AGC and limiter for audio

[Don Greening]

You haven’t provided much information about what you’re recording and if you’re using line level input (from a house mixing board) or mic level from a radio transmitter or a hard wired mic. I think you might be talking about mic level but I’ll touch on line level just in case.

If it’s from a mixing board here’s some recommendations. First of all, a professional mixing board’s peak signal is +10dBu whereas your EX peaks at -12dBu. Most audio people round off the -12dBu peak signal from a video camera to -10dBu and refer to this as the “ten+ten” rule. As you can see, there’s a huge difference in signal strength between the two. Setting your camera’s inputs to line level will solve the mismatch in most cases but in others it’s simply not enough to knock the board’s signal down for the camera to deal with. If the signal coming from the board is distorting, no amount of camera gain lowering will fix it because the signal is too much for the camera’s pre amp. The solution for this is to purchase one or two inline adjustable attenuators like the ones at the link below:

https://www.audio-technica.com/cms/electronics/a05620466ab0ce16/index.html

These plug in to the XLR cables the mixing console has sent to you then in turn plug into yours before the camera. You can adjust them to minus 30dBu in 10dBu increments.

If you’re requesting advice about mic level signals then I invite you to read the recommendations at this link:

https://forums.creativecow.net/readpost/142/878123

– Don

Don Greening
A Vancouver Video Production Company
Reeltime Videoworks
http://www.reeltimevideoworks.com

[Jim Stamos]

don, i was shooting a wedding reception as i have many times before.
i had my agc on high and my limiter on . is there any audio software that can improve this audio? all my dance footage at the reception sounds hot.has to be something to improve it to a level that bride wont notice

[Jim Stamos]

maybe i should keep the audio on agc low from now or go with a small shotgun. someone suggested the rode nt5.

[Don Greening]

Whatever mic you were using to record the loud music was too sensitive (too hot) for the job. The signal was over-driving the camera’s pre-amp and that’s why you got the distortion. You can try trimming the signal in the menu but I suspect you’ll still get distortion even at a quiet volume and with AGC active. To solve the issue you need to get a mic that’s much less sensitive. Since I don’t record loud music I can’t advise you on what to buy. for example, a good shotgun for recording the spoken word is not going to do a good job of recording loud music.

You also can’t fix digital audio in post once it’s distorted. Digital audio turns into hash as soon as distortion happens, whereas analogue audio is more forgiving and can be manipulated somewhat.

– Don

Don Greening
A Vancouver Video Production Company
Reeltime Videoworks
http://www.reeltimevideoworks.com

[Bob Mark]

All very true. That’s why you need to monitor the camera audio with very good set of headphones that will let you know if the audio is too hot. Relying on the meters alone is suicide.

Bob

[Dean Longfield]

Hi,

I have an EX1R and have been slowly testing it in the field. On events with loud music I have found the same problem that Jim had. I tried using both the built in mic as well as two shotguns. All I did to adjust the audio was to put the Audi-In setting on Manual and adjust the levels. That does not cut it on the EX1R. Others here on the Cow have suggested that I lower the Trim Level, which is what I’ll try next. (Ext Mic Input, Manual Audio, and bring the trim down). I’m thinking of bringing it down to the -32 or so range and adjust from there. I’m also going to try switching the high/low setting on the AGC, but am hoping that the low is not too muffled. I’m not sure about the gain setting but I initially am planning on leaving it on ‘0’ and taking it from there. This time I’m bringing an attenuator as well,
just in case all in camera methods are not providing suitable results.

Re: Mics: I made the mistake of using a Sennheiser ME-66 indoors with very amplified (LOUD) sound. Not a good combo. Then I used the mic from the old DSR cameras (300/500 series) and that wasn’t really much better.

So I’m going to purchase the Sony recommended mic: the Sony ECM-673/9x Shotgun mic.
It’s an Electret Condensor and has a Super cardiod pick up pattern, (just like the DSR mics).
AND am going to experiment with setting the levels as described above.

There has to be a workable combo of mic choice and audio settings. It’s just a matter of finding it.
With the EX1R, I’ve been recording sets that are not critical to the edit, so if they don’t come out well I
don’t use them, (I use other cameras, that I’m used to, for the critical footage).

When I find the right combo, (that works for me), I’ll report back.

Good luck.

[Bob Mark]

The problem you are experiencing comes from using microphones that do not have a high enough SPL (sound pressure level) rating. Many shotgun microphones have this problem. The ME66 is well know for this overload issue. The Sony shotgun you mentioned does not have a better SPL rating than the ME66. They are both around 125 db SPL. Some mics like the Shure SM81 (not a shotgun) have a built in pad that will take the SPL up to 146 db. AKG makes some nice mics for music recording as well. Shotguns are designed to reach for sound, so that comes into play too. Is there any place you can rent some mics to test? Good luck.

Bob

[Brent Dunn]

The limiter will limit the amount of audio, keeping some of the peaking levels to a set level. Compressor’s can also squeeze the audio.

For receptions, I use the automatic gain, since the audio is all over the place and I don’t have any silent spaces where my gain will boost. It’s worked very well for me and I don’t have to worry about distortion. I use a wireless either plugged into the board or a handheld mic on a stand in front of the speaker, as well as an on camera mic for the 2nd track of audio. For better audio, you may want to invest in a Zoom H4N recorder.

Brent Dunn
Owner / Director / Editor
DunnRight Films
DunnRight Video.com
Video Marketing Toolbox.net

Sony EX-1,
Canon 5D Mark II
Canon 7D
Mac Pro Tower, Quad Core,
with Final Cut Studio

HP i7 Quad laptop
Adobe CS-5 Production Suite

[Jim Stamos]

i never had a problem with this issue with my dsr300 and i shot 100s of receptions.
is the recommended mic for the ex1r going to be as bad as the oncam mic? would hate to throw money and time away if it wont do the trick

[Bob Mark]

It all comes down to how well the microphone handles loud sound levels (SPL). If the mic is clipping you are a dead duck. No amount of mixer or camera audio adjustment will save you.

Bob