Audio Synching Question

Carl Gilbert · March 31st, 2013, 11:15 AM

Its mid side. That recorder has a mid-side pair in one direction for sure. And an xy in the other. Its all over the documentation. http://www.zoom.co.jp/products/h2n/
I suppose with what you say, I'll have more options for the encoding. Just need to decipher the mid-side in the front direction.

There will be wind but in previous recordings with my camcorder its not bad and I've never used a windshield. Plus this is mountain biking, its slower. Anyway, its all in fun plus if the wind sounds right and is based on bike speed it can add to the ambience.

Greg Miller · March 31st, 2013, 12:55 PM

My mistake, I opened the manual for the H2, and not the H2N.

Even so, I doubt you will need to do any decoding for 4-ch surround.

The manual makes it clear that there are two different recording modes using the M/S capsules. You can record in "Raw M/S" mode, which records the M signal to one track of the final file, and the S signal to the other track. But there is also an "M/S Stereo mode" where the matrix is applied in the recorder, so that the recorded file contains a left-channel track and a right-channel track.

It appears (p.22 step 2) that if you adjust the S mic gain = 0 dB (stereo width = 120º) before recording, then the "M/S" file will still contain normal stereo information, rather than raw M and S information. In that case, you'd just assign the "M/S" stereo track to the two front speakers, and the "X/Y" stereo track to the two rear speakers.

Bill Davis · March 31st, 2013, 01:27 PM

Your biggest issue is not likely to be stereo perspective.

Understand that that's only an issue if you're playing the audio back on a 5.1 theatrical style system - which represents about .5% of the playback situations in the world.

Your work is MUCH more likely to be consumed on stereo (personal playback via earphones) or mono (any phone or small speaker that sums to mono)

Of much more importance is the quality of the recorded sound. If you're recording while in motion - you're going to have to deal with AIR MOVEMENT - no matter what mics or devices you use.

If you don't address that via air movement baffling - your audio will get infected with all sorts of wind noise which is much more critical than stereo perspective.

FWIW.

Carl Gilbert · April 1st, 2013, 06:36 AM

I am aware of the air movement issue. I have filmed while riding my bike before. Its not that bad. Plus, I plan to add some additional protection so I am expecting things to improve. We will see. Its going to take some work I'm sure, but its not a show stopper. I won't be selling these so I just need to keep the sound below the annoyance level.

Mostly it won't be played on 5.1. I imagine most of the play will be on my tablet showing people a few minutes of some places I have biked. I'll need good sound for that. But also I will play it on my own home AVR where I do have 5.1 and where I will be looking to enjoy the full sound. Or at least learn a thing or two about how its made.

Greg, for 2 channel recording you have the option of doing XY or MS. For MS you can record it raw and tweak the S later, or you can set the S now, and get a basic LR stereo signal recording. So I could in essence, get the MS decoded on the spot. I won't do that though because I have no experience with MS so its not likely I would pick a good setting on the spot. After a few runs I might be better at guessing and after that, I will go with the pre-mixed MS so that I only have to deal with two stereo channels.

But honestly, I don't know. Its all good information for me. The weather is breaking here in Michigan so I should be out there within a month.

Greg Miller · April 1st, 2013, 06:56 AM

Carl,

If you want to end up with good surround sound for playback on your home system, you should record the 4-track surround mode. Set the S width to either 90º or 120º and your front-facing pair (the mics pointed AWAY from the controls) will be a nice normal stereo soundfield. The rear-facing pair (the mics pointed TOWARD the controls) will also be a nice normal stereo soundfield.

Then if you want to create a 2-channel mix for your tablet (UGH! how will a tablet possibly sound good?), just mix the front left + rear left, and mix the front right + rear right.

Carl Gilbert · April 1st, 2013, 09:49 AM

OK. I will definitely take those settings for a ride.

Joe Garrick · April 11th, 2013, 05:52 PM

I believe the H4n is similar to my DR-40 in that it can record stereo M/S or X/Y, not both. There's only one pair of built-in mics, plus inputs for two others. You can either plug in another stereo mic and record whatever kind of stereo you want to the other two channels, or you can plug in two mono mics for the other two channels. That's how my DR-40 works. When I was researching them before I bought the DR-40, the feature set was nearly identical for 4 channel recording.

In any case, you're not going to get M/S and X/Y out of the one pair of built-in mics.

Greg Miller · April 11th, 2013, 10:39 PM

We're talking about the H2n here, (not the H4). It has a total of five mic capsules.

Two are "front facing" which means facing toward the side of the recorder that has the controls. (To my way of thinking, that is facing toward the rear but... oh well.) These are always X/Y.

The other three capsules are "rear facing" which means they face away from the side of the recorder that has the controls. (To my way of thinking, that is facing toward the front but...) One of these capsules faces directly along the front/rear axis of the recorder. It's considered to be the M capsule. The other two apparently face directly left and directly right, and I guess there's some sort of matrix that derives a "S" signal from these.

What's more, there is a switch on the top of the machine that changes what is recorded from the M/S capsules. You can record two raw tracks, one M and one S, for later mixing in post. Or you can have the mixing take place internally, before recording; in that case, you have a choice of 90º spread or 120º spread (presumably obtained by different ratio of S signal to M signal).

And yes, the recorder has a mode that allows you to record four simultaneous audio tracks. The "Front" pair of tracks (which I call rear) is always X/Y. The "Rear" tracks (what I call "front") can be configured as 90º X/Y (or 120º X/Y if you prefer). So yes, the recorder can simultaneously record two sets of stereo tracks, four tracks in all, for LF / RF / LR / RR surround if you like.

Check out the manual, it's available online. Be sure you fine the manual for the H2n, because the original H2 did not have all these capabilities.

March 31st, 2013, 11:15 AM	#16
Carl Gilbert New Boot Join Date: Mar 2013 Location: Detroit, MI Posts: 16	Re: Audio Synching Question Its mid side. That recorder has a mid-side pair in one direction for sure. And an xy in the other. Its all over the documentation. http://www.zoom.co.jp/products/h2n/ I suppose with what you say, I'll have more options for the encoding. Just need to decipher the mid-side in the front direction. There will be wind but in previous recordings with my camcorder its not bad and I've never used a windshield. Plus this is mountain biking, its slower. Anyway, its all in fun plus if the wind sounds right and is based on bike speed it can add to the ambience.

March 31st, 2013, 12:55 PM	#17
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,792	Re: Audio Synching Question My mistake, I opened the manual for the H2, and not the H2N. Even so, I doubt you will need to do any decoding for 4-ch surround. The manual makes it clear that there are two different recording modes using the M/S capsules. You can record in "Raw M/S" mode, which records the M signal to one track of the final file, and the S signal to the other track. But there is also an "M/S Stereo mode" where the matrix is applied in the recorder, so that the recorded file contains a left-channel track and a right-channel track. It appears (p.22 step 2) that if you adjust the S mic gain = 0 dB (stereo width = 120º) before recording, then the "M/S" file will still contain normal stereo information, rather than raw M and S information. In that case, you'd just assign the "M/S" stereo track to the two front speakers, and the "X/Y" stereo track to the two rear speakers.

March 31st, 2013, 01:27 PM	#18
Bill Davis Trustee Join Date: Jan 2004 Location: Scottsdale, AZ 85260 Posts: 1,538	Re: Audio Synching Question Your biggest issue is not likely to be stereo perspective. Understand that that's only an issue if you're playing the audio back on a 5.1 theatrical style system - which represents about .5% of the playback situations in the world. Your work is MUCH more likely to be consumed on stereo (personal playback via earphones) or mono (any phone or small speaker that sums to mono) Of much more importance is the quality of the recorded sound. If you're recording while in motion - you're going to have to deal with AIR MOVEMENT - no matter what mics or devices you use. If you don't address that via air movement baffling - your audio will get infected with all sorts of wind noise which is much more critical than stereo perspective. FWIW. __________________ Classroom editing instructor? Check out www.starteditingnow.com Turnkey editor training content including licensed training footage for classroom use.

April 1st, 2013, 06:36 AM	#19
Carl Gilbert New Boot Join Date: Mar 2013 Location: Detroit, MI Posts: 16	Re: Audio Synching Question I am aware of the air movement issue. I have filmed while riding my bike before. Its not that bad. Plus, I plan to add some additional protection so I am expecting things to improve. We will see. Its going to take some work I'm sure, but its not a show stopper. I won't be selling these so I just need to keep the sound below the annoyance level. Mostly it won't be played on 5.1. I imagine most of the play will be on my tablet showing people a few minutes of some places I have biked. I'll need good sound for that. But also I will play it on my own home AVR where I do have 5.1 and where I will be looking to enjoy the full sound. Or at least learn a thing or two about how its made. Greg, for 2 channel recording you have the option of doing XY or MS. For MS you can record it raw and tweak the S later, or you can set the S now, and get a basic LR stereo signal recording. So I could in essence, get the MS decoded on the spot. I won't do that though because I have no experience with MS so its not likely I would pick a good setting on the spot. After a few runs I might be better at guessing and after that, I will go with the pre-mixed MS so that I only have to deal with two stereo channels. But honestly, I don't know. Its all good information for me. The weather is breaking here in Michigan so I should be out there within a month.

April 1st, 2013, 06:56 AM	#20
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,792	Re: Audio Synching Question Carl, If you want to end up with good surround sound for playback on your home system, you should record the 4-track surround mode. Set the S width to either 90º or 120º and your front-facing pair (the mics pointed AWAY from the controls) will be a nice normal stereo soundfield. The rear-facing pair (the mics pointed TOWARD the controls) will also be a nice normal stereo soundfield. Then if you want to create a 2-channel mix for your tablet (UGH! how will a tablet possibly sound good?), just mix the front left + rear left, and mix the front right + rear right.

April 1st, 2013, 09:49 AM	#21
Carl Gilbert New Boot Join Date: Mar 2013 Location: Detroit, MI Posts: 16	Re: Audio Synching Question OK. I will definitely take those settings for a ride.

April 11th, 2013, 05:52 PM	#22
Joe Garrick New Boot Join Date: Feb 2013 Location: Anoka MN Posts: 9	Re: Audio Synching Question I believe the H4n is similar to my DR-40 in that it can record stereo M/S or X/Y, not both. There's only one pair of built-in mics, plus inputs for two others. You can either plug in another stereo mic and record whatever kind of stereo you want to the other two channels, or you can plug in two mono mics for the other two channels. That's how my DR-40 works. When I was researching them before I bought the DR-40, the feature set was nearly identical for 4 channel recording. In any case, you're not going to get M/S and X/Y out of the one pair of built-in mics.

April 11th, 2013, 10:39 PM	#23
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,792	Re: Audio Synching Question We're talking about the H2n here, (not the H4). It has a total of five mic capsules. Two are "front facing" which means facing toward the side of the recorder that has the controls. (To my way of thinking, that is facing toward the rear but... oh well.) These are always X/Y. The other three capsules are "rear facing" which means they face away from the side of the recorder that has the controls. (To my way of thinking, that is facing toward the front but...) One of these capsules faces directly along the front/rear axis of the recorder. It's considered to be the M capsule. The other two apparently face directly left and directly right, and I guess there's some sort of matrix that derives a "S" signal from these. What's more, there is a switch on the top of the machine that changes what is recorded from the M/S capsules. You can record two raw tracks, one M and one S, for later mixing in post. Or you can have the mixing take place internally, before recording; in that case, you have a choice of 90º spread or 120º spread (presumably obtained by different ratio of S signal to M signal). And yes, the recorder has a mode that allows you to record four simultaneous audio tracks. The "Front" pair of tracks (which I call rear) is always X/Y. The "Rear" tracks (what I call "front") can be configured as 90º X/Y (or 120º X/Y if you prefer). So yes, the recorder can simultaneously record two sets of stereo tracks, four tracks in all, for LF / RF / LR / RR surround if you like. Check out the manual, it's available online. Be sure you fine the manual for the H2n, because the original H2 did not have all these capabilities.