A .nrg file is a proprietary CD image file format used by Nero Burning ROM, a
utility suite made by Nero AG, to create and burn CD images.
Other than Nero Burning ROM, a variety of software titles can use these image
files. For example, PowerISO, Alcohol 120%, or Daemon Tools can mount NRG
files onto virtual drives for reading. Contrary to popular belief, .nrg files
are not ISO images with .nrg extension and a header attached.
Converting nrg files There are several tools available to
convert a .nrg data file into an ISO 9660 CD image. Note that converting a cd
image .nrg multitrack to ISO involve the loss of audio tracks.
Open Source command line tools include: nrg2iso — cross-platform. Hardcoded to
read all nrg files as disc at once type causing it to fail on track at once type
images. iat — cross-platform. Tool for detecting
the structure of many types of CD/DVD image and convert image CD/DVD to
ISO9660. fusenrg — for Unix-like systems.
Hardcoded to read all nrg files as disc at once.
nrg4iso — for Unix-like systems. Can convert both DAO and TAO images into ISO
9660 CD images. Does NOT support DAO with multiple tracks.
eNeRGy — Mac OS X, based on nrg4iso, has a graphical user interface.
Shareware tools include: PowerISO — converts from nrg to ISO as
well as allows for browsing and extracting individual files from a nrg
data file. MagicIso — Is another powerful tool
converts from nrg to ISO as well as allows for browsing and extracting
individual files from a nrg data file. The data contents of NRG files can be
extracted directly without creating an ISO image using freeware file archivers
such as IZArc. File format
The file format specification below is unofficial and as such is lacking some
data. There may also be errors. The nrg file format uses a variation of
the Interchange File Format and stores data in a chain of "chunks". All integer
values are stored unsigned in big endian byte order. Version 1 nrg format stores
values as 32bit integers. Nero Burning ROM v5.5 introduced a new nrg file
format, version 2, with support for 64bit integers.
= Header = The nrg format does not store its data
as a header at the beginning of a file. It is instead attached at the end of the
file like a footer. Image information is stored as a serialized chain of IFF
chunks. To get the offset of the first chunk one must read the nrg footer from
the last 8 or 12 bytes of the file. = Chunks =
Cue Sheet Available in all versions of nrg file
format. The CUEX chunk is the concatenation of
fixed-size blocks, each one representing a cue point.
The index0 points are present even when they are identical to the index1 ones.
The index0 points in audio tracks are incorrect if Nero has been asked to
record all the sub-channel data. No index other than 0 or 1 has been
encountered, although the chunk format allows for such cue points to be
recorded; thus the number of cue blocks seems to be always 2*(#track + 1): two
indices for each track, an index0 for the lead-in and an index1 for the
lead-out. DAO Information
Available in all versions of nrg file format.
DAOI chunks store disc at once sessions specific information in two parts. The
first part contains data that is specific for the session only. The
second part repeats track specific information once for each track. Parse
the SINF chunks to get the number of tracks for a specific session.
CD-text Available in version 2 nrg file format.
The CDTX chunk is the concatenation of raw CD-text packs of 18 bytes each.
Extended Track Information Available in all versions of nrg file
format. ETNF chunks are used to store track
information for track at once sessions. The data is repeated once for each
track. Parse the SINF chunks to get the number of tracks for a specific session.
Session Information Available in all versions of nrg file
format. Session information chunks should be
used to quickly scan the image for session and track count. SINF chunks are
always listed in sequential order corresponding to the sessions order. To
get more details information about a specific session one must parse the
corresponding DAOI or ETNF chunk. Media Type?
Available in all versions of nrg file format.
This chunk and its use is unknown. A value of 1 was found in images of
several CD. Disc Information?
Found in TAO images in version 2 of nrg file format. Found in DAO images in
version of nrg file format only if Nero was asked not to close the disc.
This chunk and its use is unknown. TOC T?
Found in TAO images in version 2 of nrg file format.
This chunk and its use is unknown. Found in TAO images in version 2 of nrg
file format. This chunk and its use is unknown.
End of chain Available in all versions of nrg file
format. End of chain chunk is signals that there
are no more chunks to be read. See also
Disk image DMG
ISO image = Emulating/editing software supporting
NRG = Alcohol 120%
CDemu Daemon Tools
IsoBuster MagicISO
PowerISO Roxio Toast
UltraISO WinCDEmu
External links nrg4iso — BSD licensed command line
utility. Does not fully support nrg format. Currently abandoned.
nrg2iso — GPL licensed command line utility. Does not fully support nrg
format. IAT — GPL licensed command line utility
without support for CD-AUDIO fusenrg — GPL licensed command line
utility. Converts NRG to ISO on the fly. Does not fully support nrg format.
nrg2iso — Windows graphical utility. Does not fully support nrg format.
IMGBURN — Windows Freeware ISO burning software capable of managing the nrg
format. eNeRGy' — GPL Mac OS X utility, based on
nrg4iso, has a graphical user interface nrgtoiso — Windows Freeware graphical
utility. Converts nrg format to iso format.