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Compressor reducing 5.1 to stereo?
I exported my tracks for a 5.1 project out of FCP successfully, but when I add a new surround sound in Compressor, drag in each of the channels, and then apply the Dolby Professional 5.1 preset to it, well, you see the results below. The first set are the originals, the second, the exports from FCP, the third, the resulting .ac3 file.
Can someone tell me what I’m doing wrong?
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29 Replies
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An ac3 file is a data stream which contains the 5.1 in a stereo file. I have no idea what you have dropped into the FCP timeline, but it isn’t an ac3 file.
An ac3 file is just pure data so it looks like full level unmodulated noise. If you listen to it it sounds like pure noise at high level so I don’t recommend you try to play it through speakers.
You don’t need the audio to be in FCP to make an ac3 file with Compressor. It can encode directly from multi channel wavs or mono wavs or aifs. Can you explain better your settings and what the third output files actually are.
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Everything that MIchael says AND if exporting from FCP (like the multichannel mix you have there) you export your timeline broken it into 6 discrete channels (you know how to do that, right?) as a channel grouped aif file. That will make 6 aif files. You then add those as the surround.
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Yes, that’s exactly what I did. And yes, that is an .ac3 file, dragged into the timeline:
So here’s my workflow:
My Sequence settings are for 6 channels, all set to 0 db (I had left them at the defaults, but changed them when all this din’t work to see if it would help), all set to Dual Mono.
I then set each audio channel from 1-6 in the timeline. I then exported the tracks you see as the first set in the timeline as Audio as Aiff, using 48k, 16-bit, Channel Grouped. I got the resulting files which I then checked by importing and placing them on the timeline as well (This is the second set in the timeline).
I then open Compressor, and select Add Surround Sound. I add all the 6 exported .aif’s into the window to their corresponding channels, and click ok. I then drag the Dolby Digital Professional 5.1 preset onto the source, and click submit. I then drag the resulting .ac3 into fcp to check the audio, and that is the third set in the timeline.
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[Jeffrey Ellis] “I then drag the resulting .ac3 into fcp to check the audio, and that is the third set in the timeline.”
Makes no sense. The third file has six channels and the two channels with waveforms are showing the same basic waveform as the 5.1 channels. An ac3 file should be stereo and have nothing but data so a squared waveform at full level.
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What Michael says. the dolby decoder at the other end will decode and route the 5.1 The ac3 file is not going to show you the 6 discrete channels as they aren’t encoded as such.
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Michael–
I’m sorry, but I am telling you exactly the steps that i’ve taken. I’m not trying to hide some weird procedure, or anything else you may think I’m leaving out. I’ve even tried it 3 times now, just to be sure.
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Oh.
Ok, but then why, when I actually burn the file to blu-ray, am I not hearing any of the other channels?
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Is there another way to test if the information is actually there aside from that?
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What happens when you author the DVD with that ac3 file? Does it play back OK?
I have no idea why an ac3 file would reimport into FCP looking like that but the bottom line is, is there a problem with your DVD playback using the Compressor file?
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Ah, so there is a playback problem. What are your Compressor settings.
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