I'm not really sure if it is correct. Perhaps someone could make things more clear.
Full Version: MP3 decoders test : MAD isn't so good! (for me...)
I think that if Vorbis decoder decodes do 16-bit, it will already be 16-bit (constant) stream that will be fed to Peter's DSound SSRC plugin. So I believe it won't mess up with it anymore. Now, if you turn off Dithering on Vorbis decoder but tell it to decode at 16-bit it will truncate the file and the final stream will also be 16-bit, constant, truncaded. I think that if you want to use Pete's dither algorithm you should tell Vorbis decoder to decode to 24-bit non dithered.
I'm not really sure if it is correct. Perhaps someone could make things more clear.
I'm not really sure if it is correct. Perhaps someone could make things more clear.
What happens if I process my music in Winamp/mpg123 plugin in 24bit/32bit (should be possible, there is an option for it) and downsample it to 16 bit with PP's out_ds using dithering and noiseshaping. Shouldn't the result be the same or very similar (considering garf's and PPs improvements done to the mpg123 base) as with foobar?
QUOTE(Rash @ Jan 20 2004, 06:04 PM)
...
fed to Peter's DSound SSRC plugin.
...
fed to Peter's DSound SSRC plugin.
...
Hi... could someone please tell me something about this DirectSound plugin? I've only just installed Winamp5, and I'm still searching for the best possible audio quality (which is why I read this thread, since I'm using the MAD input...)
I searched the plugins on Winamp's site, but I couldn't find 'peter's dsound ssrc plugin'...
thanks
d. (newbie extraordinaire)
This is another interesting site for winamp 2.x plugs:
http://support.xmplay.com/Plugins_index.html
The installers here will only install to a folder where "XMPlay.exe" is present, but any binary file with that name will do.....
http://support.xmplay.com/Plugins_index.html
The installers here will only install to a folder where "XMPlay.exe" is present, but any binary file with that name will do.....
This is really a great site:
http://www.x-sound.com/index?update=005
To bad I don't understand japanese... but they keep good track of updates for a lot of fiiine 'ole proggys....
http://www.x-sound.com/index?update=005
To bad I don't understand japanese... but they keep good track of updates for a lot of fiiine 'ole proggys....
helpful, thanks!
d.
d.
QUOTE(dryhte @ Feb 4 2004, 06:28 PM)
I searched the plugins on Winamp's site, but I couldn't find 'peter's dsound ssrc plugin'...
You can get it here (direct link).
Most of above was over my head, but this might be the right thread to ask a question about something I never understood. What is the effect and interaction of the dithering to get something higher than 16-bit audio quality on a 16-bit CD format and thence to MP3? I'm thinking about SBM and the JVC K-sumpn or other (which I thought best).
DMP Records did a re-release using such shaping/dithering technques of some of their earliest DDD recordings, intended to pass through info from the higher sampling rates they had used for Flim & the BBs -- I thought the update Cds super. As a result, I tried upsampling to 48khz (Shibatch?) many over-16bit Cds as I encoded them at the highest feasible LAME VBR settings; I thought that made the MP3s sound better, but I'll confess I was frittering to kill time in wee hours of late 2001-early 2002.
Perhaps related is why LAME results from horribly digitized analog-recorded music often improved on the CD; the most noticeable was '70s Tangerine Dream like Phaedra where, once processed by Dibrom, the music seemed clearer -- is that just that Dibrom's codecs knew what was spurious distortion and eliminated it?
DMP Records did a re-release using such shaping/dithering technques of some of their earliest DDD recordings, intended to pass through info from the higher sampling rates they had used for Flim & the BBs -- I thought the update Cds super. As a result, I tried upsampling to 48khz (Shibatch?) many over-16bit Cds as I encoded them at the highest feasible LAME VBR settings; I thought that made the MP3s sound better, but I'll confess I was frittering to kill time in wee hours of late 2001-early 2002.
Perhaps related is why LAME results from horribly digitized analog-recorded music often improved on the CD; the most noticeable was '70s Tangerine Dream like Phaedra where, once processed by Dibrom, the music seemed clearer -- is that just that Dibrom's codecs knew what was spurious distortion and eliminated it?
QUOTE(guruboolez @ Jan 18 2004, 12:58 PM)
• For this test, I didn't reproduced real listening conditions. Difference are so subtle that I have to increase the level of my amp in order to maximise the audible difference.
• In order to make it possible without being completely deaf in few seconds, I've selected very quiet samples. With classical music, it's not really hard to find such samples (even full tracks are sometimes totally quiet). I didn't evaluate any decoders on pre-instrumental silence, but only when music was playing
• In order to make it possible without being completely deaf in few seconds, I've selected very quiet samples. With classical music, it's not really hard to find such samples (even full tracks are sometimes totally quiet). I didn't evaluate any decoders on pre-instrumental silence, but only when music was playing
Sorry to bring up this over 1 year old thread (it was recently referenced).
On to business, I think this test is flawed...to listen to dither (around 1 bits worth) the volume must be increased by a large factor. The best dither on the planet would be one that kept it's noise just below audible threshold (ok there is some give an take with this, as peoples hearing differs and playback hardware is different, but only to an extent), and by just below I mean right upto the threshold. A dithers strength is proportional to the strength of this inaudible noise, multiplying up the dither noise (and making it audible) proves nothing, just that there is noise that can be heard when multiplied, with such a test only the weakest dither or no dither at all would come out top.
QUOTE(spoon @ Dec 19 2005, 01:41 PM)
A dithers strength is proportional to the strength of this inaudible noise, multiplying up the dither noise (and making it audible) proves nothing, just that there is noise that can be heard when multiplied, with such a test only the weakest dither or no dither at all would come out top.
You are completely wrong, and apparently misunderstand why dither is used at all.
It's also quite easy to prove this assertion wrong by actually doing what you describe.
As for the test being flawed; I think it's stated several times in this thread the effects of dither are below the audible threshold for any practical purpose. So any comparison will push practicality, and I think guruboolez` stated approach is sensible. But do the results matter? I would say they usually don't, and thats why dither defaults to off in fb2k.
>apparently misunderstand why dither is used at all
I was under the impression it was to increase perceived bit depth, there are other reasons?
I am not questioning that part of the test (ok I will also...an mp3 created from a 16 bit CD? so suddenly there is 20 bits worth of dynamic range? a great test for dither).
Instead generate test sines (uncompressed) on the 16th+n bit and dither down to 16 bit then run listening tests, that would be a good test for dither.
>effects of dither are below the audible threshold for any practical purpose
So it is ok to multiply these up so they can be heard and pass comments on how one has more noise than the other? (I am aware there are many different types of dither, in this test only the ones which push the created noise into the higher frequencies would come out well), AFAIK most strong commercial dithers (as actually used on CDs) are not this type.
I was under the impression it was to increase perceived bit depth, there are other reasons?
I am not questioning that part of the test (ok I will also...an mp3 created from a 16 bit CD? so suddenly there is 20 bits worth of dynamic range? a great test for dither).
Instead generate test sines (uncompressed) on the 16th+n bit and dither down to 16 bit then run listening tests, that would be a good test for dither.
>effects of dither are below the audible threshold for any practical purpose
So it is ok to multiply these up so they can be heard and pass comments on how one has more noise than the other? (I am aware there are many different types of dither, in this test only the ones which push the created noise into the higher frequencies would come out well), AFAIK most strong commercial dithers (as actually used on CDs) are not this type.
QUOTE(spoon @ Dec 19 2005, 02:36 PM)
>apparently misunderstand why dither is used at all
I was under the impression it was to increase perceived bit depth, there are other reasons?
I was under the impression it was to increase perceived bit depth, there are other reasons?
"Wrong reason"
There are a lot of threads about dithering and dithering + noiseshaping around here; look for posts by KikeG, 2BDecided etc...
http://www.hydrogenaudio.org/forums/index....showtopic=29912
You dither to decorrelate the quantization error from the input signal.
QUOTE
I am not questioning that part of the test (ok I will also...an mp3 created from a 16 bit CD? so suddenly there is 20 bits worth of dynamic range?
Sure!
Nobody says there are 20 bits of dynamic range in the mp3 itself. However, if you lower the volume of the MP3 decoded output (in floating point), dither when converting to 16 bits, and up your amplifier, you are certainly going to hear how the sub-16th-bit resolution affects the output.
QUOTE
Instead generate test sines (uncompressed) on the 16th+n bit and dither down to 16 bit then run listening tests, that would be a good test for dither.
Maybe. But why do this when it can be tested with actual music, too?
QUOTE
>effects of dither are below the audible threshold for any practical purpose
So it is ok to multiply these up so they can be heard and pass comments on how one has more noise than the other?
So it is ok to multiply these up so they can be heard and pass comments on how one has more noise than the other?
Know another method to evaluate differences in something that should not be inaudible?
You can instead go to 10 bit resolution instead of 16 bit or so. Then no amplification is needed - the dither quality will be observable in normal conditions.
I don't know which comparison is more valid. I believe results will be similar if not identical.
QUOTE
(I am aware there are many different types of dither, in this test only the ones which push the created noise into the higher frequencies would come out well), AFAIK most strong commercial dithers (as actually used on CDs) are not this type.
The high end ones most certainly are.
QUOTE(Garf @ Dec 19 2005, 07:27 PM)
QUOTE
(I am aware there are many different types of dither, in this test only the ones which push the created noise into the higher frequencies would come out well), AFAIK most strong commercial dithers (as actually used on CDs) are not this type.
The high end ones most certainly are.
See here:
http://www.hydrogenaudio.org/forums/index.php?showtopic=9192
Thanks for the links, will research.
QUOTE(spoon @ Dec 19 2005, 12:41 PM)
On to business, I think this test is flawed...to listen to dither (around 1 bits worth) the volume must be increased by a large factor. The best dither on the planet would be one that kept it's noise just below audible threshold (ok there is some give an take with this, as peoples hearing differs and playback hardware is different, but only to an extent), and by just below I mean right upto the threshold. A dithers strength is proportional to the strength of this inaudible noise, multiplying up the dither noise (and making it audible) proves nothing, just that there is noise that can be heard when multiplied, with such a test only the weakest dither or no dither at all would come out top.
I did this test, which included dithered¹ and undithered² decoded files. According to your claim, the undithered decoding should end on top. But according to my results, they end last.
I didn't translate the test in english, so I guess you can't read my detailed results. But the marks are a good indication: undithered and inferior dithering (MAD) produce a more annoying form of distortion than a good dithering (perceptible by a tiny HF noise).
In one case (one Mahler sample), the reference CD (which is undithered) is lower quality than the MP3 encoding decoded with dithering!
¹ MAD and foobar2000
² LAME and Fraunhofer decoders.
QUOTE(guruboolez @ Jan 18 2004, 01:58 PM)
...(less aliasing, less naturel and less synthetic sound)
What do you mean by "aliasing" here? I'm curious as to how an MP3 decoder could affect the AA filter of a DAC (or SRC)..
QUOTE(CosmoKramer @ Dec 23 2005, 02:02 AM)
QUOTE(guruboolez @ Jan 18 2004, 01:58 PM)
...(less aliasing, less naturel and less synthetic sound)
What do you mean by "aliasing" here? I'm curious as to how an MP3 decoder could affect the AA filter of a DAC (or SRC)..
The sample is still online:
http://foobar2000.net/mp3decoder/files/lossless_mahler3.ofr
Result and comment are here:
http://foobar2000.net/mp3decoder/test7.htm
QUOTE(guruboolez @ Dec 24 2005, 01:15 PM)
The sample is still online:
http://foobar2000.net/mp3decoder/files/lossless_mahler3.ofr
Result and comment are here:
http://foobar2000.net/mp3decoder/test7.htm
http://foobar2000.net/mp3decoder/files/lossless_mahler3.ofr
Result and comment are here:
http://foobar2000.net/mp3decoder/test7.htm
I don't doubt that you heard what you heard. My problem is that you used the word "aliasing".
My understanding of aliasing is as follows:
Aliasing in digital audio is a phenomenon that occurs due to the fact that several waveforms can mathematically occupy the same sample points; the illegal waveforms are aliases. All the aliasing waveforms are frequencies > fs/2 --> an oversampling DAC contains a low pass filter to remove those frequencies. A SRC also needs to deal with this issue.
Of course, I could be wrong. In that case, please correct me.
By aliasing I meant a weird form of "geometric" distortion easily audible with resampling (16->8 bits for example).
I defined it (in french) in the beginning of sample-02.
I put online this extreme example to illustrate this phenomenon:
http://foobar2000.net/mp3decoder/files/aliasing.ape
You can see the geometric distortion (something like a wave form) on the middle.
I defined it (in french) in the beginning of sample-02.
I put online this extreme example to illustrate this phenomenon:
http://foobar2000.net/mp3decoder/files/aliasing.ape
You can see the geometric distortion (something like a wave form) on the middle.
QUOTE(guruboolez @ Dec 25 2005, 01:39 AM)
By aliasing I meant a weird form of "geometric" distortion easily audible with resampling (16->8 bits for example).
Ok, that's not aliasing - in all likelihood it's just dithering noise.
Aliasing has a very specific look in the frequency plane - the signals are mirrored around fs/2 (22.05 kHz if the source is 44.1 KS/s).
Anyway, this was just a sidetrack. Thank you for your tests.
Btw, it appears that your testing procedure for dither evaluation is flawed. This is what Dan Lavry of Lavry Engineering (famous DAC/ADC maker) has to say:
http://recforums.prosoundweb.com/index.php.../48/0#msg_num_1
QUOTE(Dan Lavry)
Dithered noise shaping technology has been incorporated into a handful of hardware devices. While all are based on the same concepts, some perform better than others. After simulating and listening to all available public domain algorithms, Lavry Engineering came to some conclusions in forming a basis for Acoustic Bit Correction™. The principal conclusions are:
a. The practice of greatly amplifying low level signals to determine triangular flat PDF (probability density function) dither reveals the effectiveness of distortion and noise modulation elimination. This practice yields misleading results when testing unflattened dithers and/or noise shapers. It conflicts directly with L. Fielder’s findings showing completely different threshold delectability curves for quiet and loud levels. Noise shaping listening tests must be done at "reasonable" volume levels.
b. Given the above requirement, our listening tests concluded a strong preference for "triangle high pass" dither (this dither is produced by simultaneously adding a new random number and subtracting the previous value). Such dither is frequency-shaped to carry more high frequency energy (the energy content at low frequencies is minimal).
c. Listening tests revealed a preference for smoothly varying noise-shaping curves. Peaks and notches seem to irritate the listener (admittedly while turning the volume up). In addition, despite the temptation to optimize the noise shaping curve to the average listener’s hearing threshold, given a significant variation from listener to listener requires reasonable compromises in tailoring such a curve. In other words, smooth the curve.
The improvements offered by dither and noise shaping vary with source material and final word length. An A/B/X test at 16-bit level, requires a quiet environment and low level (loudness) audio. The listener must resist the temptation to turn the volume up to unreasonable levels. The practice of truncating to short word length (8-12 bits) should be avoided. The ideal noise-shaping curve may be irritating at loud levels.
Lavry Engineering’s listening tests were based on test tones and repeating loops of quiet passages of various material (mostly classical music) with flat amplifier response. Listening to test tones was straightforward: we used the Model AD122-96 MKIII test tone generator mode switching the Acoustic Bit Correction™ on and off. The frequency and amplitude programmability was very useful.
a. The practice of greatly amplifying low level signals to determine triangular flat PDF (probability density function) dither reveals the effectiveness of distortion and noise modulation elimination. This practice yields misleading results when testing unflattened dithers and/or noise shapers. It conflicts directly with L. Fielder’s findings showing completely different threshold delectability curves for quiet and loud levels. Noise shaping listening tests must be done at "reasonable" volume levels.
b. Given the above requirement, our listening tests concluded a strong preference for "triangle high pass" dither (this dither is produced by simultaneously adding a new random number and subtracting the previous value). Such dither is frequency-shaped to carry more high frequency energy (the energy content at low frequencies is minimal).
c. Listening tests revealed a preference for smoothly varying noise-shaping curves. Peaks and notches seem to irritate the listener (admittedly while turning the volume up). In addition, despite the temptation to optimize the noise shaping curve to the average listener’s hearing threshold, given a significant variation from listener to listener requires reasonable compromises in tailoring such a curve. In other words, smooth the curve.
The improvements offered by dither and noise shaping vary with source material and final word length. An A/B/X test at 16-bit level, requires a quiet environment and low level (loudness) audio. The listener must resist the temptation to turn the volume up to unreasonable levels. The practice of truncating to short word length (8-12 bits) should be avoided. The ideal noise-shaping curve may be irritating at loud levels.
Lavry Engineering’s listening tests were based on test tones and repeating loops of quiet passages of various material (mostly classical music) with flat amplifier response. Listening to test tones was straightforward: we used the Model AD122-96 MKIII test tone generator mode switching the Acoustic Bit Correction™ on and off. The frequency and amplitude programmability was very useful.
http://recforums.prosoundweb.com/index.php.../48/0#msg_num_1
...so I am not alone in my thinking. It it like those who dare question that the world is not flat, discussion is good and shouldn't be counted with a 'do the results matter?', of course they matter. It is the basis of all scientific testing, as apposed to theological ideas.
Dither is one of those difficult areas, since my original post I have spent a further 20 hours reading up and still think (70% sure) you cannot mess with the signal as it invalidates the process. I am of the view the best way to test dithers is in the frequency domain, this deternimes if the dither is effective (such as > -100 db dynamic range at certain frequencies) and here is the clincher, as long as the noise added remains inaudible in normal circumstances then the dither is working as should.
Dither is one of those difficult areas, since my original post I have spent a further 20 hours reading up and still think (70% sure) you cannot mess with the signal as it invalidates the process. I am of the view the best way to test dithers is in the frequency domain, this deternimes if the dither is effective (such as > -100 db dynamic range at certain frequencies) and here is the clincher, as long as the noise added remains inaudible in normal circumstances then the dither is working as should.
Well, if I read the quote, they used low volume music and *did* turn the volume up, just not unreasonably loud.
Again, I don't see any other way to practically test this. You can analyse the dither in other ways, but the actual tuning of the noise shaper is a psychoacoustics process.
Hearing beyond the 15th bit is extremely hard, how are you going to test different dithers for audibility there? You'll have to go a similar way, set up a soundproof room and spend a lot on time on listening tests.
Don't misunderstand me. I fully agree that the most solid test is in the actual playback conditions, 16 bit, volume at a default setting. It's just very hard. Each time you turn the knob, testing gets easier, and you will deviate very slightly. It's not like the hearing curves suddenly turn upside down. I think you are right to criticise the test, but it's not sensible to say the results are completely flawed if you haven't been able to perform a better one - because while the hearing curves do change with loudness, they change smoothtly, it's not like they turn upside down.
It's like saying Newton is wrong because you observed a relativistic effect. Yes, you might be right, but until Einstein comes along Newtons results are certainly very usable
If I get your proposal, you want to evaluate the SNR gain in the frequency domain, and then turn up the dither as loud as possible while still being inaudible.
This sounds great in theory, but you might run into practical issues. You'll end up blasting VERY LOUD HF noise through the reproduction system, and not all of them will like that. Think blown tweeters, so be carefull
Good luck!
PS. The fact that audibility and masking levels are dependant on loudness and the listener isn't news...You will be able to apply a lot more dither if the person listening is 40 years old and deaf to 13kHz than against a 15 year old that hears 18kHz.
Again, I don't see any other way to practically test this. You can analyse the dither in other ways, but the actual tuning of the noise shaper is a psychoacoustics process.
Hearing beyond the 15th bit is extremely hard, how are you going to test different dithers for audibility there? You'll have to go a similar way, set up a soundproof room and spend a lot on time on listening tests.
Don't misunderstand me. I fully agree that the most solid test is in the actual playback conditions, 16 bit, volume at a default setting. It's just very hard. Each time you turn the knob, testing gets easier, and you will deviate very slightly. It's not like the hearing curves suddenly turn upside down. I think you are right to criticise the test, but it's not sensible to say the results are completely flawed if you haven't been able to perform a better one - because while the hearing curves do change with loudness, they change smoothtly, it's not like they turn upside down.
It's like saying Newton is wrong because you observed a relativistic effect. Yes, you might be right, but until Einstein comes along Newtons results are certainly very usable
If I get your proposal, you want to evaluate the SNR gain in the frequency domain, and then turn up the dither as loud as possible while still being inaudible.
This sounds great in theory, but you might run into practical issues. You'll end up blasting VERY LOUD HF noise through the reproduction system, and not all of them will like that. Think blown tweeters, so be carefull
Good luck!
PS. The fact that audibility and masking levels are dependant on loudness and the listener isn't news...You will be able to apply a lot more dither if the person listening is 40 years old and deaf to 13kHz than against a 15 year old that hears 18kHz.
I'm getting a 403 Forbidden response from http://www.foobar2000.net/.
Is this just me, or does Guruboolez need to kick his server administrator?
Is this just me, or does Guruboolez need to kick his server administrator?
Garf: Nope Mr Lavry doesn't suggest listening to dither at levels where you just start to hear it. Quite the opposite. Since, as Mr Lavry says, the threshold detectibility curves are completely different for quiet and loud levels --> "Noise shaping listening tests must be done at "reasonable" volume levels."
I'd hate to appeal to authority, but do you know who Dan Lavry is? If you don't I recommend spending some time at the forum I linked to above. Regular posters include Mr Lavry himsel and also Bob Katz and Nika Aldrich (it's a scientific and objectivist forum).
I'd hate to appeal to authority, but do you know who Dan Lavry is? If you don't I recommend spending some time at the forum I linked to above. Regular posters include Mr Lavry himsel and also Bob Katz and Nika Aldrich (it's a scientific and objectivist forum).
QUOTE
Garf: Nope Mr Lavry doesn't suggest listening to dither at levels where you just start to hear it.
Where on earth did I say this?
Garf, answer to your question:
Furthermore, you also state that it isn't right to criticize the test as flawed unless you come up with a better test. I suggest you read what Mr Lavry wrote again since that is exactly what he has done.
QUOTE(Garf @ Jan 10 2006, 10:28 AM)
If I get your proposal, you want to evaluate the SNR gain in the frequency domain, and then turn up the dither as loud as possible while still being inaudible.
This sounds great in theory, but you might run into practical issues. You'll end up blasting VERY LOUD HF noise through the reproduction system, and not all of them will like that. Think blown tweeters, so be carefull
This sounds great in theory, but you might run into practical issues. You'll end up blasting VERY LOUD HF noise through the reproduction system, and not all of them will like that. Think blown tweeters, so be carefull
Furthermore, you also state that it isn't right to criticize the test as flawed unless you come up with a better test. I suggest you read what Mr Lavry wrote again since that is exactly what he has done.
QUOTE(CosmoKramer @ Jan 10 2006, 07:54 PM)
Garf, answer to your question:
QUOTE(Garf @ Jan 10 2006, 10:28 AM)
If I get your proposal, you want to evaluate the SNR gain in the frequency domain, and then turn up the dither as loud as possible while still being inaudible.
This sounds great in theory, but you might run into practical issues. You'll end up blasting VERY LOUD HF noise through the reproduction system, and not all of them will like that. Think blown tweeters, so be carefull
This sounds great in theory, but you might run into practical issues. You'll end up blasting VERY LOUD HF noise through the reproduction system, and not all of them will like that. Think blown tweeters, so be carefull
Gah! I'm not talking about the volume level in the test there, I'm talking about TUNING THE NOISE THE NOISESHAPER ADDS. That's exactly why it says "while still being inaudible" and not what you say.
QUOTE
Furthermore, you also state that it isn't right to criticize the test as flawed unless you come up with a better test. I suggest you read what Mr Lavry wrote again since that is exactly what he has done.
He's doing exactly the same thing! He warns against the effect changing the volume level has on the shape of the audibility curves, and that too large volume levels hence invalidate the test. Spoon already warned against this and I agree with the principle. My previous posts elaborates on that; I explain that there is a smooth tradeoff between making the testing easier and getting a large error on the curve you will end up with. Furthermore, practical limitations of playback material might cause limits contrary to what a theorethically optimal test or dither design will produce. The dither you design should be resistant against those, or it's not going to be very usable in practise.
Clearer now?
Edit: PS. I say it seems they also turn up the volume, just not to an unreasonable level, because of this quote: "The listener must resist the temptation to turn the volume up to unreasonable levels." They could have said "to turn the volume up. PERIOD", but they didn't.
Well I don't know what you are arguing then. I stated that Guru's test is flawed, which you apparently agree with, so what exactly are you in disagreeance with?
QUOTE(Synthetic Soul @ Jan 10 2006, 03:13 PM)
I'm getting a 403 Forbidden response from http://www.foobar2000.net/.
Is this just me, or does Guruboolez need to kick his server administrator?
Is this just me, or does Guruboolez need to kick his server administrator?
I'm getting it too.
Thanks for the confirm. I thought it was just me for a while.
Unfortunately I think guruboolez has other things on his mind.
Unfortunately I think guruboolez has other things on his mind.
QUOTE(CosmoKramer @ Jan 10 2006, 09:13 PM)
Well I don't know what you are arguing then. I stated that Guru's test is flawed, which you apparently agree with, so what exactly are you in disagreeance with?
I compared it to saying Newton was wrong because we know what Einstein said. Yes, but...
We can work with a suboptimal, less accurate result if it allows us to do practical things easier. Of course, the theorethically correct method would be even better.
But that doesn't mean the original was "flawed" in as so much the the results are worthless. Just like the test you qoute isn't, although they apparently did adjust the volume. I would be impressed if anyone actually manages to ABX dither vs truncation at completely normal playback volume. It would be a stricter version of the "MAD Challenge" and even that is insanely hard to pass. Let alone repeat it to determine an optimal dither.
The tradeoff is "less accurate" vs. "more accurate". Not "fatally flawed" vs. "100% correct".
Given that auditory capabilities change even between humas, you won't get a 100% method, anyway. Might as well call any test "flawed" then. But I will ignore you and make something that demonstrably works, despite being based on slightly inaccurate results
QUOTE(Garf @ Jan 11 2006, 12:55 PM)
The tradeoff is "less accurate" vs. "more accurate". Not "fatally flawed" vs. "100% correct".
Nobody has said anything about fatally flawed. Just flawed. Huge difference.
When it's all said and done more professional people have conducted solid ABX test evaluating the efftects of dither, come to conclusions, while also recommending guidelines for how to evaluate dither. Guidelines which says a big no-no to tests such as performed by Guru.
The scientific minded audio world does not begin or end with HA.
Amplification of low-level dithered and requantized test signals up to clearly audible levels is useful for checking if the dither is properly eliminating quantization distortion and does not produce noise modulation. And is useful for this whether the dither is flat or noise shaped. In this context, MAD dither amplitude was (last time I checked) insufficient because it caused both artifacts, and this could be checked by the mentioned amplification procedure.
Said this, I find useful the procedure of comparing just dither noise audibility (I mean dither without any test signal, that is, dithered "silence") at barely audible levels, given that there is little background noise and dither noise levels are low enough. If the noise cause by one of the dithers at test is barely audible and the other is not audible, then the one not audible is better for sure, under those conditions.
For tests at real world conditions, when not applying extra amplification in order to make dither noise audible, if no one of the dithers is audible by itself... then it really doesn't matter.
Said this, I find useful the procedure of comparing just dither noise audibility (I mean dither without any test signal, that is, dithered "silence") at barely audible levels, given that there is little background noise and dither noise levels are low enough. If the noise cause by one of the dithers at test is barely audible and the other is not audible, then the one not audible is better for sure, under those conditions.
For tests at real world conditions, when not applying extra amplification in order to make dither noise audible, if no one of the dithers is audible by itself... then it really doesn't matter.
Sorry for delay.
Btw, it appears that your testing procedure for dither evaluation is flawed.
A listening test performed on unusual (and impracticable in real life!) condition is inherently flawed In my case, I could only conclude that dither x is better than dither y on the tested conditions: over-amplified playback of ultra-quiet recordings. I can’t extrapolate the result to normal playback condition: conclusion won’t be valid anymore I suppose. The practical purpose of my test is therefore close to zero. I did it by curiosity, and because it was for me the only way to evaluate the performance of different MP3 decoders. My poor hearing abilities don’t allow me to differentiate MAD from another MP3 decoder (excepted the reputed Nitrane?). And even with these extreme testing conditions, the test was difficult to perform (my audio hardware is rather inexpensive and my amp produce a strong amount of noise at high volume).
BTW, I’m amazed to see that some people are able to make a distinction between different dithered noise shaping technology on 16 bit or more material. I haven’t reached this state – far from it!
QUOTE(CosmoKramer @ Jan 9 2006, 05:13 PM)
Btw, it appears that your testing procedure for dither evaluation is flawed.
http://recforums.prosoundweb.com/index.php.../48/0#msg_num_1
http://recforums.prosoundweb.com/index.php.../48/0#msg_num_1
Btw, it appears that your testing procedure for dither evaluation is flawed.
A listening test performed on unusual (and impracticable in real life!) condition is inherently flawed
In my case, I could only conclude that dither x is better than dither y on the tested conditions: over-amplified playback of ultra-quiet recordings. I can’t extrapolate the result to normal playback condition: conclusion won’t be valid anymore I suppose. The practical purpose of my test is therefore close to zero. I did it by curiosity, and because it was for me the only way to evaluate the performance of different MP3 decoders. My poor hearing abilities don’t allow me to differentiate MAD from another MP3 decoder (excepted the reputed Nitrane?). And even with these extreme testing conditions, the test was difficult to perform (my audio hardware is rather inexpensive and my amp produce a strong amount of noise at high volume).BTW, I’m amazed to see that some people are able to make a distinction between different dithered noise shaping technology on 16 bit or more material. I haven’t reached this state – far from it!
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