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 ISO 9660 CD images.
Other than Nero Burning ROM, a variety of software titles can use these image files. For example, Power ISO, 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. For technical details on the nrg format see below.
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Converting nrg files
There are several tools available to convert a .nrg data file into an ISO 9660 CD image.
- Open Source command line tools include:
- nrg2iso — cross-platform. hardcoded to read all nrg files as disc at once (DAO) type causing it to fail on track at once (TAO) type images.
- fusenrg — for Unix-like systems. Hardcoded to read all nrg files as disc at once (DAO)
- nrg4iso — for Unix-like systems (including Mac OS X). Can convert both DAO and TAO images into ISO 9660 CD images.
- Shareware tools include:
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 (IFF) 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.
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Chunks
(CUES) Cue Sheet
Available in all versions of nrg file format.
Cue sheet information. Not yet documented
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(DAOI) 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 (grey) once for each track. Parse the SINF chunks to get the number of tracks for a specific session.
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(CDTX) CD-text
Available in version 2 nrg file format.
CDTX chunks contain raw CD-text data.
| Size (bytes) | Type | Value / Purpose |
|---|---|---|
| 4 | Chunk ID | "CDTX" |
| 4 | 32bit | Chunk size (bytes) |
| 18 | CD-text pack |
(ETNF) 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.
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(SINF) 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.
| Size (bytes) | Type | Value / Purpose |
|---|---|---|
| 4 | Chunk ID | "SINF" |
| 4 | 32bit | Chunk size (bytes) |
| 4 | 32bit | # tracks in session |
(MTYP) Media Type?
Available in all versions of nrg file format.
This chunk and its use is unknown.
| Size (bytes) | Type | Value / Purpose |
|---|---|---|
| 4 | Chunk ID | "MTYP" |
| 4 | 32bit | Chunk size (bytes) |
| 4 | ? |
(END!) 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.
| Size (bytes) | Type | Value / Purpose |
|---|---|---|
| 4 | Chunk ID | "END!" |
| 4 | 32bit | Always zero |
See also
Emulating/editing software supporting NRG
External links
- nrg4iso — BSD licensed command line utility with full nrg format support (POSIX)
- nrg2iso — GPL licensed command line utility. Does not fully support nrg format. (Linux)
- 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. (Linux)
- nrg2iso — Windows graphical utility. Does not fully support nrg format. (Windows)
- IMGBURN — Windows Freeware ISO burning software capable of managing the nrg format.
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