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flac — Free Lossless Audio Codec


flac [OPTIONS] [infile.wav | infile.rf64 | infile.aiff | infile.raw | infile.flac |
infile.oga | infile.ogg | - ] ...

flac [-d | --decode | -t | --test | -a | --analyze ] [OPTIONS] [infile.flac |
infile.oga | infile.ogg | - ] ...


flac is a command-line tool for encoding, decoding, testing and analyzing FLAC streams.


A summary of options is included below. For a complete description, see the HTML

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)

Do not print anything of any kind, including warnings or errors. The exit code
will be the only way to determine successful completion.

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

-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

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).

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.

Output files have their timestamps/permissions set to match those of their
inputs (this is default). Use --no-preserve-modtime to make output files have
the current time and default permissions.

If encoding, save WAVE, RF64, 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 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.

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 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'.

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
Includes the residual signal in the analysis file. This will make the file very
big, much larger than even the decoded file.

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
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 completion. Note that errors may cause the
decoded audio to be missing some samples or have silent sections.

Applies ReplayGain values while decoding.


The equals sign and <specification> is optional. If omitted, the default is

The <specification> is a shorthand notation for describing how to apply
ReplayGain. All components are optional but order is important. '[]' means
'optional'. '|' means 'or'. '{}' means required. The format is:


preamp A floating point number in dB. This is added to the existing gain

a|t Specify 'a' to use the album gain, or 't' to use the track gain. If
tags for the preferred kind (album/track) do not exist but tags for
the other (track/album) do, those will be used instead.

l|L Specify 'l' to peak-limit the output, so that the ReplayGain peak
value is full-scale. Specify 'L' to use a 6dB hard limiter that kicks
in when the signal approaches full-scale.

Specify the amount of noise shaping. ReplayGain synthesis happens in
floating point; the result is dithered before converting back to
integer. This quantization adds noise. Noise shaping tries to move
the noise where you won't hear it as much. 0 means no noise shaping,
1 means 'low', 2 means 'medium', 3 means 'high'.

For example, the default of 0aLn1 means 0dB preamp, use album gain, 6dB hard
limit, low noise shaping.

--apply-replaygain-which-is-not-lossless=3 means 3dB preamp, use album gain, no
limiting, no noise shaping.

flac uses the ReplayGain tags for the calculation. If a stream does not have
the required tags or they can't be parsed, decoding will continue with a
warning, and no ReplayGain is applied to that stream.

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.

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).

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.

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 is optional; it is a number from one of:

0: Other

1: 32x32 pixels 'file icon' (PNG only)

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 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" loading="lazy" 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

Align encoding of multiple CD format files on sector boundaries. See the HTML
documentation for more information. This option is DEPRECATED and may not exist
in future versions of flac.

When encoding to flac, ignore the file size headers in WAV and AIFF files to
attempt to work around problems with over-sized or malformed files.

WAV and AIFF files both have an unsigned 32 bit numbers in the file header which
specifes the length of audio data. Since this number is unsigned 32 bits, that
limits the size of a valid file to being just over 4 Gigabytes. Files larger
than this are mal-formed, but should be read correctly using this option.

-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. 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).

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.

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

-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 -A tukey(0.5) -A partial_tukey(2)

-7, --compression-level-7
Synonymous with -l 8 -b 4096 -m -e -r 6 -A tukey(0.5) -A

-8, --compression-level-8
Synonymous with -l 12 -b 4096 -m -e -r 6 -A tukey(0.5) -A
partial_tukey(2) -A punchout_tukey(3)

--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), partial_tukey(n[/ov[/P]]), punchout_tukey(n[/ov[/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").

For partial_tukey(n) and punchout_tukey(n), n apodization functions are added
that span different parts of each block. Values of 2 to 6 seem to yield sane
results. If necessary, an overlap can be specified, as can be the taper
parameter, for example partial_tukey(2/0.2) or partial_tukey(2/0.2/0.5). ov
should be smaller than 1 and can be negative.

Please note that P, STDDEV and ov are locale specific, so a comma as decimal
separator might be required instead of a dot.

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.

-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..15). min defaults to 0 if
unspecified. Default is -r 5.

Format Options
Set the byte order for samples

Set number of channels.

--bps=# Set bits per sample.

Set sample rate (in Hz).

Set the sign of samples (the default is signed).

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,
--cuesheet, 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 input (when encoding) or output (when decoding) to be treated as raw
samples (even if filename ends in .wav).

Force the decoder to output AIFF format. This option is not needed if the
output filename (as set by -o) ends with .aif or .aiff. Also, this option has
no effect when encoding since input AIFF is auto-detected.

Force the decoder to output RF64 format. This option is not needed if the
output filename (as set by -o) ends with .rf64. Also, this option has no effect
when encoding since input RF64 is auto-detected.

Force the decoder to output Wave64 format. This option is not needed if the
output filename (as set by -o) ends with .w64. Also, this option has no effect
when encoding since input Wave64 is auto-detected.

Negative Options




















These flags can be used to invert the sense of the corresponding normal option.

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