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At 6:11 AM -0700 8/17/10, James Shatto wrote:
>
>
> >
>> --- On Tue, 8/17/10, Dan Dugan
>><<dan%40dandugan.com>> wrote:
>>
>> From: Dan Dugan <<dan%40dandugan.com>>
>> Subject: Re: [Nature Recordists] M/S recording setup
>> To:
>><naturerecordists%40yahoogroups.com>=
om
>> Date: Tuesday, August 17, 2010, 12:09 AM
>>
>>
>> What Rob said, except I think it would be clearer to use the
>> term "matrix" rather than "encode."
>>
>>
>> James wrote,
>>
>> > ...if you mix to stereo in the field, even though you can
>> > derive most of the non-stereo version in post. You lose
>> > resolution by doing do. So your 44100Hz sample is for all
>> > intents 22050Hz once you split it apart. Which isn't as
>> > useful when you need to do severe edits like EQ or time
>> > adjustments to sync with another device.
>>
>>
>> I don't understand that. A 44.1KHz stereo interleaved WAV
>> file (also called "poly" because any number of channels can
>> play) splits into two 44.1KHz mono files with no loss. The
>> utility "Interleaver" does this easily. Stereo files are
>> just as long in playing time but twice as big in storage,
>> because they have all the data for two channels.
>>
>> All my stereo and 4-channel files get split into mono files
>> by Pro Tools when I load them in for post. No losses.
>>
>>
>>
>> -Dan
>
>22050 was a bit of an exaggeration on my part. But, I'm talking
>about taking a file that was already matrix'd into stereo (LR) from
>MS to derive the original MS raw tracks. You have a finite set of
>bits per channel. When you apply other bits you lose bits of
>information. It may not be enough loss to be audible. But you have
>less information than you had or would have had before the audio was
>matrix'd.
>
>Deriving M + S from L + R is what I was hinting towards.
>
>Converted to mono by combining L and R into ONE channel, gives you
>M, because +S and -S cancel each other out.
>
>M plus L or R into one channel gives you (+ or -) S.
>
>BUT you've done many edits from the original files to get to that
>point, leaving you less information than you would have had, had you
>just recorded M and S to their own tracks and matrix'd to L and R in
>post. Yes you can derive M and S from L and R, but quality wise
>you've lost something in the translation. If you need to do massive
>EQ and widen or narrow your stereo image, you would have had higher
>quality if you had recorded M + S and not L + R.
>
>- James
>
James-
Converting from MS -> L/R and then converting back again L/R -> MS
does not result in the loss or gain of a single sample. Further, the
test shows that if one uses two +Matrix plug-ins at unity setting to
perform both steps, one can obtain an exact copy of the original
file. If one inserts EQ between the plugs and equalizes or changes
the stereo image, the output files will retain the same data
rate/file size. I don't recall anyone writing anything about edits.
The term "mono" gets understandably confusing in this discussion
context. A stereo file can be "de-interleaved" into two, single
channel files and this format is typically called, "Split Stereo."
Rob D.
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