Title says it all, couldn't find any info in the 7D manual or on this forum, here are my questions:

Is the external mic input mic level or line level?

What is the sample rate / bit depth of the recording?

Is there any sort of built in audio limiter?

Are there any noise issues / audio quality issues?

Sound quality doesn't have to be great but has to be useable. Trying to avoid using an external recording device if possible.

Any / all help greatly appreciated. Thanks! heh

_Andrew Oswald

To give background on the project:

I am helping out a really close friend, as a personal favor, who is making a zero budget short film. He knows nothing about production sound (aside from that the onboard mic on a 7D is unusable) and isn't very experienced in film making.

If the sound quality is up to par, I want him to record directly to the 7D, because he doesn't have knowledge of the basics of syncing audio to picture and am afraid that he won't be able to properly set up an external recorder.

Nowadays I work exclusively in music production, am experienced in post production (mostly ADR and dialogue editing), and have only done production sound twice in my life. I won't be there on set because I don't have time. I am only giving him technical advice and giving him a day with me for post. All indoor shots. I'm letting him borrow a vintage AKG451 with a shotgun capsule and an outboard preamp (I know it's not ideal but I only own equipment that I use for music so it's the closest thing).

The only thing I am sure of is that the 7D has pretty awful automatic gain (compressor), which is not defeatable.

The only thing that I've heard from the 5D/7D world is that the built-in audio recording is the biggest thing that causes the camera to be a nightmare for small-end video production. I don't know if it's sync issues or auto-gain issues, but I've never heard of someone using the internal audio on these cameras. I only hear that you NEED a separate audio recorder to do audio with picture.

Do a test for auto-gain and sync. Record for 10 minutes with someone sitting in a noisy room, seated fairly near the camera talking/reading in a loud voice with some 5 second pauses thrown in. If AGC is a problem you will hear the room noise rise up during pauses. If sync is an issue you will notice that around the end of the clip.

The mic input is probably mic level as with most consumer camcorder setups. Buy a cheapie mic on ebay and plug it in. Sample rate and bit depth are likely to be the very least of your worries with this system. Converter quality and internal processing that you have no control over will probably be at the top of the list.

If I were to guess, I'd say that your tests will confirm the reason that every DSLR production is a double system setup, whatever those reasons are. If you do decide you need to go this route, then your friend may just have to learn how to sync audio. For Mac on Final Cut Pro, there is Plural Eyes that is supposed to be a very easy tool for syncing dual system audio to what is recorded on the camera itself with little room for user error.

If nothing else, learning to use a slate is a nice lesson for any video shooter/editor. Audio sync is a problem that we all have to deal with from time to time and it's nice from a sound guy's point of view to be working with a video guy who knows what the problems are and how to address them.

Best of luck!

Input is mic level only. You can make this work by padding down a line level signal (+4) by about 50 db.

A 7D is auto-gain only--you can't change this without a firmware hack.

The sound, like the 5D etc, is like that of a cheap "burrito-cam" camcorder: thin, no headroom, noisy, some distortion.

The audio recorded is not pcm--it is MPEG4 at whatever frame rate you set.
I believe the SR is 44.1 but I haven't checked that in a while.

The main obstacle is the AGC. I have worked with a lot of 7D and 5D audio in post, and if the AGC can be shut off then you have a fighting chance. Otherwise I would advise an external recorder. There are accessory boxes that claim to fool the AGC of a cam like 7D, but they are expensive, bulky, do nothing about the other audio shortcomings of the camera, and add a high-Hz signal to the audio.

phil p

Trying to use the audio-in of the 7D is a pointless exercise in frustration. The AGC, which Canon stupidly doesn't let you disable, makes it impossible for any reasonable audio quality to be recorded via the mic jack, regardless of the format it's recording to anyways.

You WILL NOT get away with not using an external recorder, unless you buy an adapter that costs as much as the recorder would anyways.

The 600D has selectable AGC On/Off.

WT

You can use the Magic Lantern Hack to disable AGC on the 7D. It's not destructive, boots off your memory card when you boot the camera. It has a few other nice tricks up it's sleeve also.

The input is mic level, but you can buy a beachtek adapter to give you two XLR and a line input for it. They aren't powered so no condensers and are going to starve any decent dynamic mic so I'd only use it to bring line in from a mixer or something. Unless you are needing serious fidelity, you'll probably get roughly equal results running a mixer into the mic input at a very, very low level.

The company BeachTek also make a box that can defeat AGC by blasting a high-end tone into it. Even then, I would only send a scratch track to a 7D.

Please tell your friend to record separate sound! The 5D/7D mic pre SUCKS and the auto gain is a nightmare. Use the cheap but good enough 4 ch. Zoom h4n with a boom and lavs if needed. He can use the camera on board mic as a guide track and simply line up the wave forms with the separate sound with the software pluraleyes that works as a plug-in for final cut pro etc...

Singular Software - PluralEyes

Omg -- i need to make the call to recent client and retract my possition on ability to shoot promo video for their band at live performance in small venue -- very small bar setting with about 6-8 huge speakers blasting out from stage front ... haaa wow -- capturing them with still images and video clips with 7D yes -- recording audio with video and expect results for promotional clips -- not gonna happen :/ even with a boom mic , as so i read ...!!