Blackmagic Forum

Hello, I have been doing some tests with my BMC and I have found something interesting that happens when testing audio. If the level on the camera clips for too long (maybe 4 seconds?) the camera stops excepting audio input. And when I try to switch from mic leve to line level and then back again, the switch stays at line and will not go to mic. this does not fix itself until you re-boot the camera.

This is not good! If I have some issue where I have some peaking for a few seconds, all the rest of my audio will be muted.

I am testing for other issues, like the Signal to Noise ratio etc. I will get back to you on those... but I just thought I would submit this right away.

I can now confirm that it does in fact switch to line level only.

Interesting problem, hope an engineer can drop by and read this soon. A bug reporting forum for the BMCC (and other products) would probably be a good idea, too.

This seems to eliminate the BMC for in-camera audio recording at mic level doesn't it? I mean, even if you were recording with a DAR and only feeding the BMC a scratch track for syncing, if the audio went away, it would be disastrous. Right now with my 7D, I split a headphone feed out of my DAR to the mic input on the 7D for a scratch track. It sounds horrible but works fine for syncing. If the BMC just quit recording audio and the lack of VUs on camera kept me from knowing about it...well, I don't even want to think about that.

mbeck wrote:I can now confirm that it does in fact switch to line level only.

Michael,

Thanks for the report. Let us look into it.

Kristian Lam wrote:

mbeck wrote:I can now confirm that it does in fact switch to line level only.

Michael,

Thanks for the report. Let us look into it.

Yay!! A BMD rep
mbeck are you doing any external adr?

Kristian Lam wrote:

mbeck wrote:I can now confirm that it does in fact switch to line level only.

Michael,

Thanks for the report. Let us look into it.

No problem!

Here is another issue.

http://www.youtube.com/watch?feature=pl ... T-2I8BGgNY

The meters seem to stay the same regardless of the input.
My setup there was a phantom powered mic plugged into my juicedlink and then into the camera. The camera is set to Mic level at 5%

Michael,

Have you tried altering the BMCC input from, say, 5% to 10% and seeing if there is a similar increase in the audio levels ceiling point or where it clips on the VU's..

I know it doesn't make sense, and there's definitely an issue but it might explain where the issue is?? If you can remove the two constants of fixed 5% IN BMCC and fixed clipping level then we can remove the possibility of a problem in the monitoring path, pre/post etc...

Could you just explain the complete signal path from mic to vu meter? Where are you getting the vu's from? is a mac connected to the BMCC. I'm not familiar with the juicedlink - thats all.

The other issue BTW is just odd.. Good luck,

SK

Ok, here is my last test for the night:



It shows the differenced in metering in Ultrascope and Media Express.

mbeck wrote:Hello, I have been doing some tests with my BMC and I have found something interesting that happens when testing audio. If the level on the camera clips for too long (maybe 4 seconds?) the camera stops excepting audio input. And when I try to switch from mic leve to line level and then back again, the switch stays at line and will not go to mic. this does not fix itself until you re-boot the camera.

See page 12 in the BMCC user manual. It switches at overload to line, to protect the camera from damage.

Frank

Thanks Frank.
Who reads manuals?! Lol. I wonder why you have to re-boot to fix it though.

Frank Glencairn wrote:

mbeck wrote:Hello, I have been doing some tests with my BMC and I have found something interesting that happens when testing audio. If the level on the camera clips for too long (maybe 4 seconds?) the camera stops excepting audio input. And when I try to switch from mic leve to line level and then back again, the switch stays at line and will not go to mic. this does not fix itself until you re-boot the camera.

See page 12 in the BMCC user manual. It switches at overload to line, to protect the camera from damage.

Frank

I suspected this and almost posted my suspicions in my previous post, but left it out since I didn't have a BMCC in-hand to check. :X

mbeck are you still finding issues with the Mic level with your BMCC?
read your posts today at <insert forum here> and wondering if you have opened dialogue with BMD tech support.
this is a huge deal for most of us pre-orders.

Here is some quick test I did:

http://depositfiles.com/files/7ses9ab2x

Hi Guys,

I'm doing the best I can to help solve these problems without a BMC on hand so forgive me if I make some mistakes or get a touch annoying with my comments and probing just trying to help.

On professional audio equipment line level inputs & outputs are preset to 0dbu or +4dbu (the later being more common)

If the output is sending +4dbu and the input is expecting +4dbu then things should be right at 100. Though there's some wriggle room on the BMC to bring the input down. But in reality the output can't send more than the input is expecting.

unless... the mixer is sending too hot a signal.

I've done some research and may have found the mystery.

The Riggy micro only outputs mic level, not line level.

Frank, I think the Wendt has line level output. (there should be some switches under the XLR outs MIC/LINE)

Michael, The only way around the mic overload safety, if it needs to stay in the BMC, is to get a field mixer with clip limiting. ie sound devices of the top of my head and probably some others. In a controlled environment, setting the levels a touch lower can avoid this too. But where's there's the possibility of loud peaks, a clip limiter is the way.

I hope you all are having a great day!

Paul

During my research I come upon this http://www.professionalsound.com/specs/dv_3.htm this unit looks the goods and just over $400. A review, http://www.professionalsound.com/reviews/sleeper_3_rev.html
Professional Sound Corporation are based in Valencia, Ca. Good price worth a look.

Yup, I tried both, mic and line out from the Wendt X2.
Have you listened to the file I posted Paul?

Riggy with the Rode and Oktava into the mic input sounds good. (love the sound of that oktava mic so rich and full) The Wendt sounds good too. The S/N is good with the levels you have set up.

Michael Beck mentioned he has a firmware update that fixes a few audio things. Not sure what, he seemed to be having all sorts of problems.

It does seem the BMC inputs are rather hot?

Anyway, what can we do but speculate until someone from the audio tech side of BMD look into it.

Again only speculation but if there is this "built-in microphone" that Phil Bloom identified as a "crappy little thing on the front" I wonder if the bmcc's input IS a little hot to accommodate this?

SK