7D Audio: Disabling (Canceling Out) Automatic Gain Control

[Sean Setters]

I've been quite interested in the video capabilities of my 7D, but the audio always turned me off. I did some initial research, and found that most people were buying a sound recorder (like the Zoom H4n) and syncing the audio in post. The Zoom H4n is not necessarily cheap, and I didn't want to fool with syncing the audio in post.


Recently, I started looking into different mics that I could simply plug into the 7Ds mic port and place on the hotshoe. I wanted a solution that would be easily workable by one person (yes, having someone boom a mic is ideal, but not practical in many situations). As I was pouring over tons of reviews, I realized that Canon's Automatic Gain Control was still going to cause audio issues even with a decent mic. So what's the point in buying a decent mic to plug into the 7D if the camera is going to basically ruin the audio anyway? Thankfully, I came across a workaround for dealing with Canon's AGC. The following three videos explain (with varying degrees of detail) how to cancel out Canon's AGC and easily fix it in post.





This video got the ball rolling.


[View:http://www.youtube.com/watch?v=91xw_NX0Qm8]





Here the narrator has to do a few more steps to cancel out AGC with the popular Rode VideoMic.


[View:http://www.youtube.com/watch?v=fnQAd23wFes]





In this video, the same guy from above reviews a Y splitter cable that serves the same function as the one he soldered together.


[View:http://www.youtube.com/watch?v=SqVu4cDvjmg]





Another method of piecing together an AGC solution when using the Rode VideoMic. You'll likely have to pause the video several times as it runs through the parts/setup very quickly.


[View:http://www.youtube.com/watch?v=Qq-JXngqypM]





I think this is a novel technique for dealing with the problem, assuming Canon doesn't add AGC control in a future firmware update (which I highly doubt). I plan on buying a decent mic with the aid of some B&H gift cards I got for Christmas, and will likely try this out.

[nickds7]

Sadly there isn

[Sean Setters]

Yeah. Apparently the main guy behind Magic Lantern basically bricked his 7D. He finally figured out how to get modified firmwares to pass the 7D's signature verification. However, the latest official firmware release basically bricked his 7D test camera. Now he can't load official or modified firmwares.

[andnowimbroke]

I don't think it would be that hard in post if you used a portable rig for audio( http://pro-audio.musiciansfriend.com/recording/portable-field-recorders). Of course, like you said, another $100-300 for the unit and then a clapperboardkinda sucks. I REALLY wish I would have bought this class for $79 or something like that (it's up to over $140 now)on using your camerafor video. He talked about all kinds of stuff like this and how to work around it in the free sections. Oh well.

[peety3]

Consider something like this: http://www.lensrentals.com/rent/canon/accessories/audio/audio-adapter-beachtek-dxa-5da

[TakahiroW4047]

I

[Sean Setters]

Not that I

[TakahiroW4047]

'Decibel Meter' might be what I was looking for. I've been searching online, but I can't seem to find a decently priced one with a phone jack to plug in an external mic for real time metering.


There's a lot of 'decibel meter' phone apps with 'external mic' feature, but i hardly believe they're accurate. But could be consistent enough that I could determine the proper audio level after some trial and error? [*-)]


99cents wouldn't be much of a loss if it doesn't work haha


dB/SPL Sound/Audio Levels for Android