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Audio Issues and Workaround for File Based Delivery of Broadcast Content to DG Fastchannel
Hi there,
I recently delivered a broadcast commercial campaign to DG Fastchannel using Premiere Pro to generate ProRes HQ quicktimes to DG’s specs and uploaded to their regional dropbox. Historically I’ve delivered HDCAM-SR and digibeta tapes to ensure highest quality, but the file-based delivery is incredibly cost effective for campaigns with a small number of spots, especially for the standard definition portion of the delivery.
Unfortunately, the files we delivered were bounced back with the report that the audio was showing up on their oscilloscopes as mono instead of stereo. Our media export parameters were using the Uncompressed audio codec and the mono/stereo option was set to stereo, so this was a mystery.
I’ve worked with Raul Mendez at DG over the last couple days to suss out the problem, and the culprit does indeed seem to be Premiere. Before I go on, here’s the workaround:
Set the audio codec to Apple Lossless or AAC (Apple Lossless is the only one of those two options suitable for broadcast delivery, btw, but good to know if you’re posting for review that AAC will give you the appropriate stereo audio imaging).
Here are few more details: DG uses either Final Cut Pro or AJA TV to test the ProRes HQ files they receive for broadcast delivery. They send the signal through an oscilloscope and the scope is what they’re using to determine whether the audio image is stereo or mono. Raul at DG did his own tests with CS6 at DG and confirmed the results I was getting, so I’m reasonably confident that the issue isn’t a quirk of my install of Premiere.
It would be great if this could get resolved, however the workaround is fairly simple and doesn’t noticeably effect audio quality. The overall concern, though, is whether Premiere will output stereo audio that will be universally interpreted as stereo.
To verify the problem, interestingly, you don’t need an oscilloscope. From a Premiere sequence, select File > Export Media. Select ProRes HQ for your video codec and Uncompressed for your audio codec and confirm you’re exporting stereo. When the file is finished exporting, bring it into Final Cut Pro. You’ll notice that FCP does not interpret the file as a stereo pair, rather, it sees it as dual mono. If you have AJA TV and an oscilloscope, you can bypass FCP and you’ll see that the signal the scope receives through AJA TV is mono. Next, replicate the steps above, only use Apple Lossless as your audio codec. You’ll see that FCP correctly imports the audio as a stereo pair.
I’ve posted a bug report to Adobe and I’m pasting the last message I got from Raul here, in case anyone’s interested.
From Raul:
“The audio uncompressed setting in Adobe Media Encoder 6 is the culprit. When the setting is set to Uncompressed it pans the audio to MONO. Unfortunately. If you choose AAC or Apple Lossless then the Stereo Imaging stays intact. Export some files with these settings and you will notice that FCP will recognize the Stereo Imaging.”So there ya go.
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5 Replies
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Thanks for the report and workaround. Also for the bug report. I’ll make sure the proper people know about this issue.
Kevin Monahan
Sr. Content and Community Lead
Adobe After Effects
Adobe Premiere Pro
Adobe Systems, Inc.
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I ran into this problem today in CS6….has it been fixed in the CC version of Premiere?
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Haven’t had to deliver something out of CC yet, so I don’t know. It did turn out, in my case anyway, that the bug was on DG’s side of things and Adobe worked with them in resolving it.
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Looks to me like it’s a bug in CS6…if you export audio as Linear PCM/stereo and then bring the file into FCP it will see it as dual mono. I had to use the Apple Lossless work-around.
It’s possible I’m doing something incorrectly…Maybe Kevin can chime back in?
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Technically it was a bug in FCP. Quicktime correctly sees the file as stereo. Makes a bit of sense since FCP hasn’t been supported in a couple years and hasn’t updated in several more. The quickest workaround, if you have to have the file as stereo in FCP after exporting from Premiere, is to simply highlight the audio and click option+L to make the audio a stereo pair in FCP.
“If you wish to see the truth, then hold no opinions for or against anything. To set up what you like against what you dislike is the disease of the mind.” – Sengstan
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