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ProRes Audio Setting?
Question regarding encoding ProRes files. I have an Uncompressed 1080p HD file that is huge. I’m archiving this file to DVD but want to keep a ProRes file on our server for quick access. The ProRes file is perfect because of the file size. 3.5 Gbs for the uncompressed and about 400 mbs for ProRes.
My question is, because the uncompressed file has 16 channels of mono audio (which was weird to me, this came from an outside source), I want to re-encode the audio to 2 channel stereo. Once I’ve selected ProRes in Compressor, click on the Encoder tab and Enable the Audio settings vs. using Pass-Through, which format should I use, Linear PCM stereo L R or the default of Apple Lossless. The Apple lossless format then gives me a red render bar in FCP. Is Linear PCM better to use? Or maybe IMA 4:1? Which will give me uncompressed audio, without having to render in FCP?
OS 10.6.3, Mac Pro 2 x 2.66 ghz quad-core intel xenon, 16 gb ram, with BM Intensity Pro card
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4 Replies
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Linear PCM is the uncompressed option, which gives greatest quality and compatibility. I’m not sure how your 16 channels will fold down to mono, though. That could be pretty tricky. Usually, the channel allocation in the metadata is used to matrix the mixdown. As there is no true standard for 16-channel audio, there is probably no flag that could define what has been done with those 16 channels. If they are seen as 16 discrete channels and not a standard configuration, they will probably all be mixed down to stereo, in the center of the image, which is effectively mono. That could sound like a trainwreck.
I’d recommend you use Pass-Through for your audio, as the Uncompressed already contains Linear PCM in the correct channel configuration. It’s already what you want it to be.
IHTH,
JC Boulay
Technical Director
Audio Z
Montreal, Canada
http://www.audioz.com -
Thanks for the reply. I did try the Pass-Through setting and it came out fine, but when I took that file into Adobe Media Encoder to create a FLV file, AME said the file was corrupt, when in fact it isn’t. FCP was able import the same file but once opened in the viewer there were 16 mono channels as per the original. Channels 1 & 2 have audio and 3-16 have nothing. Not sure how our post house digitized the master to get 16 channels. 14 of which have nothing.
So because AME couldn’t read the file, I wanted to try re-compressing the uncompressed file to either Linear PCM 2 channel stereo or the IMA 4:1 setting to get rid of those 14 extra channels.
My other ProRes files have worked in AME before but I just don’t know what audio was used. I’ll try the Linear PCM route and see what happens. I’m going to assume that since only 2 channels of the 16 contain waveforms that this method of should result it a normal stereo mix. I guess we’ll see shortly.
OS 10.6.3, Mac Pro 2 x 2.66 ghz quad-core intel xenon, 16 gb ram, with BM Intensity Pro card
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It’s pretty normal for acquisition from an HD-SDI source to come in with 16 audio channels. Since they’re empty just delete channels 3-16 and be done.
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Thanks Mark, I was unaware of that. I’ve never had to capture from HD-SDI nor can I. I think selecting Linear PCM 2 stereo from Compressor worked.
But I guess if I wanted to try your method, I’d have to use FCP, drop the uncompressed file in a new timeline and option drag to delete the blank tracks, 3 & 4. Leaving me with 2 mono channels, 1 & 2. Does that sound correct? Don’t think I can do this in Compressor.
And why when opened in the viewer does the uncompressed file show 16 channels but once in the timeline, only 4 come in?
OS 10.6.3, Mac Pro 2 x 2.66 ghz quad-core intel xenon, 16 gb ram, with BM Intensity Pro card
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