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GL2 audio question


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#1 Tony Murray

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Posted 19 December 2008 - 01:43 PM

If I record in 16bit, is it possible to add music in post. If yes, than will that degrade the quality of the audio that was previously recorded?
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#2 Walter Graff

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Posted 19 December 2008 - 01:54 PM

If I record in 16bit, is it possible to add music in post. If yes, than will that degrade the quality of the audio that was previously recorded?



You will be fine. Those numbers are like different size buckets. The larger the number, the more robust the sound quality. Once the sound is recorded and you later mix it with new music, you do not affect the original file. Rather two files are rerecorded to a new file so music does not degrade anything.
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#3 Tony Murray

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Posted 19 December 2008 - 02:08 PM

You will be fine. Those numbers are like different size buckets. The larger the number, the more robust the sound quality. Once the sound is recorded and you later mix it with new music, you do not affect the original file. Rather two files are rerecorded to a new file so music does not degrade anything.


Walter, thanks for the speedy reply!
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#4 Tony Murray

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Posted 17 January 2009 - 04:12 PM

When I have my GL2 in auto audio I notice the levels reach 0DB on a regular, why does this happen? If I had my audio in manual and turned all the way up a level reaching near 0DB would sound horrible. But in auto it sounds just fine.
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#5 Chris Bowman

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Posted 27 January 2009 - 06:21 PM

When I have my GL2 in auto audio I notice the levels reach 0DB on a regular, why does this happen? If I had my audio in manual and turned all the way up a level reaching near 0DB would sound horrible. But in auto it sounds just fine.


The answer is that the camera can adjust the volume much faster than you can. Any time the volume exceeds the 0dB level, the volume is in excess of a digital recorder's ability to reproduce fully, and clipping occurs. Auto volume controls are designed with compressors which decrease the gain on the signal very rapidly as volumes approach the 0dB level so that the sound gracefully reaches the the loudest sound that can be faithfully reproduced but does not exceed it. If the sound manages to build quickly enough that it outruns the compressor and exceeds max levels, the electronics continue reducing the gain, to produce as little clipping as possible. As soon as the signal level has dropped down again, the compressor begins to raise the gain up so that even quiet signals are recorded at high volume, this creates a desensitizing effect that makes minor clipping less noticeable, but has a negative effect if you are trying for broad dynamics in your sound.

Manually adjusted volumes that hit that 0dB level tend to blow right through it, and the sound clips and distorts. If the gains were set so that the volume maxed out exactly at 0dB there would be no problem, but you can't respond fast enough to turn down the gains as the signal approaches max , while the electronics can and do respond in milliseconds. Remember, the volume may be reading 0db, but if it is less than the next level (say +3dB) it can still be above 0dB it will not show the excess, but will clip noticeably.
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