48 KHz audio at DVinfo.net

Tramm Hudson · September 2nd, 2009, 12:24 PM

Another feature to try to tease out of the 7D firmware when it is available -- 48 KHz audio:

Quote:

Higher audio sample rate: The 7D's audio sample rate is 48khz, up from 44.1khz in the 5D Mark II

The ak4646 in the 5Dm2 supports it. Hopefully it is just a matter of selecting the right bits in the sample rate register.

Chris Hurd · September 2nd, 2009, 12:32 PM

Hmm, this gets more interesting by the day. Thanks Tramm,

Jon Fairhurst · September 2nd, 2009, 01:16 PM

I'll say this, Canon's photo people have definitely spent time with their video people. Not only is the 7D getting 29.97, 25, and 23.976 fps, but 48 kHz too. Canon is taking this video stuff seriously - at $1,700 and up. I can't wait to see what they announce at NAB.

48 kHz would be very nice in the 5D2. Currently, the JL/ML is really quiet, but is a smidge crunchy to my ears. My guess is that I'm hearing some aliasing. (This is due to the camera, not the juicedLink. It could probably be solved with an external anti-aliasing filter, though I haven't tried it.) 48 kHz would make the camera that much less susceptible to aliasing. In fact, the filter rejection band might be set for 24 kHz, rather than 20.5.

I'm confident that Tramm can change the bits to deliver 48kHz from the audio chip. I'm not confident that the DIVIC will receive it and interleave it into the video files properly though. My hunch is that the encoder will need some bit twiddling as well.

Fingers crossed...

Roger Shealy · September 4th, 2009, 05:31 AM

So, what audio quality do we expect from the 7D if we run a good mic to it's 3.5mm plug? I know it has AGC, but is the sound otherwise clean and accurate. I hope someone (Canon?) will eventually crack the AGC.

If I can run my NTG-2 and Sennheiser wireless thru 1/8" jack and get good sound, I'd be very happy. I really want to avoid having to sync audio on an external Zoom.

Don Miller · September 4th, 2009, 06:22 AM

Quote:

Originally Posted by Roger Shealy

So, what audio quality do we expect from the 7D if we run a good mic to it's 3.5mm plug? I know it has AGC, but is the sound otherwise clean and accurate. I hope someone (Canon?) will eventually crack the AGC.

If I can run my NTG-2 and Sennheiser wireless thru 1/8" jack and get good sound, I'd be very happy. I really want to avoid having to sync audio on an external Zoom.

Likely the same electronics as the 5DII. Cheap. You can certainly get much better sound than the internal mike. Does Canon make anything with great audio?

Roger Shealy · September 4th, 2009, 06:43 AM

But if you supply a good externall mic to the 3.5mm jack, will the electronics in the 7D (probably similar to 5D) capture it audio accurately?

Tramm Hudson · September 4th, 2009, 06:53 AM

Quote:

Originally Posted by Roger Shealy

But if you supply a good externall mic to the 3.5mm jack, will the electronics in the 7D (probably similar to 5D) capture it audio accurately?

Jon Fairhurst did a series entitled http://www.dvinfo.net/conf/canon-eos...k-cx231-3.html

His results were that if the (cheap) preamp in the 5D is disabled or set to very low gain and a high quality preamp like the juicedLink CX231 is used instead, then the results are as good as a standalone audio recorder. Even better, if you consider the time saved in post trying to sync the audio and video without timecode.

It remains to be seen what audio chip the 7D is using. My guess is that it is the same AK4646, but until we've looked in the firmware we won't know.

Bill Pryor · September 4th, 2009, 09:42 AM

Can you turn off the auto gain?

Jon Fairhurst · September 4th, 2009, 09:52 AM

Magic Lantern can set a fixed gain in the 5D2. Not sure about the stock 7D. All indications are that Magic Lantern will be on the 7D before too long, and should also be able to set a fixed gain.

The standard disclaimer about predicting the future applies...

Chris Barcellos · September 4th, 2009, 09:53 AM

Quote:

Originally Posted by Roger Shealy

So, what audio quality do we expect from the 7D if we run a good mic to it's 3.5mm plug? I know it has AGC, but is the sound otherwise clean and accurate. I hope someone (Canon?) will eventually crack the AGC.

If I can run my NTG-2 and Sennheiser wireless thru 1/8" jack and get good sound, I'd be very happy. I really want to avoid having to sync audio on an external Zoom.

Roger:

I just got the NTG-2, as well as a free Rode M3 as part of their free mic offer. I tested on the 5D, which I would expect to comparable to the 7D. The NTG-2 kit I got from BH came with an XLR to mini adapter. Using Magic Lantern to disable automatic gain, and directly plugging into the camera with the mini adapter, I have shot decent levels running the camera setting at +23 gain analog, and +12 gain digital without using the Juiced Link. With Mic right up on the talent, these can go down to 17, 12 levels.

Bill Pryor · September 4th, 2009, 10:45 AM

Thanks, Jon. Yeah, we really don't know all that much about the yet-to-be-on-the-market 7D at this time. I'm still torn between shooting double system sound with something like the Tascam DR-100 or Zoom H4N or going with a Beachtek or Juicedlink (in the somewhat likely event I buy the 7D in a few months).

September 2nd, 2009, 12:32 PM	#2
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,366 Images: 513	Hmm, this gets more interesting by the day. Thanks Tramm, __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

September 2nd, 2009, 01:16 PM	#3
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	I'll say this, Canon's photo people have definitely spent time with their video people. Not only is the 7D getting 29.97, 25, and 23.976 fps, but 48 kHz too. Canon is taking this video stuff seriously - at $1,700 and up. I can't wait to see what they announce at NAB. 48 kHz would be very nice in the 5D2. Currently, the JL/ML is really quiet, but is a smidge crunchy to my ears. My guess is that I'm hearing some aliasing. (This is due to the camera, not the juicedLink. It could probably be solved with an external anti-aliasing filter, though I haven't tried it.) 48 kHz would make the camera that much less susceptible to aliasing. In fact, the filter rejection band might be set for 24 kHz, rather than 20.5. I'm confident that Tramm can change the bits to deliver 48kHz from the audio chip. I'm not confident that the DIVIC will receive it and interleave it into the video files properly though. My hunch is that the encoder will need some bit twiddling as well. Fingers crossed... __________________ Jon Fairhurst

September 4th, 2009, 09:52 AM	#9
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	Magic Lantern can set a fixed gain in the 5D2. Not sure about the stock 7D. All indications are that Magic Lantern will be on the 7D before too long, and should also be able to set a fixed gain. The standard disclaimer about predicting the future applies... __________________ Jon Fairhurst

September 4th, 2009, 05:31 AM	#4
Roger Shealy Major Player Join Date: May 2007 Location: Fayetteville, GA Posts: 772	So, what audio quality do we expect from the 7D if we run a good mic to it's 3.5mm plug? I know it has AGC, but is the sound otherwise clean and accurate. I hope someone (Canon?) will eventually crack the AGC. If I can run my NTG-2 and Sennheiser wireless thru 1/8" jack and get good sound, I'd be very happy. I really want to avoid having to sync audio on an external Zoom.

September 4th, 2009, 06:43 AM	#6
Roger Shealy Major Player Join Date: May 2007 Location: Fayetteville, GA Posts: 772	But if you supply a good externall mic to the 3.5mm jack, will the electronics in the 7D (probably similar to 5D) capture it audio accurately?

September 4th, 2009, 09:42 AM	#8
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	Can you turn off the auto gain?

September 4th, 2009, 10:45 AM	#11
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	Thanks, Jon. Yeah, we really don't know all that much about the yet-to-be-on-the-market 7D at this time. I'm still torn between shooting double system sound with something like the Tascam DR-100 or Zoom H4N or going with a Beachtek or Juicedlink (in the somewhat likely event I buy the 7D in a few months).