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Clip audio 6dB louder in Browser than in Timeline - further discussion

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Bob Woodhead
Clip audio 6dB louder in Browser than in Timeline - further discussion
on Oct 28, 2014 at 1:05:15 pm
Last Edited By Bob Woodhead on Oct 29, 2014 at 1:12:03 pm

There's 2 other threads on this topic, but neither had a resolution.

Quick recap; several here have commented how clips played in Browser have levels that are 6dB higher than when edited into timeline. It's not related to phase, silent tracks, or mono/stereo settings in the clip.

HOWEVER, when the timeline Project is set to surround, the levels are correct.

So since it seemed tied for some reason to panning, I changed Pan Mode for the clip from None to Stereo Left/Right with Pan Amount set to 0, or centered. NOW the audio levels match from Browser to timeline.

Seems like there should be no difference whether Pan is set to None or Stereo/Centered.

Thoughts? Others seeing/not seeing the audio disparity?


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Robin S. Kurz
Re: Clip audio 6dB louder in Browser than in Timeline - a "workaround"
on Oct 28, 2014 at 2:13:10 pm

Any chance you could post an example file of sorts, because I'm not seeing it. But I've seen it discussed before, yes.

- RK

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Bob Woodhead
Re: Clip audio 6dB louder in Browser than in Timeline - a "workaround"
on Oct 28, 2014 at 3:47:41 pm

More testing... think I'm on to something. Need to confirm elsewhere. Will post results.


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Bob Woodhead
Re: Clip audio 6dB louder in Browser than in Timeline - a "workaround"
on Oct 28, 2014 at 11:28:44 pm
Last Edited By Bob Woodhead on Oct 28, 2014 at 11:29:21 pm

OK, tested on different clips, including a Prores edit master from a week or so ago out of FCPX. Clip codec doesn't matter, you should be able to replicate with any clip. (I used a tone generator app to create a mono 0dB wav clip for reference testing.)

Take a mono clip, it can be two channel mono or single channel, same result. Confirm that Pan Mode is set to "None". Edit into a timeline (stereo, since surround doesn't exhibit the behavior). Play clip in browser, mark peaks. Play clip in timeline, you'll see peaks are -6 from browser levels. Select the clip in the browser, then change Pan Mode in Inspector to Stereo Left/Right. Play the clip, it has dropped -6 dB. Look at the timeline edited clip, and pan mode will still be "None", but it's -6dB. Matches the adjusted source clip.

Though I've noticed this in the past, I never thought much about it, as I almost always adjust audio in the timeline. My current edit has many multi cams, and I wanted to adjust levels and apply initial filters "upstream" in the clip's own timeline. And that brought the 6dB to the forefront.

I talked to a few audio guys today, and they all agreed that 0 in a clip should be 0 on a timeline, however one mentioned that most stereo panners attenuate 3 or 6dB in the center.

Tested this in PPro, and result was -3dB in timeline.

So, interested in hearing thoughts as to the "why" of it.


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Paul Figgiani
Re: Clip audio 6dB louder in Browser than in Timeline - a "workaround"
on Oct 29, 2014 at 4:10:14 am

[Bob Woodhead] "I talked to a few audio guys today, and they all agreed that 0 in a clip should be 0 on a timeline, however one mentioned that most stereo panners attenuate 3 or 6dB in the center. "

Are you dealing with Mono files?

I can explain common -3dB attenuation: Constant Loudness

Consider this:

On many analog audio consoles (mixers) - hard panning a mono channel left or right results in equal apparent (perceived) loudness. OTOH If the channel is panned center, the output would be hotter due to the combined or mixed output level of the audio. In order to maintain constant apparent loudness, the output level of center panned audio would need to be attenuated by (in most cases ) -3 dB.

Now try this exercise in FCPX using a -12dBFS sine wave test tone:

Edit the clip into timeline. Set Channel Configuration to Left. The meter will read -12 dBFS.

Now set the Channel Configuration to Right. Again, the meter will read -12dBFS.

Now set the Channel Configuration to Center. The meter now displays a -3dB attenuation.

Now set the Channel Configuration to Mono. The meter now displays a -6dB attenuation.


* * *

Also Try This:

Duplicate the mono test tone clip in timeline. Set up L/R panning for each. So one Left and one Right. Meters will show -12 dBFS. Of course I'm adding clutter to timeline, so ...

Select the hard panned mono clips and make a Compound Clip. Again, meters will read -12 dBFS.

Make sense?

.-paul.


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James Ewart
Re: Clip audio 6dB louder in Browser than in Timeline - a "workaround"
on Oct 29, 2014 at 8:51:37 am

Thank you for this. Most informative.


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