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Comment by pla3rhat3r | Hacker News Reader

This has been an age old question since Mp3s were created. However, I'm going to disagree with you there on saying that CD quality = 192kb. I've heard 192kb files and they sound like complete garbage. If you're looking for true "CD quality" that would be LPCM 44100 Hz 16 bits stereo for a bitrate of 1411 kbps.

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> I've heard 192kb files and they sound like complete garbage.

I'm curious, did you blind test yourself? I blind tested a friend of mine who kept saying so, and he did barely better than random.

It's very easy to tell the difference between 192kbps and FLAC if you have a decent subwoofer and the song ever goes below 30hz. On run-of-the-mill speakers and earbuds, probably not.

It's extremely rare for music to contain anything below 30Hz. Even below 40Hz is rare. The only place you're likely to find such low frequencies is sound effects in movie soundtracks.

I'm sorry, I pulled that number out of my ass.

I should have said 'if the frequency goes sufficiently low'.

Unless you are into Bassnectar and the like... ;)

Interestingly, a lot of "bass heavy" music focuses on frequencies around 50Hz, not the really deep sub-bass. This makes sense when you consider human hearing. Those higher frequencies sound much louder to us, and they're still low enough to get the tactile feeling.

It really does depend on the file. However, if we're talking about most 192KB music files, they tend to sound "tinny" or shallow. There's not a lot of depth to the sound as compared to quality you would get from a CD.

I've heard this before elsewhere and the response then was that the person was confusing kilobits with kilobytes. 1411kbps/8bits/byte = 176.375Kbps. The closest you can get to that is 192Kbps. There's a big difference there.

MP3 bitrates are conventionally given in kilobits per second, not bytes.

From Wikipedia's page on Compact Disc Digital Audio:

Each audio sample is a signed 16-bit two's complement integer, with sample values ranging from −32768 to +32767. The source audio data is divided into frames, containing twelve samples each (six left and right samples, alternating), for a total of 192 bits (24 bytes) of audio data per frame.

https://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio#Dat...

That has nothing to do with the bitrate -- the fact that you're getting a different unit on your 192 should be in an indication (bits or bits/frame, as opposed to kilobits/second).

CDs store audio as 16 bit samples, with 44100 samples per second. This gives a bitrate of 16 bits * 44100 Hz = 705600 bits/second (705.6 Kbps). This is per channel, so the total bitrate of the format is 1411.2 kbps, as stated (modulo rounding) by the GP.

EDIT: in fact, the article you link specifically says (a couple sections further down) that the bitrate is 1411.2 kbps.

This means CDs should have ~800MB of usable space. Why only 700MB?

    705600 * 2 = 1411200              # bits/s for stereo channel
    80 * 60 = 4800                    # seconds in 80 minutes
    1411200 * 4800 = 6773760000       # bits in a 80 minutes CD
    6773760000 / 8 / 1024 /1024 = 807 # In MB

Error correction.

While a 'raw' redbook CD can hold ~850 MB, it is standard to included error correction codes so that a slightly scratched CD can still work.

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