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Topic: What percentage of original data do you LOSE at 320kbps? (Read 7014 times) previous topic - next topic
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What percentage of original data do you LOSE at 320kbps?

Hi all,

I was thinking, how much data is actually lost (as opposed to compressed) when ripping a CD to 320 kbps MP3?
I am not familiar with how the algorithms work or if you even could you put a number to what percentage of the original data that is still there?

Thanks,

Nick

What percentage of original data do you LOSE at 320kbps?

Reply #1 –
Bitrate of lossless compression (such as FLAC) is in the range 700-1000 kbps.

Lossy mp3 320 kbps can be compared with the above lossless bitrates.

So, in terms of bitrate, 320 kbps is about 30-40 % of original, and you "lose" about 60-70 % of "data".

Please note that this is just pure arithmetics only to answer your direct question. This is not related to sound quality.

What percentage of original data do you LOSE at 320kbps?

Reply #2 –
None of the original data is still there, you lose 100% of it. It is replaced with something that is entirely different yet close enough to be audibly identical.

What percentage of original data do you LOSE at 320kbps?

Reply #3 –
Lossy compression is PERCEPTUAL compression. This means that it is not about bits and bytes but instead about HOW IT SOUNDS LIKE TO A HUMAN. No computer can measure that, only humans. But since every human is a little bit different, there are no exact generic answers. In addition to this, how much is "lost" varies at every second of a song, because some samples need more bits than others. And last of all: MP3 DOES NOT "REMOVE" ANY INFORMATION. What mp3 does, is storing some information less accurately. To oversimplify it: MP3 works by blurring the sound, not by removing parts of it. So, to make an analogy to lossy image compression, mp3 is a bit like JPEG.

Thus, there is no meaningful arithmetic answer to your question. The only thing there is, is a practical average:

Nothing or almost nothing for almost everyone. Note that this rating only applies to how it sounds like without postprocessing - if you start to modify an mp3 by applying effects and stuff, minor inaccuracies may turn into noticable inaccuracies.
I am arrogant and I can afford it because I deliver.

What percentage of original data do you LOSE at 320kbps?

Reply #4 –
For digital silence, the correct answer is 0%.

For more complex signals, both the numerical and perceptual answer is signal dependent. Numerically, the losses increase dramatically. Perceptually, the losses are often irrelevant.

You asked the wrong question.

The right question is usually addressed using carefully controlled listening tests. There haven't been any public tests at 320kbps simply because so few people ever hear a difference. Search HA for isolated problems at 320kbps.

Cheers,
David.

What percentage of original data do you LOSE at 320kbps?

Reply #5 –
Quote from: Lyx on
Nothing or almost nothing for almost everyone. Note that this rating only applies to how it sounds like without postprocessing - if you start to modify an mp3 by applying effects and stuff, minor inaccuracies may turn into noticable inaccuracies.


Could you expand on this - what kind of postprocessing would be wise to avoid? I am generally looking for answers related to digital DJing - if that helps.

Thanks for all answers.

What percentage of original data do you LOSE at 320kbps?

Reply #6 –
Quote from: adress on
Quote from: Lyx on
Nothing or almost nothing for almost everyone. Note that this rating only applies to how it sounds like without postprocessing - if you start to modify an mp3 by applying effects and stuff, minor inaccuracies may turn into noticable inaccuracies.


Could you expand on this - what kind of postprocessing would be wise to avoid? I am generally looking for answers related to digital DJing - if that helps.

Thanks for all answers.

Surround sound decoding depends on information that is nearly inaudible in stereo. Since lossy encoding assumes stereo listening, it can distort this additional information and cause problems.
Also, major changes in volume setting or frequency response from flat can cause problems.

What percentage of original data do you LOSE at 320kbps?

Reply #7 –
Quote from: pdq on
Surround sound decoding depends on information that is nearly inaudible in stereo. Since lossy encoding assumes stereo listening, it can distort this additional information and cause problems.
Also, major changes in volume setting or frequency response from flat can cause problems.

To elaborate further on this: among other tricks, mp3 makes extensive use of what is called "masking" in combination with the "absolute threshold of hearing" (ATH). Normal music from a CD contains lots of information which in normal circumstances we cannot hear - either because it is way quieter than humans can hear, or because a sound is masked by another sound - or a mix of both. When quiet passages get significantly attenuated, so that they are almost as loud as the loud passages.... or if massive EQing is done..... then the asumptions on which the encoder based its decisions are no longer true. This does not mean that a few dB more would cause troubles - heck, even low-end speakers have some weird freq-response... stuff like this is in the "safety margin". But extensive postprocessing is not covered by that.

As a rule of thumb, lossy encoding is meant for normal listening only. As soon as you do something highly ususual, you may run into problems. Lossy encoding isn't meant as a source for audio-editing. Then again, in a room with an incredibly high noisefloor, like a club, it may be questionable if people could actually notice those problems.

- Lyx
I am arrogant and I can afford it because I deliver.