Nero AAC

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Nero AAC Codec

Developer(s) Nero AG
Release information
Initial release {{{released}}}
Stable release See table
Preview release n/a
Operating system Windows, Linux
Additional information
Use Encoder/Decoder
License see site for license
Website Information
Current AAC encoders
(most to least recommended)
1 Apple AAC M/W
2 FhG AAC (Winamp) W
3 Fraunhofer FDK AAC S/L/M/W
4 Nero AAC L/W
5 FFmpeg 3.0+ AAC encoder S/L/M/W
7 Libav (pre-3.0 FFmpeg) AAC encoder S/L/M/W
S Source code available; L Linux; M macOS; W Windows
List of AAC encoders

Nero AAC is a freely available software suite that includes a high-quality LC and HE AAC codec and metadata tool. It was released by Nero AG for personal non-commercial and/or technology-evaluation purposes. The download package contained binaries for both Windows and Linux. It was the same codec that was used in Nero's other, then current, commercial products.

It was generally perceived to have the highest quality VBR HE-AAC and good enough LC-AAC implementation in past. The codec could also create HEv1/v2 AAC streams for extremely low bitrates and supports multi-channel surround sound encoding.


The suite includes three command-line tools.

Tool Role Latest Version
neroAacEnc AAC encoder (Feb 18 2010)
neroAacDec AAC decoder (Dec 17 2009)
neroAacTag MP4 metadata editor (Dec 17 2009)


The codec was originally part of Nero Digital, a complete MPEG-4 Audio/Video solution. The ASP/AVC (video) codec was developed by a French company called Ateme. Nero built an in-house team to develop the AAC (audio) codec that included Ivan Dimkovic, Menno Bakker, and others. Dimkovic was the author of the PsyTel codec, and the Nero AAC codec is said to be based on this work. Menno Bakker was the developer of FAAC, one of the earliest widely-available AAC encoders, and also what would be become its companion decoder, FAAD. The Nero AAC codec became a stand-alone package around 2006, although still called Nero Digital Audio until 2009. Nero apparently still uses the codec in its products. Neither Dimkovic nor Bakker currently work at Nero, and development of the codec has stalled, but the software is stable and remains a reliable, and high-quality, option for AAC encoding.

  • Original release, version, on 2006-05-01.
  • Tagging utility added in version (2006-05-18).
  • Linux officially supported in version (2007-08-06).
  • Renamed from Nero Digital Audio to Nero AAC in version (2009-12-17).
  • SSE2 no longer required in version (2009-12-29).
  • Disappeared from on 2014-07-23.
  • Re-appeared on in 2014-09.



Developer(s) Nero AG
Release information
Initial release May 1, 2006; 18 years ago
Stable release (February 18, 2010; 14 years ago)
Preview release
Operating system Windows, Linux
Additional information
Use Encoder
License Freeware

This is the encoder command-line tool. It is used to encode a .WAV file containing PCM data into an .MP4 file containing an AAC stream.



neroAacEnc.exe [options] -if <input-file> -of <output-file>


./neroAacEnc [options] -if <input-file> -of <output-file>

Note: Make sure the binary is executable.


Path to source file to encode.
The file must be in Microsoft WAV format and contain PCM data.
Specify - to encode from stdin.
Note that multiple input files can be specified, they will be encoded together into a single output file with chapter marks indicating source file divisions.
Path to output file to encode to, in MP4 format.


Quality/bitrate control
-q <number>
Enables "target quality" mode. (VBR)
<number> is a floating-point number in 0...1 range. I.e. 0.5 or 0.75, etc. with 1 being the highest quality and thus also having the largest output file size.
-br <number>
Specifies "target bitrate" mode. (ABR)
<number> is target bitrate in bits per second ranging from 8000 to 400000.
-cbr <number>
Specifies "target bitrate (streaming)" mode. (CBR)
<number> is target bitrate in bits per second ranging from 8000 to 400000.

When neither of above quality/bitrate options is used, the encoder defaults to equivalent of -q 0.5

The following VBR quality settings result in the following average bitrates:

Quality Bitrate (kbit/s), stereo
0.05 16
0.15 33
0.25 66
0.35 100
0.45 146
0.55 192
0.65 238
0.75 285
0.85 332
0.95 381
Multipass encoding
Enables two-pass encoding mode.
Note that two-pass mode requires a physical file as input, rather than stdin.
Using two-pass encoding is not recommended when using VBR.
-2passperiod <number>
Overrides two-pass encoding bitrate averaging period, in milliseconds.
Specify zero to use least restrictive value possible (default).
Advanced features / troubleshooting
Forces use of LC AAC profile (HE features disabled). (LC = Low Complexity)
Forces use of HE AAC profile (HEv2 features disabled). (HE = High Efficiency)
Forces use of HEv2 AAC profile
Ignores length signaled by WAV headers of input file. Useful for certain frontends using stdin.


NeroAacDec is the command-line decoder. It is currently at version and was last updated Dec 17th, 2009. It decodes an .MP4 file into a .WAV file



neroAacDec.exe -if <input file> -of <output file> [-chapter <number>]


Path of source input file to decode, in MP4 format.
Path to decode the file to, in WAV format.
Specify - to decode to stdout.


-chapter <number>
Specify the chapter mark within the input MP4 file.


NeroAacTag is used to list or edit an MP4 file's meta-data. It is currently at version and was last updated Dec 17th, 2009. By default is writes iTunes-compatible tags.



neroAacTag.exe <file.mp4> <command> [<command> [<command> ...]]

Available commands

Lists existing metadata entries.
Sets specified metadata field to specified value. Eg. -meta:artist="Pink Floyd"
Sets specified metadata field to specified value. Allows non-standard metadata fields to be added.
WARNING: fields added using -meta-user are not guaranteed to be read back on all Nero Digital compliant software/hardware.
Displays a list of field names usable with -meta command.
Displays a list of iTunes field names. (Usable with -meta-user)
Displays a list of iTunes field names.
Lists cover art entries.
Write cover art also to ND tags. Default is to write only to iTunes tags.
Creates a cover art entry from specified JPEG file. <type> specifies type of cover art entry and can be "front" or "back". If specified cover art entry already exists, its contents are overwritten. Eg. -add-cover:back:hello.jpg
Dumps specified cover art entry contents to a JPEG file.
Removes specified cover art entry.
Removes all cover art entries.
Lists chapters present in the file.
Sets chapter index metadata edits apply to. Value of 0 (default state) applies edits to all present chapters. Also affects -list-meta output.
Generates track number metadata according to the chapter list.

Supported metadata fields

Strings are all encoded in utf8.

Tag name Usage MP4 block modified Comment
title -meta:title=<string> ©nam
artist -meta:artist=<string> ©ART
year -meta:year=<string> ©day Block actually supports full YYYY-MM-DD
album -meta:album=<string> ©alb
genre -meta:genre=<string> gnre or ©gen Stores an ID3 genre number (-1) as integer in the gnre block if one exists for the given string, or stores the string in the "user-defined" ©gen block if not
track -meta:track=<int> trkn Block stores both track and totaltracks in one binary value
totaltracks -meta:totaltracks=<int> trkn Block stores both track and totaltracks in one binary value
disc -meta:disc=<int> disk Block stores both disc and totaldiscs in one binary value
totaldiscs -meta:totaldiscs=<int> disk Block stores both disc and totaldiscs in one binary value
url -meta:url=<string> ---- Stored in
copyright -meta:copyright=<string> ---- Stored in
comment -meta:comment=<string> ©cmt
lyrics -meta:lyrics=<string> ©lyr
credits -meta:credits=<string> ---- Stored in
rating -meta:rating=<?> ---- Stored in
label -meta:label=<string> ---- Stored in
composer -meta:composer=<string> ---- Stored in (See writer for ©wrt)
isrc -meta:isrc=<string> ---- Stored in (International Standard Recording Code)
mood -meta:mood=<string> ---- Stored in
tempo -meta:tempo=<int> tmpo Beats per minute, stored as a 16-bit integer
writer -meta-user:writer=<string> ©wrt
contentgroup -meta-user:contentgroup=<string> ©grp
album artist -meta-user:'album artist'=<string> aART
description -meta-user:description=<string> desc
network -meta-user:network=<string> tvnn
show -meta-user:show=<string> tvsh
season -meta-user:season=<int> tvsn Stored as 32-bit integer
episode -meta-user:episode=<int> tves Stored as 32-bit integer
episodename -meta-user:episodename=<string> tven
sorttitle -meta-user:sorttitle=<string> sonm
sortalbum -meta-user:sortalbum=<string> soal
sortartist -meta-user:sortartist=<string> soar
sortband -meta-user:sortband=<string> soaa
sortwriter -meta-user:sortwriter=<string> soco
sortshow -meta-user:sortshow=<string> sosn
itunescompilation -meta-user:itunescompilation=<0,1> cpil iTunes only. More common to use something like "Various Artists" in the Album Artist field
itunespodcast -meta-user:itunespodcast=<0,1> pcst
tool read-only ©too NeroAacEnc sets this value to "Nero AAC codec / <version>"
covers -add-cover:<type>:<jpegfile>
covr Types: front, back


neroAacTag has a quirk related to its memory-stick tag capability. Meta tag values that contain one or more semi-colons (;) will get split up into multiples of that tag.

For example, you run the following command:

neroAacTag test.m4a -meta:artist="Artist A; Artist B; Artist C"

Instead of having a single artist tag listing all three artists (artist="Artist A; Artist B; Artist C"), you get three artist tags with an artist listed in each (artist="Artist A" artist=" Artist B" artist=" Artist C").

neroAacTag will show your tag as correctly applied but iTunes or Mp3tag will not see that. (Mp3tag will show you the duplicate tags in the Extended tags view.)



bash script to transcode FLAC to AAC in Linux preserving metadata:

# Transcode FLAC to AAC (M4A) using:
#   flac, metaflac, neroAacEnc, neroAacTag

# Creates M4A versions of all FLAC in the current directory.


gettagvalue_metaflac () {
	local SRCF="$1"
	local BLOCK="$2"
	local VALUE=$(metaflac "$SRCF" --show-tag="$BLOCK")
	shopt -s nocasematch	
	if [[ $VALUE =~ ^"$BLOCK"=(.*?) ]]; then
	shopt -u nocasematch
	echo "$VALUE"

for f in *.flac
	TITLE=$(gettagvalue_metaflac "$f" "TITLE")
	ARTIST=$(gettagvalue_metaflac "$f" "ARTIST")
	ALBUMARTIST=$(gettagvalue_metaflac "$f" "ALBUMARTIST")
	ALBUM=$(gettagvalue_metaflac "$f" "ALBUM")	
	TRACKNUMBER=$(gettagvalue_metaflac "$f" "TRACKNUMBER")
	TRACKTOTAL=$(gettagvalue_metaflac "$f" "TRACKTOTAL")
	DISCNUMBER=$(gettagvalue_metaflac "$f" "DISCNUMBER")	
	DISCTOTAL=$(gettagvalue_metaflac "$f" "DISCTOTAL")
	DATE=$(gettagvalue_metaflac "$f" "DATE")
	GENRE=$(gettagvalue_metaflac "$f" "GENRE")

	if [ -e "$TMPCVR" ]; then
		rm "$TMPCVR"
	metaflac --export-picture-to="$TMPCVR" "$f"

	fm4a=$(echo "$f" | sed s/\.flac$/.m4a/g)
	flac -s -d -c "$f" | "$AACENC" -ignorelength -q 0.5 -if - -of "$fm4a"

	"$AACTAG" "$fm4a" \
		-meta:title="$TITLE" \
		-meta:artist="$ARTIST" \
		-meta-user:'album artist'="$ALBUMARTIST" \
		-meta:album="$ALBUM" \
		-meta:year="$DATE" \
		-meta:track="$TRACKNUMBER" \
		-meta:totaltracks="$TRACKTOTAL" \
		-meta:disc="$DISCNUMBER" \
		-meta:totaldiscs="$DISCTOTAL" \

	if [ -e "$TMPCVR" ]; then
		"$AACTAG" "$fm4a" -add-cover:front:"$TMPCVR"
		rm "$TMPCVR"


EAC Settings

The following settings are examples of what one might use for music and spoken word sources, respectively. Files will be tagged properly using these commands via neroaactag.exe. These commands do run ReplayGain on the files.

This is the syntax for older versions of EAC. For 1.0 beta 2 and above, variables have a changed syntax. See [[1]]

320kbps CBR AAC (Forced LC)

Program, including path, used for compression: C:\Windows\system32\cmd.exe
Additional Command Line Options: /c ""C:\path\to\neroaacenc.exe" -cbr 320000 -lc -if %s -of %d && "C:\path\to\Neroaactag.exe" %d -meta:artist="%a" -meta:album="%g" -meta:track="%n" -meta:title="%t" -meta:genre="%m" -meta:year="%y""

Q0.3 VBR AAC (Forced HE)

Program, including path, used for compression: C:\Windows\system32\cmd.exe
Additional Command Line Options: /c ""C:\Program Files\Exact Audio Copy\neroaacenc.exe" -q 0.3 -he -if %s -of %d && "C:\Program Files\Exact Audio Copy\Neroaactag.exe" %d -meta:artist="%a" -meta:album="%g" -meta:track="%n" -meta:title="%t" -meta:genre="%m" -meta:year="%y""


The Nero AAC Codec can be used inside Foobar2000's convert function.


External links