Audio stuff--GO DAT!

[Steve Mullen]

<<<-- Originally posted by Jeremiah Hall : Originally posted by Steve Mullen:

"As an editor you should want access to the raw audio so you can control it in post.

I agree. Unfortunately all the AGC circuits I've dealt with on cameras (DVCPro, Beta) all have the same problem. The circuit drops the level initially too far, then struggles to bring it back up."

Heath has already tested the JVC and found this not to be true. And it's not true on many cameras these days days.


"And, pitch and levels are all irrelevant with digital audio. It's a "pipe" from mic to post. Exactly, what you want!

Levels are not irrelevant. Hot audio sounds just as bad in digital as it does in the analog world. "

The solution to hot audio is to match your mic to the camera input. That's why mics have a level spec, for example, -60dB. And why camcorders have a similar spec. And, why Panasonic camcorders have setting at -50dB, -60dB. All these features are designed to solve the problem you worry about.

Now JVC doesn't provide a spec, but the AGC will auto-lower the level to prevent clipping. I measured the number of samples with clipping. Even on a NYC street it was a fraction of a percent! In other loud situations it was NONE.

"Double-system sound, though a little cumbersome and expensive, is a lot better than just plugging the mic into the camera. It gives you an extra set of ears."

You don't need double-system to get a second set of ears. Just plug a set of headphones into the camcorder.

In short, the craft was built on analog technology, not digital. -->>>

[Steve Mullen]

<<<-- Originally posted by Jay Nemeth : "The process typically is to turn on the field mixer's 1khz tone generator and set the master to 0db on the mixer's meter. Now calibrate the camera by adjusting it's input level to also be 0db (if an analog recorder) or -20db (I think, if using the digital range)."

First, you do not want to feed a mixer into the JVC. A mixer outputs at LINE level not MIC level. So you must put an attenuator between the two. It can be fixed because the signal drop is common in the industry. Or you can use a variable and calibrate it ONCE.

"And if the level on the mixer's meter is too low, he knows he isn't giving the recording device a signal that uses it's full dynamic range."

Steve screaming ANALOG BE GONE! With 16-bits of dynamic range you do not have to worry about too low a signal. The JVC will record over over a 100dB range, near that of a CD.

If you see a green light flashing on the JVC, then you are fine.


"Since the JVC uses auto gain on the audio, if you hit it with a loud external signal, it will try to react by turning down the level, you will notice background noise get quiet when someone talks loudly, and then when they stop talking, the background noise slowly creeps up as the camera increases the gain to put the audio signal where it thinks it should be."

Jay, Heath already ran tests and determined this does NOT happen. So are you saying you tested the JVC or are passing on old wives' tales. :)

[Steve Mullen]

All this talk about audio has given me an idea.

We know the camera records great sounding audio using its built-in mic.

I've assumed the XLR adapter is bad. And the suggestion to test a third-party one is a good one.

But it's possible that JVC goofed on the level conversion. Perhaps it's feeding audio at too high a level into the JVC forcing its AGC to clamp consistently. This COULD cause a reduction in frequency response.

Nevertheless, I still suspect the XLR adapter is rolling off the high end and would not use it until I could confirm it was good.

[Barry Green]

I'm sure it has nothing to do with the JVC XLR adapter, because Jay has the HD1, not the HD10, so he doesn't have the JVC XLR box.

He didn't even know about this thread. He complained to me about the audio because they shot a film and when they played back the tapes, it sounded bad. I pointed him here, saying that people were discussing the audio situation, but Jay & crew discovered it quite on their own. And the audio engineer on the shoot is an extremely skilled pro. Professional equipment was used all the way through the production chain, terminating in the 1/8" minijack in the JVC. I will guarantee you the audio sounded exquisite up until it hit the camera. There's no concern about mismatched line vs. mic level, that was accounted for during production. Feeding line into a mic jack would result in wildly blown out audio, and that is not what they got -- they got "canned" audio, just like Heath did.

I can't imagine why audio recorded with the built-in microphone would be acceptable, but audio piped into the camera through its mic jack wouldn't be, but that is the case. And until someone figures out a workaround, it seems that Heath's advice would be well-heeded: go double-system.

[Jay Nemeth]

<<<-- Originally posted by Steve Mullen :
First, you do not want to feed a mixer into the JVC. A mixer outputs at LINE level not MIC level.-->>>

This is not true of any professional field mixer used in the industry. All of the Shure mixers including the FP33 have selectable LINE or MIC level on both the left and right output. And I don't know of anyone who just plugs a mic straight into a recording device because the impedance and level match. The whole industry uses field mixers whether film or television. People whisper sometimes and scream at other times. You don't leave the iris at one setting when you travel from indoors to outside, there is a sweet spot for sound as well as images and it needs to be adjusted.

<<<--So you must put an attenuator between the two. It can be fixed because the signal drop is common in the industry. Or you can use a variable and calibrate it ONCE.-->>>

The LINE / MIC switch on mixers IS a pad or attenuator as it's otherwise known. There is no need to use a variable attenuator, that is what the input and output controls on the mixer are for.

I know these are consumer / prosumer level cameras, but sound men treat them the same as any other camera and use the same equipment. The schoeps microphone on our boom and the FP33 cost more than the JVC camera.

<<<--"And if the level on the mixer's meter is too low, he knows he isn't giving the recording device a signal that uses it's full dynamic range."

Steve screaming ANALOG BE GONE! With 16-bits of dynamic range you do not have to worry about too low a signal. The JVC will record over over a 100dB range, near that of a CD.

If you see a green light flashing on the JVC, then you are fine. -->>>

No audio engineer would ever be sloppy with the sound just because digital has more range. There is an optimum level for sound in every given situation. Yes, it is better to err on the low side with digital recording, but let's get it right.


<<<--"Since the JVC uses auto gain on the audio, if you hit it with a loud external signal, it will try to react by turning down the level, you will notice background noise get quiet when someone talks loudly, and then when they stop talking, the background noise slowly creeps up as the camera increases the gain to put the audio signal where it thinks it should be."

Jay, Heath already ran tests and determined this does NOT happen. So are you saying you tested the JVC or are passing on old wives' tales. :) -->>>

This forum and others seem to be littered with wives tales. My aim is to understand the camera as thoroughly as possible and determine if it has any use as a story telling medium. And I will share any info I obtain if I can. As I stated in other posts, I have the GR HD1. The HD10 was not available when I bought mine. It most definitely cranks down the gain when fed a hot signal, then cranks it back up in it's absence. The XLR adapter on the HD10 is still connecting to the camera with an unbalanced 1/8" mini. I have built a custom cable that adapts from the FP33's mult to the JVC. I have tested with transformers and without, Pins 1 and 3 joined and not joined (no shield), pads in and out.

Simply put, my camera has a distinctive sound that can be best described as "canned" or "boxy". There is also a low level hiss. The sound men who have listened and commented likewise are the top guys in their field who do motion picture and television sound for a living. It is subtle, but compared to DigiBeta or even regular DV sound, it has a definite quality (or lack of). The camera mic doesn't suffer from the AGC "pumping" but it also has the canned sound.

I suspect the canned sound is an artifact from the MPEG1 Layer2 16 bit Stereo, 384 kbps digital compression used. It is not PCM like regular DV cameras. I suspect the hiss is due to poor analog circuitry in the camera. Yes it records sound digitally, but a microphone is analog and there is an A/D step in the camera.

In my opinion, Double system sound for serious users.

Jay

[Steve Mullen]

<<<-- Originally posted by Jay Nemeth :
You adjust iris because you do not have 16-bits of video dynamic range. :)

And I've seen plenty of shooting with one mic fed to a camcorder. Who can afford a soundman who's shooting with a $3000 camcorder. :)

"No audio engineer would ever be sloppy with the sound just because digital has more range."

Using technology with an understanding of how it works is not being "sloppy." Sounds like a union warning. :)

"It most definitely cranks down the gain when fed a hot signal, then cranks it back up in it's absence."

It's not I who claimed it didn't. I don't know. Heath ran tests and said it didn't.

"I have built a custom cable that adapts from the FP33's mult to the JVC. I have tested with transformers and without, Pins 1 and 3 joined and not joined (no shield), pads in and out.

Simply put, my camera has a distinctive sound that can be best described as "canned" or "boxy". There is also a low level hiss. The camera mic doesn't suffer from the AGC "pumping" but it also has the canned sound. I suspect the canned sound is an artifact from the MPEG1 Layer2 16 bit Stereo, 384 kbps digital compression used."

Almost all camcorders have a low level hiss. My feeling shooting in NYC, China, and India--who can hear it over the din? And who's living room is quiet enough to hear it during playback? Sounds like the kind of worry that leads to buying $100 audio cables.


I fully agree about the nature of the sound, but I asked if everyone used XLR on the HD10. I got no answers as folks tend to post but not say what they were using. Now we got the answer from someone who isn't using an HD10. But it is strange that before this week there were no posts about bad audio.

And, given the nature of MP2 audio -- lower quality than MP3 -- it's either the compression or a low-pass filter before compression. Think of comparing MP3 audio against CD audio!

Or, they didn't apply the correct EQ. Tthere are several options for MPEG audio.)

By the way, has anyone listened to camera analog output?

"In my opinion, Double system sound for serious users."

That's a major pain for many of us with no crew.

But, it doesn't hurt during editing because for sync sound it's double system anyway.

[Joe Russ]

...i tested the xlr adapter by itself into my sound card through its break out box......none of that 'canned' stuff.....so i examined the audio from the camera itself...its making a stereo sound from mono sound....so, i just seperated the channels and took the left (i assumed it was more likely to be the original), the slight delay is literal between the channels. if you examine the wave form they are slightly different, but my mic was mono, so it should be the same signal. anyway, the sound is fine when i just take the left channel, a little bit under emphasized on the high end but nothing eq cant fix...

thoughts?

[Steve Mullen]

A friend brought by material he shot with one Samson mic into jack #1.

Appears he used the XLR1 switch position because he got audio on both channels.
In XLR1, the one input signal feeds both output lines. Nothing exotic. One is not different than the other.

His sound was great from both channels!

So given the built-in mic sounds good and his Samson mic via XLR sounds good, it means either:

1) The mic makes a real difference! I'll find out which one he used.

2) There are sample to sample variations. His was new from B&H. Mine was one of the very first into the USA.

I've gotten slight hints from JVC there was/is a problem on "some" HD10's. If that's true, and it was fixed after the first boatloads, the HD1 may not have been fixed at all.

So, we should not assume HD1 and HD10 are the same.

We need to look at dates by SN.

[Jay Nemeth]

I also wondered about a slight delay in one of the channels, especially after one of the sound men described the canned sound as "an extremely fast slap echo". I listened to just L and just R and it sounded the same to me, but maybe I should go revisit that.

The mike we used is a $2500 Schoeps MK-41, the same mike we use on film jobs. Both the Schoeps and the built in camera mike have the "canned" sound. I am using one of the first GR-HD1s that were sold, so maybe there is a model or S/N difference.

And it may also be that some people aren't sensitive to the canned sound, but are hearing other differences between mics and levels, eq, etc.

Jay

[Joe Russ]

all i know is that the left and right channels arent the same (delay and what not) and they should be cos my mic is mono.

[Jay Nemeth]

Ok, an update. I just got off the phone with our editor who is doing the off-line. I asked him to listen to one channel only, either L or R, and he says there is a definite improvement in the sound quality. He's not sure that the canned sound is completely gone, but it is much better.

Another thing he found, is that the audio sync problem changes from take to take. We knew there was a sync issue the first time we saw the marker close on the slate, but it isn't a fixed value. The audio is delayed from 1 to 3 frames depending on the take. We thought we could slip the entire camera audio track a fixed amount when the project was done, but it looks like scene to scene correction is required.

A possible explanation for the canned sound being more or less noticable would be a random delay between individual channels. Maybe the L channel is delayed 1 frame but the R frame is delayed by 1 or 2 more frames, thusly aggravating the situation. It certainly explains the quasi-stereo effect from mono sources.

Technical notes on our offline: We downconverted in the camera to 480i 16x9 and output to DigiBeta. The offline is being done on the discreet *fire system.

[Steve Mullen]

If the out of phase recording ever got mixed to mono--it would certainly cancel the high end.

But, you start with mono equally to both channels. and no one has said they go back to mono.

I assume you are feeding stereo the whole way to the speakers.

Which would mean the phase cancelation is happening in your room!

Possible, yes. probable, I don't know.

Headphones anyone?

But it probably makes sense to take only one Channel from the tape. Then turn it to two channels.

[Jose Cavazos]

I'm using an Azden SGM-1X with short Audio-technica ASP-00127 cable, which was suggested by a JVC engineer. It has been working very well using the input XLR1.

[Steve Mullen]

<<<-- Originally posted by Jose Cavazos : I'm using an Azden SGM-1X with short Audio-technica ASP-00127 cable, which was suggested by a JVC engineer. It has been working very well using the input XLR1. -->>>

Didn't the Azden come with a 1/8-inch plug? Why add the weight of the XLR when you can just attach the camera to the camera and plug in?