I'm disappointed that Panasonic calls it a Limiter if it's actually AGC. There is a difference, and the terms are NOT interchangeable. The former will only reduce the signal to prevent clipping, the later will both raise and reduce the signal to reduce the dynamic range.
GH4 audio bug discovered
- Thread starter tacotim
- Start date
I'm disappointed that Panasonic calls it a Limiter if it's actually AGC. There is a difference, and the terms are NOT interchangeable. The former will only reduce the signal to prevent clipping, the later will both raise and reduce the signal to reduce the dynamic range.
It actually appears to be both AGC and a limiter, and I have no use for the AGC circuitry at all.
It says on the website: It incorporates passive components which provide impedance matching and DC blocking; allowing a wide variety of microphones to be used with the device.
http://www.bhphotovideo.com/bnh/con...L_q_qvin74CFc5ffgod_gkASA&Q=&is=REG&A=details
Isn't that the DC Blocking Capacitors your talking about?
Hi Ed,
Here's a really quick check of your file 0011.MTS, which looks perfect to me. It's showing a noise-floor better than -63 dB, which is what I've seen with my GH3 camera, my HMC-150 camera, and another GH4 camera. Looking at this dB RMS display, the loudest audio in your recording is below -63 dB RMS, which gives you a clean 63 dB of dynamic range to work with. This is about as good as it gets for DSLR cameras. I will try and test the rest by Friday.
...I have a hard time believing that you can hear it, as anything below -60 dB RMS is inaudible in normal listening conditions. At -60 dB RMS most people will hear absolutely nothing at all. It's only when you either boost the audio levels in post beyond the -60 dB threshold or over amplify the recording in playback by setting your headphone or audio monitor volume too loud, that you start to hear the noise-floor.
The typical ambient noise level in a very quiet empty household or office room is going to be somewhere in the range of -40 dB to -50 dB RMS, so we are talking about hearing sound that is 13-23 dB below the ambient noise of a very quiet empty room.
The GH2 / GH3 / GH4 mirrorless cameras have one of the lowest noise-floors for cameras in their price range. Canons and Nikons often have noise-floors that are 10 dB or more louder than these Panasonic cameras, and most portable low cost audio recorders are only marginally better with noise floors between -66 dB RMS ( Zoom H4n ) to -75 dB RMS. ( Tascam DR-40 ) If you can hear audio at these levels then you have truly exceptional ears.
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Ed Kishel
Veteran
I don't think that having the headphone volume turned to the default setting on the GH4 is too loud. At -12db I could still hear it when played back in camera. I can't control what people believe. Like I've said before (a few times now), it's subtle at the -12dB setting and so for many, a non-issue. I use Sennheiser hd280 pro headphones to monitor audio from my cameras. They're closed type and isolate outside sound very well- and they allow me to be very critical.
Am I being too critical? Maybe, and maybe not. I think people just can't get their heads around how I could return mine over this while so many are clamoring for it. I don't like the buzz, and I don't like Panasonic's FB response. I am a consumer, and the way I can voice my opinion is where- and where I don't, spend my money.
I had a limited return period, and am hoping that Panasonic will make a fix, be it hardware or firmware. But if they don't and leave it as-is, I'll probably re-order once I know I won't be missing out on that possible fix. The camera is just too good otherwise. And I'll probably learn to live with the buzz (if I get another one that exhibits it). I learned to live with my AF100's highlight handling
Am I being too critical? Maybe, and maybe not. I think people just can't get their heads around how I could return mine over this while so many are clamoring for it. I don't like the buzz, and I don't like Panasonic's FB response. I am a consumer, and the way I can voice my opinion is where- and where I don't, spend my money.
I had a limited return period, and am hoping that Panasonic will make a fix, be it hardware or firmware. But if they don't and leave it as-is, I'll probably re-order once I know I won't be missing out on that possible fix. The camera is just too good otherwise. And I'll probably learn to live with the buzz (if I get another one that exhibits it). I learned to live with my AF100's highlight handling
Ed, I can hear it as well (with the basic in camera settings), so it's not just you. If I could return mine, I would do it, but at this point I think it's too late, so I guess I'll have to deal with it. I don't understand how panasonic can be so ignorant/useless to be honest. Their response just didn't make sense, at least to me. If I had Facebook, I would have definitely written a long response to them (maybe I should make a Facebook account).
Ed Kishel
Veteran
That's an interesting find. Maybe panasonic was trying to raise the bar for the typically consumer 3.5mm jack- by moving to TRRS. Isn't it better than TRS because the right and left channel has it's own separate ground? This cable is mono- but I terms of stereo mics using this jack.
Ed Kishel
Veteran
Sescom makes many specialized cables for dslr audio- I bet they could come with something that goes from TRS to TRRS properly- the way the GH4 wants it. I think they even made a custom mic out cable for the GH2 once.
http://www.sescom.com/sescom-product-index.asp
http://www.sescom.com/sescom-product-index.asp
What's odd for me is that the GH4 recording is performing exactly the same way a recording with a GH2 or GH3 camera would, in that the actual recorded noise-floor is essentially identical, so we are getting the same 63 dB of clean audio that we would with either of the previous GHx cameras. ( or even my HMC150 camera ) To be able to hear anything at this very low audio level is surprising.
Ed Kishel
Veteran
Clean? That's the crux of this whole thing I guess. There are others here and in the FB thread that might disagree that their GH4 is recording the same as their GH3. Perhaps your camera doesn't actually exhibit this issue? Can you post an example from yours? No-one here who says they don't hear it will post an example from thier "clean" GH4... properly setup to hear it.
1) hook up a mic with a 3.5mm jack, and turn the mic off
2) hook up headphones
3) turn your headphones vol to med (10)
4) turn your mic input level to default (0dB)
5) record a file in manual movie mode
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When I listen to your 0011.MTS recording ( and eliminate the audio blip at the start of the recording ) I hear absolutely nothing, with my headphone volume set so a 1 kHz test tone at 0 dB sounds very loud but not ear-splittingly loud. When I check the audio meters for your recording ( the loudest sound in the recording is listed at the top of the meters in dB RMS ) the peak audio is quieter than -63 dB, with a range that extends down to -66 dB RMS, so the audio meters are confirming that nothing louder than -63 dB was recorded. This is exactly what I see when I record with my GH2 and GH3 cameras, and my HMC-150 camera.
stoneinapond
Veteran
Aw sh*t,
That's where I do all of my recording. Deal breaker....... camera's being returned. I mean if you can't record in a closet, where can you.....:furious3:
Ed Kishel
Veteran
We get your point- this is not a real world situation. This is just a way to facilitate knowing whether or not you have the issue Mr. Smarty Pants :cheesy:
I think some people don't want to admit that the GH4 has a weakness. It's the gear right now, so it can create a fanboy mentality where it's infallible. It's ok if you camera does this, if it's not an issue for you- no problem. At -12dB in real world shooting you'll probably never hear it. You don't have to follow this thread. No camera is perfect, each one has some weakness that can be worked around. I myself have kind of mellowed to this issue since I first learned about it- if Panasonic doesn't change anything I'll re-purchase and work around it. This is minor compared to its many many strengths.
stoneinapond
Veteran
Ah, my friend just explained the reference. So I have to go and watch the videos now.
@Ed Kishel
No offense meant. Just joking around you know.......
...I doubt we'll ever see this the same way, but as I've stated previously I think the issue you are experiencing is modulation of the GH4 noise-floor audio, which should never be an issue as the noise-floor is never meant to ever be heard. A simple fix to eliminate ever hearing the noise-floor modulation is to use a noise-gate that will truncate all recorded audio from just before the noise-floor and lower. So in the example below I've set up a noise-gate to remove any recorded audio quieter than -62.5 dB, which will remove the noise-floor on any GH4 audio recorded at the -12 dB setting.
You would need to do some tests to figure out where to set the noise-gate threshold for other camera audio settings, but it would not take long to build a complete set of noise-gate filters for every audio level of the GH4. ( I think it's still a total of 19 increments for the GH4, just like the GH3 )
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