Convert lossless m4a to flac

Question

I tried to convert a file with pacpl, but I get the well-known "256" error. With the -v flag, the FAQ of pacpl tells me:

"The file you are trying to convert is a lossless .m4a file. The format is not yet supported by FAAC/FAAD."

Since faac/faad seems to be used in every other converting tool on Ubuntu, how can I successfully convert formats?

How is the lossless m4a a 24 bit sample? CD's are 16 bit, and SACD's are not rippable by any means, which means it was pointlessly "upconverted" to 24 bit, which is stupid. — , Jan 29 '13 at 03:25

score 31 · Accepted Answer · edited Oct 15 '17 at 05:56

31

You can convert an m4a file to flac with the ffmpeg command-line tool:

To install ffmpeg:

sudo apt-get install ffmpeg

To convert:

ffmpeg -i filein.m4a -f flac fileout.flac

edited Oct 15 '17 at 05:56

David Foerster

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answered Jan 15 '12 at 21:56

duffydack

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works for me:) Hopefully the pacpl devs will fix the problem – Simon Lenz Jan 15 '12 at 22:38
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`` for file in *.m4a; do echo $file; ffmpeg -i "$file" -f flac "`basename "$file" .m4a`.flac"; done `` To do a batch conversion of all *.m4a files in directory. – zetdotpi Jun 13 '13 at 00:04

score 13 · Answer 2 · answered Apr 27 '12 at 14:56

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sudo aptitude install libav-tools

for file in *.m4a; do avconv -i "$file" -f flac "`basename "$file" .m4a`.flac"; done

answered Apr 27 '12 at 14:56

Sociologist

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score 4 · Answer 3 · answered Aug 16 '12 at 17:50

While both the answers involving ffmpeg/avconv (which I think are essentially the same tool) both work, they currently have a flaw. Namely that lossless m4a is often 24 bit sample, and currently ffmpeg/avconv will generally force the conversion to end up in 16 bit sample.

I believe using sndfile-convert (libsndfile) does not have this problem. Likewise, I believe it can be avoided by using mplayer to decode the m4a before encoding it with ffmpeg or flac. I think soundKonverter on KDE may do this for you.

In any case, whatever you do, I suggest checking whether the original and the converted file have the same bit depth of samples.

But sndfile-convert can not read iTunes AAC-LC. – Martin Schröder Nov 30 '12 at 18:49 — Martin Schröder, Nov 30 '12 at 18:49

score 1 · Answer 4 · answered Feb 08 '21 at 11:53

Personally I use this code. for file in *.m4a; do fname=$(basename "$file" .m4a); ffmpeg -i "$file" -vn -ar 48000 -f flac "$fname".flac; done.

So the output file don't have *.m4a.flac as extension.

And this is the ouput from ffprobe on a flac file:
Stream #0:0: Audio: flac, 48000 Hz, stereo, s32 (24 bit)
And don't forget to check the tags/metadata on the file. I was surprised to see my mail address in the tag/metadata. And ffprobe show more mtag/metada as Easytag.

thanks to zetdotpi and https://stackoverflow.com/a/2664758

Also, conversion from m4a to flac does seem to lose a metadata picture that was written to the files. — bomben, Jun 03 '21 at 07:15

score 0 · Answer 5 · answered Dec 20 '20 at 19:52

Just combining all the useful information from the other three answers.

To check the bit depth on your mp4 files:

# cd into desired directory then... 
ffprobe -show_streams ./[pick one file to test].m4a | grep -e codec_name -e bits_per_raw_sample

This should show the bit depth at the bottom of the output.

To use ffmpeg and for all files in a folder (assuming they are not 24 bit (or higher)):

# cd into desired directory then... 
for file in *.m4a ; do ffmpeg -i "$file" -f flac "$( basename "$file" .m4a ).flac" ; done

Hope that helps.

Convert lossless m4a to flac

5 Answers5