mp3fs - Man Page

mounts and transcodes FLACs and OGGs to MP3s on the fly




The mp3fs(1) command will mount the directory IN_DIR on OUT_DIR. Thereafter, accessing OUT_DIR will show the contents of IN_DIR, with all FLAC/Ogg Vorbis files transparently renamed and transcoded to MP3 format upon access.


-b,  -obitrate=RATE

Set the bitrate to use for encoding. Acceptable values for RATE are any which are allowed by the MP3 format. According to the manual for LAME, this means:

For sampling frequencies of 32, 44.1, and 48 kHz, RATE can be among 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, and 320.

For sampling frequencies of 16, 22.05, and 24 kHz, RATE can be among 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, and 160.

When in doubt, it is recommended to choose a bitrate among 96, 112, 128, 160, 192, 224, 256, and 320. If not specified, RATE defaults to 128.

-d,  -odebug

Enable debug output. This will result in a large quantity of diagnostic information being printed to stderr as the program runs. This option will normally not be used. It implies -f.


Run in the foreground instead of detaching from the terminal.

--gainmode,  -ogainmode=MODE

Set mode to use for interpreting ReplayGain tags. The allowed values for MODE are:

0 - Ignore all ReplayGain tags.

1 - Prefer album gain tag, but fall back to track gain if album gain is not present.

2 - Use track gain if present.

--gainref,  -ogainref=REF

Set the reference loudness in decibels to adjust ReplayGain tags. ReplayGain software usually defaults to a loudness of 89 dB, but if this is too quiet, a higher value can be set here, causing adjustment of ReplayGain values in tags.

-h,  --help

Print usage information.

--log_format,  -olog_format=FORMAT

Specify the format to use for log messages, with the following substitutions:

%I - thread ID

%L - log level

%M - log message

%T - time, formatted as YYYY-MM-DD HH:MM:SS

The default is "[%T] tid=%I %L: %M".

--log_maxlevel,  -olog_maxlevel=LEVEL

Set the maximum level of messages to log, either ERROR, INFO, or DEBUG. Defaults to INFO, and forced to DEBUG in debug mode. Note that this does not enable logging; other log flags must be set to specify where to log.

--log_stderr,  -olog_stderr

Output logging messages to stderr. Enabled in debug mode.

--log_syslog,  -olog_syslog

Output logging messages to the system log.

--logfile,  -ologfile=FILE

Set the file to log to. By default, no log file will be written.

--quality,  -oquality=QUALITY

Set quality for encoding, as understood by LAME. The slowest and best quality is 0, while 9 is the fastest and worst quality. The default value is 5, although according to the LAME manual, 2 is recommended.


Force single-threaded operation.

--statcachesize,  -ostatcachesize=SIZE

Set the number of cached stat entries to store. This is needed for reasonable performance when VBR is enabled. Each entry takes 100-200 bytes of memory. Entries are evicted from the cache in least recently used order.

--vbr,  -ovbr

Use variable bit rate encoding. When enabled, the -b or -obitrate options set the maximum bit rate. If enabled, the --statcachesize or -ostatcachesize options are strongly recommended.

-V,  --version

Output version information.


March 2021 mp3fs 1.1.1