# qaac

Canonical URL: https://encode.wiki/tools/software-encoders/qaac/
Content version: ca42e61ede0a24f789d7287a0001244ad22f4abf
Status: current
License: CC BY-SA 4.0
Checksum (SHA-256): a322c7632ce83bdebc3ba14278563e3145555e21efe762af230f8b1e4a29508f

> **Repository:** [nu774/qaac](https://github.com/nu774/qaac). CLI QuickTime AAC/ALAC encoder. Latest release: [v3.07](https://github.com/nu774/qaac/releases/tag/v3.07), Sep 10, 2026. Last commit: Sep 10, 2026. Stars: 999.

`qaac` is a command-line frontend to Apple's Core Audio [AAC encoder](/codecs/audio/aac/). 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](https://github.com/nu774/qaac/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](https://forum.doom9.org/archive/index.php/t-182671.html):

| --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).

```sh
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:

```sh
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](https://github.com/nu774/qaac/blob/v3.07/options.cpp). 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. |