reshare this, please, tell your friends, etc, etc!! we have music faster than any other place, and faster speeds, even if you're paying for your downloads, tribalmixes community of 55k people will max out any connection you have with our cumulative speed... my downloads are always at or over 20mbps, and my max is 24..
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First of all, what is a sound spectrum?
The sound is a wave of pressure we hear when it propagate through the air. A sensor-microphone can generate an electrical signal to mach exactly the pressure wave. This electrical signal I an analog signal meaning it is determined at every moment of a time range and its value is every value in a range of values.
The computers don't process such signals. Instead, they work with discrete time signals. A discrete time signal is determined at discrete moments of time in some time range, so these moments are finite number and its values are taken from a finite set of values, for example the set of all 16-bit binary numbers. Such signals are represented by discrete time functions. We will call the discrete time functions that represent some sound wave digital sound. In order to be played a digital sound needs to be converted back to analog signal.
There exist strict mathematical transforms which can transform a function of a time, like a function representing an analog sound signal, to a function of parameter, called frequency. Based on such transform are functions called spectra. Among them is the Power Spectrum or simply spectrum which I'm going to use.
The scientific researches have establish that a human can percept sounds whose spectrum parameter is in the range 20 Hz - 22 kHz.
According to this the Red Book - the Sony-Philips standard for digital recording of audio CD a digital sound needs to be generated by sampling the analog sound signal at a rate of 44,100 samples per second and the sample digital value needs to be a 16-bit digital number. 44.1 kHz sampling rate has been chosen based on the theory stating that an analog signal can be perfectly reconstructed from an digital time signal if the analog signal is band limited and the sampling rate is at least twice as high as the band limit.
There are discrete time transforms to process the discrete time functions and we are using them.
Finally, as long as the transforms are strict mathematical operations everything one can conclude from a transform (spectrum) applies to the discrete time function (digital sound) also. In particular, if one conclude that two spectra are close then the digital sound functions are close also.
Now, there is a spectrum shown on the figure below. It has two views: in a logarithmic scale, which allows for the low frequency range to be observed and in linear scale, which actually hides the low frequency range.
The spectrum is calculated based on the Tiesto's remix of the Delerium [Featuring Sarah McLachlan] - Silence.
It is a CD rip. So, you can see the spectrum is band limited with upper limit of 22.05 kHz.
This spectrum is of a quality sound:
It has almost flat area until frequency 10.5 kHz, then slowly declines until 20 kHz, and there is a transient area 20 - 22 kHz.
A worse quality sound usually is below this one. Of course, it depends on the sound itself.
Important things to remember:
- all audible (20 Hz - 22 kHz) frequencies are present in the spectrum. The spectrum bandwidth is 22 kHz.
- There is a simple sound quality rule saying the sound quality is the bandwidth.
Fig 1
Further on I'm going to use only the linear scale representation because the changes I'm going to show are easy visible in the high frequency spectrum range.
Next figure shows five spectra:
Lossless - it is the original CD rip,
Next four are from mp3 (-q0) default encoded at 320 kbps, VBR max quality ( V0), 192 kbps, and 128 kbps digital sounds.
Fig 2
As you can see it's almost impossible to draw some conclusions based on the differences seen the low and middle frequency range. And I'm not interesting in them. So, further I'm going to show the frequency range I'm going to focus.
Fig 3
The bandwidth quality rule here:
320 kbps - 20 kHz, 251 kbps (VBR) - 19 kHz, 192 kbps - 18.5 kHz, 128 kbps - 16.5 kHz.
Next, I'm going to discus to sounds:
01-gramatik_-_live_at_the_electric_zoo_(new_york)-sat-09-04-2011-talion.mp3 you can download it from tibalemixes.com
gramatik___live_at_the_electric_zoo__new_york__sat_09_04_2011_talion.mp3 you can download through a link provided by mixing_dj
Because they both have the same name I'll rifer them talion and mixing.
First, let's see the talion release.
If you take information about the file using MediInfo you'll get:
Encoding settings: -m j -V 0 -q 0 -lowpass 19.5 --vbr-new -b 32
This is exactly the default settings lame is using if you start it this way: lame -q0 -V0. Lame adds the rest.
Here is its spectrum along with three more as references.
Fig 4
The talion's spectrum is below the others obtained from the CD rip. It is different sound indeed.
As it is seen talion's spectrum is band limited at 15 kHz while lame low pass limit imposed by lame's filter would be 19.5 kHz. It's band limit is 15 kHz and this is because their source is band limited.
As I have already said in my previous post, their source is Sirius channel of the satellite radio Sirius XM and it is some kind of FM radio. (Analog FM radios are band limited to 16 kHz.)
Because TALiON don't specify the low pass filter to be used by LAME it uses it's default with a band limit of 19.5 kHz. Because of that it uses 44.1 kHz as a sampling rate, also. And a sample is encoded in average with 216 kbps/44.1 kHz = 4.978 bit per sample. Had they used parameter -lowpass 15 or resample 32, LAME would use 32 kHz as a sampling rate. With such a sampling rate lame vbr encoded Silence (Tiesto remix) has 201 kbps which gives 201/32 = 6.28125 bit per sample in average. Having in main that the source CD rip uses 16 bit/sample it is obvious a 32 kHz sampled encode would be of better quality. (The lower bit per sample introduces so called "quantization noice".)
Besides, this is true for any analog FM radio. They broacast band limited at 16 kHz sound. So, the perfect encode would be sampled at 32.0 kHz.
Finally, let's see the differences between talion and muxing.dj releases.
Fig 5
I would say there are not visible differences. You can see them in the transient range but there they are not important at all.
But nevertheless there are differences. The quality of and re-encode if no special processing has been made, is worse than that of the it's losy encoded source. The best re-encode would be a lossless encode which will perfectly reconstruct its losy source. But this is meaningless.
Со, the reason is as follow.
The re-encode is made using a decoded losy encoded source. The chances that the encoder will throw the same information as during the encoding of the original source is ZERO. That's way the encoder will throw different information which means it will increase the information lost from the source.
So, I don't see any good reason for the TALiON's release to be re-encoded @320 kbps. The result is increased file size and lower sound quality.
last edited by SpasV at 2011-09-24 21:15:07 gmt
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Skype:spas.velev
thanks to SPAS for this wonderful investigation! and here's what i have to say about it: thanks alot, SPAS, for doing this all! with charts and diagrams people must trust this better, than when i said "mixingdj is upencoding their mixes". noone cared. now i hope some people will open their eyes!
for those, who doesn't see the idea of this article... it is here to show, that files some people download from mixing_dj site are A WASTE OF YOUR BANDWIDTH! mixing_dj is out there to have you pay for your downloads, but they don't do it directly, they want you to download huge upencoded files so that you'd spend your daily/hourly whatever limits with the file sharing host where they store the upencoded mp3s, and in the end you can't take all the waiting and pay $10 for the fast downloading access with that file sharing host...
i hope you see the difference now... sites like tribalmixes, themixingbowl and maybe 2-3 others provide FREE MUSIC for FREE with no (or very limited) advertising. while sites like mixing_dj and similar blogs do it for money, they get percentage and stuff, they put so much advertising on their site, that you can hardly click the right link without triggering some add... this is truly sad... and i really hope everyone will realize at some point, that FREE stuff must be FREE.,,
and on tribalmixes.com you can download DJ Mixes free and fast and secure via torrents, while we also offer direct downloads now, we don't insist on them, and surely we don't up-encode our mixes..
slash @ tribalmixes
what sites like mixing.dj are doing is UNETHICAL, they have NO RIGHT to mess with the original mp3s that people from mp3-scene are being so nice to provide to them (and to everyone else), and those who RESPECT THE SCENE and the work of the sceners - they re-share those mixes as is, including infos, group logos, anything. that's what we do on www.tribalmixes.com, we respect, value and praise those who spend countless hours recording those sets from sirius, radio1, kiss fm, delta and other stations all over the world, we don't paint over someone else's painting, NO! we hang it on the wall and give it a nicew dusting every day, but we don't furnish it with unneeded SECOND frame to make it 50% bigger (their up-encoding from 192 to 320kbps), we do not write our name on it (and they do, they leave their name on someone else's work? how SCREWED UP is that? they write their site name into make 5-10 fields of IDv3 tags), we don't even take it out of the wrapper (share it as folder with included group/ripper info, etc)... and why? cause WE CARE for our listeners and for our providers, we don't pretend we did something we've never done, and half of our content is recorded by OUR own users, or passed to us by DJs themselves, thus we have either master copies of the best quality or we have mp3s of as high a quality as it can be, if we record 128kbps stream - we share it as 128kbps bit-rated mp3 file, or VBR which gives less size.. remember, REAL SCENE MP3s come as VBR, if you see something that says TALION or 1KING on it and it's 320kbps - you will know someone is trying to screw you (and others). watch for the right bitrates and the right mp3s. tribalmixes comes from a long time ago when bandwidth costed alot, and people in their homes and work places couldn't just seed all the time, even nowadays some users have limited monthly bandwidth allocations.. would they rather get 2 smaller files than one blown up with EMPTY sound? everyone knows - up-encoding cannot better an mp3, if you save 192kbps mp3 into 320kbps - you're trying to pull sound out of thin air, and in the end, mp3 becomes that - half freaking air... this is really an issue of everyone's self-respect as well. do you want to keep being f$$ked??? i don't. that is why MIXING.DJ sets are prohibited on tribalmixes from now on. if you want to share a set, and have nowhere else to get the proper version than sites that up-encode, - YOU BETTER SHARE NOTHING on tribalmixes. that's all i have to say.
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