The Myth Of Dynamic Range

I have to run quickly so can't answer in great detail... but the clearest example that comes to mind is the decision when and how to use compression. I have a 16-bit multitracker that's sometimes the most convenient way for me to record (my usual rig is a big ProTools-based setup). When recording, say, an opera, I'd sometimes use light compression on the stage mics on that machine since the range is so huge and the precision is low at the average level. With the 24-bit setup, I can't imagine a situation where I'd use compression during a live performance. The 16-bit system, however, does fine for many other things I record without needing to resort to compression.
 
Petrus said:
Where do you get this dBFS scale goes from "0 to 1" idea?
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FS is the reference point, 1, or 0dB, whichever you prefer. 0 is -inf, or 0. Every slice of the range represents 1/(2 raised to the number of bits) * FS.
 
this 16bit / 24bit compression difference is a reason why on many 16bit dvcams, its best to set gain using tone on a manual setting, and then turn on the AGC or ALC (auto-gain / auto-level depends on your camera) to regulate the small fluctuations. ALC is essentially a compressor. If cams had 24bit capability, i doubt many sound people would use this trick. but i could, as always, be wrong.
 
I haven't heard an agc or alc yet that didn't suck up the sound in quiet moments. (your mileage may differ and PLEASE let everyone know if you do have one.) The way to improve S/N is to use a good mixer with a good limiter, like a Sound Devices 302 or 442. Use the limiter to catch audio peaks. This lets you record at higher levels without fear of recording too hot.

And about the fact that HDV audio isn't even 16-bit, 48 kHz ... Please don't get me started! :0 !!

Regards,

Ty Ford
 
ALC on the DVX is a limiter, and never increases gain. I'm not sure what you're saying Timaptr - 16/24 bit has nothing to do with compression. And turning on auto GAIN control will nullify manual settings. It's just on the DVX (as far as I know) that ALC is a peak limiter that respects your gain settings.
 
well, check up on this with oleg - im aware that the DVX has no auto gain, but when recording on the Z1 and PD150, using my SD302 mixer, Oleg told me the best way to set up the system is to run the tone, set it up as usual (0 on mixer is -20 on cam) and then ENABLE the autogain controller (naturally I also do use the limiters on the 302). Ive been using this method for a while now and it kicks ass, no pumping in quiet parts, not noticable to me anyway.

Yeah, ullanta I do know that bit depth and compression are completely different things, you said above:

"When recording, say, an opera, I'd sometimes use light compression on the stage mics on that machine since the range is so huge and the precision is low at the average level. With the 24-bit setup, I can't imagine a situation where I'd use compression during a live performance. The 16-bit system, however, does fine for many other things I record without needing to resort to compression."

Im just saying (and like I said, Im no expert, but Oleg is and this technique came from him), that perhaps this AGC method I mentioned plays a part in getting more out of your 16bit recorder.

Im not saying Im right, Im just bringing the info to the party for discussion. If we are lucky, maybe oleg will drop in and straighten this up.

Cheers
 
timapter said:
well, check up on this with oleg - im aware that the DVX has no auto gain, but when recording on the Z1 and PD150, using my SD302 mixer, Oleg told me the best way to set up the system is to run the tone, set it up as usual (0 on mixer is -20 on cam) and then ENABLE the autogain controller (naturally I also do use the limiters on the 302). Ive been using this method for a while now and it kicks ass, no pumping in quiet parts, not noticable to me anyway.

Yeah, ullanta I do know that bit depth and compression are completely different things, you said above:

"When recording, say, an opera, I'd sometimes use light compression on the stage mics on that machine since the range is so huge and the precision is low at the average level. With the 24-bit setup, I can't imagine a situation where I'd use compression during a live performance. The 16-bit system, however, does fine for many other things I record without needing to resort to compression."

Im just saying (and like I said, Im no expert, but Oleg is and this technique came from him), that perhaps this AGC method I mentioned plays a part in getting more out of your 16bit recorder.
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Is there something you adjust on the mixer when setting the gains? Otherwise, I can't see how the manual setting affects recording with AGC, unless those cameras are somehow biased towards a manual setting even under AGC? Sounds weird, and I'd doubt it.

As for me... NO! Can't use AGC. Ever. Not with what I record! Anyway, the way to get the most out of any recorder - 12 bit, 16-bit, 24-bit - is to set your levels correctly.
 
the 150 /170 dosent have auto gain( agc) , this is a fix input stage with hard limiter on -2dbfs
you work this way since the recording less noisy ,the audio flow is different and it get less self camera noise -
on z-1 you work as usual no agc ,calibrating the camera for -20 dbfs .
the agc as agc is the worst way to work with any device
 
ah, well that clears that up. although i knew the dvxs "alc" stands for the limiter i was unaware it was the same deal on the 170 - i was just following exiles recommendation. same deal on the z1.

aw well, im wrong, the world is right.

just for the record, i also hate auto gain control, and only started with this method when i misunderstood oleg.. as it turns out, i wasnt ever turning it on anyway. :) thanks for clearing it up oleg.

agreed on the setting levels correctly to get the best result business.
 
timapter said:
aw well, im wrong, the world is right.
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Hey, we're all a little wrong, thinking only the DVX had a limiter rather than AGC... I guess it's common in the higher-end cameras?
 
ha ha! yeah, thats why i made the mistake - its more common to have agc than just a limiter and i figured the dvx was the exception. what features does the new hvx sport? im sure you know oleg...
 
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