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Old February 22nd, 2008, 07:23 AM   #1
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FCP Audio Issues: Distorted Playback

I have a clean piece of buy-out production music (AIFF) that sounds perfectly fine when I play it on my iMac and insert it into FCP projects. Playback in FCP is perfect. However, once I render it out as a .mov and burn it via DVDSP, the track becomes horribly distorted when I play the DVD on my TV. Any ideas why this is happening? That one stupid track is the only victim of this weird distortion--everything else plays fine.

The track plays fine when I preview the .mov file in DVDSP or QT. It also plays fine on my PC laptop. Only on my TV does the track come out all crazy-distorted.
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Old February 22nd, 2008, 07:37 AM   #2
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Quote:
Originally Posted by Jim Duggins View Post
Only on my TV does the track come out all crazy-distorted.
Have you tried turning the gain of the imported music track down in FCP to -12dB?

Audio sourced from libraries and CDs usually use the entire dynamic range and most modern music is a little, erm, compressed, so peaks are at -0.01dB and most tracks bubble along at -3 to -6dB. On data sources (PC, web, Hifi), this is absolutely fine, but on a TV set to standards around -12 to -18dB, the speaker will probably be overdriven most of the time.

I do two audio mixes: one for web/data, one for DVD. There is, however, a sort of audio levels command in Compressor 3 that, if I were to truly understand it, I could be crafty and output everything as if for data, then have compressor lower things appropriately. But I feel safer doing it manually.
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Old February 22nd, 2008, 08:09 AM   #3
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The tips Matt brings up are rock-solid; DVD audio does get easily overdriven with music files that are set to RedBook audio standards.

The AC3 encoder for DVD audio in Compressor does have some compression settings enabled by default which would prevent this problem however, depending on how the audio levels were mixed in FCP this could also cause "pumping" between high & low audio levels.

Unfortunately there's no single or easy way to know how your audio is going to perform on a DVD, you'll simply have to test the audio tracks using various settings. The good news is, once you've found that sweet spot you can save those settings in Compressor and make them your default audio encoding settings for DVD.

You can also speed up this testing process; take your chapters that you've built from FCP and import them into Compressor using the various settings as tests; do an "audio-only" encode for the various chapters, then author your DVD normally. The DVD will still play the tracks just as it would otherwise, there just won't be any video to go along with the audio. The benefit in doing this, is that audio takes far less time to encode which would allow you to test an entire project several times without the horrendous wait it would take to re-render all the video.
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Old February 22nd, 2008, 04:58 PM   #4
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Thanks for the advice! I'm kind of new to FCP and have never used Compressor. How do I change the gain of a particular track in FCP? I tried to edit the audio track in FCP and it opened up SoundtrackPro instead, another program I have absolutely no idea how to use! :(

Will HDTVs have the same playback problem as my current SD set?
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Old February 22nd, 2008, 05:37 PM   #5
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You don't need to edit the levels outside of Final Cut, you can modify the levels and even set fades and use keyframes just like opacity.

Audio standards for video are universal regardless if it's SD or HD.
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Old February 23rd, 2008, 01:21 AM   #6
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[QUOTE=Jim Duggins;831075]Thanks for the advice! I'm kind of new to FCP and have never used Compressor. How do I change the gain of a particular track in FCP? I tried to edit the audio track in FCP and it opened up SoundtrackPro instead, another program I have absolutely no idea how to use! :(

The three easiest ways probably are...

double click your audio track to open it in the Viewer.

Then either...

1- put your curser over the red line and drag it down.
2 - drag the "level" slider to the left or,
3 - select the track directly go to the "Modify" menu - and modify your LEVELS down by whatever number you want.

Since you're learning to modify levels in the timeline, you might want to grab your manuals and read up on setting keyframes.

Keyframeing combined with dragging audio levels up and down (rubberbanding) is a simple and visual way to do useful stuff like audio fades and mixes.

Good luck.
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