
What Data Compression Does to Music (2012) - colinprince
https://www.soundonsound.com/techniques/what-data-compression-does-your-music
======
ovao
It’s interesting that the author seems keen to discuss the concept of
psychoacoustic encoding only to dedicate much of the article to looking at
waveforms and making condemnations based on looking at those waveforms. Which
misses the point entirely.

This is a _somewhat_ older article, but most lossy encoders at the time were
still very good even at fairly low (sub-96 kbps) bit rates.

~~~
imhelpingu
The author explains that it's a psychoacoustic model and then demonstrates how
various artifacts in various waveforms are the result of compromises within
this model. As an aside, I don't understand why people take the position that
lossy transcodes are indistinguishable from one another when, right out of the
gate, it's well-understand that compromises are being made in the highs, well
within the range of human hearing. In fact, CDs can only replicate frequencies
below 22kHz and even _that 's_ within the hearable range of many (mostly
younger) people.

I just really don't understand this widespread need to believe "lossy" doesn't
really mean "lossy." It's a psychoacoustic model and people are different, and
further you can (as demonstrated by the article) even show where various
encoding artifacts are feasibly audible to plenty of people. I just don't get
it.

~~~
tchaffee
I used to believe these things were audible until I got into A / B testing
with people claiming to hear the difference. The vast majority cannot. I
barely ever can. And that's when I'm focusing to try to detect a difference.
It's not something I'll notice when listening for enjoyment. YMMV, but I
highly suggest doing listening tests yourself.

~~~
joegahona
Same. NPR Music published a quiz of this sort a few years ago
([https://www.npr.org/sections/therecord/2015/06/02/411473508/...](https://www.npr.org/sections/therecord/2015/06/02/411473508/how-
well-can-you-hear-audio-quality)), and I failed pretty hard. I learned to play
piano by ear too, so it's not like my ear is crap.

~~~
darkerside
Ha, I just picked 5/6 the 128Kbps tracks. Maybe my ear has become accustomed
to the compression artifacts and misses them when they're not there!

~~~
33degrees
This is apparently a thing, that people will prefer what they’re used to and
these days that’s low bitrate audio played through phone and laptop
speakers...

~~~
tchaffee
I question how often people regularly listen to music through laptop speakers.
Isn't it mostly through earphones or headphones?

~~~
33degrees
Not necessarily, lots of students don’t speakers hooked up to their laptops,
abd I see kids listening to music on their phone speakers all the time

------
mark-r
Many people don't realize that Bluetooth requires compression applied to audio
too. Theoretically the latest revisions allow already compressed music in
certain formats to be transmitted as-is without recompression, but I'm
guessing the data paths to allow that to happen don't usually exist. Double
compression will be far more damaging.

~~~
vlovich123
They do. Most headsets on the market these days support mp3/aac and the OSes
support it too (can't recall if iOS supports mp3).

~~~
mark-r
But does the entire chain end-to-end support sending a file unmodified? If for
example there's a mixer involved so that your ringtone can interrupt your
music, that music can't be piped through without decoding. Is the volume
control handled in the headset or does it come earlier? That can't be applied
without decoding either.

~~~
vlovich123
When no mixing is occurring I believe there's no decode/re-encode happening so
that battery savings are realized. If there are multiple audio streams then
the mixer kicks in and for that time period there would be re-encoding
occurring but from an acoustic quality perspective that wouldn't matter since
the multiple audio streams would already alter the perceived quality relative
to the reference.

------
0xf8
Doesn’t the equipment used for reproducing the soundstage matter in A/B
testing? I haven’t done a rigorous test myself, because I’m comfortable having
a predilection for high fidelity audio even if it isn’t
demonstrably/empirically superior. But in my experience listening to music on
a “audiophile” or “studio reference” setup, when the equipment is sufficiently
sensitive and well engineered as to most accurately render the audio signal, I
recall rather obviously noticing a difference in sound quality.

I can’t imagine if you compare a 192kbps MP3 with a DSD256 audio file played
on reference monitors from a high performance DAC there’d be no audible
difference. Personally, using a McIntosh integrated amp and Focal Utopia
headphones the first time I listened to a DSD track, 1-bit word depth sampled
2.8M times per second, it was unlike anything I’d ever heard before. I
acknowledge that’s not a direct comparison, but all i’m saying is maybe the
lossy vs lossless test performed on a low fidelity audio chain where the
signal is always meaningfully subject to harmonic distortion before you hear
it is the reason most people can’t tell a difference?

~~~
w1nt3rmu4e
Personally I have zero problems A/B-ing DSD, PCM and lossy formats on my
reference system (headphones). I also know (award winning) people in the audio
industry who can walk into a listening room and tell you where the dominate
resonances are or tell you if a reconstruction filter is linear or minimum
phase.

The idea you can take a group of non-professionals and run tests with no
requirements on equipment quality and then draw conclusions about what _any_
human can hear is absurd.

Those tests (Hydrogenaudio was one of the main proponents back when lossy
codecs were more important) are a decent way to tell if something is audible
for _the average listener with average equipment_. It cracks me up when people
start telling me what _I_ can or cannot hear based on those tests without
knowing anything about me or what kind of equipment I own. This happened just
the other day on an audio forum.

Another dimension to this is that DAC quality has been increasing steadily
while the prices of high fidelity DACs have been dropping. The DAC chips on
the market today are really the best ever made (ESS and AKM notably). More
people than ever have access to (near-)reference quality DACs. When lossy
compression tests were popular _few_ people had access to reference quality
DACs. I remember people talking about using their _computer sound cards_ as
sources for those tests.

I think a lot of people react negatively to this topic because it's considered
elitist (expensive toys). The good news is just about anyone can afford a
near-reference quality, inexpensive headphone setup these days. You have to do
your homework and read reviews but they definitely exist. I recently picked up
a DAP and IEMs for ~$300 total (for running) and it's 90% of the quality of my
reference rig. I listen to it instead of my reference rig sometimes. It's that
good, despite the price.

(Even on that, I can easily ABX FLAC and 192kps AAC, which has been
universally declared "transparent" more than once.)

If you think your smartphone's audio jack sounds good, you really need to
listen to a device with a proper amount of output power (you need more than
you think for headphones) and a high resolution DAC. You need both to be good,
though they can be part of the same device. When you have them, music really
becomes holographic and, for lack of a better word, alive.

~~~
ZoomZoomZoom
>It cracks me up when people start telling me what I can or cannot hear based
on those tests without knowing anything about me or what kind of equipment I
own. This happened just the other day on an audio forum.

Just disprove them with data! Until then, casually mentioning "award-winning"
acquaintances and telling people they need "proper" gear reads a bit
condescending and probably turns some people defensive.

~~~
w1nt3rmu4e
I generally don't name drop and I never tell people to get better gear. The
burden of proof is not on me. I simply _do not give a shit_ what they believe.

I only take issue with people telling me what I do or do not experience --
because of the absurdity of that. The fact that this is about audio is
coincidental.

~~~
ZoomZoomZoom
If they tell you this in a personal dialogue, than I concur, it's silly and
probably pointless. However, in a public online discussion they are probably
just trying to mark for others some information which they see as false as
something to disregard. And if they're reasonable, they will add some
statistical data to prove their point.

------
cyberferret
To say nothing of what _audio_ compression does to music (Ref: loudness wars
[0])

I was intrigued by this paragraph in the article:

>> Psychoacoustics is the study of how humans perceive sound, and it's
relevant here because advocates of lossy data compression argue that when
listening to CD-quality audio, it is impossible for our brains to perceive all
the data reaching our ears. It is, therefore, unnecessary — the argument goes
— to store and reproduce all of that data. But which data can be removed is
another question, and this is why various psychoacoustic principles are
exploited in different amounts by different perceptual audio coding
algorithms.

I wonder if different people will perceive sound differently (in terms of
frequency and dynamics) purely based on physiological/psychological traits?

[0] -
[https://en.wikipedia.org/wiki/Loudness_war](https://en.wikipedia.org/wiki/Loudness_war)

~~~
mark-r
I've wondered if some of the loudness wars are driven by an attempt to
compensate for lossy compression? The wars haven't abated - the latest by
Panic At The Disco is the loudest I've ever ripped.

~~~
sandov
Worse than release day Death Magnetic by Metallica?

~~~
mark-r
I don't have that one so I can't compare. I certainly won't claim to have seen
the worst, I can only relate a general observation that things aren't getting
better.

------
Fannon
There's one point i've read somewhere that really made methink differently on
this subject: It was claiming that listening to lossy formats will increase
brain activity, because you're brain makes up for some missing information on
thy fly. This is not a conscious proccess. But after listening to music for a
while, lossless music could be less exhausting and more relaxing because of
that.

Not completely sure, if this is true, I couldn't find the study for it right
away.

~~~
colechristensen
I would believe that some of the distortion on the edge of perception might
cause a little bit of stress (like, say, the barely audible whine of bad
fluorescent lighting), but not really the bit about the brain working harder.

------
zrav
Compared to the many anti-scientific audiophile articles, this one was quite
decent.

A bit that bothered me was the description of how the encoders work. It
mentions the discarding of frequencies, which is not entirely correct. The
only real discarding of frequencies happens with the lowpass filter that is
typically applied as a pre-processing step, not the actual encoding. The
encoding of the frequency components happens with coefficients, which are
quantized (coarsely encoded), not zeroed. This introduces noise to the signal,
which is weighted against the computed masking threshold, driving bit
allocation to the different frequency bands.

As for the format recommendation for people ripping their own CDs, I'd say
stick to a lossless format for storage at home. That way you're future-proof.
For mobile use, make encodings from those files using whatever best lossy
format is available at the time.

~~~
Severian
This is what I do at home. I rip CDs using EAC (Exact Audio Copy) to FLAC with
a .CUE file. That way I can recreate the image if needed. I usually upload the
FLAC to Google Music to add to my library for my portable needs.

------
eponeponepon
I don't really understand how the lossy vs lossless argument turned into a
chest-beating contest about whose ears are the best.

The point of lossless audio compression is archiving - knowing that you can
make a first-generation encoding of the audio you have stored for any new
device or format in future.

If you want to listen to your FLAC files, great, you're not losing anything by
doing that - just don't try and tell me that it's an aesthetic choice that
makes the slightest bit of difference to the experience.

~~~
taneq
> I don't really understand how the lossy vs lossless argument turned into a
> chest-beating contest about whose ears are the best.

It's just basic human nature. As soon as you say "you can't
see/hear/taste/perceive the difference between X and Y" some dick-waver will
come in and start saying they can do it. And of course, the first to admit
they can't hear a difference loses, and then you end up with things like
Monster Cables, and the Emperor's new hi-fi setup.

I've seen people seriously claim they can hear the difference between the same
audio signal burned onto different brands of CD-Rs.

------
willtim
Does anyone know if the audio samples are still available somewhere?

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tomcooks
Compression glitches can also produce beautiful harmonics as samples' quality
degrades: Mille Plateaux just released Bienoise's "Most beautiful design"[0],
an LP that can fit on a 1.44 floppy disk thanks to mp3 compression and clever
mixing

[0]([https://forceincmilleplateaux.bandcamp.com/album/most-
beauti...](https://forceincmilleplateaux.bandcamp.com/album/most-beautiful-
design))

------
scns
Very interesting article about inter sample peaks in cd recordings which
result in clipping in the DAC

[https://benchmarkmedia.com/blogs/application_notes/intersamp...](https://benchmarkmedia.com/blogs/application_notes/intersample-
overs-in-cd-recordings)

