Audio Popping/ Cracking???

K

keentave

Member
Hi everyone,

So i just recently got my HMC150 about a week ago and have been trying it out non-stop. Something I've noticed is that when I record something really loud like a band playing or loud music the audio will pop and crack when played back? I have the volume level turned down sufficiently where it is not peaking and have the mic gain set to -60db. It also does it at -50db.

Is there any way to get the audio to not do this. It does not do it on my DVX100A so is this something that specifically has to do with this camera or am I just missing something?

Thanks!
 
You probably want to have the limiter on.. the attenuator or whatever it's called.. You are probably over modulated in those crackling loud spots.. you need it on for loud concerts and such.
 
Keentave - I've had a few similar experiences where it seems like the audio in the headphones is crackling when the audio clearly isn't peaking. I haven't thoroughly investigated (since I always shoot double-system)... but it's interesting to hear your report.
 
Had weird audio glitches too. They were definitely not related to digital clipping - the problem was much more severe and occurred even though the peak level was way below 0dBFS. I will try to find and post some audio clips later...
 
I may have experienced this as well.
I had an event where I used the HMC150 as a second camera, and as such, had the volume way below peaking, as it's audio was only to be used as a guide track.
Even this audio had some cracking.

I just assumed it was from the board, as I had a direct feed from the board.
 
I have had similar experiences as well, many times. When recording, the audio in the headphones sounded ok but when i played back the clip the audio crackled. The audio waveform itself looks ok in the NLE or any audio editing application, so the distortion happens in the camera and "embedds itself" into the audio, before writing the file to the SDHC card. Yes, the audio crackles in my NLE and in my audio editing app. It seems that the cameras pre-amplifiers are not suited for the job.

I think the audio is this cameras weakest spot.
 
Hmmm....I had this as well- "pop" and fuzzy sound...I am using an seinnhieser(sp?) wireless lav and rode shotgun. I thought it was maybe the lav but now I'm not so convinced. This sucks...any thoughts on how to deal with this as it could really be a major problem.
 
Well this is certainly a big concern.. I dont think I've experienced the same issue but I'll keep aware of it.
 
I'm going to be doing some tests today recording a band practice. i'm going to be testing on camera mic as well as several others, shotgun and condenser mic.

I read in the manual it says to set MIC ALC to ON in the recording setup menu when recording loud noises to prevent distortion. I will be trying this setting today to see if it solves the problem.

Haven't done much testing so I don't know for sure but I feel like the DVX on camera mic was superior to this one.
 
By the way - it happened to me when using external condenser mic with phantom on, as far as I remember. About 50% of my footage suffered from this. The mic is ok - works perfect with many different preamps in my studio. I'm sure I can find samples on my external drive at home - I won't be able to do it by the end of this week, though.
Now that other users report the same issue it starts to look quite scary. I'm gonna be doing some serious job soon and can't afford to loose the audio. I hoped there was something wrong with my setup (even though I had no clue about what could've been wrong, which was alarming)...
 
I should say that, in my case, it seems as if the crackling is there in the headphones while monitoring live, but does not seem to be apparent in the recorded audio (which I've not played back from the camera, only via computer).

Again, I'm not 100% sure this is always the case, but certainly seemed to be on one or two occasions.

-Barry
 
I recorded a band practice yesterday and tested 4 different mics. The camera was on a tripod about 10 feet in front of the band. I used the on camera mic, a shotgun mic, and two different condenser mics.

I had MIC ALC turned ON, -50db, and the audio set to about 2 to 3 notches above the -12db line. Fortunately, this time I did not have any cracking or popping with any of the mics. The on camera mic seemed muffled and blended many of the instruments together. The shotgun mic was too sensitive and was distorted most of the time but this was a mic issue and not the same issue as before. The two condenser mics sounded the best with crisp recording and could really here all the instruments pretty well.

I did not move the camera around so perhaps this could have been why there was no popping and cracking like before. Although I do not know why the motion of the camera would make a difference?
 
I also shot a band last week. Same popping noise. I was loose though. And it seemed that the closer I got to the band and loudspeakers, the more distortion I heard. But strangely, NOT constantly like an analog mic would do.

I had the onboard mic working but the knobs effectively off, because I was also recording with a Roland digital 16 track recorder separately. I wasn't taking any chances! Anyway, I attribute the popping to "digital clipping". I'm thinking there are spikes at certain frequencies that are not being blocked. Possibly because of voltage loss, due to camera functions and writing.

A solid, digital audio recording should have a clean, constant voltage for distortion free sound. Also, clock jitter or Quantization noise are other byproducts of poor digital quality. And "all" have the potential to create what we are hearing.

I'm not saying it's fact, but a possibility that what I know about the subject points to inferior ADC (analog to digital convertor) components. On a Pro sound recorder these babies can cost thousand$ for each channel, and determine a god or a dog!

We may have found the HMC150's Achilles Heal!
 
I noticed a similar problem doing unplanned recording a band. The situation wasn't great (standing 2 feet away, loud and couldn't move) and I didn't have headphones, so I can't say it wasn't user error. Problem only came up in channel 2 which was using phantom power and an external mic. Haven't noticed it since... but I do have to wonder... if there was a problem if it may have been addressed in the firmware update. Not sure if you guys have also updated.
 
Here's a clip of what I recorded on tripod with a condensor mic. no clipping in this clip.

http://www.youtube.com/watch?v=iraydH98FPk

ronedee, i think you're right. i got clip and distortion while moving and getting closer to the amps/ pa. it didn't do it constantly but every so often on loud hits. i'll also try to upload a clip of it popping.

that would suck pretty bad if there was no solution for this except get an external audio recorder.
 
Before we panic, let's hear a clip or two and see if they are similar issues. Then we can start a process to get it fixed IF there is really an issue. Can someone post a clip that actually has the issue?

Andrew Hoffman
Vice President
Specialized Communications Corp.
20940 Twin Springs Dr.
Smithsburg, MD 21783-1510 USA
800-359-1858 (US)
301-790-0103
Fax: 301-790-0173
andrewh@spec-comm.com
www.spec-comm.com
 
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