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    The Canon DSLR Audio thread
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    Canon DSLR Moderator M. Gilden's Avatar
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    UPDATE: Scroll down for video demonstration of in-camera audio, and recommended ways to get audio directly into the camera!

    If I may be so bold, I decided to start this thread as an official "Canon DSLR Audio Bible", in the hopes that it will clear up a lot of confusion and be a useful source of information and starting point for those who are new to this.

    As you already know, Canon's latest crop of DSLR cameras can produce some great looking imagery for making movies, however have limitations that must be understood if you want to get good results. One glaring problem right out of box for most of Canon's popular DSLRs (including the 5D, 7D and T2i/550D) is audio.

    "Why, what's wrong with the camera's audio?"
    Two things:
    AGC (automatic gain control) and weak pre-amps.

    If you try to record someone speaking, you'll notice the AGC problem right away. That is, the camera will automatically adjust the audio levels (analog and digital gain) to find a good volume by listening to what is coming in off the mic. That means that when someone starts speaking, it will adjust to the volume of their voice. However, as soon as they stop or pause, the camera will raise the volume looking for some noise to amplify, and a very noticeable hiss will become evident. That is, until they start speaking again. This will happen whether you use an external mic plugged into the jack or the internal camera mic.

    Now, if you're wondering WHY Canon would think this was a good idea, this concept actually is used a lot in consumer electronics. Canon did not originally anticipate how these would be used, and AGC is in fact the way most cell phone and cheap camcorders record audio with video. It is assumed that automatically making sure whatever you want to record is loud enough to hear is more important than quality of the audio recording. The problem is, Canon didn't have the foresight to give us the ability to turn it off!

    Trying to clean up background noise from audio that keeps changing its volume is a nightmare.

    "So what do people do about recording audio?"
    Most people immediately dismissed DSLR audio as unusable, and resorted to using external recorders like the Zoom H4N for sound, which they would then sync up in post production.
    Ironically, this is actually how Hollywood shoots, since film only records pictures (Ever wonder what the Clapper is used for on film shoots? Its to sync up the film with the proper recorded audio track).
    So, people coming from shooting film found this workflow normal.
    However those of us coming from camcorders and other DV prosumer equipment found the extra step of syncing external audio kind of a nuisance.

    "Are there any ways to get around AGC that don't involve having to record audio externally on a seperate device?"
    Thankfully, yes.
    There are two really interesting tricks out there to get around AGC.
    The first is a physical hack in which you splice an audio cable so that the left and right channels go to two different sources. On one side, you connect your microphone. On the other side, you connect an mp3 player or some other device pre-loaded with a loud continuous noise.
    When you hit play on the music player, the camera hears the noise and adjusts the audio level down since AGC works on the volume of both sides simultaneously. And it stays that way as long as the sound keeps playing. Meanwhile, the other channel is clean and empty, free of pesky volume adjustments, and you can now record your audio right in. Since most external microphones are monaural anyway, you only need that one channel. Then, in your NLE of choice, just delete the noisy channel, leaving you with only the good audio, already in sync with your video.

    For a more visual explanation of this hack and how it works, take a look at Dave Dugdale's blog here:
    http://www.learningdslrvideo.com/t2i...rode-videomic/
    He also mentions that there are some pre-made cables to do this if you're not into DIY splicing.

    The second way around AGC is the venerable Magic Lantern Hack.
    If you haven't heard of Magic Lantern, I suggest you google it, or at least look at the thread here: http://www.dvxuser.com/V6/showthread...0D-in-progress!
    Update: New Magic Lantern sticky thread- http://www.dvxuser.com/V6/showthread...-Firmware-Hack

    This is actually the result of some brilliant minds who managed to reverse engineer a lot of the code from Canon's developers, creating a firmware of their own that can boot off an SD card. Magic Lantern is still a work in progress, however the features that it offers already are worth having if you own a supported camera (currently only available on the 5D and the T2i- Sorry 7D owners, Canon seems to have made that one harder to hack). Features like live histograms, zebra overlays, focus peaking, custom ISO and manual kelvin values, etc... I just can't sing enough praises for Magic Lantern. Of course, one of the first features of the hack was to disable AGC, and give full manual control of all gain levels to the user.
    Because you're not pushing the audio volume down like the previously mentioned physical wire hack, you can actually get much cleaner sounding audio that is more removed from the sound floor this way.

    "So, if we disable AGC, we should be good, right?"
    No, not exactly. There's still the weak pre-amp to worry about.
    I'm not an audio engineer, but the way I understand it is that the amp on the Canon DSLRs aren't strong enough to offer a good range of volume. This means the hiss and noise floor is higher and closer to the maximum volume level than your standard professional sound recorder (which has a wider range between the max and the lowest volume before noise/hiss). With our cameras, if your mic's volume is too low, you will get a lot of hiss and noise. Turn it too high, your audio gets blown out.

    "So is it impossible to get good sound out of the camera at all?"
    Some folks will tell you that, but I disagree. If you use a powered microphone (as in, one that has its own preamp so you are essentially feeding the camera a "hot" line) you can get perfectly usable audio for something in which the volume remains around the same level, like a documentary style spoken interview. Since most of my work is interview/documentary style shoots, I already had a Sennheiser wireless lav mic (G2) which happens to have some gain control on the receiver.

    By adjusting the gain up on the receiver and turning it down in the camera (using Magic Lantern on my t2i), I have managed to get some pretty good sounding audio directly into the camera for my purposes.

    Here's an example of me rambling on about audio like an idiot, using the wireless lav and mic directly into the camera:


    Now, this works for me and what I use the camera for, however for telling a narrative film, I don't recommend doing it this way. For that kind of story telling, you want the wide dynamic range of sound offered by a dedicated recorder (Zoom H4N, etc) and then sync it up in post.

    The truth is, for that type of story telling, generally you are operating with more than one camera anyway, and perhaps even with more than one microphone... so syncing audio in post is a must no matter how you slice it.

    "What about the 60D and t3i? They advertise manual audio?"
    Yes, the 60D and T3i finally allow you to turn off the AGC without a hack (although I'd still recommend Magic Lantern for other things as soon they are ported to the new cameras). But you are still stuck with the weak camera preamp, which means you should really use a powered mic if you want to separate your sound from the noise floor.

    -----------------------

    So in conclusion, what are recommended ways to get good in-camera audio?
    So now that we've concluded that there are times the in-camera audio would be perfectly acceptable, here are my recommended most-efficient ways of doing it:

    -For documentary style, I recommend the Senheisser wireless mic as demonstrated above, with the settings detailed in the video. You can attach either a lav or a handheld mic to it.

    -For a shotgun mic, I recommend the Rode VideoMic PRO (not the regular one), as the PRO version has a significant +20db amp built in for exactly this sort of use. This can be used directly into the camera without anything else needed.
    If running Magic Lantern, turn all gains to 0 and set the mic to +20. If very far away from the mic, you can try raising the analog gain in camera a bit, but you then run the risk of overblown audio if any loud noises occur.

    -For interview hand-held mic style, I recommend a "plug on" transmitter used in tandem with the Senheisser (as Chad demonstrates for us in this post http://www.dvxuser.com/V6/showthread...=1#post2298018 )



    For more information, check out the audio section of the forum here: http://www.dvxuser.com/V6/forumdisplay.php?29-Audio
    Last edited by M. Gilden; 10-24-2011 at 03:13 PM. Reason: added new ML thread.

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    Allow me to add two cents about manual audio levels on the T3i, 60D, and MKII.

    If you're using an external recorder (such as a Rode Videomic Pro) make sure to send a hot signal (that will be something like a +db swith or a +20db switch) to your camera. Then, adjust the audio levels on your Canon DSLR almost all the way to the left, meaning turning them a few notches from being off.

    By sending a hot (high) signal from your external mic to a low gain level on your DSLR, you're avoiding the aforementioned crappy camera preamps as much as possible. In my experience with the 60D and Rode VideoMic Pro, you can actually get FANTASTIC sound this way. On par with the Zoom H4N.

    One other trick that I've never seen written about is monitoring audio. There's a great trick using a Fiio E5 mini pre-amp. Check out this video for more:


    If you don't want to get into the trickery, there's another way you test/monitor your audio. Bring up the manual audio menu where you can adjust the levels. Have your subject (or someone else) pretend to be your subject and talk from a determined distance from the mic. The bars will move -- essentially giving you audio meters. However, you can only do this pre-recording. So look at the meters and adjust the level accordingly. (If your meters are running high, bring down the manual audio even more). Once you find a good level, do a quick record test. Record the clip, then play it back. It will be much different when using different mics, so do this quick check each time you attach a new mic.

    There's 100 or so other suggestions.... but I'll wait for someone with more time to explain them. That's just my 0.02.


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    Canon DSLR Moderator M. Gilden's Avatar
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    Nice... I actually mentioned hot feeds and turning down the camera gain if you read the whole thing (I know its long), and I have the video to demonstrate. I know its not the greatest example, but sounds good to me.

    Magic Lantern is still the best option if available (and it probably will be on the 60d and t3 soon) because it allows meters to move during recording, and also allows live monitoring via headphones using the composite plugs (as far as I know, this can't be done with the 60D, t3i, or other native "manual audio" cameras without ML). In that video, the guy is using ML with the composite hack, the Fiio preamp just lets him adjust the volume to his headphones. I actually don't feel like I need that as I can hear the audio straight off the cable with my studio headphones. I suppose if you're using weak little earbuds that would come in handy. Either way, would this even work on a 60D?

    My experience with a 60 and t3 have been pretty limited, so I appreciate your contribution to the thread!
    Last edited by M. Gilden; 03-02-2011 at 07:50 AM.

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    Canon DSLR Moderator M. Gilden's Avatar
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    On second thought, that fiio preamp might an interesting option for hooking up my older XLR shotgun mics... I bought an XLR to 1/8 adapter to try it out after I discovered how well the sennheiser lav worked, but found that my Azden shotgun was way too quiet, even if turned up. I'm assuming that XLR mics in general are supposed to be like this because everyone I tried with the adapter was barely audible (another Azden and a Sony), whereas plugging in a 3.5mm minijack dynamic mic sounded more normal.

    I guess that's what the juicedlink options are supposed to be- they have an XLR input and output a 3.5mm output battery powered "phantom power" preamp for for DSLRs specifically (one of them even has an automatic single-channel-noise for defeating AGC as described above as an option).
    I guess the reason those products exist is because XLR feeds aren't as hot by nature? This is kind of news to me.
    But, Juiced Link amps are out of my budget at the moment, so I decided I can't use my old mics on this camera yet.

    But if that cheapo little preamp does a good job, maybe I could use it to raise the volume before hitting the camera? What are the chances that thing's preamp is better than the camera's? I'd love to hear some feedback if anyone here has tried it...

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    Senior Member Chadfish's Avatar
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    I just ordered the Fiio E5 mini pre-amp and cables in order to monitor right off the T2i as I make some audio related videos. This is sweet! I hope it can work with the GH2 as well.
    Work Examples - Vimeo - My Music
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    Canon DSLR Moderator M. Gilden's Avatar
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    Quote Originally Posted by Chadfish View Post
    I just ordered the Fiio E5 mini pre-amp and cables in order to monitor right off the T2i as I make some audio related videos. This is sweet! I hope it can work with the GH2 as well.
    As far as I know, the GH2 doesn't support monitoring off the camera of any kind. Your only option would be to split the signal before it hits the camera, which is not really a recommended way to do things.

    But let me know how the Fiio is! I'm actually more interested in using it to boost the audio levels before they hit the camera, as I've found my XLR mics such as the Azden SGM 2x are coming in very soft to the camera, leaving far too much gain required on the camera (which is bad news).

    I've noticed in general that XLR input mics tend to run softer than 1/8(3.5mm) mini jack microphones do. I never noticed that before- my theory is that XLR recording devices are assumed to have a wider dynamic range, so the mic can start softer to allow more room for loud versus quiet sounds, and be raised in post without too much hiss if needed. But devices like our camera, which do not offer as much range between the noise floor and peak volume benefit from a louder mic and more consistent volume.

    Maybe the Fiio on my shotgun mic would yield usable results?
    Last edited by M. Gilden; 03-07-2011 at 05:06 PM.

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    Senior Member Chadfish's Avatar
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    I doubt it. I'd strongly suggest a JuicedLink mixer to hook up an XLR mic to your camera. You need phantom power (unless your mic runs on battery) to run a good mic, and the JuicedLinks have volume adjustment. That headphone booster will not be as clean of a boost as a real preamp like the JuicedLinks.
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    Canon DSLR Moderator M. Gilden's Avatar
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    Quote Originally Posted by Chadfish View Post
    I doubt it. I'd strongly suggest a JuicedLink mixer to hook up an XLR mic to your camera. You need phantom power (unless your mic runs on battery) to run a good mic, and the JuicedLinks have volume adjustment. That headphone booster will not be as clean of a boost as a real preamp like the JuicedLinks.
    Yeah, I read about the juicedlinks, and they seem pretty nice. Not convinced I need it enough to spend the money now, but thanks for confirming my observation about XLR mics. Are all XLR mics like this (less boosted) by design? Is that just the nature of the connection?
    I never mixed 1/8" and XLR equipment until moving to DSLR, so this whole territory is something new for me that I'm still learning about.

    Meanwhile, my Azden actually has a little aaa battery with 2 settings on the front that seem to add a bit of gain... but still not enough to register anything usable in the camera. I guess I need phantom power, but JuicedLink's options seem too expensive for me at the moment. For that price, it seems cheaper to go with a separate recorder that includes XLR inputs and sync in post.
    Last edited by M. Gilden; 03-08-2011 at 09:21 AM.

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    I'm considering getting the Rode Videomic Pro for my T2i, but sometimes I would want to mount it on a boom pole for recording dialogue, which means I would need a fairly long cable. Is it possible to use a long cable with the camera audio input without degrading the quality? I've read somewhere that mini-plug cables are not good for long distances and that's one of the main advantages to XLR.


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    Quote Originally Posted by bis22 View Post
    I'm considering getting the Rode Videomic Pro for my T2i, but sometimes I would want to mount it on a boom pole for recording dialogue, which means I would need a fairly long cable. Is it possible to use a long cable with the camera audio input without degrading the quality? I've read somewhere that mini-plug cables are not good for long distances and that's one of the main advantages to XLR.
    Yeah, for that kind of thing maybe an XLR mic going into a JuicedLink would be your best bet (although not as cheap) if you want to go into camera to record. Or, if you want to keep it cheaper and use the rode videomic, maybe purchase a Zoom H1 (about $99) to record directly from the pole, and sync up in post.

    I haven't experimented with mini plug cable length, so I'm not sure how real the problem is, but that might be difficult to do and still record in camera properly.

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