3.5mm Mic Input Level Controls Going Reverse? Pocket 4K

Hi,

I plugged a microphone into the camera via the 3.5mm jack input. Then I set the audio inputs to 3.5mm left mic and 3.5mm right mic.

As the levels where too low, I tried to increase the gain on both inputs.
But when I slide to the right from +38dB to +65dB, or to the left from +35dB to +10dB, the input gets weaker until there is hardly any input.


I recorded a video showing that here: https://drive.google.com/file/d/1HIdsAeyU4tIcPWVVDimfDkywLeKBL_tc/view?usp=sharing

On the left side I assigned the in-camera microphone (which works as expected), on the right side the 3.5mm jack input.

I tested it with two several microphones and the result where the same.

I expect this to be a bug. Can anyone replicate that?

Edit: I also just reset the camera, that didnt work.

Yes, I can confirm this - surely it's a firmware bug? On my BMPCC4K with v8.1 recording the sound from a tone generator website:

• the internal camera mics work as expected, i.e. the more you move the slider to the right, the more the meter goes up
• but with a 3.5mm external mic (Rode VideoMicro), as you move the slider up, the meter hits a peak at about half way through the slider range then drops off to zero as you move the slider more to the right.

The external mic used to work fine in previous firmware versions. Here's my video showing the exact same same problem as yours. Left, right or mono makes no difference - the problem is there in all options:

I thought it might be a phasing issue but it only seemed to affect the external mic, so probably not.

The other weird thing is the level of +65db. That's literally 2000 times louder than the input signal. Mic level is typically 40-60db less than line so I guess in some ways the UI makes sense, I'm probably assuming there's actually a different mic preamp and there's not.

It looks like +38 is "unity gain" for the internal mic. That would be the amount of gain necessary to boost a mic into line level territory. At that point (+38db gain) the mic signal is at about -12db. This means that at +50db gain and above the signal will be clipped, which is what appears to be happening.

What happens if you move the tone generator back 10 feet? Does the gain reversal happen at the same point?

Good Luck

What happens if you move the tone generator back 10 feet? Does the gain reversal happen at the same point?

The only difference is that the meter peaks at a lower point as you would expect (i.e. in the green region rather than the yellow). The reversal still happens at approximately the same point.

I can understand why it would clip beyond a peak and then stay at the same level on the meter, but what could explain it dropping right back to zero at the slider maximum gain position? Seems like an internal software overflow issue of some sort?

I've never done a tone generator test before and I don't use the 3.5mm mic socket often enough to have noticed the problem in normal use. So I can't be sure when this issue started. Maybe it's been there for a long time? Like Mathis, I have just tested with 3 different 3.5mm mics and the problem occurs with all three of of them, so it's definitely an issue in the camera.

Looks like a bug.

Cameras clip to white, I don’t know what the sound of a pure-ish 1k tone clipping sounds like. Ostensibly if the tone itself is pushed too far up beyond the AtoD (analog) you’re only left with the noise foor.

Good luck

YMMV but I haven’t pushed audio in camera in a long time as I don’t want the noise floor raised.

I contacted the support and they couldn't reproduce the problem on their camera.

Even though I told them that I am not the only one with that issue, they offered me to repair the camera, as I still have warranty. Yet, I need the camera until end of september, so I will send it in then.

I can confirm there's definitely an issue when recording using the 3.5mm jack with the current firmware. At least for the 4K Pocket Camera. The levels rise till you hit +38, then seems to reset to something lower when going higher. But when you hit +65, the sound goes out entirely.

I am probably way out sending-down-a-rabbit-hole wrong in this comment however here goes. Is the wiring onto your 3.5mm plug correct for the camera? Does the plug have the correct number of conductors?

Is the wiring onto your 3.5mm plug correct for the camera? Does the plug have the correct number of conductors?

I tested with 3 stock mics: a Rode VideoMicro, a Rode Go lav and a Zoom F2 lav. All three have standard TRS plugs which match the BMPCC4K's 3.5mm socket. The problem is easy to reproduce as per my video above. I used onlinetonegenerator.com to generate something at a fixed level to record. Start filming it with your BMPCC4K (v8.1 firmware) using a 3.5mm mic to record the sound. Then slowly push the mic level slider all the the way up. You can watch the level meter rise to a peak then drop back to zero as the mic level slider reaches maximum.

Maybe this is by design as some sort of overload protection? Seems odd though.

Yep, exactly the same is happening as the video above on my 4k. It's possible that a hardware revision is the reason BMD haven't been able to replicate and that it's not happening for 100% of pockets, regardless it's just another in the long list of untested firmware updates.

+1

Here is a test by using no microphone but only the noise floor:

https://www.youtube.com/embed/c_rNH2pENcU

What happens when you roll back the firmware?

What happens when you roll back the firmware?

Nice idea, but roll back to which version? There's no easy way to find the firmware update history for a particular camera model, and to test them all in reverse date order until the bug disappears would be well beyond my patience level. That's a job for BMD - assuming they have the will and/or resources to chase an obscure bug on an old camera.

Slightly off-topic rant here: Much as I admire BMD, its ethos and products, it's hard to love their support page. Instead of having a filter by individual camera model, you have to scroll down the peculiar three column page which mixes up all the updates for all the cameras along with all the BRAW updates. It would help if they listed the affected cameras in the first sentence in the intro paragraph. But they don't, so you have to do a read more on every single post to see whether it affects your camera(s) or not. The whole page needs a re-think in my view.

If you are currently on firmware 8.1, you can rollback to 7.9.2 or 7.9.1.

If you are currently on firmware 8.1, you can rollback to 7.9.2 or 7.9.1.

Thanks Rick, that's good to know, but this bug actually is not too much of an issue for me personally - or at least not enough to bother with firmware rollbacks. I'm not a big user of the 3.5mm socket - I tend to record sound externally when using the Pocket 4K. I just posted in this thread to make it clear that the problem is affecting more than just the original poster. Hopefully BMD will address it in the next firmware update.

Yes, I can confirm this - surely it's a firmware bug? On my BMPCC4K with v8.1 recording the sound from a tone generator website:

• the internal camera mics work as expected, i.e. the more you move the slider to the right, the more the meter goes up
• but with a 3.5mm external mic (Rode VideoMicro), as you move the slider up, the meter hits a peak at about half way through the slider range then drops off to zero as you move the slider more to the right.

The external mic used to work fine in previous firmware versions. Here's my video showing the exact same same problem as yours. Left, right or mono makes no difference - the problem is there in all options:

Hi,

I owm 3 bmpcc4k
and this is a bug I noticed too
Here is a video test with all my 3 bmpcc4k, firmware 8.1
Sound test made with https://onlinetonegenerator.com/

Video:

Hoping the bm support will fix the issue.
Best,

I downgraded my Pocket to 7.9.1, and can confirm that fixed the issue. So it's definitely more of a software bug.

I can confirm there's definitely an issue when recording using the 3.5mm jack with the current firmware. At least for the 4K Pocket Camera. The levels rise till you hit +38, then seems to reset to something lower when going higher. But when you hit +65, the sound goes out entirely.

I've just found the same with my Pocket 4K when testing some cheap video mics... glad to hear that it seems to be a general problem and not an issue with my particular camera. Hopefully it could be fixed with an update (I'm on the latest version 8.1 firmware).

I've just found the same with my Pocket 4K when testing some cheap video mics... glad to hear that it seems to be a general problem and not an issue with my particular camera. Hopefully it could be fixed with an update (I'm on the latest version 8.1 firmware).

It got fixed in Firmware Version 8.6! Good job Blackmagic!

I've just found the same with my Pocket 4K when testing some cheap video mics... glad to hear that it seems to be a general problem and not an issue with my particular camera. Hopefully it could be fixed with an update (I'm on the latest version 8.1 firmware).

It got fixed in Firmware Version 8.6! Good job Blackmagic!

Eh? My camera is showing the latest available firmware version for the Pocket 4K is 8.1

I'm running the Camera Setup v8.5.1 app, so maybe the I need to upgrade the app before I can upgrade the camera?

[UPDATE: yes, my assumption was correct; I updated the Camera Setup app to 8.7 beta and the 8.6 firmware was available.

I'll test the 3.5mm audio gain controls later to see if the issue has been resolved.... ]

I can confirm it seems to be fixed with the latest beta.