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enzo1982 / freac

The fre:ac audio converter project
https://www.freac.org/
GNU General Public License v2.0
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When trying to convert data purchased on iTunes, the volume is attenuated in some files. #472

Open AoiKagase opened 1 year ago

AoiKagase commented 1 year ago

Describe the bug Some M4A files purchased on iTunes have volume reduction after conversion. Decoding using FAAD2 directly did not cause this problem. (And this is not limited to fre:ac, there are a few other software programs that seem to experience the same phenomenon. However, since there are of course software programs that do not generate this problem, we believe that it is related to differences in the implementation of the decoding logic.)

To Reproduce I tried to convert a specific M4A file to Flac.

  1. Add the file to the list.
  2. Play the file to try it out, the volume will be lowered at this point.
  3. Convert to Flac. A Flac file with reduced volume will be created.

Expected behavior The volume is not attenuated when decoded.

Screenshots Nothing.

System (please complete the following information)

Additional context The iTunes used is 12.12.8.2 latest, purchased data includes previous versions. The following two types of iTunes data were purchased. https://music.apple.com/jp/album/sunny/1556015178 => No problem. (itunes is previous version.) https://music.apple.com/jp/album/love-holic/1643459416 => volume reduced.

leon332157 commented 1 year ago

I am having similar issue, when I convert a m4a file from itunes to wav using ffmpeg, there's no such issue, it seems like the volume reduction comes from the aac decoder? image Audacity screenshot for reference.