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Welcome to the Sea of Misinformation
#3061739 09/08/20 11:21 PM
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Also known as the internet.

So...I wanted to find out the absolute lowest bit rate for an MP3 file. Yes, I have programs that can render to MP3 at low bit rates, but wanted to know if those were the lowest possible bit rates...maybe there's a 2 kbps setting for data logging in Antarctica, right?

I came across a web site that said "A Sample Rate of 44100 Hz and a Bit Depth of 16/Bit Rate of about 320 kbps is known as the Red Book standard for audio CDs." Does the Red Book standard for audio CDs have anything to do with MP3s? I think not. Or am I the one who's ignorant?

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Re: Welcome to the Sea of Misinformation
Anderton #3061747 09/09/20 12:28 AM
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Who offended you such that you'd send them a 2 kbps MP3 in 2020? eek


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Re: Welcome to the Sea of Misinformation
Anderton #3061753 09/09/20 01:05 AM
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Just a bunch of 1's and zeroes.
Zeroes are nothing.

So it could be 160 kps instead of 320 kbs if they made a mistake and counted the zeros. laugh


There is never enough time to be in a hurry...
Re: Welcome to the Sea of Misinformation
David Emm #3061755 09/09/20 01:17 AM
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Originally Posted by David Emm
Who offended you such that you'd send them a 2 kbps MP3 in 2020? eek

I'm editing a glossary, and wanted to be able to state the minimum and maximum allowable bit rates for MP3s...particularly since the version I was editing said 384 kbps was the maximum rate for MP3s, which is not the case. That's what caused me to wade into the Sea of Misinformation. I think I'll need to take a shower afterward smile

Re: Welcome to the Sea of Misinformation
Anderton #3061789 09/09/20 12:26 PM
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Originally Posted by Anderton
I came across a web site that said "A Sample Rate of 44100 Hz and a Bit Depth of 16/Bit Rate of about 320 kbps is known as the Red Book standard for audio CDs." Does the Red Book standard for audio CDs have anything to do with MP3s?

No, the Red Book is a set of standards and requirements to assure than any compliant CD will play in any CD player. This includes physical media specifications, time periods, error correction encoding and decoding, and other such things. Part of the standard specifies the audio format as 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz. MP3 files weren't even invented (1987) when the first CD standard was published (1982).

The "Red Book standard for audio CDs" only suggests - and doesn't guarantee - that the 320 kbps, 44.1 kHz audio format has the equivalent frequency response and resolution of a standard CD - it actually exceeds it in some respects. One big difference, that separates the MP3 from the Red Book standard is the encoding method - MP3 vs. PCM. The difference is in the flavor and amount of distortion that each introduces. PCM encodes every sample in the same way. MP3 examines every sample and decides whether it would matter to the average listener if it was left out. This is why some types of music encoded as MP3 is virtually indistinguishable from the PCM that it probably came from, while other types of music sound obviously different. It has to do with the spectral content of the program material.

[EDIT] I'd better straighten this out before someone calls me out on it. The MP3 encoder doesn't look at every sample and decide whether to throw it out or not. That's just a broad brush example of statements like ". . . . the Red Book standard . . ." What MP3 encoding really does is analyzes the mix, looking for sounds in the recording that will be, are already are being masked by other sounds, and throwing those masked sounds away. It could be a single toot, or maybe a part played on a particular instrument while other things are going on. It's not a simple process. Those Fraunhofer folks are pretty smart. [END EDIT]

So, yeah, it's horse manure, but invoking "Red Book CD" sounds mighty impressive, especially to someone who doesn't know what the Red Book specifies.

Last edited by Mike Rivers; 09/09/20 07:48 PM.
Re: Welcome to the Sea of Misinformation
Anderton #3061815 09/09/20 03:43 PM
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I can't give you the scientific answer but just get put on hold during a phone call - you'll at least experience the lowest bit rate possible for an MP3.

Re: Welcome to the Sea of Misinformation
Anderton #3061834 09/09/20 05:56 PM
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Someone at IRCAM or Fraunhofer would be able to say with some authority, wouldn't they? I would think an engineer or product manager at Avid, Steinberg or other DAW manufacturer would know as well. Bob Katz or other A-list mastering engineers probably know. I doubt this is common internet knowledge. The only people that have to know are developers implementing the code. I never encode MP3 below 160kb, and usually at 192 or higher since that's about the point that no one can tell under blind ABX testing. Increasingly, there is enough bandwidth available that the need to heavily compress audio is just going away. Amazon and Tidal will both stream at CD rates.

Re: Welcome to the Sea of Misinformation
Anderton #3061921 09/10/20 10:56 AM
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There's quite a good article on wikipedia about MP3.

It seems to imply that the following rates are allowed.

"32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kbit/s".

So that 32 kbits/s would be the minimum.


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Re: Welcome to the Sea of Misinformation
BenWaB3 #3061951 09/10/20 04:25 PM
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Originally Posted by BenWaB3
I can't give you the scientific answer but just get put on hold during a phone call - you'll at least experience the lowest bit rate possible for an MP3.
Plus a "sound system" with a smaller, more focused frequency response and a crap speaker.

If a song sounds pretty OK through that, the mastering engineer's job is well done!


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Re: Welcome to the Sea of Misinformation
Anderton #3061999 09/10/20 10:47 PM
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I don't have any technical depth on this question.
I just opened up Audacity, selected the Export Audio with mp3 option, and then opened up the "Quality" dropdown menu to see which bit rates it supports.
I have the "lame_enc.dll" installed, which is distributed separately.

These are the bitrate options which were listed (all are in kbps):

8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256, 320

I think I used the 128 kbps option once, for a recording of spoken dialog, and I have never attempted to use any bit rate lower than that.

Re: Welcome to the Sea of Misinformation
harmonizer #3062015 09/11/20 12:56 AM
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Originally Posted by harmonizer
These are the bitrate options which were listed (all are in kbps):

8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256, 320

8 kbps is what I see for the minimum as well. The Fraunhofer site isn't of much use, because they've moved on and license more advanced codecs.

Quote
I think I used the 128 kbps option once, for a recording of spoken dialog, and I have never attempted to use any bit rate lower than that.

Then clearly, you are a person of refinement and taste. smile

Re: Welcome to the Sea of Misinformation
Anderton #3062057 09/11/20 11:22 AM
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Indeed, Audacity does go as low as 8kbps ... but ... Audacity uses the LAME encoder which goes further than the ISO standard, AFAIK.

I believe, officially, 32kbps is the lowest rate.

Does it also not vary depending whether you use ABR, CBR or VBR?


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