I'm editing a wedding I shot recently. I had a wireless receiver on one channel and my shotgun on another channel. and I've noticed that whenever the groom breathed heavily on the wireless lav, and causing a clipping on the wireless channel, it would cause a drown-out of the audio on the other channel. Anyone noticed this? any idea why it would do this? AGC was turned on, so could the AGC be doing its thing on both audio channels even if it only detected that one was clipping?
One audio channel affecting the other?
- Thread starter booggerg
- Start date
J.R. Hudson
Spirit Animal
Re: One audio channel affecting the other?
Tell the groom to contol his breathing!
Tell the groom to contol his breathing!
Re: One audio channel affecting the other?
Boog - that's really interesting. I'm not sure what the answer is but it seems possible the ALC doesn't discriminate between channels. That being said, I recently shot a scene from my short film with two characters having a conversation while driving in a mustang convertible. I knew wind noise was going to be a problem so I ran a wired lav from channel one and had my camera mounted shotgun on channel two. When I edited the scene this week I noticed wind noise totally blew out the shotgun at times but didn't affect the lav at all. Now I'm not sure if the ALC kicked in or not with the wind rumble but either way I had usable sound from the first channel.
Boog - that's really interesting. I'm not sure what the answer is but it seems possible the ALC doesn't discriminate between channels. That being said, I recently shot a scene from my short film with two characters having a conversation while driving in a mustang convertible. I knew wind noise was going to be a problem so I ran a wired lav from channel one and had my camera mounted shotgun on channel two. When I edited the scene this week I noticed wind noise totally blew out the shotgun at times but didn't affect the lav at all. Now I'm not sure if the ALC kicked in or not with the wind rumble but either way I had usable sound from the first channel.
scottchapin
Well-known member
Re: One audio channel affecting the other?
I would think that ALC would clamp down on both channels based on the louder one. Otherwise, the dynamic range of stereo recordings might be distorted. Albeit, in stereo, both mics should basically be reording the same thing.
I would think that ALC would clamp down on both channels based on the louder one. Otherwise, the dynamic range of stereo recordings might be distorted. Albeit, in stereo, both mics should basically be reording the same thing.
scottchapin
Well-known member
Re: One audio channel affecting the other?
I don't think so. I believe the ALC is linked stereo. When one channel threatens to pass 0dBFS, both channels are clamped equally.
If this were not true, it could mess up stereo recordings badly. Say left channel is -12dBFS and right channel is 0dBFS. That's 12 dB separation. If only right channel is clamped on and attenuated to -6dBFS, the separation would be only 6dBs. The dynamics of the stereo recording would be sadly altered.
Your best bet is to normalize both of your channels individually in Sound Forge, Audition, or such.
I don't think so. I believe the ALC is linked stereo. When one channel threatens to pass 0dBFS, both channels are clamped equally.
If this were not true, it could mess up stereo recordings badly. Say left channel is -12dBFS and right channel is 0dBFS. That's 12 dB separation. If only right channel is clamped on and attenuated to -6dBFS, the separation would be only 6dBs. The dynamics of the stereo recording would be sadly altered.
Your best bet is to normalize both of your channels individually in Sound Forge, Audition, or such.
Carlos_E._Martinez
Well-known member
Re: One audio channel affecting the other?
[quote author=booggerg link=board=Events;num=1069861878;start=0#0 date=11/26/03 at 07:51:18]I'm editing a wedding I shot recently. I had a wireless receiver on one channel and my shotgun on another channel. and I've noticed that whenever the groom breathed heavily on the wireless lav, and causing a clipping on the wireless channel, it would cause a drown-out of the audio on the other channel. Anyone noticed this? any idea why it would do this? AGC was turned on, so could the AGC be doing its thing on both audio channels even if it only detected that one was clipping?[/quote]
That's an AGC problem. Only very sophisticated AGCs work separately in stereo. Seriously doubt the DVX100 does.
In such cases always set audio to manual. In fact you should not use AGC except on takes where the audio is not importante (public ambiance, stadium, etc.). AGCs work better when the background is uniform, but do so very badly when there's silence and sudden noises.
Set your levels manually and learn to handle them. Disregard AGC if you can. You audio will suffer with it.
Carlos
[quote author=booggerg link=board=Events;num=1069861878;start=0#0 date=11/26/03 at 07:51:18]I'm editing a wedding I shot recently. I had a wireless receiver on one channel and my shotgun on another channel. and I've noticed that whenever the groom breathed heavily on the wireless lav, and causing a clipping on the wireless channel, it would cause a drown-out of the audio on the other channel. Anyone noticed this? any idea why it would do this? AGC was turned on, so could the AGC be doing its thing on both audio channels even if it only detected that one was clipping?[/quote]
That's an AGC problem. Only very sophisticated AGCs work separately in stereo. Seriously doubt the DVX100 does.
In such cases always set audio to manual. In fact you should not use AGC except on takes where the audio is not importante (public ambiance, stadium, etc.). AGCs work better when the background is uniform, but do so very badly when there's silence and sudden noises.
Set your levels manually and learn to handle them. Disregard AGC if you can. You audio will suffer with it.
Carlos
scottchapin
Well-known member
Re: One audio channel affecting the other?
Carlos,
I believe he boogerg was using ALC which differs from AGC. ALC does not compress or pump. It is a limiter. My experience is that a steady signal will not break through the third red bar no matter how loud it is, but transient spikes will.
Low levels will remain low. Loud signals will be attenuated. I see AGC menioned in the auto sw section of the manual, but I don't think it is true AGC. Most users have said there is no AGC on the DVX100, and I have not found it yet (if there is).
Carlos,
I believe he boogerg was using ALC which differs from AGC. ALC does not compress or pump. It is a limiter. My experience is that a steady signal will not break through the third red bar no matter how loud it is, but transient spikes will.
Low levels will remain low. Loud signals will be attenuated. I see AGC menioned in the auto sw section of the manual, but I don't think it is true AGC. Most users have said there is no AGC on the DVX100, and I have not found it yet (if there is).
Re: One audio channel affecting the other?
THe only bummer for double system use and timecode, is that there is not a separate AGL for each audio channel. So feeding timecode to one channel is affected by level on the other channel used for reference audio. Room level goes up, timecode goes down...
THe only bummer for double system use and timecode, is that there is not a separate AGL for each audio channel. So feeding timecode to one channel is affected by level on the other channel used for reference audio. Room level goes up, timecode goes down...
Re: One audio channel affecting the other?
the dvx doesnt have agc it has very hard limmiters (separate) about -4,5dbfs
for normal work you can use line or mike input but if you use line try to pad it down for -10dbv level (consumer) than you will not distort the mike pre ,the camera doesnt love full+4dbu .
if you are working with mixer that have +4db out you can pad down the outs or just go down on your master pot.
the first red mark on the camera is -12 dbfs ,when the all reds lit you are in 0dbfs .the right way if you work with uv mitters mixer and it give you +4 db is to put a reference ton on -18 and open the camera limmiters it will give you at least 12 db of dynamic rang ,if youare working with ppm miters in most of the mixers the referense ton is 0db so you might put a ton on -12 and still have 8 db until the limmiter
on most of the conventional mixers the limmiter on he mixer is about 8db above the reference ton and more supirior to thos on the camera.
some mixers have changeble limiters (sond devices442,302 mix pre ,s0ny dmx and others ) in that case
the limiters could be +16 above the reference o dbu ,it gives you 16 db of dinamic range and you can close the camera limiters
the picks on averege conversaition can be at least +10db
the right trick with that camera is to run as hot as possible for beter sn ratio ( the camera has 60db in line and 58 db on mikeinputs -very poor),the pics can go until the 2 red mark without any problem.
for wind noise ( on convertble shotes )use zeppelin or softy, you can put flexi glas befor the mike to prevent wind hits or booming from bellow .
the dvx doesnt have agc it has very hard limmiters (separate) about -4,5dbfs
for normal work you can use line or mike input but if you use line try to pad it down for -10dbv level (consumer) than you will not distort the mike pre ,the camera doesnt love full+4dbu .
if you are working with mixer that have +4db out you can pad down the outs or just go down on your master pot.
the first red mark on the camera is -12 dbfs ,when the all reds lit you are in 0dbfs .the right way if you work with uv mitters mixer and it give you +4 db is to put a reference ton on -18 and open the camera limmiters it will give you at least 12 db of dynamic rang ,if youare working with ppm miters in most of the mixers the referense ton is 0db so you might put a ton on -12 and still have 8 db until the limmiter
on most of the conventional mixers the limmiter on he mixer is about 8db above the reference ton and more supirior to thos on the camera.
some mixers have changeble limiters (sond devices442,302 mix pre ,s0ny dmx and others ) in that case
the limiters could be +16 above the reference o dbu ,it gives you 16 db of dinamic range and you can close the camera limiters
the picks on averege conversaition can be at least +10db
the right trick with that camera is to run as hot as possible for beter sn ratio ( the camera has 60db in line and 58 db on mikeinputs -very poor),the pics can go until the 2 red mark without any problem.
for wind noise ( on convertble shotes )use zeppelin or softy, you can put flexi glas befor the mike to prevent wind hits or booming from bellow .
Re: One audio channel affecting the other?
loud levels from one channel do squash levels on the other channel when the ALC is on on the DVX100. We found the audio TC we laid down (on one input via a deneke TC box)would get squashed so it was not machine readable if the onboard mic was too hot. (which was plugged into the other input) But we decided ALC is damn good otherwise and decided to live with it.
loud levels from one channel do squash levels on the other channel when the ALC is on on the DVX100. We found the audio TC we laid down (on one input via a deneke TC box)would get squashed so it was not machine readable if the onboard mic was too hot. (which was plugged into the other input) But we decided ALC is damn good otherwise and decided to live with it.