qaac

nu774/qaac

CLI QuickTime AAC/ALAC encoder

Latest release

v3.07Sep 10, 2026

Last commit

Sep 10, 2026

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999

qaac is a command-line frontend to Apple’s Core Audio AAC encoder. Apple’s encoder is generally regarded as the best AAC encoder available, which is why people use qaac on Windows: it gives you Apple’s AAC-LC, HE-AAC and ALAC from a normal command line, without iTunes.

It is Windows-only. The Apple encoder itself is not bundled and not redistributable, so it has to come from an Apple installer. On macOS use afconvert (or FFmpeg’s aac_at) instead. On Linux the repository only builds refalac, the ALAC-only sibling.

Install

1. Download qaac_3.07.zip from the GitHub releases. It contains 32-bit (x86) and 64-bit (x64) builds; use qaac64.exe on 64-bit Windows.
2. Get Apple Application Support (it contains CoreAudioToolbox.dll). Download the iTunes installer from Apple’s “other versions” link, not the Microsoft Store version, which does not work. You do not have to install iTunes: unpack the installer with 7-Zip and install the AppleApplicationSupport64.msi inside, or just install iTunes.
3. Optionally add libFLAC.dll, wavpackdll.dll or libsndfile DLLs next to qaac64.exe so qaac can read FLAC, WavPack and others directly. Without them, pipe the input from FFmpeg.

Run qaac64 --check to see the loaded Apple library versions and qaac64 --formats to list the rate and channel combinations your installation supports.

Caution

CoreAudioToolbox 7.9.8 and newer (through at least 7.10.9.0) can put glitches in AAC CBR output, according to the qaac README. Avoid --cbr; the problem was only found in CBR mode.

Good settings

True VBR (--tvbr, quality 0–127) is the normal choice for music. The resulting bitrate depends on the material. Typical stereo music averages, measured on Hydrogenaudio and quoted on Doom9:

—tvbr	Approx. kbit/s (stereo)
127	320
109	255
91	195
82	165
73	150
64	135

The default for AAC-LC is --tvbr 90. Apple’s encoder snaps the value to 15 steps (0, 9, 18 … 91, 100, 109, 118, 127), so 90 and the often-quoted 91 encode identically; step up to 100 or 109 for more margin. 127 only makes sense if you want the largest file the encoder can produce. Multichannel sources scale up a lot (a 5.1 file at --tvbr 91 ran at roughly 450 kbit/s in the same thread).

qaac64 --tvbr 91 -o output.m4a input.wav
ffmpeg -i input.flac -f wav - | qaac64 --tvbr 91 -o output.m4a -

--quality (0–2, default 2) is encoder effort, not an audio-quality setting; leave it at 2.

HE-AAC has no TVBR; use constrained VBR with a bitrate:

qaac64 --he --cvbr 64 -o he-aac.m4a input.wav

Apple ALAC (lossless) is qaac64 -A -o output.m4a input.wav.

Things that bite

• Only one rate mode (--tvbr, --abr, --cvbr, --cbr) may be given.
• qaac keeps the input sample rate when it can (-r keep). Pass -r 48000, or -r auto to let the encoder choose.
• Gapless playback metadata is written in iTunes style by default. --no-smart-padding disables the boundary extrapolation that makes gapless transitions smooth; it exists as a workaround for a Core Audio HE-AAC bug, and can break gapless playback.
• --drc and --gain change the audio samples; they do not write AAC metadata.
• -o - writes to stdout only for ADTS or WAV output, not M4A.

Full option reference

Every qaac 3.07 option, with defaults from the option parser. Which sample rates, bitrates and HE-AAC modes are accepted depends on the installed Apple encoder; --formats lists them. The --fast switch in the source belongs to refalac, not qaac.

Codec, rate, and container

Pick one of -V, -a, -v or -c; qaac rejects more than one.

Parameter	Default	Values / units	Effect
-V, --tvbr N	90 (the default mode for AAC-LC)	0–127	True VBR quality. Apple uses 15 steps (0, 9, 18, 27, 36, 45, 54, 63, 73, 82, 91, 100, 109, 118, 127) and maps other values onto them, so 90 encodes as q91. Not available with --he.
-a, --abr N	Off	kbit/s; 0 = highest available	Average bitrate.
-v, --cvbr N	Off; 0 with --he	kbit/s; 0 = highest available	Constrained VBR. The default mode for HE-AAC.
-c, --cbr N	Off	kbit/s; 0 = highest available	Constant bitrate.
--he	Off (AAC-LC)	Flag	HE-AAC (SBR). TVBR is unavailable, so the default becomes -v 0.
-q, --quality N	2	0–2	Encoder effort; 2 is slowest and best. Separate from the TVBR quality.
-A, --alac	Off	Flag	Encode ALAC (lossless) instead of AAC.
-D, --decode	Off	Flag	Decode to WAV instead of encoding.
--play	Off	Flag	Decode and play to a WaveOut device.
--peak	Off	Flag	Print the peak level after any DSP options; writes no file. Can’t be combined with an encoding mode or -D.
--adts	Off (M4A)	Flag	Write raw ADTS instead of M4A. AAC only.
--caf	Off	Flag	Write CAF instead of M4A, WAV or ADTS. Not with --adts.
--no-optimize	Off	Flag	Accepted, but has no effect in 3.x.
--no-smart-padding	Off	Flag	Disable the extrapolation at the start and end that gives smooth gapless transitions. Output then matches iTunes bit for bit, but gapless playback can suffer, especially with HE-AAC. Can’t be combined with --num-priming.
--gapless-mode N	0	0 iTunSMPB, 1 ISO (elst + sbgp + sgpd), 2 both	How encoder delay and padding are signalled.
--num-priming N	2112	0–2112 samples	Experimental: change the AAC-LC encoder delay (priming). LC only.
--no-delay	Off	Flag	Same as --num-priming 0: prepends 960 samples of silence and trims the first three AAC frames so the output has no encoder delay. Intended for A/V sync in video.

PCM processing, sampling, and channels

Parameter	Default	Values / units	Effect
-r, --rate VALUE	keep	keep, auto or Hz	Output sample rate: keep the input rate where the encoder supports it, let the encoder choose, or resample to the given rate.
--lowpass N	0 (Apple default)	Hz	Use a lower cut-off than Apple’s default.
--native-resampler[=MODE,QUALITY]	Off	line, norm or bats, then quality 0–127	Use Core Audio’s resampler instead of libsoxr. Without arguments it uses bats (best), quality 0. Arguments must follow =, e.g. --native-resampler=norm,96.
--builtin-resampler	Off	Flag	Use qaac’s built-in polyphase resampler instead of libsoxr. It is used anyway when libsoxr is missing.
-b, --bits-per-sample N	From input	2–32	Output bit depth, WAV and ALAC only.
--no-dither	Off	Flag	Don’t dither when reducing bit depth.
--gain N	0	dB	Change the level; use a negative value to avoid clipping after DSP.
-N, --normalize	Off	Flag	Peak-normalize in two passes. Piped input is spooled to a temporary file, which can be huge.
--drc SPEC	Off	threshold:ratio:knee:attack:release[:statfile]	Dynamic range compressor applied to the samples: threshold below 0 dBFS, ratio above 1, knee in dB, attack and release in ms. Repeatable.
--limiter	Off	Flag	Soft-clip peaks that reach about 0 dBFS.
--matrix-preset NAME	None	Preset name	Remix channels with a user-defined matrix preset.
--matrix-file FILE	None	Filename	Remix channels with coefficients from a file.
--no-matrix-normalize	Off	Flag	Don’t normalize the matrix coefficients.
--chanmap LIST	Input order	1-based list, e.g. 2,1	Reorder input channels; 2,1 swaps left and right.
--chanmask N	From input	Decimal or 0x hex; 0 ignores the input mask	Override the input channel mask (speaker layout). Doesn’t remix.

Trimming and input interpretation

Parameter	Default	Values / units	Effect
--start TIME	Start of input	[[hh:]mm:]ss[.sss], <n>s (samples) or <mm:ss:ff>f (cue frames)	Start point. A negative value prepends silence instead.
--end TIME	End of input	As --start	End point (exclusive).
--delay TIME	None	As --start	--start with the sign reversed: a positive value prepends silence. Not with --start.
-R, --raw	Off	Flag	Read headerless PCM described by the --raw-* options.
--raw-channels N	2	1–8	Raw channel count.
--raw-rate N	44100	Hz	Raw sample rate.
--raw-format SPEC	S16L	S, U or F, bit width, optional L/B	Raw sample format, case-insensitive (S24L, F32L). F needs 32 or 64 bits.
-i, --ignorelength	Off	Flag	Treat the input as WAV and ignore its data-chunk length, for piped WAV. Not with --raw.
--concat	Off	Flag	Encode all inputs into one file; needs -o.
--cue-tracks LIST	All tracks	n[-n][,n[-n]]…, 0–99	Tracks to extract from a cue sheet; 2-99 skips track 1 and the hidden pregap.

Output, files, and reporting

Parameter	Default	Values / units	Effect
-o FILE	Input name, new extension	Filename; - for stdout (ADTS or WAV output)	Output file, for a single input or with --concat.
-d DIR	Current directory	Directory	Output directory.
--fname-from-tag	Off	Flag	Name output files from the input tags, using --fname-format.
--fname-format TEXT	${tracknumber}${title& }${title}	Template	Output filename template for --fname-from-tag.
--tmpdir DIR	%TMP%	Directory	Directory for temporary files.
--sort-args	Off	Flag	Sort input filenames before processing.
--text-codepage N	0 (auto-detect)	Code page, e.g. 65001 UTF-8, 1252 Latin-1	Encoding of cue sheets, chapter and lyrics files; set it when auto-detection writes garbled tags.
--threading	Off	Flag	Run decoding and DSP on a separate thread from the encoder (AAC and ALAC).
-n, --nice	Off	Flag	Run at lower process priority.
-s, --silent	Off	Flag	No console output.
--verbose	Off	Flag	More detailed console output.
-S, --stat	Off	Flag	Save per-frame bitrate statistics to <output>.stat.txt.
--log FILE	None	Filename	Also write messages to a file.
-h, --help	—	Flag	Print help.
--check	—	Flag	Print the versions of the loaded Apple and helper libraries, then exit.
--formats	—	Flag	List the AAC formats, sample rates and bitrates your Apple encoder supports, then exit.
--exec COMMAND ARG...	Off	Program and arguments; must come last	Decode each track and pipe it as WAV (or CAF with --caf, which also carries tags) to a program, e.g. --exec ffmpeg -i - -c:a libopus {}.opus. {} becomes the output name without extension. No shell is involved.

Tags, artwork, and chapters

Tags from the input are copied; these options set or override them. The same values go to every file in one invocation.

Parameter	Default	Values / syntax	Effect
--title TEXT	—	Text	Title.
--artist TEXT	—	Text	Artist.
--band TEXT	—	Text	Album artist.
--album TEXT	—	Text	Album.
--grouping TEXT	—	Text	Grouping.
--composer TEXT	—	Text	Composer.
--comment TEXT	—	Text	Comment.
--genre TEXT	—	Text	Genre.
--date TEXT	—	Text	Date.
--track N[/TOTAL]	—	N or N/TOTAL	Track number.
--disk N[/TOTAL]	—	N or N/TOTAL	Disc number.
--compilation[=N]	Off	0/1; the bare flag means 1	iTunes compilation flag.
--lyrics FILE	—	Filename	Lyrics from a text file.
--artwork FILE	—	Image file; repeatable	Attach cover art.
--artwork-size N	0 (no limit)	Pixels	Downscale attached or copied artwork whose width or height exceeds this.
--copy-artwork	Off	Flag	Copy the front cover from the input. Ignored when --artwork is given.
--chapter FILE	—	Filename	Chapters from a file.
--tag FCC:VALUE	—	FCC:VALUE	Set an iTunes atom by four-character code; a three-character code gets the © prefix.
--tag-from-file FCC:FILE	—	FCC:FILE	As --tag, with the value read from a file.
--long-tag NAME:VALUE	—	NAME:VALUE	Custom iTunes (----) tag, stored as UTF-8.