ISO Audio Tracks

[Jean-christophe Boulay]

ISO is the International Standards Organization. You could use the acronym ISO to describe any number of processes in any given industry, as the letters alone mean nothing without the number of the standard they relate to. For example, ISO disc images are files based on the ISO 9660 filesystem. Exposure values also relate to an ISO standard. Heck, the window frame manufacturer close to my home is ISO 9002-certified.

The three letters themselves mean pretty much nothing, which is why it’s a very good idea not to use “iso” as an abbreviation for “isolated”. Someone somewhere is going to be really confused. When requesting sound elements separated from the rest of the mix, ask for “split tracks” or “mixouts”. Pretty much every sound person should understand that.

As for channels and tracks, on most gear and in most software a “track” is an audio stream which can have one or more channels. Channels are independant components of the track, usually allocated to speakers. So a stereo track will contain two channels, a 5.1 track will contain 6 channels, etc… Hence, one mono track can not contain two channels, left and right. That would necessarily be a stereo track. Most production sound I’ve worked with comes on two channels, but they are not left and right. They’re usually Lav and Boom, the separate mics. Some production sound also comes in with a stereo mix on two channels, but we rarely use that in post. That would be your “production sound mix”, but your audio post guy will need “production split tracks” to work. Don’t take this differentiation of tracks and channels for granted, though. In many instances, the terms are used as if they meant the same thing.

IHTH

JC Boulay
Audio Z
Montreal, Canada
http://www.audioz.com

[Rob Neidig]

As to channels vs tracks:

I typically think of channels as relating to a mixer and tracks to a recorder. Thus, for example, a Sound Devices 302 has three channels, that is 3 inputs, for different things. The output is then sent out as typically a stereo output, that is a left and right track. Within the mixer you determine on which tracks the channels will be recorded. Carry this view on and you get for example 48-channel mixers, with 48 different sources all being mixed down to two audio tracks (stereo).

Then there are recorders that have more than 2 tracks. Sometimes you may send each channel to its own track, sometimes you will mix several sources to one track.

As to the “iso” issue, yes “ISO” can mean a number of things, but I often hear video/audio people talking about recording mics to “iso” tracks. This would mean that if you have 2 people in a scene you would pan one mic all the way Left so it only gets recorded on track number 1, and pan the other mic all the way Right so it only gets recorded on track number 2. As JC says, this is more often called split tracks, but I have heard the term iso used. Where you start having to make decisions about how to split is when you have more than 2 sources, but are recording to stereo.

Hope this helps. Have fun!

Rob

Rob Neidig
R&R Media Productions
Eugene, Oregon

[Ty Ford]

You nailed it JC, but I have minor additions.

“As for channels and tracks, on most gear and in most software a “track” is an audio stream which can have one or more channels. Channels are independant components of the track, usually allocated to speakers. So a stereo track will contain two channels, a 5.1 track will contain 6 channels, etc… Hence, one mono track can not contain two channels, left and right. That would necessarily be a stereo track. Most production sound I’ve worked with comes on two channels, but they are not left and right. They’re usually Lav and Boom, the separate mics. Some production sound also comes in with a stereo mix on two channels, but we rarely use that in post. That would be your “production sound mix”, but your audio post guy will need “production split tracks” to work. Don’t take this differentiation of tracks and channels for granted, though. In many instances, the terms are used as if they meant the same thing.”

A channel is usually something on a piece of audio hardware, a console, for example. It’s not uncommon to refer to the left and right channels or left and right tracks of a video camera.

An audio track down here usually refers to one channel or track of audio. A track was historically a track on a tape recorder, but now is a track on a piece of software running on a computer.

There’s also the possibility of a dual mono mix where all mics go to both channels. This is sometimes done to prevent postproduction people from just choosing one track for the audio.

Some sound mixers also feed dual mono but run the level of one channel on the camera down a few dB to allow for accidental overs. It’s a safety net in case things get too loud. The, hopefully, the reduced channel isn’t clipped.

Regards,

Ty Ford

Confusing? A little.

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar

[Ryan Krickow]

Thanks for all the info! That was definitely more complex than I had thought. So, if I wanted to get a mixed mono track (audio file) for picture editing would that come in 2 tracks (left and right speakers) and what terminology would I use to ask for it? Then, would I also ask for split tracks (instead of iso’s) if I wanted to get 1 separate file per channel/mic for post sound? Would these audio files also be 2 tracks (left and right speakers)?

As an overview I’m looking for the correct terminology to use when asking production sound for audio files for the picture editor and audio files for post sound.

Thanks again, Ryan

[Ty Ford]

>>[Ryan Krickow] “So, if I wanted to get a mixed mono track (audio file) for picture editing would that come in 2 tracks (left and right speakers) and what terminology would I use to ask for it?

Ryan, if you were feeding one camera with two audio tracks, you would ask the audio person for a mono mix to both tracks.

>>Then, would I also ask for split tracks (instead of iso’s) if I wanted to get 1 separate file per channel/mic for post sound? Would these audio files also be 2 tracks (left and right speakers)?

Ryan, if you only have two mics you can split track them one to each channel/track. Most of the time that’s what’s done whether you have boom and lav on one person or two lavs each on a different person, or a boom on one person and a lav on another person.

If you have three or more mics and only two channels of audio on the camera and you want maximum flexibility in post, then you have to decide what’s most important and put that mic on its own channel/track. This gets very tricky if you are a one person audio department. You can’t really swing a boom ride its level and ride two other lav levels at the same time. Well you CAN, but eventually, you’ll screw up, especially if the speaking is extemporaneous.

If you can’t go back and redo because of a bad sound move, or if someone inadvertently speaks before you expect them to and you don’t have their pot up, then you get what you get.

Paying attention to riding gain on three or more mics has required pretty much all of my attention, leaving me without the ability to swing a boom.

Hope this helps,

Regards,

Ty Ford

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar

[Ryan Krickow]

We’re shooting dual system sound (with a production sound mixer and a boom operator) so we won’t have the audio going to the camera. The main thing I’m trying to figure out in terms of tracks/channels & mono/stereo is the correct terminology to use when asking for the mixed audio (for picture editing) and separate audio files for each channel/mic (for post sound). Based on what has been said I believe that I would ask for a mixed mono track and split tracks. Is that correct? Thanks, Ryan

[Ty Ford]

[Ryan Krickow] “We’re shooting dual system sound (with a production sound mixer and a boom operator) so we won’t have the audio going to the camera. The main thing I’m trying to figure out in terms of tracks/channels & mono/stereo is the correct terminology to use when asking for the mixed audio (for picture editing) and separate audio files for each channel/mic (for post sound). Based on what has been said I believe that I would ask for a mixed mono track and split tracks. Is that correct? Thanks, Ryan”

Ryan,

Dual system still usually runs audio to the camera for safety and possible sync up later. That’s why it’s called DUAL. This is new information you didn’t mention before. How many tracks does the recprder have?

You can have mixed mono (one or two tracks) or mixed stereo in two tracks. Unless you have enough tracks, you can’t have both mixed and iso. If you only have two tracks, you can mix mono to one and have one iso track for one source ONLY.

I advise you to stand aside and let the location audio folks talk to the post folks rather than trying to interpret something you are unfamiliar with. Listen to what they say. Ask questions. Learn.

Regards,

Ty Ford

Ty Ford

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar

[Ryan Krickow]

I’m editing the project so I’d like to have a handle on the general procedures of getting audio during production and passing it along to post sound. We’re in early pre-production and haven’t hired the sound mixer but I’m almost positive it is going to be recorded on a 788T or similar audio recorder and there’s a good chance the audio won’t be recorded on the camera in which case I was mistaken in mentioning dual system sound. Here are the two main pieces of information I’m trying to get a firm handle on…

1. The correct audio file(s) for picture editing would be a mono mix track. What I’m not quite sure of is if there would be an advantage to having 2 mono mix tracks vs. 1 mono mix track? It seems like 1 mono mix track is all you would need for picture editing but I could be wrong.

2. The correct audio files for post sound would be isolated “iso” tracks or production split tracks.

Thus I would request a mono mix track(s?) and iso tracks. If audio gets recorded on the camera then all need is the iso tracks. Thanks for all your help! Ryan

[Ty Ford]

[Ryan Krickow] “1. The correct audio file(s) for picture editing would be a mono mix track.

>>Yes, if he does a mono mix track

What I’m not quite sure of is if there would be an advantage to having 2 mono mix tracks vs. 1 mono mix track? It seems like 1 mono mix track is all you would need for picture editing but I could be wrong.

>>As I mentioned before. With two tracks of mono, some folks like to run one track a few dB lower than the other in case of unexpected outbursts. the main track might clip, built the lower one (hopefully) won’t. Don’t know if the mixer used will allow that.

2. The correct audio files for post sound would be isolated “iso” tracks or production split tracks.
If you want to have each mic on a separate track, yes. I think “Split Tracks” usually refers to the sending of different audio to each of two tracks. Whereas “Splits” frequently refers to dialog, music or effects tracks. Dialog splits, Music splits, and EFX splits. The word “stems” is also used the same way.

Thus I would request a mono mix track(s?) and iso tracks.
>>For what?

If audio gets recorded on the camera then all need is the iso tracks.
>>Yes, but having a single mono mix on a camera track would be prudent.

Ty Ford

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar

[Ryan Krickow]

I would request a mono mixed track and iso tracks from production sound for picture editing (mono mixed track) and delivery to post sound (iso tracks). You said “Yes, if he does a mono mix track”, in what case would a production sound mixer not be able to provide this? Thanks, Ryan