FLAC(1) FLAC(1)
14 September 2007
NAME
flac - Free Lossless Audio Codec
SYNOPSIS
flac [ OPTIONS ] [ infile.wav | infile.aiff | infile.raw | infile.flac
| infile.oga | infile.ogg | - ... ]
flac [ -d | --decode | -t | --test | -a | --analyze ] [ OPTIONS ] [
infile.flac | infile.oga | infile.ogg | - ... ]
DESCRIPTION
flac is a command-line tool for encoding, decoding, testing and
analyzing FLAC streams.
OPTIONS
A summary of options is included below. For a complete description,
see the HTML documentation.
GENERAL OPTIONS
-v, --version
Show the flac version number
-h, --help
Show basic usage and a list of all options
-H, --explain
Show detailed explanation of usage and all options
-d, --decode
Decode (the default behavior is to encode)
-t, --test
Test a flac encoded file (same as -d except no decoded file is
written)
-a, --analyze
Analyze a FLAC encoded file (same as -d except an analysis file
is written)
-c, --stdout
Write output to stdout
-s, --silent
Silent mode (do not write runtime encode/decode statistics to
stderr)
--totally-silent
Do not print anything of any kind, including warnings or errors.
The exit code will be the only way to determine successful
- 1 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
completion.
--no-utf8-convert
Do not convert tags from local charset to UTF-8. This is useful
for scripts, and setting tags in situations where the locale is
wrong. This option must appear before any tag options!
-w, --warnings-as-errors
Treat all warnings as errors (which cause flac to terminate with
a non-zero exit code).
-f, --force
Force overwriting of output files. By default, flac warns that
the output file already exists and continues to the next file.
-o filename, --output-name=filename
Force the output file name (usually flac just changes the
extension). May only be used when encoding a single file. May
not be used in conjunction with --output-prefix.
--output-prefix=string
Prefix each output file name with the given string. This can be
useful for encoding or decoding files to a different directory.
Make sure if your string is a path name that it ends with a
trailing `/' (slash).
--delete-input-file
Automatically delete the input file after a successful encode or
decode. If there was an error (including a verify error) the
input file is left intact.
--keep-foreign-metadata
If encoding, save WAVE or AIFF non-audio chunks in FLAC metadata.
If decoding, restore any saved non-audio chunks from FLAC
metadata when writing the decoded file. Foreign metadata cannot
be transcoded, e.g. WAVE chunks saved in a FLAC file cannot be
restored when decoding to AIFF. Input and output must be regular
files (not stdin or stdout).
--skip={#|mm:ss.ss}
Skip over the first number of samples of the input. This works
for both encoding and decoding, but not testing. The alternative
form mm:ss.ss can be used to specify minutes, seconds, and
fractions of a second.
--until={#|[+|-]mm:ss.ss}
Stop at the given sample number for each input file. This works
for both encoding and decoding, but not testing. The given
sample number is not included in the decoded output. The
alternative form mm:ss.ss can be used to specify minutes,
seconds, and fractions of a second. If a `+' (plus) sign is at
- 2 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
the beginning, the --until point is relative to the --skip point.
If a `-' (minus) sign is at the beginning, the --until point is
relative to end of the audio.
--ogg
When encoding, generate Ogg FLAC output instead of native FLAC.
Ogg FLAC streams are FLAC streams wrapped in an Ogg transport
layer. The resulting file should have an '.oga' extension and
will still be decodable by flac.
When decoding, force the input to be treated as Ogg FLAC. This
is useful when piping input from stdin or when the filename does
not end in '.oga' or '.ogg'.
--serial-number=#
When used with --ogg, specifies the serial number to use for the
first Ogg FLAC stream, which is then incremented for each
additional stream. When encoding and no serial number is given,
flac uses a random number for the first stream, then increments
it for each additional stream. When decoding and no number is
given, flac uses the serial number of the first page.
ANALYSIS OPTIONS
--residual-text
Includes the residual signal in the analysis file. This will
make the file very big, much larger than even the decoded file.
--residual-gnuplot
Generates a gnuplot file for every subframe; each file will
contain the residual distribution of the subframe. This will
create a lot of files.
DECODING OPTIONS
--cue=[#.#][-[#.#]]
Set the beginning and ending cuepoints to decode. The optional
first #.# is the track and index point at which decoding will
start; the default is the beginning of the stream. The optional
second #.# is the track and index point at which decoding will
end; the default is the end of the stream. If the cuepoint does
not exist, the closest one before it (for the start point) or
after it (for the end point) will be used. If those don't exist,
the start of the stream (for the start point) or end of the
stream (for the end point) will be used. The cuepoints are
merely translated into sample numbers then used as --skip and --
until. A CD track can always be cued by, for example, --
cue=9.1-10.1 for track 9, even if the CD has no 10th track.
-F, --decode-through-errors
By default flac stops decoding with an error and removes the
partially decoded file if it encounters a bitstream error. With
-F, errors are still printed but flac will continue decoding to
- 3 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
completion. Note that errors may cause the decoded audio to be
missing some samples or have silent sections.
ENCODING OPTIONS
-V, --verify
Verify a correct encoding by decoding the output in parallel and
comparing to the original
--lax
Allow encoder to generate non-Subset files. The resulting FLAC
file may not be streamable or might have trouble being played in
all players (especially hardware devices), so you should only use
this option in combination with custom encoding options meant for
archival.
--replay-gain
Calculate ReplayGain values and store them as FLAC tags, similar
to vorbisgain. Title gains/peaks will be computed for each input
file, and an album gain/peak will be computed for all files. All
input files must have the same resolution, sample rate, and
number of channels. Only mono and stereo files are allowed, and
the sample rate must be one of 8, 11.025, 12, 16, 22.05, 24, 32,
44.1, or 48 kHz. Also note that this option may leave a few
extra bytes in a PADDING block as the exact size of the tags is
not known until all files are processed. Note that this option
cannot be used when encoding to standard output (stdout).
--cuesheet=filename
Import the given cuesheet file and store it in a CUESHEET
metadata block. This option may only be used when encoding a
single file. A seekpoint will be added for each index point in
the cuesheet to the SEEKTABLE unless --no-cued-seekpoints is
specified.
--picture={FILENAME|SPECIFICATION}
Import a picture and store it in a PICTURE metadata block. More
than one --picture command can be specified. Either a filename
for the picture file or a more complete specification form can be
used. The SPECIFICATION is a string whose parts are separated by
| (pipe) characters. Some parts may be left empty to invoke
default values. FILENAME is just shorthand for "||||FILENAME".
The format of SPECIFICATION is
[TYPE]|[MIME-
TYPE]|[DESCRIPTION]|[WIDTHxHEIGHTxDEPTH[/COLORS]]|FILE
TYPE is optional; it is a number from one of:
0: Other
1: 32x32 pixels 'file icon' (PNG only)
- 4 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
2: Other file icon
3: Cover (front)
4: Cover (back)
5: Leaflet page
6: Media (e.g. label side of CD)
7: Lead artist/lead performer/soloist
8: Artist/performer
9: Conductor
10: Band/Orchestra
11: Composer
12: Lyricist/text writer
13: Recording Location
14: During recording
15: During performance
16: Movie/video screen capture
17: A bright coloured fish
18: Illustration
19: Band/artist logotype
20: Publisher/Studio logotype
The default is 3 (front cover). There may only be one picture
each of type 1 and 2 in a file.
MIME-TYPE is optional; if left blank, it will be detected from
the file. For best compatibility with players, use pictures with
MIME type image/jpeg or image/png. The MIME type can also be -->
to mean that FILE is actually a URL to an image, though this use
is discouraged.
DESCRIPTION is optional; the default is an empty string.
The next part specfies the resolution and color information. If
the MIME-TYPE is image/jpeg, image/png, or image/gif, you can
- 5 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
usually leave this empty and they can be detected from the file.
Otherwise, you must specify the width in pixels, height in
pixels, and color depth in bits-per-pixel. If the image has
indexed colors you should also specify the number of colors used.
When manually specified, it is not checked against the file for
accuracy.
FILE is the path to the picture file to be imported, or the URL
if MIME type is -->
For example, "|image/jpeg|||../cover.jpg" will embed the JPEG
file at ../cover.jpg, defaulting to type 3 (front cover) and an
empty description. The resolution and color info will be
retrieved from the file itself.
The specification "4|--
>|CD|320x300x24/173|http://blah.blah/backcover.tiff" will embed
the given URL, with type 4 (back cover), description "CD", and a
manually specified resolution of 320x300, 24 bits-per-pixel, and
173 colors. The file at the URL will not be fetched; the URL
itself is stored in the PICTURE metadata block.
--sector-align
Align encoding of multiple CD format files on sector boundaries.
See the HTML documentation for more information.
-S {#|X|#x|#s}, --seekpoint={#|X|#x|#s}
Include a point or points in a SEEKTABLE. Using #, a seek point
at that sample number is added. Using X, a placeholder point is
added at the end of a the table. Using #x, # evenly spaced seek
points will be added, the first being at sample 0. Using #s, a
seekpoint will be added every # seconds (# does not have to be a
whole number; it can be, for example, 9.5, meaning a seekpoint
every 9.5 seconds). You may use many -S options; the resulting
SEEKTABLE will be the unique-ified union of all such values.
With no -S options, flac defaults to '-S 10s'. Use --no-
seektable for no SEEKTABLE. Note: '-S #x' and '-S #s' will not
work if the encoder can't determine the input size before
starting. Note: if you use '-S #' and # is >= samples in the
input, there will be either no seek point entered (if the input
size is determinable before encoding starts) or a placeholder
point (if input size is not determinable).
-P #, --padding=#
Tell the encoder to write a PADDING metadata block of the given
length (in bytes) after the STREAMINFO block. This is useful if
you plan to tag the file later with an APPLICATION block; instead
of having to rewrite the entire file later just to insert your
block, you can write directly over the PADDING block. Note that
the total length of the PADDING block will be 4 bytes longer than
the length given because of the 4 metadata block header bytes.
- 6 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
You can force no PADDING block at all to be written with --no-
padding. The encoder writes a PADDING block of 8192 bytes by
default (or 65536 bytes if the input audio stream is more that 20
minutes long).
-T FIELD=VALUE, --tag=FIELD=VALUE
Add a FLAC tag. The comment must adhere to the Vorbis comment
spec; i.e. the FIELD must contain only legal characters,
terminated by an 'equals' sign. Make sure to quote the comment
if necessary. This option may appear more than once to add
several comments. NOTE: all tags will be added to all encoded
files.
--tag-from-file=FIELD=FILENAME
Like --tag, except FILENAME is a file whose contents will be read
verbatim to set the tag value. The contents will be converted to
UTF-8 from the local charset. This can be used to store a
cuesheet in a tag (e.g. --tag-from-file="CUESHEET=image.cue").
Do not try to store binary data in tag fields! Use APPLICATION
blocks for that.
-b #, --blocksize=#
Specify the block size in samples. Subset streams must use one
of 192, 576, 1152, 2304, 4608, 256, 512, 1024, 2048, 4096 (and
8192 or 16384 if the sample rate is >48kHz).
-m, --mid-side
Try mid-side coding for each frame (stereo input only)
-M, --adaptive-mid-side
Adaptive mid-side coding for all frames (stereo input only)
-0..-8, --compression-level-0..--compression-level-8
Fastest compression..highest compression (default is -5). These
are synonyms for other options:
-0, --compression-level-0
Synonymous with -l 0 -b 1152 -r 3
-1, --compression-level-1
Synonymous with -l 0 -b 1152 -M -r 3
-2, --compression-level-2
Synonymous with -l 0 -b 1152 -m -r 3
-3, --compression-level-3
Synonymous with -l 6 -b 4096 -r 4
-4, --compression-level-4
Synonymous with -l 8 -b 4096 -M -r 4
- 7 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
-5, --compression-level-5
Synonymous with -l 8 -b 4096 -m -r 5
-6, --compression-level-6
Synonymous with -l 8 -b 4096 -m -r 6
-7, --compression-level-7
Synonymous with -l 8 -b 4096 -m -e -r 6
-8, --compression-level-8
Synonymous with -l 12 -b 4096 -m -e -r 6
--fast
Fastest compression. Currently synonymous with -0.
--best
Highest compression. Currently synonymous with -8.
-e, --exhaustive-model-search
Do exhaustive model search (expensive!)
-A function, --apodization=function
Window audio data with given the apodization function. The
functions are: bartlett, bartlett_hann, blackman,
blackman_harris_4term_92db, connes, flattop, gauss(STDDEV),
hamming, hann, kaiser_bessel, nuttall, rectangle, triangle,
tukey(P), welch.
For gauss(STDDEV), STDDEV is the standard deviation
(0<STDDEV<=0.5).
For tukey(P), P specifies the fraction of the window that is
tapered (0<=P<=1; P=0 corresponds to "rectangle" and P=1
corresponds to "hann").
More than one -A option (up to 32) may be used. Any function
that is specified erroneously is silently dropped. The encoder
chooses suitable defaults in the absence of any -A options; any
-A option specified replaces the default(s).
When more than one function is specified, then for every subframe
the encoder will try each of them separately and choose the
window that results in the smallest compressed subframe.
Multiple functions can greatly increase the encoding time.
-l #, --max-lpc-order=#
Specifies the maximum LPC order. This number must be <= 32. For
Subset streams, it must be <=12 if the sample rate is <=48kHz. If
0, the encoder will not attempt generic linear prediction, and
use only fixed predictors. Using fixed predictors is faster but
usually results in files being 5-10% larger.
- 8 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
-p, --qlp-coeff-precision-search
Do exhaustive search of LP coefficient quantization (expensive!).
Overrides -q; does nothing if using -l 0
-q #, --qlp-coeff-precision=#
Precision of the quantized linear-predictor coefficients, 0 =>
let encoder decide (min is 5, default is 0)
-r [#,]#, --rice-partition-order=[#,]#
Set the [min,]max residual partition order (0..16). min defaults
to 0 if unspecified. Default is -r 5.
FORMAT OPTIONS
--endian={big|little}
Set the byte order for samples
--channels=#
Set number of channels.
--bps=#
Set bits per sample.
--sample-rate=#
Set sample rate (in Hz).
--sign={signed|unsigned}
Set the sign of samples (the default is signed).
--input-size=#
Specify the size of the raw input in bytes. If you are encoding
raw samples from stdin, you must set this option in order to be
able to use --skip, --until, --cue-sheet, or other options that
need to know the size of the input beforehand. If the size given
is greater than what is found in the input stream, the encoder
will complain about an unexpected end-of-file. If the size given
is less, samples will be truncated.
--force-aiff-format
Force the decoder to output AIFF format. This option is not
needed if the output filename (as set by -o) ends with .aiff.
Also, this option has no effect when encoding since input AIFF is
auto-detected.
--force-raw-format
Force input (when encoding) or output (when decoding) to be
treated as raw samples (even if filename ends in .wav).
NEGATIVE OPTIONS
--no-adaptive-mid-side
- 9 - Formatted: October 27, 2025
FLAC(1) FLAC(1)
14 September 2007
--no-decode-through-errors
--no-delete-input-file
--no-exhaustive-model-search
--no-lax
--no-mid-side
--no-ogg
--no-padding
--no-qlp-coeff-precision-search
--no-residual-gnuplot
--no-residual-text
--no-sector-align
--no-seektable
--no-silent
--no-verify
--no-warnings-as-errors
These flags can be used to invert the sense of the corresponding
normal option.
SEE ALSO
metaflac(1).
The programs are documented fully by HTML format documentation,
available in /usr/share/doc/flac/html on Debian GNU/Linux systems.
AUTHOR
This manual page was written by Matt Zimmerman <mdz@debian.org> for
the Debian GNU/Linux system (but may be used by others).
- 10 - Formatted: October 27, 2025
