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Last second gets cut off when converting from AIFF to AC3

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Michael Paul
Last second gets cut off when converting from AIFF to AC3
on Aug 20, 2010 at 11:00:20 am

I am not sure if this is the RIGHT forum- I'm sorry if it isn't but I thought it might be since it's an Audio related problem:


So I am using Compressor 3.5.2 that comes with Final Cut Pro to convert an AIFF to AC3.

The problem is: The LAST SECOND of my AC3 will be CUT OFF and I have no idea how to fix this.

I am using the ac3 convertor that comes with compressor called "Dolby Digital Progressional (Auto)"
i've already tried the other settings you find under Audio in Compressor that convert to AC3 and they ALL cut of the LAST SECOND

what can I do?


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Bouke Vahl
Re: Last second gets cut off when converting from AIFF to AC3
on Aug 20, 2010 at 3:57:01 pm

[Michael Paul] "what can I do?"

Export your sound with an extra second at the end.
If you go to DVD, video length will be master anyways.

Bouke

http://www.videotoolshed.com/
smart tools for video pros


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Terry Mikkelsen
Re: Last second gets cut off when converting from AIFF to AC3
on Aug 20, 2010 at 4:12:34 pm

That's pretty wild. What program created the AIFFs? What format are they (bit & sample rate)?

Tech-T Productions
http://www.technical-t.com


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Ty Ford
Re: Last second gets cut off when converting from AIFF to AC3
on Aug 21, 2010 at 10:21:43 pm

Hello Michael and welcome to the Cow Audio Forum.

Usually audio is compressed by reducing bit rate and sample rate, not length. Maybe the AC-3 is doing something more like video where groups of samples are being truncated, as they are in video.

iTUNES can be set to crossfade files in preferences. As a result the files are faded at the end when you hear them. At least they used to be that way. Pretty weird. Just an errant thought.

Bouke's thought is a good one.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Michael Paul
Re: Last second gets cut off when converting from AIFF to AC3
on Aug 23, 2010 at 7:49:50 am

I guess adding an extra second at the end of my audio file is indeed a good solution yet it is quite weird I've gotta admit.

If you want to know what EXACTLY I did to get my AC3 here is the whole process:
(it might be the fault of some codec or a certain program)

-Created a mov with Apple ProRes 422 codec.
-Converted that mov to Photo JPG so I could convert that m2v & ac3 on a Windows PC with TMPEGEnc
-Converted the ac3 to AIFF with Apple's compressor (im back on a mac at this point)
-Dragged the AIFF into Levelator 2 (the result still got the last second)
-Then converted the AIFF back to AC3 and BAM my second is missing?!

I've also tried it with ffmepgX but even this cuts off the last second???

--

So I guess the solution is indeed to open up the aiff I converted with Levelator into say Soundtrack Pro and add an extra second at the end of it which I can later cut in DVD Studio Pro for my DVD Project.

It just does this with EVERY AUDIO and quite frankly its a pain in the … you know.

Here is a simple solution I've found: I just export the audio as AIFF from my mov and then I put it in the Levelator and convert it to AC3. That way the audio will have the exact length it's supposed to have. But here is the WEIRD part: Once I put those into DVD Studio Pro SOME audio will be shorter (cut off!) than the video footage- I JUST DONT GET IT :C


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Bouke Vahl
Re: Last second gets cut off when converting from AIFF to AC3
on Aug 23, 2010 at 7:55:04 am

Few things i don't get.
Why on earth are you converting to AC-3 and back to uncompressed, then to AC-3 again?
Just export the sound out of your QT, or do a second export as uncompressed sound from FCP.

Next, are you sure that with the latest QT, or with the Prores codec for windows installed, TMPG enc is not able to do it?

And why even go trough this, as you got Compressor? (I know, not the best MpegII encoder, but at high bitrates, it does the job.

I suspect you end up with timing issues trough the conversion.
Did you try other durations of clips, and is it then also exactly one second?

I don't know levelator, but if you have a Wave or AIFF from source as input, does it also happen?

Bouke

http://www.videotoolshed.com/
smart tools for video pros


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Michael Paul
Re: Last second gets cut off when converting from AIFF to AC3
on Aug 27, 2010 at 10:06:05 am

Well I use the program "Levelator" for my audio so there wont be great differences in volume for each clip on the DVD.
Sadly Levelator doesn't support AC3- only AIF. So I need to convert my AC3 to AIF for Levelator and then back to AC3 for the DVD.

Actually THX a lot. ApplePro Res DOES indeed work on Win (since 2008). I've been told it doesn't and never bothered.

I'm using TMPEGEnc because I've been told it's the best for the job and got a bunch of features Compressor won't offer.

I've tried a lot of clips with different durations and they all had that LAST SECOND missing issue.

And yes "but if you have a Wave or AIFF from source as input, does it also happen?"
I guess that is the solution. It doesn't. If I use an AIFF from my original Quick Time and put this in Levelator it won't cut off the last second.


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