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Added silence when saving

 
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coverland



Joined: 16 Nov 2007
Posts: 2

PostPosted: Fri Nov 16, 2007 10:45 pm    Post subject: Added silence when saving Reply with quote

(I am neither an audiophile nor technophile, so please bear with me! Smile )

I'm trying to create basic waveforms (sine, 440Hz) of very precise durations (to the nearest millisecond, actually) as mp3 files for an experiment I'm running.

After making files with the Waveform Generator, all looks well - graphs in the main window appear as intended. However, after saving and reopening waveforms I've made, I find that the durations have been changed slightly.

Specifically, about 20ms of near-zeroed data is added to the beginning of each file, creating a (granted, inaudible) gap before playback begins. The overall duration of the sample is thereby subsequently shortened. I've tried cropping this out and resaving, but the near-zeroed data returns.

Is there some kind of meta-tag info that's stitched on the beginning of mp3 files that I can turn off? Could this be some kind of artifact that Amadeus adds during saving? I'm stymied...

Any help would be greatly appreciated!
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Martin Hairer
Site Admin


Joined: 08 Nov 2006
Posts: 1615

PostPosted: Fri Nov 16, 2007 10:49 pm    Post subject: Added silence when saving Reply with quote

Quote:
Is there some kind of meta-tag info that's stitched on the beginning
of mp3 files that I can turn off? Could this be some kind of
artifact that Amadeus adds during saving? I'm stymied...

Mp3 files are chopped up into "frames", their smallest constituents
(think of it as an atom). Each frame contains about 1500 samples,
which is about 30ms, so millisecond precision is just not achievable
with Mp3 files. Furthermore, most Mp3 encoders (like LAME which is
what Amadeus Pro uses) will add "dummy" frames at the beginning / end
of a file in order to reduce some artifacts. Some other compressed
formats will have similar problems. I therefore suggest to use
uncompressed AIFF or WAVE files instead. Regards,

Martin

HairerSoft
http://www.hairersoft.com/


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coverland



Joined: 16 Nov 2007
Posts: 2

PostPosted: Sat Nov 17, 2007 3:24 am    Post subject: Reply with quote

Many thanks! This was very helpful!
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lyden



Joined: 25 Jan 2008
Posts: 1
Location: Denmark

PostPosted: Fri Jan 25, 2008 4:37 pm    Post subject: Reply with quote

Hi!!

I have the same issue here, I am trying to make a smooth loop without any clicks or similar with "succes". But every time I save, and on reopen there has been added silence in the beginning and end and my loop is no longer smooth

I do understand your reply, but is there really no way to make a smooth loop using mp3 then? (I have to use mp3).

Best Jonas

NB. thank you for a great product!
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