Audio Synching Question

[Carl Gilbert]

I plan to shoot some mountain biking video. I would like to grab some 4 channel audio with an H2n. I'd like to merge that with my video. Obviously I have to do this after the fact since my camera will only record stereo. The questions are;

Will synching the two be a big deal?
The camera has a mic input, should I send the H2n line out into the camera in for an easy reference?
What exactly will the h2n send to the line out while recording in 4 channel mode?

I'm very new at this so please excuse me if I asked something that does not make sense.


Thanks!

[Steve House]

Originally Posted by Carl Gilbert

I plan to shoot some mountain biking video. I would like to grab some 4 channel audio with an H2n. I'd like to merge that with my video. Obviously I have to do this after the fact since my camera will only record stereo. The questions are;

Will synching the two be a big deal?
The camera has a mic input, should I send the H2n line out into the camera in for an easy reference?
What exactly will the h2n send to the line out while recording in 4 channel mode?

I'm very new at this so please excuse me if I asked something that does not make sense.


Thanks!

I'm not sure recording 4-channel in the field makes sense for this sort of project. What are you trying to accomplish by doing so?

[Carl Gilbert]

Get more atmosphere and positional feel. Its a single track through the woods with bikers in the front and back sometimes. Its an experiment too. When someone passes me it be nice if the sound would reflect that.

[Don Bloom]

Carl,
If I were doing this I would record audio to the camera (2 channels) and use the Zoom to record the other channels for sync in post. the camera will only record so many channels and 2 is it. Left and right.
Like I said sync in post and mix to taste but don't be surprised if you're not a bit disappointed in the quality of the sound. Stuff like this usually has a lot of gear and dedicated audio people working it plus a lot of sounds are added in post-called Foley.
When I did NASCAR, I would watch the audio guys setting up around the track. Ever wonder how TV gets all those sounds around the track? It's because even on a 1 mile track they might have 15 or more mics set up on the fence and that's just for the sounds of the cars. Then add more facing towards the fans to get the crowd noises, mix to taste in the audio truck, send it to the production truck for the feed out and you're done.
You can get some of what you want using what you have but you'll probably have to add some later. It'll be a great learning experience.

[Carl Gilbert]

I'm not that good at audio. So I am concerned that the sound the camera picks up will be somewhat different feel to it than the H2n's audio. So when I mix them I might have to equalize or somehow change the quality of the sources to match each other while I am mixing them. Seems daunting. I only have Cyberlink PowerDirector with Audio Director.

Anyway, I can do it both ways. It will be interesting. The H2n is a bit expensive for a toy though so in the end I think I will have to make it work.

[Steve House]

What camera are you using? If it's a DSLR you might want to give serious consideration to forgoing use of the camera's mics and audio.

[Carl Gilbert]

Its a POV. Contour +2. But I'm not looking to use the cameras audio. It does not record in surround.

[Steve House]

Originally Posted by Carl Gilbert

Its a POV. Contour +2. But I'm not looking to use the cameras audio. It does not record in surround.

Then the issue of whether the camera audio's tonality matches that from the H2n becomes moot ... you won't be mixing them.

[Carl Gilbert]

I think Don was suggesting that I record the standard audio with the camera and get the surround audio channels with the H2n. But I don't really know how to do that anyway. The Camera is recording stereo which includes front/back/left/right. Its just that they are all mixed in together. The H2n records the same thing, but it separates them out. so if I mixed the camera audio with the H2n, I wouldn't know which H2n channels to use!?

Again, Im new so my thinking could be completely wrong.

Presently, this is what my first experiment will look like.

H2n in 4 channel mode mounted on apex of helmet with wind screen.
Contour +2 mounted on side of helmet.
Audio out channel of H2n connected to mic input of Contour +2 in order to aid in syncing the audio.


I'm unfortunately assuming a lot. Like I can take these 4 channels, and mix them into a Dolby 4 channel surround format when the channels I have will be front/back/left/right but the channels dolby uses are LF/RF/LR/RR, etc..

[Rick Reineke]

"I can take these 4 channels, and mix them into a Dolby 4 channel surround format when the channels I have will be front/back/left/right but the channels dolby uses are LF/RF/LR/RR, etc.. I"
- Only if your NLE/DAW can encode to your desired format

[Steve House]

Originally Posted by Carl Gilbert

...The Camera is recording stereo which includes front/back/left/right. Its just that they are all mixed in together. The H2n records the same thing, but it separates them out. so if I mixed the camera audio with the H2n, I wouldn't know which H2n channels to use!?

Again, Im new so my thinking could be completely wrong.

Presently, this is what my first experiment will look like.

H2n in 4 channel mode mounted on apex of helmet with wind screen.
Contour +2 mounted on side of helmet.
Audio out channel of H2n connected to mic input of Contour +2 in order to aid in syncing the audio.


I'm unfortunately assuming a lot. Like I can take these 4 channels, and mix them into a Dolby 4 channel surround format when the channels I have will be front/back/left/right but the channels dolby uses are LF/RF/LR/RR, etc..

Stereo is left/right, not left/right/front/back. When you mix a stereo signal to 4-channels stereo 'left' becomes 'LF' (left-front) and right becomes 'RF' (right-front). Dialog is recorded mono and mixed equally into the LF and RF channels in post to make it centred on the screen and makes up the front-center channel of a 5.1 mix.

Plugging your Zoom's output into the camera's mic jack will most likely disconnect the camera's internal mic so you won't be getting any audio from the camera mics themselves. (I can't say for sure because looking in the camera manual it doesn't say but that's usually the way it works.) The resulting stereo track in the camera will be a copy of the stereo output from the Zoom, a scratch track to use as a reference for syncing but NOT a usable stereo track to mix in with the Zoom's tracks. And there's another issue as well that you need to take into account ... the Zoom's output will be line level but the camera input expects mic level, which is much, much lower. Plugging them together requires an attenuating cable else the incoming signal will overload the camera's input, resulting in very high distortion.

Windscreens are designed to reduce the noise of relatively mild air movement, not the gale-force winds passing over the mics from the motion of the mic/recorder through the air while mounted on the head of a bike rider moving at speed. I would expect mounting the recorder on your helmet as you described will produce completely unusable tracks due to the wind and handling noise.

[Carl Gilbert]

Thanks for the replies. I'm not a professional, just a tinkerer trying to slightly improve his videos. So some flaw is not too bad for me.

The h2n itself records 4 channels. My expectation is to get all 4 channels from the h2n. I'll feed the signal out of the H2n into the video recorder only as a way to sync the h2n's audio to the camera's video. Since the camera's audio and video will be synched, I'm expecting that synching the h2n to the camera's audio will effectively sync it to the video as well. Perhaps this is not necessary since they will be basically next to each other during record? I won't render the camera's audio to the output of the track. Its only for synching. The more I think about this, its probably not necessary. I can just synch it by eye/ear I guess. But having the audio signals next to each other and synching it that way seemed safer.

I'll start a new thread asking about NLE's that can do this. I've searched for a few days looking and haven't come up with much. That is, NLE that can take multiple channel data and mix it into 5.1 output (which will actually just be 4 channel with no center I'm thinking)

[Greg Miller]

First of all, I question what you said about the Zoom's outputs: left, right, front, back. That would be a very unusual track assignment; no playback system is arranged like that. (Well, back in the old days of CBS/Dynaco quadraphonic LPs there was LF, CF, RF, and center rear; but that never caught on anyway.)

I'm pretty sure the zoom will give you a front pair which is LF and RF. And also a rear pair which is LR and RR. If that's the case, you won't need to do any mixing to position the tracks on the correct channels for playback.

I wouldn't bother to connect the Zoom to the camera. They will both be mounted on your helmet, and both will pick up the same sounds at the same time. They'd need to be 30 feet apart before there would be even one video frame of time difference. You will then just sync the Zoom tracks to the camera's scratch tracks.

If I were you, I'd make some test runs with just the Zoom, to see how bad the wind noise will be. I suspect that will be your biggest challenge. You may need some foam plus a fuzzy to try to kill the wind. You'll look as if you're riding down the trail with a dead skunk on your helmet, but hey... maybe nobody will sideswipe you!

[Carl Gilbert]

You're right. I'm not sure where I got that impression. Its definitely a front MS pair, and a rear XY pair I believe. But even still, won't I sort of mix all 4 into each channel to some degree?

My initial thoughts were that I would take an existing 5.1 track, and replace the audio in the 4 corner channels, leaving the front and .1 empty. But I now think that won't sound right, and so am looking for different mixing software. But a friend has Logic Pro which should work.

I'm pretty sure there will be wind noise. I have made several records with a previous camera which probably has better audio than the zoom. But I also think the fuzzy thing should help quite a bit because mostly I ride in the trees where its not that fast and not that open to breezes.

I'll be doing some test rides around the block to test all the equipment before I take it out for sure.

[Greg Miller]

I'm curious where you found the info that the front pair is M/S. I didn't notice that anywhere in the online manual. And I don't think that's consistent with their claim that the front pair has a 90º mic angle.

At any rate, a mic does not work like a lens. With a lens, a given object either is, or is not, within the lens's field of view. A microphone picks up all the sound around it, in a 360º sphere. Even if it's a "directional" mic, the sound in the desired direction is just louder than the sound in the other directions (and often the frequency response in the desired direction is flatter than in the other directions).

Thus, every channel of your recording will contain sound from a 360º sound field... it will just favor the desired direction. So I doubt that you'll need to do any further mixing... that would just dilute the directionality of what you've captured. Except that if you do have a LF subwoofer, you might want to mix the LF information from all four channels into that .1 LF channel.

Originally Posted by Carl Gilbert

mostly I ride in the trees where its not that fast and not that open to breezes

Just the fact that your bike is moving will create "wind speed" equal to your bike's velocity... even on a perfectly still day, even indoors.