same file but different peak level in different computer

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same file but different peak level in different computer

Permanent link to this post Posted by siamak » Sun Feb 04, 2018 10:34 am

I have audio files (mostly mp4). When loaded to my Audacity 2.2.1 on iMac intel Core i5 with OSX 10.13.3(latest) peak levels are normal and are below 0.0 db. However when same files are loaded on Audacity 2.2.1 on my older computer Mini mac Mid 2007 with OSX 10.7.5 most of the peaks are shown as exceeded 0.0 db( audio wave mostly or all shown in red)! I can normalize them in my older computer. But I am not sure which file would be correct and could be shared? Please advise and direct.
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Re: same file but different peak level in different computer

Permanent link to this post Posted by billw58 » Sun Feb 04, 2018 4:34 pm

Do you have "Show Clipping" enabled on both machines?
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Re: same file but different peak level in different computer

Permanent link to this post Posted by kozikowski » Sun Feb 04, 2018 6:46 pm

That and it's not particularly good practice to jam everything up against 0dB.

Different systems may treat that value differently, particularly because most file systems can't go over that value. You never know how much damage you have, if any. Red bars in Audacity doesn't mean you have sound damage, it just means you got really close.

It gets better. Some sound formats such as MP3 create their own peak damage.

I don't remember which value is recommended, but I'd be surprised if it was over -0.5dB. I've seen one recommendation of -1dB. ACX Audiobooks requirements are no sound values over -3dB, to cover post production problems and other accidental damage.

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Re: same file but different peak level in different computer

Permanent link to this post Posted by siamak » Mon Feb 05, 2018 5:53 am

Koz, I agree with you 100% and I do normalize all my files to -1.0db. My original post was for initial loading of the files that indicates peaks are exceeding and are red in old computer and bellow or acceptable in new computer.
But as you said this could be due to the different systems treat the values differently. Is there a way to conform in my case that this is actually happening. And if so, do I have to label each file if I do normalize or any other effect to each file for each computer. I usually work on my files on newer computer for faster results and then move them to older computer which only playbacks on my Hifi system. This can become a nightmare for file management.

Bill, "Show clipping" is on in new computer that does not indicates file is exceeding 0db. So this is not the problem in my case.
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Re: same file but different peak level in different computer

Permanent link to this post Posted by billw58 » Mon Feb 05, 2018 5:51 pm

I have no idea why running the same Audacity on different version of OS X would cause the symptoms you describe.

There are two audio format conversion tools you could try, to see if they show any difference between the two machines.

They are Max and xACT. Max is very old (2009) but I use it all the time on 10.11.4. xAct is more up to date but seems less flexible than Max. Each of them should be able to convert MP4 to AIF. Then you could load the AIF files into Audacity to analyze them.

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Re: same file but different peak level in different computer

Permanent link to this post Posted by siamak » Tue Feb 06, 2018 12:31 am

Thanks Bill.
I am familiar with Max and xACT. Do you mean convert to Aiff? Other than Aiff is uncompressed format, what is purpose of the this conversion before the comparison. How do you compare other than visually checking for peaks in each computer? That going to be tough act since both computers are NOT portable and located in different location.

Could be the difference is due to that each Audacity may have different version of mp3 library? mp3 lib 3.98.2 and 3.99.5 in old and newer computer respectively. Is this is the reason you recommended to convert to AIFF?
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Re: same file but different peak level in different computer

Permanent link to this post Posted by siamak » Tue Feb 06, 2018 1:11 am

I am happy to report that problem was due to different mp3 library in my two computers. I upgraded the library in older computer to 3.99.5 and now both computers have same library and problem was solved.
it is surprising a minor library update gives a such different result in loading a file.
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Re: same file but different peak level in different computer

Permanent link to this post Posted by billw58 » Tue Feb 06, 2018 4:17 pm

That is, indeed, odd, since the LAME library is meant for MP3 export, not for import.
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