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OT: understanding kbps, mp3, iTunes
Hey all, my research is not enlightening me,
We need to make an audio-only version of our program available on the web (geared toward dial-up users). Originally, I was just told to just give I.T. a WAV file – then I got to thinking about it and said “Hey,” I said to myself, “a WAV file is going to be way to huge to benefit anyone on dialup.” So, I dumbed it down (it was originally 16-bit 48khz) to 16-bit 22khz, imported that file into FCP, and looked at the “data rate” column. 28K/sec. Good, this will work great. Of course, it sounds like AM radio, but hey, it’s mainly dialogue and at least they can hear it.
Hmmmmm.
“Now wait a minute,” I remember, “what about MP3s? They’re highly compressed, would sound better than a dumbed-down WAV file, and would probably even be more universally playable than a WAV. So far so good – now for the confusing part. What kpbs should the MP3 be encoded at? I’m currently doing the converting in iTunes. What is confusing me is that I’m getting two different sets of numbers, depending on where I look. If I set iTunes to encode at 32kbps (which seems a reasonable stream for a dialup user), and then import that file into FCP and look at the “data rate” column, it reads “1.9K/sec”. I can actually set iTunes to encode at 96 kbps (which would seem way to high for dialup connecting at 48.8 or so), drag that into FCP, and the data rate reads 11.7K/sec.
Which one do I go by? Or am I reading these numbers wrong and using bad logic altogether? As you can tell, my partial knowledge in these areas is adding up to a sum of zero.
Many thanks.
Nick
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8 Replies
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48.8 is KB a sec (kilobytes). It actually equates to 5 or 7K for some reason.
Anyway, your 32kb is kilobits per sec, which is resulting in 1.9 kiloBYTES a sec. So, you can actually triple or quadruple that to fit in a 48.8 modem connection.
Which just happens to be close to the standard iTunes 128kbps for stereo. If you make it mono, 64kbps is fine. If you don’t mind it sounding compressed, 32 will work for mono as well.
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Sorry I can’t help with the question, but to clear something up:
The 48.8 is *not* kilobytes, it’s kilobits.
There are 8bits to a byte.
There are 1,000 bits to a kb (kilobit).
A 56k modem (dial-up), which never maxxes out to the full 56k, is bits, not bytes. It maxxes out to 6KB (Bytes) or less.
Ed[Bret Williams] “48.8 is KB a sec (kilobytes). It actually equates to 5 or 7K for some reason.
Anyway, your 32kb is kilobits per sec, which is resulting in 1.9 kiloBYTES a sec. So, you can actually triple or quadruple that to fit in a 48.8 modem connection.
Which just happens to be close to the standard iTunes 128kbps for stereo. If you make it mono, 64kbps is fine. If you don’t mind it sounding compressed, 32 will work for mono as well.”
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I’m not an infomatic, but the idea I’ve got is more or less like that:
1Byte is the same that 8 Bits, because in the beguining of the digital world were used 8 bits “words”.So when we talk about MEGAS (i.e. : This is a 20M file) that means that the file is composed of 20.000.000 words with 8 bits ( “0” or “1”) each. So that means that 1M is the same that 8.000.000 bits= 8Mbs.
For example when we record DV we get files of 3.5M each second (aprox). If you multiply 3.5 x 8 you get around 25Mbs, That match the data-rate of the DV format.
So more or less if you want translate “Kilobytes” or “Megabytes” in to “Kbs” or “Mbs” just multiplie it by 8. This also match the data shows in FC when you import yours MP3. If you multiplie the 11.7K/se x 8, you get the 96 Kbs.
Cheers
rafael -
Thanks all,
I get it now. Modem connection is kiloBITS, kpbs in iTunes is kiloBITS, FCP is listing data rate in kiloBYTES. Kilobytes x8 = kilobits. Huzzah!
Nick
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Mr. Ryan, we’re going to keep you here in class till you get it right. 🙂
kilobits x8= kilobyte (8 kilobits to 1 kilobyte), not the other way around.
Ed[Nick Ryan] “I get it now. Modem connection is kiloBITS, kpbs in iTunes is kiloBITS, FCP is listing data rate in kiloBYTES. Kilobytes x8 = kilobits. Huzzah!”
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No Ed,
A BIT is a single digit and can have only two values: 0 or 1.
A BYTE is a word of 8 BITS, and you can get 256 different values.
Cheers,
rafael -
Oh, er, heh, yeah, that’s what I meant.
Nick
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Yes Rafael,
8 bits to a byte, or as I said, 8 kilobits to 1 kilobyte.
Ed[rafalaos] “No Ed,
A BIT is a single digit and can have only two values: 0 or 1.
A BYTE is a word of 8 BITS, and you can get 256 different values.
Cheers,
rafael”
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