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Low volume audio from Compressor
So I’m having this weird problem. I have a 5.1 project, and I’m exporting out of FCP as Channel grouped aiff’s. The audio sounds great in the timeline, but when I use Compressor to create the .ac3, it’s very low in volume.
The steps I’m taking are to add a surround sound track, manually drag each aiff into it’s place in the next dialog, and then use the standard Dolby Digital Professional 5.1 preset.
I ran a spectrum analyzer on the original tracks, and they’re averaging about -12 to -6db.
What am I doing wrong?
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14 Replies
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If you want the levels to remain unchanged, set the dialog norm level to -31db. This stops the decoder from setting an output level and should pass on unity.
One other thing that effects volume is leaving the default “Film Compression” which lets the dodgy dynamics processor in a Dolby chip compress the dynamic. Set to none so there is no horrible processing by the Dolby decoder. After all that, it might still sound a bit flatter. That is just the ancient Dolby codec doing its normal lousy job.
Save this as your new default. Compressors default is what Dolby thinks is right, but it isn’t.
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Hi, Michael–
Thanks for the tip. I’ll definitely try that. You say even after that, it still may be flat. Is there some other preset you use?
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Oh, I also noticed that even when I set Film Compression to None, LFE Low Pass is still checked, and there’s a -3db downmix setting for Center and LFE that can’t be set to 0. I did notice that those channels were downmixed during playback of the .ac3 as well. Is there anything I can about that? Can I perhaps use my Sequence Audio Settings to increase the center and lfe channels by +3db to compensate?
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[Jeffrey Ellis] “You say even after that, it still may be flat. Is there some other preset you use?”
Not really. ac3 is a really old CBR codec and it just tends to flatten dynamics. It isn’t that noticable on material that has dynamic range restriction like broadcast mixes.
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[Jeffrey Ellis] “Can I perhaps use my Sequence Audio Settings to increase the center and lfe channels by +3db to compensate?”
That will change the actual 5.1 mix which will cause the wrath of the mixer. Downmix is a compromise formula. I make a stereo downmix and encode that as a separate 2.0 stream.
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Ah, ok.
Can I tell you one other thing I tried? I used FCP’s Share–>Blu-Ray. This actually made an excellent track, but for one thing. The LFE was shaking the floors with every bass hit. Is there a way to stop that? That *isn’t* in the tracks at all. But I like the way it sounds as far as everything else goes.
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Oh, and if there is something non-broadcast safe, that’s ok. This isn’t for distribution.
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[Jeffrey Ellis] “The LFE was shaking the floors with every bass hit. Is there a way to stop that?”
That might be from the discrepancy in Dolby encoding that trims sub levels -10db in ac3 for cinemas. Try trimming the clip level -10 on the sub channel only and see if that gets the correct balance back
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I’m afraid I don’t know where that setting is. Do you mean in the preset? Or the timeline?
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Timeline.
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