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Measuring audio quality degradation
Rotareneg
post Feb 25 2014, 02:49
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In order to come close to being able to define a "better/worse" scale, you'll have to be very specific about the scenario you are targeting. One scale that targets young listeners who like to sit in a quiet room with good equipment and pay close attention to the music is going to be very different than a scale targeting older people who visit heavy metal concerts all the time and who will be listening with crummy noise-canceling headphones while working in a noisy factory.

That's why people say that, for example, a 128 kbps MP3 made with a decent encoder is likely to be perceived as the same as the original by most people, most of the time, with most music, not all people all of the time with all music. Even if we has a "perfect" psycoacoustic model, you'd still run into the fact that the particular situation of each individual listener is going to be different.

As for your original question: Without reference to the original recording you won't be able to be certain that any audio you obtain is going to sound "authentic" as there's nothing keeping someone from running the audio through an EQ or other processing before compressing it, even for lossless files, and this even applies to physical media like CDs, where you might run into remastered versions with more DRC or different EQ, or whatever.
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AstralStorm
post Feb 25 2014, 09:14
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Indeed, that's what properly ran ABC/HR trials are for and why you need anchors in the scale, both top anchor and bottom anchor. (Unless you're measuring the extreme top, then you might need two bottom anchors.) Even with bad equipment you might be able to hear the difference. (Or perhaps actually it might be easier.)

Generally the differences compress but the rating ordering still remains. The differences may turn insignificant though.

This post has been edited by AstralStorm: Feb 25 2014, 09:19


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ruxvilti'a
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Arnold B. Kruege...
post Feb 27 2014, 13:56
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QUOTE (AstralStorm @ Feb 25 2014, 03:14) *
Indeed, that's what properly ran ABC/HR trials are for and why you need anchors in the scale, both top anchor and bottom anchor. (Unless you're measuring the extreme top, then you might need two bottom anchors.) Even with bad equipment you might be able to hear the difference. (Or perhaps actually it might be easier.)

Generally the differences compress but the rating ordering still remains. The differences may turn insignificant though.


Seems to completely miss the point is that when measured performance is sufficiently high (e.g. the 100 dB rule) subjective tests are a complete and total waste of time.
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