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[GH-ISSUE #324] [Bug Report] / Audio quality downgraded #277
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Originally created by @hbtvs59 on GitHub (Jan 14, 2026).
Original GitHub issue: https://github.com/afkarxyz/SpotiFLAC/issues/324
[Bug Report]
Problem
Audio files are first downloaded in M4A (AAC) format at the highest available quality, then converted to FLAC.
However, during the conversion process, some audio characteristics that do not actually exist in the source file are preserved or artificially recreated.
Example:
A source file reported as 24-bit is converted to FLAC while keeping higher technical characteristics.
In reality, the audio content corresponds to CD quality (16-bit / 44.1 kHz), but the resulting FLAC file still contains or advertises higher specifications.
Output file
Audio
Format : FLAC
Format/Infos : Free Lossless Audio Codec
Durée : 2 min 18 s
Type de débit : Variable
Débit : 370 kb/s
Canal(aux) : 2 canaux
Agencement des canaux : L R
Échantillonnage : 44,1 kHz
Profondeur binaire : 16 bits
Mode de compression : Sans perte
Taille du flux : 6,13 Mio (98%)
Bibliothèque utilisée : flacvorbis 0.1.0
MD5 du contenu non codé : 64208F6BF4E45B08E97E26990A05DC72
Input File
Audio
ID : 1
Format : FLAC
Format/Infos : Free Lossless Audio Codec
Identifiant du codec : fLaC
Durée : 29 s 995 ms
Type de débit : Variable
Débit : 2 241 kb/s
Canal(aux) : 2 canaux
Agencement des canaux : L R
Échantillonnage : 96,0 kHz
Profondeur binaire : 24 bits
Mode de compression : Sans perte
Taille du flux : 8,01 Mio (100%)
MD5 du contenu non codé : 73932B6695B661B3D6210B0CB5308DDD
This can be misleading for users regarding the actual audio quality of the final FLAC file.
Type
Track / Album
Spotify URL
https://open.spotify.com/album/0JLN7JryQ2T7lBEYIrSQF1
Version
SpotiFLAC v0.7.5
OS
macOS (also reproducible on Windows and Linux)
Additional Context
The expected behavior would be for the FLAC conversion to automatically limit bit depth and sample rate to match the real characteristics of the source M4A file, avoiding any artificial upscaling of audio quality.
@Silvergish commented on GitHub (Jan 15, 2026):
Just making sure I understand this. Are you saying that some 24-bit files that get converted to FLAC have some audio that is "upscaled" and not true 24-bit?
Does this happen on every 24-bit file?
@hbtvs59 commented on GitHub (Jan 15, 2026):
When the files are downloaded, they are in 24-bit, but the final file ends up being 16-bit / 44.1 kHz.
This happens with all the files where I select a 24-bit source, whether automatically or manually.
I had the same issue again with:
https://open.spotify.com/album/0JLN7JryQ2T7lBEYIrSQF1
In my folder, I still have the temporary files (fortunately), the .m4a.tmp files, as well as the FLAC files.
The .m4a files are indeed 24-bit / 96 kHz,
but the FLAC files are 16-bit / 44.1 kHz.
I therefore delete the FLAC files and manually convert the .m4a.tmp files to FLAC, which then correctly results in 24-bit / 96 kHz files.
Maybe there could be an option to keep the .m4a files without post-processing, or to check the output conversion settings.
Knowing that by default, ffmpeg, without parameters, will use 44.1 kHz / 16-bit stereo.
I use the following command:
for f in *.m4a.tmp; do
ffmpeg -i "$f" -c:a flac -map_metadata 0 -compression_level 8 "${f%.m4a.flac}"
done
Thank you.
@Silvergish commented on GitHub (Jan 15, 2026):
An option to keep the m4a files would be great! I don't mind converting them to FLAC using FFmpeg myself. I've had a few m4a files not get converted and I'll just convert them "manually".
But one thing I'm not understanding is, some of the 24-bit files that i download that do get converted to FLAC, I always bring the files into a music tagging macOS app called Meta before adding them to my music library. (I like to properly tag every song.) The Meta app tells me that those files are 24-bit FLAC files. Does what you found out mean that those "24-bit" FLAC files are just appearing as 24-bit files to other apps or music software even though they are 16-bit?
What about the increased file size? Is the larger file size just upscaled audio data?
@MolehLuka commented on GitHub (Jan 16, 2026):
If you use spectrogram analysis you can clearly see that the downloaded files aren't true lossless FLAC. It seems to be upscaling/converting, whatever format it's initially downloading, to FLAC which automatically increases the file size and makes it seem as if it's the actual FLAC file. As far as I know there's no way to download the true lossless files as of now.
@ItsNoot3rch commented on GitHub (Jan 16, 2026):
What do I have to be doing to expose the temporary M4A files? I would like to try this for myself!
@hbtvs59 commented on GitHub (Jan 16, 2026):
look your download directory and during the download you have your m4a.tmp file