Editing Converting FLAC audio files

== Mac OS ==

[https://developers.google.com/tag-manager/devguide Recommended software]:

=== ffmpeg ===

This is a command line utility which relies on the `libfdk_aac` library, which is a separate install. See [[#Troubleshooting|troubleshooting]].

[https://trac.ffmpeg.org/wiki/Encode/AAC AAC encoding documentation]

Variable bit rate AAC files seem to come out smaller in size than constant bit rate files.

==== Constant bit rate ====

With AAC, 128k is supposedly indistinguishable from CD quality.

<pre>
$ ffmpeg -i input.flac -c:a libfdk_aac -b:a 128k output.m4a
</pre>

==== Variable bit rate ====

A variable bit rate setting of 3 is supposedly indistinguishable from CD quality.

<pre>
$ ffmpeg -i input.flac -c:a libfdk_aac -vbr 3 output.m4a
</pre>

==== Batch conversion ====

Wrap the `ffmpeg` command in a loop:

<syntaxhighlight lang="bash">
# using mac os's built-in aac library
$ for i in *.flac; do ffmpeg -i "$i" -c:a aac_at -vbr 3 -c:v copy "${i%.*}.m4a"; done
# using libfdk_aac
$ for i in *.flac; do ffmpeg -i "$i" -c:a libfdk_aac -vbr 3 -c:v copy "${i%.*}.m4a"; done
</syntaxhighlight>

==== Troubleshooting ====

===== "Could not find tag for codec h264 in stream #0" =====

AAC output files are 0 bytes after an error to the effect of `Could not find tag for codec h264 in stream #0`. 

Adding `-c:v copy` as a parameter to the `ffmpeg` command fixed this.

===== "Unknown encoder 'libfdk_aac'" with Mac OS =====

Use Mac OS's built in codec (`aac_at`) instead:

<syntaxhighlight lang="bash">
$ ffmpeg -i input.flac -c:a aac_at -vbr 3 output.m4a
</syntaxhighlight>

===== Message that variable bitrate not supported =====

Running `ffmpeg` with `libfdx_aac` results in the following warning: <pre>Note, the VBR setting is unsupported and only works with some parameter combinations</pre>

Use Mac OS's built in codec (`aac_at`) instead:

<syntaxhighlight lang="bash">
$ ffmpeg -i input.flac -c:a aac_at -vbr 3 output.m4a
</syntaxhighlight>

=== Audacity ===

* '''File''' > '''Chains''' > '''Apply Chain'''
* Select '''MP3 Conversion'''
* Click '''Apply to Files...''' button
* Navigate to directory containing FLAC files.
* Select FLAC files to convert.
* Conversion process will start automatically (default conversion rate is 320kps)
* mp3 files are deposited in a directory in the source directory named `cleaned`

=== Other software options ===

* '''[https://tmkk.undo.jp/xld/index_e.html XLD]''' - (X Lossless Decoder) This gets mentioned and recommended a lot 
* xACT (does converting and splitting)
* dBpoweramp
* `ffmpeg` (command line)

== Windows ==

* '''AVS Audio Converter'''
* Drag the `.flac` files into the files pane. 
* Settings
** '''Codec''': mp3
** '''Channels''': stereo
** '''Bitrate''': 192kps
** '''Sample Rate''': 44100 Hz
** '''Sample Size''': 16 bit