Stereo vs. Ch 1 + Ch 2

Question

Stereo vs. Ch 1 + Ch 2

Hi,

I’ve been having major issues with the differences between “Stereo” and “Ch 1 + Ch 2” in FCP HD. I basically filmed with a shotgun on Ch 1 and the on-camera mic with Ch 2, so the audio levels and clarity on Ch 1 are much better and that is what I will use in the cut. All my footage was captured with “Ch 1 and Ch 2” under clip settings. When I look under the audio column in the browser, my clips are listed as “A1 + A2”. My question is:

1. When I watch a video clip with “A1 + A2” audio in the viewer, why do the levels in the audio meter (right of timeline) rise together as if it was recorded in stereo? But the waveform of the 2 channels in the timeline appear different.
2. Vice-versa, “stereo” files play in that audio meter at different levels for Ch 1 and Ch 2, which seems to me to be the reverse of what should happen.
3. When I use that “A1 + A2” clip in other projects, sometimes it changes to “stereo”. Why is that?
4. While capturing, does Final Cut Pro ever mix the Channels 1 & 2 into 2 channels of identical (mono) sound? I do NOT want that.

Am I the only one confused by this terminology? I’ve read the manual and Lisa Brenneis’ book about the differences. Should I just reverse my previously held view of what combined stereo and separate Ch 1 & 2 mean? This whole problem originated when I gave footage to my transcibers and they complained that the audio was not clear in many parts (yes, I know I used a shotgun). So while watching the footage I discovered that some parts had Ch 1 and 2 rising together, which led me to conclude that the audio was mixed together during capture. I’m hoping this did not happen as it will result in me having to recapture dozens of hours of footage.

Any help most appreciated,
Alexander

Mac OS X (10.3.9)

Posted on Apr 25, 2006 7:28 PM

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Answer 1

Apr 25, 2006 7:35 PM in response to Alexander Lee1

Boy, can you believe it's been almost a year since FCP 5 came out? I'm trying to remember what all the audio capture options were in 4.5. They finally made it easy to deal with in v.5.

I believe you did what you hope you didn't do. I think Ch1+Ch2 does mix them together on capture. The one thing you could try is to select the clip and go to Modify and try different things like checking/unchecking make stereo pair and checking/unchecking link.

What are the other options for audio capture again?

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Answer 2

Apr 25, 2006 7:59 PM in response to Alexander Lee1

1. Capturing as Ch 1 + Ch 2 will result in the audio for both channels being mono (panned to center [0]. Therefore what you're seeing in FCP's meters is correct. If you want the audio on channel 1 to only come through the left speaker, you'll need to change the pan to -1. If you want it to only come through the right speaker, pan it to 1.

2. Stereo is typically different audio on the two channels, so the meters should be different. When you capture as Stereo in FCP, Ch1 1 is panned left and Ch 2 is panned right. The only way the meters would rise and fall in unison is if the audio on both channels is identical.

3. It shouldn't change to Stereo by itself. Perhaps it was accidentally converted by the keyboard shortcut.

4. Not sure on that. As above, if you capture as Ch 1 + Ch 2, the result will be two mono tracks which can be independently adjusted. If you capture as stereo, the channels will be panned left and right so each channel is routed to its own speaker. I haven't ever had the need to capture as a "Mono Mix" so I'm not certain how FCP treats that.

-DH

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Answer 3

Apr 25, 2006 8:01 PM in response to Alexander Lee1

Typically when you capture seperate audio tracks (ie. 1 + 2) the tracks are panned to the middle. You may need to pan track 1 to the left and track 2 to the right to see a difference in the meters. However, it sounds as if you want the two tracks panned to the middle. All you will need to do is reduce the level of the track you don't want to hear.

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Answer 4

Apr 26, 2006 11:50 AM in response to Trevor Kinsey

I'm giving my transcribers only the quicktime files to listen to. So is it safe to assume that in their headphones the left side will be Ch. 1 and the right side Ch. 2 of my camera footage? My concern was that I would have to redigitize my footage to get separate channels of sound, but according to what you guys have said the difference between "stereo" and "Ch 1 + Ch 2" is just a panning function within FCP. Correct?

Thanks,
Alexander

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Answer 5

Apr 26, 2006 12:06 PM in response to Alexander Lee1

the difference between "stereo" and "Ch 1 + Ch 2" is just a panning function within FCP. Correct?<<\</div>

Well ... yes and no. In the broader sense, "stereo" means 2 channels of audio. But in more specific terms, it means a mix of the recording resulting in separated channels; i.e. a song in which some instruments are panned left and some right or dialog between two persons where one might be panned lightly left and the other slightly right depending on their position relative to the camera.

So a "stereo" recording is something more than just two discreet channels of audio.

-DH

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Answer 6

Apr 26, 2006 4:55 PM in response to Alexander Lee1

If you are exporting a Quicktime for your transcribers, just be careful of the settings you use in your export. If you are giving them the files as digitised they will hear both channels equally (i.e. panned to the centre).

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Answer 7

Apr 26, 2006 5:11 PM in response to Trevor Kinsey

the audio level meters in the timeline are correctly displaying that the signals being sent to the L and R channels are identical, if you pan a1 to the right and a2 to the left then the timeline audio meters will be showing a1 on the left meter and a2 on the right and the difference in level will be apparent. If you only want the a1 sound but coming out of both speakers then delete a2 or drop the level on it.

the timeline meters are left and right output, they bear no relation to the numbers of the tracks in the timeline, only to the panning applied to those tracks. If you pan all your tracks left then only the left meter will have anything to display.
typically editors use split (stereo) tracks so that they can easily hear the difference between two mics recording the same sound (like you have in your clip) and then centre the panning for playback to clients once they've done their mixing.

And no, FCP doesn't ever mix down your audio on capture. If you want to change your audio clips from dual mono to stereo at any time you can do so by selecting the relevant tracks and hitting alt l. This switches the panning between centred and split and also means that you can apply keyframes to both tracks simultaneously

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