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Topic: 48,000 Hz audio CDs (Read 27989 times) previous topic - next topic
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48,000 Hz audio CDs

From what I understand, CDs are 44.1kHz and DVDs are 48kHz.

  • Without up or down sampling, shouldn't the MP3 files that are created from the disc also be 44.1kHz?
  • If I have a 48kHz MP3 file, does that mean that someone, somewhere down the line up/down sampled the file?
  • Are other CD formats such as SACD or HQCD II 48kHz?

48,000 Hz audio CDs

Reply #1 –
1 Yes
2 MP3 can go up to 48kHz http://en.wikipedia.org/wiki/Comparison_of...chnical_details. If the source was a CD so yes, it was upsampled but if the source was 48kHz then the MP3 hasn't been resampled.
3 More info here: http://en.wikipedia.org/wiki/Compact_Disc_..._Audio#Bit_rate and http://en.wikipedia.org/wiki/Super_Audio_CD#Technology

I'm not an expert here, this is all I can tell you and still may be wrong. I am sure someone will reply with a better explanation.

48,000 Hz audio CDs

Reply #2 –
48k MP3s are usually either a DVD video rip or (more likely) just some idiot resampling because 'bigger is better'.

48,000 Hz audio CDs

Reply #3 –
hmm...... thanks for the links. kinda confirms what i had preconceived

48,000 Hz audio CDs

Reply #4 –
If the source file is a CD, then 48 kHz is of course resampled.

However CDs aren't the only sources out there.  Just about every source except for CD is 48 khz or a multiple of that (96kHz).  DVDs, DATs, and nearly every computer sound card is at 48 kHz. 

All recordings or transfers from analog that I do personally, I do at 48 kHz, so I actually have quite a bit of legitimate 48 kHz audio in my library.

48,000 Hz audio CDs

Reply #5 –
Quote from: saratoga on
48k MP3s are usually either a DVD video rip or (more likely) just some idiot resampling because 'bigger is better'.

Not so long ago, many PCs/laptops supported playback only at 48k. Using 48k files, resampling is done only once (saving CPU); also it may be easier to control resampling quality settings this way. 

And since sound >22.05k can't be perceived, logically at least, a perceptually coded 48k file shouldn't be any bigger than the corresponding 44.1k.

48,000 Hz audio CDs

Reply #6 –
if i mainly use my computer for music, should i set my sound card to output at 41kHz or 48kHz?

48,000 Hz audio CDs

Reply #7 –
Certainly not 41Khz. 

For listening only, this is definitely something you shouldn't worry about. Someone more technically-savyy (I'm not one of them) might tell you why, but IMHO besides the nyquist theorem, common sense dictates there's no reason why you should lose sleep over that for this particular scenario - hence my avatar. 

Edit: nyquist theorem added up.
Listen to the music, not the media it's on.
União e reconstrução

48,000 Hz audio CDs

Reply #8 –
Back in the days of DAT I thought it was odd that that 48Khz was considered a professional master stage before being released on 44.1 considering a second brick wall alias filter stage is then required, and there is a lot of interest in the effect of steep filtering, isn't that more of a detriment than a benefit. Anyone got the reasoning on 48.

48,000 Hz audio CDs

Reply #9 –
Probably something like "bigger is better" followed by a lot of mouth breathing sounds.

48,000 Hz audio CDs

Reply #10 –
Quote from: KMD on
Anyone got the reasoning on 48.

Back in the day, it struck the right balance between cost, quality, and storage/band-width for professional audio equipment. To have used 44.1 would have pushed the price up, or the quality down.

48,000 Hz audio CDs

Reply #12 –
Quote from: includemeout on
besides the nyquist theorem, common sense dictates there's no reason why you should lose sleep over that for this particular scenario
Neither is relevant. What are important are the human auditory system, and the resulting equal loudness contour. The Nyquist sampling theorem is far more general information theory and is, like the name suggests, about sampling of quantities, rather than hearing. And common sense is hard to apply to something like the limit of your senses. A good way to make informed choices is to conduct experiments, and believe in empirical and statistical results.
It's only audiophile if it's inconvenient.

48,000 Hz audio CDs

Reply #13 –
Quote from: bandpass on
Quote from: KMD on
Anyone got the reasoning on 48.

Back in the day, it struck the right balance between cost, quality, and storage/band-width for professional audio equipment. To have used 44.1 would have pushed the price up, or the quality down.

I believe that the choice of 48kHz was even more pragmatic. It is technically sufficient, economically viable, but more importantly it was hard to convert into 44100 in the early days (the more fanatic you are, the harder it becomes).

The DAT constraints seemed to be chosen more to limit CD copying than anything else.

-k

48,000 Hz audio CDs

Reply #14 –
Quote from: knutinh on
I believe that the choice of 48kHz was even more pragmatic. It is technically sufficient, economically viable, but more importantly it was hard to convert into 44100 in the early days (the more fanatic you are, the harder it becomes).


I assume you mean the other way around (copying a CD onto DAT), but DAT didn't hit the streets until 1987, and then the pros had been using 48k for quite some years already: http://en.wikipedia.org/wiki/Digital_Audio_Stationary_Head

48,000 Hz audio CDs

Reply #15 –
I've never found a reliable source to corroborate it, but I remember hearing somewhere that CDDA was originally going to use 48 000 Hz, but it was reduced to 44 100 Hz to increase the runtime from just under 68 minutes to 74 minutes as a way to fit a particular piece of classical music on CD (either by Bach or Beethoven, IIRC). As for why 48 000 and 44 100 were chosen, the numbers needed to be divisible by both 25 and 30, so that digital audio could be stored on tapes in both PAL and NTSC format, which was the cheapest medium to use before CDs became prevalent. As digital audio expanded from the realm of CDs to media with greater capacities (e.g. DVD), using the rounder 48 000 rate became practical, so 44 100 fell out of favour.

48,000 Hz audio CDs

Reply #16 –
AFAIK, there was no significant use of 48k before Sony's DASH tape system (1982).

DASH won out commercially in the pro market over Mitsubishi's 50.4k system (which had launched in 1980) and the AES adopted Sony's 48k as the pro standard in 1985. By 1986, Mitsubishi had switched to using 48k.

There's some info and a video about DASH here: http://www.vintagerecorders.co.uk/sales/pcm3402/pcm3402.htm

48,000 Hz audio CDs

Reply #17 –
Quote from: Aleron Ives on
I've never found a reliable source to corroborate it, but I remember hearing somewhere that CDDA was originally going to use 48 000 Hz, but it was reduced to 44 100 Hz to increase the runtime from just under 68 minutes to 74 minutes as a way to fit a particular piece of classical music on CD (either by Bach or Beethoven, IIRC).


Disputed. Sources pro et contra at http://en.wikipedia.org/wiki/Compact_Disc_...nd_playing_time



Quote from: bandpass on
AFAIK, there was no significant use of 48k before Sony's DASH tape system (1982).


Which makes it even harder to understand why 48 came to prevail on the recording and processing side, as - from what I can read - all DASHes also supported 44.1.

48,000 Hz audio CDs

Reply #18 –
Quote from: Porcus on
Which makes it even harder to understand why 48 came to prevail on the recording and processing side, as - from what I can read - all DASHes also supported 44.1.

Phase distortion in the (necessary before oversampling came along) brick-wall filters was much less with 48k.

48,000 Hz audio CDs

Reply #19 –
Quote from: bandpass on
Phase distortion in the (necessary before oversampling came along) brick-wall filters was much less with 48k.


That does not explain why one would want to use 48 to record and process something that would be delivered in 44.1 before hitting the DAC.

48,000 Hz audio CDs

Reply #22 –
Well, to my understanding mp3 is kind of pointless, when you rip a 48khz source...
if one wants better quality, one should make sure to have no elements in the chain, which are very weak... because a chain is just as strong as it's weakest element...

48,000 Hz audio CDs

Reply #23 –
This really has nothing to do with the topic at hand, but there are plenty of legitimate reasons to use mp3.  The source's sample rate really has nothing to do with it.  44.1 kHz, 48 kHz, 192 kHz, it makes no difference.

48,000 Hz audio CDs

Reply #24 –
Quote from: saratoga on
48k MP3s are usually either a DVD video rip or (more likely) just some idiot resampling because 'bigger is better'.


I resample to 48k before encoding mp3. The file isn't any bigger, mp3 file size is based upon bitrate.
I do it because if everything is at 48k then it doesn't need to be resampled upon playback.

Archival lossless I leave how it was, otherwise there is no point to it being lossless, but since sample rate doesn't impact the file size of lossy and the decoded wave form isn't going to be same anyway, resampling before I encode using SoX means it doesn't need a resample during playback on my PC to mix with other sounds (which often are resampled to 48k, I doubt my e-mail alert bloop thing is 48k)

Even speech originally at 22050 I up-sample.

Maybe I'm an idiot, maybe it really isn't necessary, but it isn't because 'bigger is better' - rather it is because same sample rate and bits per sample are needed to mix sounds so why not resample lossy first?

Opus btw resamples just about everything to 48K even if you don't first.