NRG (file format)

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NRG
Filename extension.nrg
Uniform Type Identifiercom.nero.nrg-image
UTI conforms topublic.iso-image,
com.apple.disk-image,
public.archive,
public.data,
public.item,
public.disk-image
Developed byNero AG
Type of formatdisk image
Container forfilesystem and volumes
 
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NRG
Filename extension.nrg
Uniform Type Identifiercom.nero.nrg-image
UTI conforms topublic.iso-image,
com.apple.disk-image,
public.archive,
public.data,
public.item,
public.disk-image
Developed byNero AG
Type of formatdisk image
Container forfilesystem and volumes

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[edit]

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 (data + audio tracks) to ISO involve the loss of audio tracks.

The data contents of NRG files can be extracted directly without creating an ISO image using freeware file archivers such as IZArc.

File format[edit]

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[edit]

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.

Nero footer (Version 1)
Size (bytes)TypeValue / Purpose
4Chunk ID"NERO"
432bitOffset of the first chunk data chain
Nero footer (Version 2)
Size (bytes)TypeValue / Purpose
4Chunk ID"NER5"
864bitOffset of the first chunk data chain

Chunks[edit]

(CUES) Cue Sheet[edit]

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 (in that case the sector size is 2448 bytes). 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.

Version 1
Size (bytes)TypeValue / Purpose
4Chunk ID"CUES"
432bitChunk size (bytes)
Version 2
Size (bytes)TypeValue / Purpose
4Chunk ID"CUEX"
432bitChunk size (bytes)
18bitMode (values found: 0x01 for audio; 0x21 for non copyright-protected audio; 0x41 for data)
18bitTrack number (BCD coded; 0xAA for the lead-out area)
18bitIndex number (probably BCD coded)
18bitPadding? (always zero found)
432bitLBA position in sectors (signed integer value)

(DAOI) DAO Information[edit]

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.

Version 1
Size (bytes)TypeValue / Purpose
4Chunk ID"DAOI"
432bitChunk size (bytes) big endian
432bitChunk size (bytes) little endian
14 UPC
432bitToc type
18bitFirst track
18bitLast track
12 ISRC
432bitSector size
432bitMode
432bitIndex0 (Pre gap)
432bitIndex1 (Start of track)
432bitIndex2 (End of track + 1)
Version 2
Size (bytes)TypeValue / Purpose
4Chunk ID"DAOX"
432bitChunk size (bytes) big endian
432bitChunk size (bytes) (big endian already encountered; maybe also little endian on some machines)
13TextUPC (or NULLs)
18bitPadding? (always NULL found)
216bitToc type (values already found: 0x0000 for audio; 0x0001 for data; 0x2001 for Mode 2/form 1 data)
18bitFirst track in the session
18bitLast track in the session
12TextISRC (or NULLs)
216bitSector size in the image file (bytes)
216bitMode of the data in the image file (values already found: 0x0700 for audio; 0x1000 for audio with sub-channel; 0x0000 for data; 0x0500 for raw data; 0x0f00 for raw data with sub-channel; 0x0300 for Mode 2 Form 1 data; 0x0600 for raw Mode 2/form 1 data; 0x1100 for raw Mode 2/form 1 data with sub-channel)
216bitUnknown (always 0x0001 found)
864bitIndex0 (Pre-gap) (bytes)
864bitIndex1 (Start of track) (bytes)
864bitEnd of track + 1 (bytes)

(CDTX) CD-text[edit]

Available in version 2 nrg file format.

The CDTX chunk is the concatenation of raw CD-text packs of 18 bytes each.

Version 2
Size (bytes)TypeValue / Purpose
4Chunk ID"CDTX"
432bitChunk size (bytes)
18bitPack type
18bitPack type (track number)
18bitPack number in the block
18bitBlock number etc.
12TextNULL-separated text strings
216bitCRC

(ETNF) Extended Track Information[edit]

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.

Version 1
Size (bytes)TypeValue / Purpose
4Chunk ID"ETNF"
432bitChunk size (bytes)
432bitTrack offset in image
432bitTrack length (bytes)
432bitMode
432bitStart lba on disc
4  ?
Version 2
Size (bytes)TypeValue / Purpose
4Chunk ID"ETN2"
432bitChunk size (bytes)
864bitTrack offset in image
864bitTrack length (bytes)
432bitMode (values found: 0x7 for audio; 0x0 for data; 0x3 for Mode 2 data)
432bitStart lba on disc (sectors) (the start is after a lead-in of 150 sectors)
432bitUnknown (only zero found)
432bitTrack length (sectors)

(SINF) Session Information[edit]

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.

Version 1 and 2
Size (bytes)TypeValue / Purpose
4Chunk ID"SINF"
432bitChunk size (bytes)
432bit# tracks in session

(MTYP) Media Type?[edit]

Available in all versions of nrg file format.

This chunk and its use is unknown. A value of 1 (big endian) was found in images of several CD (audio or data; CD-ROM or CD-R).

Version 1 and 2
Size (bytes)TypeValue / Purpose
4Chunk ID"MTYP"
432bitChunk size (bytes)
4  ?

(DINF) Disc Information?[edit]

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.

Version 2 (and 1?)
Size (bytes)TypeValue / Purpose
4Chunk ID"DINF"
432bitChunk size (bytes)
432bitUnknown (found 0x1 for an unclosed disc; 0x0 otherwise)

(TOCT) TOC T?[edit]

Found in TAO images in version 2 of nrg file format.

This chunk and its use is unknown.

Version 2 (and 1?)
Size (bytes)TypeValue / Purpose
4Chunk ID"TOCT"
432bitChunk size (bytes)
2 Unknown (always zero found)

(RELO)[edit]

Found in TAO images in version 2 of nrg file format.

This chunk and its use is unknown.

Version 2 (and 1?)
Size (bytes)TypeValue / Purpose
4Chunk ID"RELO"
432bitChunk size (bytes)
4 Unknown (always zero found)

(END!) End of chain[edit]

Available in all versions of nrg file format.

End of chain chunk is signals that there are no more chunks to be read.

Version 1 and 2
Size (bytes)TypeValue / Purpose
4Chunk ID"END!"
432bitChunk size (always zero)

See also[edit]

Emulating/editing software supporting NRG[edit]

External links[edit]