other audio players didn't use these techniques. Is it really hard to program? Dithering/noise shaping is very common on studio mastering: most of my CDs have visible noise shaping. So if studios use them, it must be good.

They slow down the player for something which doesn't have a benefit in casual listening. This is why it defaults to off in foobar too.

I understand. But all players have a preference/option box. Allowing dithering isn't the same thing than forcing it. If people want a theoretical increase in quality, why not? It's not a bad thing... on a changelog

MP3 decoders test : MAD isn't so good! (for me...)

Reply #27 –
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MAD isn't impressive. [..] on some other samples, real improvements were noticed (less aliasing, less naturel and less synthetic sound)

less natural and less synthetic seem to contradict    Maybe you could clear up what you meant here?

Also I could not find which version of MAD you tested, (cause the PCM dithering algorithm was changed in version 14.0).

Edit: Ah it was in the French piece: est la 0.15.0 (beta, datant de juin 2003)

Thanks for testing and writing to this forum in English 
In theory, there is no difference between theory and practice. In practice there is.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #28 –
Sorry, I did a mistake. MAD is sometimes MORE natural and LESS synthetic.
But this is feeling only. I don't really know if this 'natural' sound is a consequence of noise added by MAD dithering. Small amount of noise isn't always bad. For exemple, video decoders have 'film' or 'grain' effects: image is less clean, but looks sometimes better with than without.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #29 –
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oh no, dithering is very important, especially when you reduce the resolution from 24 bits to 16 bits. it's consecutive re-dithering which is a questionable practice, especially when the source is only 16 bits. however, if we use mp3s as an example, if the bitrate is high enough, it may be possible to retrieve data above 16 bits, thus preserving more ambiance and detail which would surely be lost if we were to truncate at 16 bits. there is no guarantee, however, that you will hear a lot of difference or any difference at all. the side effect of re-dithering is more noise in the audio signal but this can be somewhat offset with proper noise shaping, although this is very subjective.

Humm, interesting... Unfortunately I don't have any 24-bit audio to test it. Thanks a lot.
Liberate tutemae ex inferis

MP3 decoders test : MAD isn't so good! (for me...)

Reply #30 –
I've quickly tested MAD 24 bits (dithered I suppose) decoded files against FB2K 24 bits dithered/noise shaped through foobar2000 ABX component, and the two files were less noisy than the best 16 bits decoded files. Both files sounded similar.

It seems that ABC/HR don't support 24 bits input files.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #31 –
So what is the point of application in plain terms for the non-technical person?  Does this mean we should use Foobar to batch encode mp3 from waves OR that playback is best when using Foobar OR some box should/shouldn't be checked when playing them back or encoding or ABXing?  Help the Average Joe here understand the real-world significance of the discussion, please.  Thanks in advance.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #32 –
Did you even try to read the discussion?
Did you even bother looking up what encoding and decoding are?
"To understand me, you'll have to swallow a world." Or maybe your words.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #33 –
Yup but I don't get it - clearly you are much smarter than I.  Or, you at least have years of training and/or experience I do not have (and can't get in the next 3 days before this thread dies off) that enables your participation in the discussion.  Take it as a challenge.  You genius try to explain, in non-tech terms, the real world application of the discussion for the average reader.  Or if you are not interested in such a discourse, perhaps someone else is.  Thanks in advance for your help.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #34 –
Since you challenged me, I'll try to do so:
Decoding is the process of uncompressing compressed (encoded) data like MP3 back to uncompressed PCM Audio. Guruboolez' tried to objectivly measure the quality of different MP3 decoders with and without different types of dithering.

You are most likely not to hear any differences at all under normal listening conditions on normal music (especially loud pop/rock music will mask most differences), but Guruboolez tried to "magnify" the differences by choosing quiet passages of music and listening to them at a high volume.

Guruboolez' liked foobar2000's decoder and noise-shaped dithering best.
"To understand me, you'll have to swallow a world." Or maybe your words.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #35 –
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So what is the point of application in plain terms for the non-technical person?  Does this mean we should use Foobar to batch encode mp3 from waves.

Only if you want to apply DSPs or volume changes (e.g. replaygain) before encoding. Volume changes can be applied after encoding as well (replaygain/mp3gain) BTW.

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OR that playback is best when using Foobar

Theoretically, yes. That's what the test results suggest. Under real listening conditions there shouldn't be an audible difference though.

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OR some box should/shouldn't be checked when playing them back or encoding or ABXing?

For theoretically best playback quality check "Dither" box in output settings if you use 16bit output. If you use 24bit output (and have a soundcard capable of 24bit  ) dither will only (slightly) increase CPU load but have no advantages.

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Help the Average Joe here understand the real-world significance of the discussion, please.

To understand the technical background better you might want to have a look at the FAQ or the Wiki ("Knowledge Base" on HA portal).
Let's suppose that rain washes out a picnic. Who is feeling negative? The rain? Or YOU? What's causing the negative feeling? The rain or your reaction? - Anthony De Mello

MP3 decoders test : MAD isn't so good! (for me...)

Reply #36 –
I think the 'real world' conclusion is:

1) Not all CD's are properly mastered

2) Differences between MP3 decoders are only audible in extreme circumstances

3) Taking 2 into account, foobar does well, and MAD isn't what it is hyped up to be

MP3 decoders test : MAD isn't so good! (for me...)

Reply #37 –
Would conclusions 2 and 3 be based only on Guru's test?

As in, I'm quite sure many of us would have already encountered many people on other forums who claim the direct opposite to 3. How are they going to be persuaded otherwise?

MP3 decoders test : MAD isn't so good! (for me...)

Reply #38 –
Thank you.  I understand.  Great article on dithering - very approachable by a lay person.  Follow up questions then (if the answers aren't beyond the average Joe's discussion and I'm using the correct terminology):  Why not do this on every recording?  Is there a way to ensure that it is when recording digitally or is it dependant on choice of equipment?  Does "upsampling(?)" to 24 bits during decoding/playback take care of the problem or is this artificial in some way?

I assume this explains some of the the background noise in some cases on soft recording passages (Jazz and classical is my main listening) or distorted/strange  tone qualities/characteristic sounds of certain instruments played at soft volumes?  Perhaps this problem isn't as uncommon as it seems to classical listeners, as turning up the volume to hear soft passages is frequently required to hear what is even being played...

Thanks everyone!

MP3 decoders test : MAD isn't so good! (for me...)

Reply #39 –
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Would conclusions 2 and 3 be based only on Guru's test?

As in, I'm quite sure many of us would have already encountered many people on other forums who claim the direct opposite to 3. How are they going to be persuaded otherwise?

Not only, I knew of the differences before he did the test but it's nice to see it confirmed

Well, there's an objective blind test showing that foobar is better. I don't know any showing the opposite, do you?

MP3 decoders test : MAD isn't so good! (for me...)

Reply #40 –
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Not only, I knew of the differences before he did the test but it's nice to see it confirmed

Well, there's an objective blind test showing that foobar is better. I don't know any showing the opposite, do you?

Don't worry, your question is indeed rhetorical.
 

MP3 decoders test : MAD isn't so good! (for me...)

Reply #41 –
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3) Taking 2 into account, foobar does well, and MAD isn't what it is hyped up to be

With the asterisk that this test was done at 16bit, and that based on gurobolez's 'quick test' MAD *might* well be about as good as fb2k at 24bit.

(edited for clarity)

MP3 decoders test : MAD isn't so good! (for me...)

Reply #42 –
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Anyway, I wish I had your ears guruboolez!

Golden ears would probably perceive a difference between different decoders on real listening conditions. Common ears, like mine, need to push the volume to extreme position.

Nonsense. You have made enough merits to be considered member of the "golden-ear" club. Some people being able to hear differences at real listening conditions? Maybe, for some really gifted people, and when listening in really good conditions (good headphones, low ambient noise), but even in this case audible differences would probably be very small. Anyway, without actual results it's hard to say.

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Try, please... I was the first to be surprise to hear differences.

I'm not very surprised, if using low amplitude music, amplifying the result, and using discriminating ears. When I tested it, MAD dithering showed to be clearly sub-optimal, due to lack of dither amplitude, that caused visible distortion and noise pumping on synthetic test signals.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #43 –
I'm not sure I understand all of this, but I have this question.

All of my MP3s or MPCs are 16 bit.  Now there are instances where there is more than 16 bits of information to decode at one time?  The option to dither (in fb2k) would allow playback without truncating these instances to 16 bits.  My audigy2 supports 24 bit playback, so if I chose 24 bit playback (in fb2k) then these instances would still not be truncated without the need of dithering?

Sorry if I have this completely wrong but I'm drinking beer right now. :X

MP3 decoders test : MAD isn't so good! (for me...)

Reply #44 –
does foobar also use the noise shaping (when enabled) on wav files or only on encoded material ? as i want bit identical output on my spdif out i guess i better leave it off.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #45 –
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All of my MP3s or MPCs are 16 bit.

They aren't.

In general, you can't say that a lossy file has a certain bit resolution.

Theoretically, an mp3 file can be decoded to any desired bit depth. And I think that by modifying e.g. gain information, you can create mp3s that would decode to something other than digital silence only, say, at 24 bits.

Whether decoding to a bit depth higher that 16 makes any difference in the real-world listening conditions is a different question, though.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #46 –
Interesting discussion about dithering.  Just a small off-point question.  In the vorbis plugin for winamp 5, there is a 'dither' checkbox.  Since lossy files are not bit resolution specific, does that mean when the vorbis plugin truncates to the (default) 16 bits, it does some sort of dithering?  Also, in the Directsound SSRC output plugin, there is a dithering option and noise shaping.  If I am doing dithering in the output plugin, does that mean the vorbis plugin dithering is redundant or vice versa?

MP3 decoders test : MAD isn't so good! (for me...)

Reply #47 –
@Quantum: I don't know if I fully understand your question. But I think that if Vorbis decoder truncate to 16-bit, then it won't be a form of dither. So I think you should enable Dither on it's decoder (on Winamp). I've always used it disabled and I really love my Vorbis.  hehe

I haven't enabled dithering on fb2k either. I've always had a sort of predujice against this word hehe. Dithering for pictures su**s.
Liberate tutemae ex inferis

MP3 decoders test : MAD isn't so good! (for me...)

Reply #48 –
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I'm not sure I understand all of this, but I have this question.

All of my MP3s or MPCs are 16 bit.  Now there are instances where there is more than 16 bits of information to decode at one time?  The option to dither (in fb2k) would allow playback without truncating these instances to 16 bits.  My audigy2 supports 24 bit playback, so if I chose 24 bit playback (in fb2k) then these instances would still not be truncated without the need of dithering?

Sorry if I have this completely wrong but I'm drinking beer right now. :X

LOL! Quite a sensible question then!

The FAQ on these pages (scroll down) may help, though you've kind of got the answer already...

http://mp3decoders.mp3-tech.org/24bit.html
http://mp3decoders.mp3-tech.org/24bit2.html

If I could find the test files, I'd even think about testing foobar. But I have 1000001 things to do first.

Cheers,
David.

MP3 decoders test : MAD isn't so good! (for me...)

Reply #49 –
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@Quantum: I don't know if I fully understand your question. But I think that if Vorbis decoder truncate to 16-bit, then it won't be a form of dither. So I think you should enable Dither on it's decoder (on Winamp). I've always used it disabled and I really love my Vorbis.  hehe

I haven't enabled dithering on fb2k either. I've always had a sort of predujice against this word hehe. Dithering for pictures su**s. Should I enable it?

Ah ok, I'll rephrase it to see if its a bit understandable. 

Essentially, there are two places in Winamp where there is a dithering option.  One is in the Vorbis input plugin, which is a check box.  I got that checked and using 16-bit decoding.  The second place to dither is in Peter's DirectSound SSRC output plugin (the one which allows you to do resampling to 48 kHz).  In this second one, you can choose noise distribution as well as dithering using a spectral shape (triangular).

Are these two dithering options different and independent of each other and should I have one turned on instead of the other?