Someone please explain audio to me
Hi. I have a Sony PMW-EX1R. It has two unbalanced XLR inputs, and records two audio tracks. These two audio tracks, when examined with Premiere, QuickTime or any other relevant product, are both monaural.
Yet, an XLR input carries left and right channels separately. That's what the L and R stand for. The microphone that I usually connect to the XLR inputs is a stereo mic. And the EX1R has a camera-mounted stereo mic, which can be selected as the audio input for either or both of the audio channels. But the recorded audio is mono. What am I missing here? What do I do to get a genuine stereo signal on one or both of these audio channels? Richard |
Re: Someone please explain audio to me
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I don't understand historically. A 3 pin cable only carries one audio channel with balanced/push-pull signaling. There may be a few audio technica single point stereo mikes that put unbalanced stereo audio on the two pins rather than balanced audio but this is not standard usage. The EX1s are setup for the normal professional usage which means one channel to one 3pin xlr. |
Re: Someone please explain audio to me
Okay, thanks.
So monaural is all I can expect, I suppose. So does this mean that if I want to record a true stereo signal I need to use a separate audio set up? Now why does the EX1R have a stereo onboard mic? Richard |
Re: Someone please explain audio to me
Concur with Dustin - 3 pin XLR is mono, balanced. Some people have used XLR cabling to route unbalanced stereo, but that's 100% not normal. I've never seen a camera or audio mixer input wired for stereo. I have some stereo balanced mics - and these use 5 pin XLRs up to the power supply/splitter and have two 3 pin outlets. The 'R' merely indicated rubber insulation on the sockets.
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Re: Someone please explain audio to me
If your stereo mic has an 1/8" output then you have to get a splitter that splits the 1/8" TRS into 2 XLRs. Then in post pan your channels L & R instead of center.
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Re: Someone please explain audio to me
The reason XLR has 2 audio signals is because the other is inverse. By design, the inverse signal is flipped when processed and that doubles amplitude and cancels out noise within the cable.
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Re: Someone please explain audio to me
Thanks for all replies. I guess if I want a stereo signal, I have to do it in post. I'm not sure why the EX1R comes with a stereo mic, then, because it seems impossible to use it under any circumstances.
I'm aware of a stereo mic that produces a 5-pin XLR output. It can be split into two 3-pin XLRs. I guess if you want a true stereo signal, you have to use both of your audio channels to record the output of that. Or you can record your audio entirely separately. Richard |
Re: Someone please explain audio to me
Richard, I'm not sure what your problem is with the built-in stereo mic. Granted, using the camera mic is usually not a smart thing to do, but you can record stereo just fine with the EX1R. Just be sure you import your footage as stereo and not dual mono and you should be fine.
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Re: Someone please explain audio to me
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Ref: http://en.wikipedia.org/wiki/XLR_connector Quote:
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If you want specific help (vs. generic discussions of XLR connectors) then you will need to reveal exactly what microphone you are working with. |
Re: Someone please explain audio to me
Dave,
Sorry for being dense here. Let's say I take my EX1R and on the back panel select "INTMIC" for both audio switches. I don't connect anything to either XLR input. Now I record some footage, and import it. As I've said before, I use XDCAM Transfer because of the unique needs of the clients. Now I examine the resulting .mov file with Premiere Pro, or OS X Finder Info, and it clearly has 2 monaural tracks. If I examine the waveforms, they're identical. So how does this constitute a stereo signal? Why does the EX1R have a stereo mic and how do I record a stereo signal from it? Richard |
Re: Someone please explain audio to me
During the conversion to MOV's process, it by nature creates dual mono tracks instead of a single stereo track.
It is a simple task in Final Cut and Premiere to lay both mono tracks down on Tracks 1 and 2 and panning them Left and Right to achieve stereo. It should be a stereo signal if your pan pots are set correctly in the editing software. I know in Premiere you can directly read folders with BPAV folders as XDCAM EX clips through it's internal Media Browser, so go to the folders you would normally use XDCAM Browser to work with and try opening up clips in the Media Browser to see if you can read it as a single stereo channel. The only way I could see the signals being the same is if "EXT CH Select" in the "Audio Input" menu is a setting other than "CH1/CH2." |
Re: Someone please explain audio to me
>The only way I could see the signals being the same is if "EXT CH Select" in the "Audio Input" menu is a >setting other than "CH1/CH2."
Aha! Thank you, Jack. That's the missing piece of my jigsaw puzzle. If I otherwise want a stereo external mic, I use a splitter to record both channels on both of my EX1R's channels. And if I want anything more complex than that, I record audio separately. Case closed. Richard |
Re: Someone please explain audio to me
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OTOH, whether those two channels define a good representation of the original depends A LOT on the microphone(s) and where they are placed. You have not revealed WHAT you are recording, but the microphones built into a camera (ANY camera) are almost NEVER a good way to record something. And an external single-point stereo mic (as the one you mention, also not identified) may not be sufficient, either. When you get into microphone selection and placement, that is a whole new area of art and science. Note that there is a separate forum here (and in most video websites) devoted exclusively to sound/audio. Microphone selection, positioning, and mixing is an endless topic of discussion. If you would like expert advice on how to record some specific kind of thing, the experienced audio people in that forum would be happy to offer their expert advice. Quote:
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Re: Someone please explain audio to me
Richard,
You may already know this but just in case, your Rode NTG-1 will not give you a stereo recording if you split the signal going into the two channels of the EX1r. It will simply give you two channels of the same audio. If your levels are set the same, all you will have are two channels of the same recording. When played back out of two speakers it will still be a mono recoding. In order for you to get stereo from external mics you will need to either use two mono mics or a stereo mic with appropriate cables to connect each mic (or mic channel for the stereo mic) into the camera. Like I said, you may already know that, I just didn't want you to go and get a splitter and think you'd get a stereo recording from your NTG-1. |
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