NeroAAC

**Nero AAC Codec**


Developer(s)	Nero AG
Release information
Initial release	{{{released}}}
Stable release	1.5.4.0 (Feb 18. 2010)
Preview release	n/a
Compatibility
Operating system	Windows, Linux
Additional information
Use	Encoder/Decoder
License	see site for license
Website	Nero AAC Codec

The Nero AAC codec has been made freely available by Nero AG for personal non-commercial and/or technology-evaluation purposes. It is a set of three command-line tools that are used to encode, decode and apply tags to MP4 files. The download contains binaries for both Windows and Linux. It is the same codec that is used in Nero's other, commercial products.

The three command-line tools are:

neroAacEnc
neroAacDec
neroAacTag

This article is still a work in progress

NeroAacEnc

This is the encoder command-line tool. It is currently at version 1.5.4.0 and was last updated Feb 18th, 2010. It is used to encode a .WAV file containing PCM data into an .MP4 file containing an AAC stream.

Usage

Windows

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

Linux:

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

Note: Make sure the binary is executable

Where:

<input-file>: 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.
<output-file>: Path to output file to encode to, in MP4 format.

Options:

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)
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

-2pass: Enables two-pass encoding mode.
Note that two-pass mode requires a physical file as input, rather than stdin.
-2passperiod <number>: Overrides two-pass encoding bitrate averaging period, in milliseconds.
Specify zero to use least restrictive value possible (default).

Advanced features / troubleshooting

-lc: Forces use of LC AAC profile (HE features disabled). (LC = Low Complexity)
-he: Forces use of HE AAC profile (HEv2 features disabled). (HE = High Efficiency)
-hev2: Forces use of HEv2 AAC profile

Note that the above switches (-lc, -he, -hev2) are not required and should normally not be used. The optimal AAC profile is automatically determined from quality/bitrate settings when no override is specified. A scenario where using the switches might be useful is to force LC when you have a device that doesn’t support HE.

-ignorelength: Ignores length signaled by WAV headers of input file. Useful for certain frontends using stdin.

NeroAacDec

NeroAacDec is the command-line decoder. It is currently at version 1.5.1.0 and was last updated Dec 17th, 2009. It decodes an .MP4 file into a .WAV file

Usage

Windows:

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

Where:

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

Options

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

NeroAacTag

NeroAacTag is used to list or edit an MP4 files meta-data. It is currently at version 1.5.1.0 and was last updated Dec 17th, 2009. By default is writes iTunes-compatible tags.