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Karl Engel
Guest
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 Posted:
Sun Nov 06, 2005 5:42 am Post subject:
Size of stereo MP3s & mono the same? |
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Because stereo wavs take up more space than mono, I've always tended to
email mono files if the file is from a mono source (eg voice-over). This
has affected how my projects are set up, which panning law I use etc. I
just discovered that MP3s of the same content are the same size, mono OR
stereo. Huh? Now this I could perhaps understand if there is no difference
in the content of each channel (still a mono source) but it seems to be the
case even if there originally is stereo content.
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Dave Morrison
Guest
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| Posted:
Sun Nov 06, 2005 5:42 am Post subject:
Re: Size of stereo MP3s & mono the same? |
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"Joe Kesselman" <keshlam-nospam@comcast.net> wrote in message
news:t6ydnb-qKucq4vDeRVn-sQ@comcast.com...
| Quote: | How have you specified the MP3 compression? If it's bits per second, a
mono version *will* be identical in size to the stereo version.
Also, I believe MP3 uses a mid/side representation, since (as in FM
stereo) you can assume that most of the information is actually in the mid
so side can be compressed more agressively. If so, a mono signal encoded
as a stereo MP3 is all mid, no side -- and the genuinely mono MP3, again,
would be essentially the same data.
So that's two possible explanations for your observation.
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I think that the Apple iTunes encoder refers to this as "Joint Stereo"
encoding. If I understand correctly how it works, the encoder optimizes the
file size whenever it can by looking for the mono component of the file.
dave |
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Joe Kesselman
Guest
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| Posted:
Sun Nov 06, 2005 5:42 am Post subject:
Re: Size of stereo MP3s & mono the same? |
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How have you specified the MP3 compression? If it's bits per second, a
mono version *will* be identical in size to the stereo version.
Also, I believe MP3 uses a mid/side representation, since (as in FM
stereo) you can assume that most of the information is actually in the
mid so side can be compressed more agressively. If so, a mono signal
encoded as a stereo MP3 is all mid, no side -- and the genuinely mono
MP3, again, would be essentially the same data.
So that's two possible explanations for your observation. |
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Scott Dorsey
Guest
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| Posted:
Mon Nov 07, 2005 9:23 pm Post subject:
Re: Size of stereo MP3s & mono the same? |
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Karl Engel <karlengel@excite.com> wrote:
| Quote: | Because stereo wavs take up more space than mono, I've always tended to
email mono files if the file is from a mono source (eg voice-over). This
has affected how my projects are set up, which panning law I use etc. I
just discovered that MP3s of the same content are the same size, mono OR
stereo. Huh? Now this I could perhaps understand if there is no difference
in the content of each channel (still a mono source) but it seems to be the
case even if there originally is stereo content.
|
When you encode an MP3, you tell the encoder how much actual bandwidth
you have available to send it. Then, the encoder throws stuff away
so that the signal can fit in that bandwidth.
If you have a stereo signal that you want to fit through a given pipe,
and a mono signal you want to fit through the same pipe, the encoder will
throw away a lot more data from the stereo signal, in order to make it
fit.
That's why it's called "lossy encoding" and the amount of loss that you
get depends on the data rate you tell the encoder you have.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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