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% FDKAAC(1)
% nu774 <honeycomb77@gmail.com>
% November, 2013
NAME
====
fdkaac - command line frontend for libfdk-aac encoder
SYNOPSIS
========
**fdkaac** [OPTIONS] [FILE]
DESCRIPTION
===========
**fdkaac** reads linear PCM audio in either WAV, raw PCM, or CAF format,
and encodes it into either M4A / AAC file.
If the input file is "-", data is read from stdin. Likewise, if the
output file is "-", data is written to stdout if one of streamable AAC
transport formats are selected by **-f**.
When CAF input and M4A output is used, tags in CAF file are copied into
the resulting M4A.
OPTIONS
=======
-h, --help
: Show command help
-o \<FILE\>
: Output filename.
-p, --profile \<n\>
: Target profile (MPEG4 audio object type, AOT)
2
: MPEG-4 AAC LC (default)
5
: MPEG-4 HE-AAC (SBR)
29
: MPEG-4 HE-AAC v2 (SBR+PS)
23
: MPEG-4 AAC LD
39
: MPEG-4 AAC ELD
-b, --bitrate \<n\>
: Target bitrate (for CBR)
-m, --bitrate-mode \<n\>
: Bitrate configuration mode. Available VBR quality value depends on
other parameters such as profile, sample rate, or number of
channels.
0
: CBR (default)
1-5
: VBR (higher value -\> higher bitrate)
-w, --bandwidth \<n\>
: Frequency bandwidth (lowpass cut-off frequency) in Hz. Available on
AAC LC only.
-a, --afterburner \<n\>
: Configure afterburner mode. When enabled, quality is increased at
the expense of additional computational workload.
0
: Off
1
: On (default)
-L, --lowdelay-sbr \<n\>
: Configure SBR activity on AAC ELD.
-1
: Use ELD SBR auto configuration
0
: Disable SBR on ELD (default)
1
: Enable SBR on ELD
-s, --sbr-ratio \<n\>
: Controls activation of downsampled SBR.
0
: Use lib default (default)
1
: Use downsampled SBR (default for ELD+SBR)
2
: Use dual-rate SBR (default for HE-AAC)
Dual-rate SBR is what is normally used for HE-AAC, where AAC is
encoded at half the sample rate of SBR, hence "dual rate". On the
other hand, downsampled SBR uses same sample rate for both of AAC
and SBR (single rate), therefore downsampled SBR typically consumes
more bitrate.
Downsampled SBR is newly introduced feature in FDK encoder library
version 3.4.12. When libfdk-aac in the system doesn't support this,
dual-rate SBR will be used. When available, dual-rate SBR is the
default for HE-AAC and downsampled SBR is the default for ELD+SBR.
Note that downsampled HE-AAC is not so common as dual-rate one. When
downsampled HE-AAC is selected, **fdkaac** is forced to choose
explicit hierarchical SBR signaling, which (at least) iTunes doesn't
accept.
-f, --transport-format \<n\>
: Transport format. Tagging and gapless playback is only available on
M4A. Streaming to stdout is only available on others.
0
: M4A (default)
1
: ADIF
2
: ADTS
6
: LATM MCP=1
7
: LATM MCP=0
10
: LOAS/LATM (LATM within LOAS)
-C, --adts-crc-check
: Add CRC protection on ADTS header.
-h, --header-period \<n\>
: StreamMuxConfig/PCE repetition period in the transport layer.
-G, --gapless-mode \<n\>
: Method to declare amount of encoder delay (and padding) in M4A
container. These values are mandatory for proper gapless playback on
player side.
0
: iTunSMPB (default)
1
: ISO standard (edts and sgpd)
2
: Both
--include-sbr-delay
: When specified, count SBR decoder delay in encoder delay.
This is not iTunes compatible and will lead to gapless playback
issue on LC only decoder, but this is the default behavior of FDK
library.
Whether counting SBR decoder delay in encoder delay or not result in
incompatibility in gapless playback. You should pick which one will
work for your favorite player.
However, it's better not to choose SBR at all if you want gapless
playback. LC doesn't have such issues.
-I, --ignorelength
: Ignore length field of data chunk in input WAV file.
-S, --silent
: Don't print progress messages.
--moov-before-mdat
: Place moov box before mdat box in M4A container. This option might
be important for some hardware players, that are known to refuse
moov box placed after mdat box.
-R, --raw
: Regard input as raw PCM.
--raw-channels \<n\>
: Specify number of channels of raw input (default: 2)
--raw-rate \<n\>
: Specify sample rate of raw input (default: 44100)
--raw-format \<spec\>
: Specify sample format of raw input (default: "S16L"). **Spec** is as
the following (case insensitive):
1st char -- type of sample
: **S** (igned) | **U** (nsigned) | **F** (loat)
2nd part (in digits)
: bits per channel
Last char -- endianness (can be omitted)
: **L** (ittle, default) | **B** (ig)
--title \<string\>
: Set title tag.
--artist \<string\>
: Set artist tag.
--album \<string\>
: Set album tag.
--genre \<string\>
: Set genre tag.
--date \<string\>
: Set date tag.
--composer \<string\>
: Set composer tag.
--grouping \<string\>
: Set grouping tag.
--comment \<string\>
: Set comment tag.
--album-artist \<string\>
: Set album artist tag.
--track \<number[/total]\>
: Set track tag, with or without number of total tracks.
--disk \<number[/total]\>
: Set disk tag, with or without number of total discs.
--tempo \<n\>
: Set tempo (BPM) tag.
--tag \<fcc\>:\<value\>
: Set iTunes predefined tag with explicit fourcc key and value. See
[https://code.google.com/p/mp4v2/wiki/iTunesMetadata](https://code.google.com/p/mp4v2/wiki/iTunesMetadata)
for known predefined keys. You can omit first char of **fcc** when
it is the copyright sign.
--tag-from-file \<fcc\>:\<filename\>
: Same as --tag, but set content of file as tag value.
--long-tag \<name\>:\<value\>
: Set arbitrary tag as iTunes custom metadata. Stored in
com.apple.iTunes field.
--tag-from-json \<filename[?dot\_notation]\>
: Read tags from JSON. By default, tags are assumed to be direct
children of the root object in JSON. Optionally you can specify
arbitrary dot notation to locate the object containing tags.
EXAMPLES
========
Encode WAV file into a M4A file. MPEG4 AAC LC, VBR quality 3:
fdkaac -m3 foo.wav
Encode WAV file into a M4A file. MPEG4 HE-AAC, bitrate 64kbps:
fdkaac -p5 -b64 foo.wav
Piping from **ffmpeg** (you need version supporting CAF output):
ffmpeg -i foo.flac -f caf - | fdkaac -b128 - -o foo.m4a
Import tags via json:
ffprobe -v 0 -of json -show_format foo.flac >foo.json
flac -dc foo.flac | \
fdkaac - -ox.m4a -m2 --import-tag-from-json=foo.json?format.tags
NOTES
=====
Upto 32bit integer or 64bit floating point format is supported as input.
However, FDK library is implemented based on fixed point math and only
supports 16bit integer PCM. Therefore, be wary of clipping. You might
want to dither/noise shape beforehand when your input has higher
resolution.
Following channel layouts are supported by the encoder.
1ch
: C
2ch
: L R
3ch
: C L R
4ch
: C L R Cs
5ch
: C L R Ls Rs
5.1ch
: C L R Ls Rs LFE
7.1ch (front)
: C Lc Rc L R Ls Rs LFE
7.1ch (rear)
: C L R Ls Rs Rls Rrs LFE