Jump to content

Canon 7D Audio Test - Redux


Steven at Coffey Sound
 Share

Recommended Posts

Any word on what frame rates/ sampling freq should be used when going the sound devices route?  I've heard that this camera rolls at a different frame rate than the 5D.  (24p?)

Also has anyone devised a reliable scheme that would allow for sync without the need to clap a slate? ..and be solid for long takes? (thinking its only a matter of time before I'll see this used on a run-n-gun gig where they'll balk at the idea of having to hit a slate every time the camera speeds) 

ie:  A lockit box/SB3 on both the sound devices and the 7D into an audio channel?  Maybe you would only need one since the 744 could just take a jam and hold code on its own..? 

Link to comment
Share on other sites

Hey Derek, the 7D does all the major timecodes, the 5D only does true 30ndf. No way to jam TC unless you do it as audio on one of the 2 audio tracks via a beachtek or juiced. The maximum time a take can be on either DSLR camera from Canon. Dumb stix or a hand clap is all you need really for sync.

CrewC

Link to comment
Share on other sites

Hey, Derek

If you're feeding the camera a scratch track, you can also send a little shot of tone to both the camera and the recorder. In FCP, it's pretty easy to sync using the audio waveforms in the timeline for the camera's audio tracks and the tracks brought in from your recorder. I'm certain you can do the same with Avid systems as well. I've used this method when a toy camera gets thrown into a setup at the last minute for those goofy cut angles that hardly ever get used. No reason you can't do the same with a 5D or 7D.

Best regards,

Jim

Link to comment
Share on other sites

You were otherwise occupied thinking great thoughts, Crew.

The idea's not new, but I fell back to it on a last minute political spot. The director pulled a toy camera out of thin air and asked if I could feed it. He got all screwy about sync, and didn't want a clap because the candidate was very distractible. Thankfully, he didn't win. I hate to think a US Senator would loose his composure 'cause somebody smacked a couple of pieces of wood together.

Best regards,

Jim

Link to comment
Share on other sites

Thanks folks.

I have put timecode into the 7D and found the following:

The timecode (recorded as audio signal) is ~4 frames off from the slate's timecode as recorded as a video.  This offset remained constant for the 12 minute test.  This is the maximum video length this camera can record at 1080p24 as it results in a 4GB file and the filesystem is FAT32.

I have not checked bleed between channels, but perhaps it won't be so bad as to render a scratch track unusable.  Timecode on one track (effectively disabling AGC for both channels), scratch audio on the other track seems like a path worth considering.

Thanks,

Robert

Link to comment
Share on other sites

  • 3 months later...

A cameraman i recently came in contact with (and future co-worker) has told me about a new firmware update to the canon 7d that allows for meters and/or level controls for the 7D.  I read the canon page about the latest updates and see nothing about audio being updated.

Anyone hear this news or come in contact with a new and improved Canon 7D?

Best,

Brett

Link to comment
Share on other sites

that new firmware you're hearing about is the magic lantern hack, but its far far from being in existence. the guy who does it has created a hack for the 5d that disables the auto gain control on the audio and adds 1 vu meter. but it is a hack, not canon certified. but a lot of user do rely on it professionally.

here's the link to the wiki of it

http://magiclantern.wikia.com/wiki/Magic_Lantern_Firmware_Wiki

Link to comment
Share on other sites

that new firmware you're hearing about is the magic lantern hack, but its far far from being in existence. the guy who does it has created a hack for the 5d that disables the auto gain control on the audio and adds 1 vu meter. but it is a hack, not canon certified. but a lot of user do rely on it professionally.

here's the link to the wiki of it

http://magiclantern.wikia.com/wiki/Magic_Lantern_Firmware_Wiki

I think it is important to mention (again) that even with some meters (that mean what, exactly?) and the AGC disabled, there is still NO MONITORING and the quality of the audio electronics, esp convertors, is about at cel-phone level.  With the camera having no monitoring, users might be better off WITH the AGC than without.

Philip Perkins

Link to comment
Share on other sites

I think it is important to mention (again) that even with some meters (that mean what, exactly?) and the AGC disabled, there is still NO MONITORING and the quality of the audio electronics, esp convertors, is about at cel-phone level.  With the camera having no monitoring, users might be better off WITH the AGC than without.

Philip Perkins

Does the vu meter offer any control to the input level? or would the only way to control it be to attenuate from the mixer end?

I am plan to do double system, but everyone wants their camera to be fed whether it is really meant to chew on quality audio or not =)

Best,

Brett

Link to comment
Share on other sites

" Does the vu meter offer any control to the input level?   "

no...

meters are only a visual representation of some values or levels...

" would the only way to control it be to attenuate from the mixer end? "

controlling levels is what mixers are for...

but the only way??  there certainly could be other options.  in the case of the DSLR you are discussing, any options are not available in the camcorder...

" there are really god (sic) cellphones these days :-) "

audio over cell phone connection is limited to 300-3000Hz.  being digital there is no 299Hz (or lower) or 3001 Hz (or higher)...

Link to comment
Share on other sites

What really impressed me about this GreenLantern video is the FIZ follow focus.  It's BlueTooth and uses the camera firmware to control the focus on the lens, therefore not requiring motors on the camera itself.  Some of the remote FIZ motors I have dealt with in the past have been rather noisy, and one of the advantages of a file-based camera (especially these DSLR) would be there lack of operating noise.

Robert

Link to comment
Share on other sites

  • 2 months later...

Interesting. Does this mean that the audio lags (or leads) picture by four frames?

If you do record timecode on one channel (even with the  frame offset), does it then allow for automatic syncing in either Avid or FCP, or does the editor have to manually match it?

--Scott

Thanks folks.

I have put timecode into the 7D and found the following:

The timecode (recorded as audio signal) is ~4 frames off from the slate's timecode as recorded as a video.  This offset remained constant for the 12 minute test.  This is the maximum video length this camera can record at 1080p24 as it results in a 4GB file and the filesystem is FAT32.

I have not checked bleed between channels, but perhaps it won't be so bad as to render a scratch track unusable.  Timecode on one track (effectively disabling AGC for both channels), scratch audio on the other track seems like a path worth considering.

Thanks,

Robert

Link to comment
Share on other sites

Audio leads video in every digital camera by at least one frame. Most F35/23/Genesis/Red are 2 frames...... Add a downconverter and the advance can be as much as 6 frames as monitored by Comtek.  If you are curious, then test the camera rig as used, otherwise make a head slate (ID it as an Audio Test) of 10 seconds (Clap at beginning and end of the mini sound/sync) or so with clapper and a notation on your Sound Report/Script Notes that the head slate is the Audio Offset for PostPro. If anyone asks, refer them to that small Video/Audio clip.....   

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...