Old 11-22-2019, 03:43 PM   #1
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Location: Hertfordshire, UK
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Default MP3/M4a timing issues

A mate made a percussion loop for me in Logic and sent me a 4 bar M4a then later an MP3. Neither would loop properly. They almost immediately went out of time to the click, and zooming in I found a short pause at the beginning of the loop and again at the end. Tried frst with M4a (he's an Apple guy) then MP3. Same problem, Funny thing is, I loaded it into Garageband - no problem at all. But the gaps are there in Wavelab too. Loads fine his end with no gaps creeping in.

WTF! I assume it's some codec thing? Incidentally he cut me a .wav of the loop and it's fine, but I'm interested to understand why this happened. Any ideas?

Screenshots show start and end of loop with gaps/overlap. Weird!
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Last edited by Twangothan; 11-22-2019 at 04:17 PM.
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Old 11-22-2019, 04:30 PM   #2
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Those are both lossy compression formats and the slight added silence to the beginning and end are one of the characteristics.

The lame FAQ has some details about MP3.

thing is, I loaded it into Garageband - no problem at all.
There are some "tricks" that can remove or ignore the added silent audio and apparently Garageband is "smart enough" to do that. But, since the length of added silence can vary it's not always easy to remove it. (AAC may be easier than MP3, but I'm not sure.)
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