Mic level? at DVinfo.net

Claus Bier · June 18th, 2008, 04:52 PM

The manual says you'll have a mic level display when an external mic is connected.

Does that display show peaks in numbers or colors? In other words: Is this level of any use? As there is "officially" no headphone output it would be nice to have at least some visual control over your audio.

I haven't seen any mentioning of any ways to change the audio levels. Did I miss something?

Barry Smith · June 18th, 2008, 08:18 PM

Quote:

Originally Posted by Claus Bier

The manual says you'll have a mic level display when an external mic is connected.

Does that display show peaks in numbers or colors? In other words: Is this level of any use? As there is "officially" no headphone output it would be nice to have at least some visual control over your audio.

I haven't seen any mentioning of any ways to change the audio levels. Did I miss something?

Sliding bars with a red zone.

Waldemar Winkler · June 18th, 2008, 08:49 PM

This is crazy. I shot a wedding two weeks ago and was constantly glancing at the lcd audio meters, and the only thing I tell you is that they are green. I distinctly remember a particularly loud sound pegging the meters, but I can't remember if the meters changed colors. There are no numbers. Too many other things going on and I close to worn out (that shoot took 18 hours).

What I can tell you is the camera's audio system is completely managed by auto-gain circuitry, and that that circuit has both a rather slow attack and release response. It really is shaped for average ambient audio. There is no manual overide. I just finished editing an interview involving two wireless lapel microphones. Both subjects wore good, but not hugely expensive microphones, maybe just under $100 each. I haven't yet been able to determine if the distortion is a microphone issue or a camera audio system issue.
Once I loaded the video into Final Cut Pro, I consistently saw the audio meters indicating distortion just about every time either of the subjects uttered a strong consonant after taking a breath. The slow release is not such a big deal, but the slow attack may be just slightly too slow. It is clear to me that any HD7 audio recording in an environment having a strong sound pressure levels will have to be exported to an audio processing application (I use Soundtrack Pro) to pull down the overloaded peaks. Problem is, once audio is distorted, it remains distorted.

As long as you work with a camera having only AGC audio controls, I believe a passive audio interface, like the Beachtek or the much less expensive and just as capable SignVideo adapters is an absolute necessity. I own four cameras. Only one has manual audio control, and I usually rely on its AGC for most run-n-gun situations.

Kieran Steele · June 18th, 2008, 09:06 PM

Claus,

I did some testing in the last few days lying timecode down as audio via the external mic input.

The inability to turn off auto gain or set the input levels manually was a huge pain, and almost stopped this working.

There are some other options if you want headphone monitoring.

1) Go out from the a/v out into a dvd player mounted on the side with headphone out. This is a cheap larger screen option for tripod work, and then you have headphones.

2) Get a rolls PM50sOB. Might be overkill for what you want, but you can use to plug headphones into the line level out. $66 isn't too bad though...

I use a XLR-BP Pro to take xlr external mics (onboard and boom) into the 3.5mm, but it does not have a headphones jack on it.

Incidently the only device I found that seems to power the external MZ-48U whilst in this xlr-bp pro (which does not supply it power) was the all601 lanc logger. Total overkill for normal use, but nice bonus if you are laying down tc.

I notice the new models (not the hd7) have a headphones jack :). They are not as good as the hd7 in many respects for my use, so wouldn't swap because of that.

For info the levels on the hd7 and the lights represent roughly the following (based on taking outputted files into soundtrack pro, and checking the levels whilst playing).

Lights - level
5.5 - -23db
6 - -21db
7 - -18db
8 - -16db
9 - -13db
10 - -6.2db

For me to get my timecode laid down between -20db and -10db based on my input from an ALL601 set to -24db was 5.5-6.5 lights. So it seems that is the real sweet spot of the range.

Cheers,

Kieran

Kieran Steele · June 18th, 2008, 09:49 PM

Waldemar,

How funny! I had finished typing my post when I saw yours :)

You should see what the agc did to my nice blocky wave for timecode. Chopped the right shoulder off!

I use an xlr-bp pro which is similar to the beachtek. This seems to work for me, so haven't needed to do anything else to it yet... But nor have I really relied on it at the main source of sound...

I guess if I am really keen to use the audio off the cam, I take the line out into a mixpre or similar mixer and use the VU's from there shoulder slung... Nasty for run and gun..?

But really, ceremony I just have someone boom, and take the lavs off to outboard mix and recording. Reception, all the steadicam is going to be sans sound, and the other cams for speaches etc, again lavs offboard... So not sure what sound I am going to need run and gun.

I think its coming down to, single camera, if it is lousy agc, not many options...?

You are right, you are never going to have the chance to look at levels run and gun, so relying on AGC working is a bit of a must.

Best you could hope for is really maybe to wear at least one earphone using a rolls or something so you could hear if it is peaking maybe...

I noticed the newer models come with a headphone jack, but not as nice controls etc...

I've not used the gz7 as my main camera yet, and all the audio is going into an A cam (if not outboard) and the bcams are for cutaways or other angles, but my sound is going into something with manual levels and a good vu, be it the main cam, or offboard mixer.

Id be interested to see your results next time out, or other people's input on how well their levels and agc are working..

Kieran

Claus Bier · June 18th, 2008, 10:39 PM

Thanks for the very exhaustive info, everyone. It is really appreciated.

I doubt I will do any professional work with this camera, besides having it as a tripod queen during workshops (the sound will be taken via the Beachtek adapter from a mixer), while doing the run around with second second camera.

Just wanted to know how it would fare on beach/family outings with a lot of shrieking/yelling of kids having fun. My cheap Sony gets a lot of clipping from the kids noise...

Jeff Nyman · June 19th, 2008, 07:32 AM

For headphones on my hd7 I use Steve's idea from his book with the hacked iPod plug from ratshack plugged into the a/v jack.

Wayne Avanson · June 19th, 2008, 11:28 AM

I use a second screen from a cheap portable DVD player package as a lo res monitor and I use the headphone socket from that which works nicely. I bought the cable as Steve's workaround suggestion but haven't yet done the cutting and soldering. I'll get round to it…

For input I use the Rode SVM which has a 10Db pad switch which I find works very well at avoiding clipping (mostly).

I agree though that the AGC could be quicker. One would have thought that for a camera such as this and the general purposes to which the camera would be put, they would have thought of catching transients quickly then releasing slowly. But then again, when you think about all the other nice little controls they've put on the HD7, why on earth did they leave out a headphone socket?! Daft.

Waldemar Winkler · June 19th, 2008, 05:35 PM

[/QUOTE] ... when you think about all the other nice little controls they've put on the HD7, why on earth did they leave out a headphone socket?! Daft.[/QUOTE]

In the 1980's Pontiac auto designers convinced General Motors management it needed to produce a low priced, attractive commuter car. Then they produced a snazzy, nimble, quick little sports car ... and it sold like wildfire. When GM management realized they had been tricked, they squashed the R&D necessary to turn this car into something really special, and it went out of production within five or six years. I think the HD7 was a similar kind of project. It has all the bells and whistles to attract the amateur videophile with really good performance characteristics that should have been given additional attention, but lacks a few key features serious videographers need, like a headphone monitor and manual override on audio gain. The marketing department didn't really understand what they had, gave it the wrong advertising spin, and thus forced new development to dumb the machine down.

Steve Mullen · June 19th, 2008, 08:27 PM

Quote:

Originally Posted by Waldemar Winkler

What I can tell you is the camera's audio system is completely managed by auto-gain circuitry, and that that circuit has both a rather slow attack and release response.
Once I loaded the video into Final Cut Pro, I consistently saw the audio meters indicating distortion just about every time either of the subjects uttered a strong consonant after taking a breath.

Hmmm -- you call it AGC which would mean it includes both a limiter and a gain circuit that increases low signal levels.

My experience is that although called an AGC by JVC -- like most all current digital camcorders it is only a Limiter. That's because low signal levels are no problem in digital so there is no reason to increase signal level.

If I'm correct -- the signal coming INTO the HD7 is way too hot.

I would dial down the signal at your wireless receiver so the signal PEAKS, on the HD7, are at Light 6 (-21dB) or Light 7 (-18dB). That means that average audio levels light only a few Lights -- just enough to confirm the mics are working.

Waldemar Winkler · June 19th, 2008, 10:28 PM

Quote:

Originally Posted by Steve Mullen

Hmmm -- you call it AGC which would mean it includes both a limiter and a gain circuit that increases low signal levels.

My experience is that although called an AGC by JVC -- like most all current digital camcorders it is only a Limiter. That's because low signal levels are no problem in digital so there is no reason to increase signal level.

If I'm correct -- the signal coming INTO the HD7 is way too hot.

I would dial down the signal at your wireless receiver so the signal PEAKS, on the HD7, are at Light 6 (-21dB) or Light 7 (-18dB). That means that average audio levels light only a few Lights -- just enough to confirm the mics are working.

Good point. Explains a lot about JVC's audio perception. However, most wireless receivers don't have gain control on input. The squelch adjustment may attenuate incoming signal, but is also impacts reception range as well, so test, test, test. Transmitter input may be a better approach. Most RF transmitters have a screwdriver adjustment that is called just about anything between volume and gain, but is really gain. Full clockwise should be around -50db. Fully counter clockwise should be +4db.

Steve Mullen · June 20th, 2008, 01:06 AM

Quote:

Originally Posted by Waldemar Winkler

Good point. Explains a lot about JVC's audio perception. However, most wireless receivers don't have gain control on input.

Are you are feeding a LINE level into a MIC jack?

If so, no wonder there's distortion.

Page 48 in book explains this and how to fix this problem.

Barry Smith · June 20th, 2008, 06:56 PM

Quote:

Originally Posted by Waldemar Winkler

This is crazy. I shot a wedding two weeks ago and was constantly glancing at the lcd audio meters, and the only thing I tell you is that they are green. I distinctly remember a particularly loud sound pegging the meters, but I can't remember if the meters changed colors.

Must be a HD-3 thing or a Europe model difference. It certainly does change colours on the HD3 PAL.

Benjamin Patrick · June 26th, 2008, 08:07 PM

I can confirm that the mic-in on my JVC HD7 has a limiter function only and not auto gain. I tested with both a Shure SM-57 dynamic mic and a Rode NT3 condenser mic. Running a 1 khz tone from my computer to an external speaker, I was able to record with both microphones. There are 9 green bars for each channel and 2 red bars (virtually impossible to count without my best reading glasses). My camera gave me a repeatable -11db to -12db when the JVC displayed 6-7 green bars per channel. Allowing the bars to ride into the red, even briefly, overloaded the input when using the NT3. I measured this in Soundtrack pro and Final Cut Express HD.

Thanks for all the useful information. Personally, I think this is preferable to having auto gain. I record most of my audio using a separate Sony PCM D50, but I may try some more audio direct with a Beachtek or alternative.

Mr. Mullen, would you please include me on your list to receive your latest updates. I've sent an email a few weeks ago, but it may not have gotten thru.

Thanks,

Ben Patrick

Kieran Steele · June 26th, 2008, 11:26 PM

I'm not that familiar with an auto limiter function vs auto gain.

Would a limiter function (not auto gain), drop the levels of one channel in response to the other?

In some audio timecode tests, I had it running smoothly into left channel, Plugged a mic into the right channel and spoke loudly into it. The result was it reduced the levels of both channels, both visibly on the lcd, and confirmed in post.

June 18th, 2008, 04:52 PM	#1
Claus Bier Regular Crew Join Date: May 2008 Location: Saipan, USA Posts: 28	Mic level? The manual says you'll have a mic level display when an external mic is connected. Does that display show peaks in numbers or colors? In other words: Is this level of any use? As there is "officially" no headphone output it would be nice to have at least some visual control over your audio. I haven't seen any mentioning of any ways to change the audio levels. Did I miss something?

June 18th, 2008, 08:49 PM	#3
Waldemar Winkler Major Player Join Date: Aug 2004 Location: Durango, Colorado, USA Posts: 711	This is crazy. I shot a wedding two weeks ago and was constantly glancing at the lcd audio meters, and the only thing I tell you is that they are green. I distinctly remember a particularly loud sound pegging the meters, but I can't remember if the meters changed colors. There are no numbers. Too many other things going on and I close to worn out (that shoot took 18 hours). What I can tell you is the camera's audio system is completely managed by auto-gain circuitry, and that that circuit has both a rather slow attack and release response. It really is shaped for average ambient audio. There is no manual overide. I just finished editing an interview involving two wireless lapel microphones. Both subjects wore good, but not hugely expensive microphones, maybe just under $100 each. I haven't yet been able to determine if the distortion is a microphone issue or a camera audio system issue. Once I loaded the video into Final Cut Pro, I consistently saw the audio meters indicating distortion just about every time either of the subjects uttered a strong consonant after taking a breath. The slow release is not such a big deal, but the slow attack may be just slightly too slow. It is clear to me that any HD7 audio recording in an environment having a strong sound pressure levels will have to be exported to an audio processing application (I use Soundtrack Pro) to pull down the overloaded peaks. Problem is, once audio is distorted, it remains distorted. As long as you work with a camera having only AGC audio controls, I believe a passive audio interface, like the Beachtek or the much less expensive and just as capable SignVideo adapters is an absolute necessity. I own four cameras. Only one has manual audio control, and I usually rely on its AGC for most run-n-gun situations. __________________ Waldemar

June 19th, 2008, 07:32 AM	#7
Jeff Nyman New Boot Join Date: Apr 2008 Location: Payson, Utah Posts: 14	headphones For headphones on my hd7 I use Steve's idea from his book with the hacked iPod plug from ratshack plugged into the a/v jack.

June 19th, 2008, 05:35 PM	#9
Waldemar Winkler Major Player Join Date: Aug 2004 Location: Durango, Colorado, USA Posts: 711	[/QUOTE] ... when you think about all the other nice little controls they've put on the HD7, why on earth did they leave out a headphone socket?! Daft.[/QUOTE] In the 1980's Pontiac auto designers convinced General Motors management it needed to produce a low priced, attractive commuter car. Then they produced a snazzy, nimble, quick little sports car ... and it sold like wildfire. When GM management realized they had been tricked, they squashed the R&D necessary to turn this car into something really special, and it went out of production within five or six years. I think the HD7 was a similar kind of project. It has all the bells and whistles to attract the amateur videophile with really good performance characteristics that should have been given additional attention, but lacks a few key features serious videographers need, like a headphone monitor and manual override on audio gain. The marketing department didn't really understand what they had, gave it the wrong advertising spin, and thus forced new development to dumb the machine down. __________________ Waldemar

June 26th, 2008, 08:07 PM	#14
Benjamin Patrick Tourist Join Date: May 2008 Location: Madison, AL Posts: 1	Confirmation of Limiter Circuit Only I can confirm that the mic-in on my JVC HD7 has a limiter function only and not auto gain. I tested with both a Shure SM-57 dynamic mic and a Rode NT3 condenser mic. Running a 1 khz tone from my computer to an external speaker, I was able to record with both microphones. There are 9 green bars for each channel and 2 red bars (virtually impossible to count without my best reading glasses). My camera gave me a repeatable -11db to -12db when the JVC displayed 6-7 green bars per channel. Allowing the bars to ride into the red, even briefly, overloaded the input when using the NT3. I measured this in Soundtrack pro and Final Cut Express HD. Thanks for all the useful information. Personally, I think this is preferable to having auto gain. I record most of my audio using a separate Sony PCM D50, but I may try some more audio direct with a Beachtek or alternative. Mr. Mullen, would you please include me on your list to receive your latest updates. I've sent an email a few weeks ago, but it may not have gotten thru. Thanks, Ben Patrick

June 18th, 2008, 09:06 PM	#4
Kieran Steele Regular Crew Join Date: Nov 2007 Location: Canberra, Australia Posts: 37	Claus, I did some testing in the last few days lying timecode down as audio via the external mic input. The inability to turn off auto gain or set the input levels manually was a huge pain, and almost stopped this working. There are some other options if you want headphone monitoring. 1) Go out from the a/v out into a dvd player mounted on the side with headphone out. This is a cheap larger screen option for tripod work, and then you have headphones. 2) Get a rolls PM50sOB. Might be overkill for what you want, but you can use to plug headphones into the line level out. $66 isn't too bad though... I use a XLR-BP Pro to take xlr external mics (onboard and boom) into the 3.5mm, but it does not have a headphones jack on it. Incidently the only device I found that seems to power the external MZ-48U whilst in this xlr-bp pro (which does not supply it power) was the all601 lanc logger. Total overkill for normal use, but nice bonus if you are laying down tc. I notice the new models (not the hd7) have a headphones jack :). They are not as good as the hd7 in many respects for my use, so wouldn't swap because of that. For info the levels on the hd7 and the lights represent roughly the following (based on taking outputted files into soundtrack pro, and checking the levels whilst playing). Lights - level 5.5 - -23db 6 - -21db 7 - -18db 8 - -16db 9 - -13db 10 - -6.2db For me to get my timecode laid down between -20db and -10db based on my input from an ALL601 set to -24db was 5.5-6.5 lights. So it seems that is the real sweet spot of the range. Cheers, Kieran

June 18th, 2008, 09:49 PM	#5
Kieran Steele Regular Crew Join Date: Nov 2007 Location: Canberra, Australia Posts: 37	Waldemar, How funny! I had finished typing my post when I saw yours :) You should see what the agc did to my nice blocky wave for timecode. Chopped the right shoulder off! I use an xlr-bp pro which is similar to the beachtek. This seems to work for me, so haven't needed to do anything else to it yet... But nor have I really relied on it at the main source of sound... I guess if I am really keen to use the audio off the cam, I take the line out into a mixpre or similar mixer and use the VU's from there shoulder slung... Nasty for run and gun..? But really, ceremony I just have someone boom, and take the lavs off to outboard mix and recording. Reception, all the steadicam is going to be sans sound, and the other cams for speaches etc, again lavs offboard... So not sure what sound I am going to need run and gun. I think its coming down to, single camera, if it is lousy agc, not many options...? You are right, you are never going to have the chance to look at levels run and gun, so relying on AGC working is a bit of a must. Best you could hope for is really maybe to wear at least one earphone using a rolls or something so you could hear if it is peaking maybe... I noticed the newer models come with a headphone jack, but not as nice controls etc... I've not used the gz7 as my main camera yet, and all the audio is going into an A cam (if not outboard) and the bcams are for cutaways or other angles, but my sound is going into something with manual levels and a good vu, be it the main cam, or offboard mixer. Id be interested to see your results next time out, or other people's input on how well their levels and agc are working.. Kieran

June 18th, 2008, 10:39 PM	#6
Claus Bier Regular Crew Join Date: May 2008 Location: Saipan, USA Posts: 28	Thanks for the very exhaustive info, everyone. It is really appreciated. I doubt I will do any professional work with this camera, besides having it as a tripod queen during workshops (the sound will be taken via the Beachtek adapter from a mixer), while doing the run around with second second camera. Just wanted to know how it would fare on beach/family outings with a lot of shrieking/yelling of kids having fun. My cheap Sony gets a lot of clipping from the kids noise...

June 19th, 2008, 11:28 AM	#8
Wayne Avanson Major Player Join Date: Feb 2008 Location: Lancashire UK Posts: 496	I use a second screen from a cheap portable DVD player package as a lo res monitor and I use the headphone socket from that which works nicely. I bought the cable as Steve's workaround suggestion but haven't yet done the cutting and soldering. I'll get round to it… For input I use the Rode SVM which has a 10Db pad switch which I find works very well at avoiding clipping (mostly). I agree though that the AGC could be quicker. One would have thought that for a camera such as this and the general purposes to which the camera would be put, they would have thought of catching transients quickly then releasing slowly. But then again, when you think about all the other nice little controls they've put on the HD7, why on earth did they leave out a headphone socket?! Daft.

June 26th, 2008, 11:26 PM	#15
Kieran Steele Regular Crew Join Date: Nov 2007 Location: Canberra, Australia Posts: 37	I'm not that familiar with an auto limiter function vs auto gain. Would a limiter function (not auto gain), drop the levels of one channel in response to the other? In some audio timecode tests, I had it running smoothly into left channel, Plugged a mic into the right channel and spoke loudly into it. The result was it reduced the levels of both channels, both visibly on the lcd, and confirmed in post.