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The '''Resource Interchange File Format''' ('''RIFF''') is a generic meta-format for storing data in tagged chunks. It was introduced in [[1991]] by [[Microsoft]] and [[International Business Machines|IBM]], and was presented by Microsoft as the default format for Windows 3.1 multimedia files. It is
The Microsoft implementation is mostly known through file formats like [[AVI]], [[ANI (animation file format)|ANI]] and [[WAV]], which use the RIFF meta-format as their basis.
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* rest of data: subchunks.
The file itself consists of one RIFF chunk, which then can contain further subchunks: hence, the first four bytes of a correctly-formatted RIFF file will spell out "R", "I", "F", "F".
More information about the format can be found in the [[Interchange File Format]] article.
== Use of the INFO chunk ==
The official Microsoft documentation for [[Windows 3.1]] states that the INFO chunk should be placed at the beginning of the file. This allows fast access to the file's descriptive [[metadata]], and lets file system software and multimedia file management applications quickly scan the top of each file and extract author information, icon thumbnails, preview audio, formatting information, and so on.
When [[Windows XP]]'s file management software encounters an RIFF-format file, it will automatically attempt to read this INFO chunk, and the user can specify some common RIFF fields (e.g. Author, Copyright date) that can be used to supplement the more usual file property fields such as file size and creation date.
== Controversies ==
* In line with their policy of using .RIFF for all Windows "multimedia" files, Microsoft introduced a new variant on the existing [[MIDI file]] format used for storing song information to be played on electronic musical instruments. Microsoft's "new" MIDI file file format consisted of a standard MIDIfile enclosed in a RIFF "wrapper", and had the extension [[.RMI]]. This caused some upset at the time, since it took a while for existing music software to be updated to use the new format, and not everyone accepted that the creation of a new file format was justified in this case.
* When dealing with large video files, expanding or contracting the INFO chunk can result in the entire file (which might be several gigabyes in size) having to be rewritten, which is a disk-intensive process. The correct workaround to this problem is to "pad out" the INFO chunk using dummy data (using a "dummy chunk" or "pad chunk") when a large file is created, so that later editing can expand or contract the "dummy" field to keep the total size of the INFO chunk constant: an intelligently-written piece of software can then overwrite just the INFO chunk when header data is changed, and does not have to modify or move the main body of the file. However, since this method requires a certain amount of additional work on the part of the software programmer, and since the full RIFF specifications were scattered amongst Microsoft's documentation, some programmers believed that it was legal (and simpler) to place the INFO chunk at the //end// of a RIFF file, and some faulty documentation began to circulate recommending this practice. Misplacing the INFO chunk in this way means that the data will not be read by all media programs, and also means that there is a risk that the entire INFO chunk may be accidentally discarded or overwritten by software that strictly adheres to the official file specification.
* Although [[CorelDRAW]]10 nominally uses a RIFF file structure, it places the INFO chunk at the end, so that any embedded preview bitmap will not be displayed under Windows' file manager by default. An add-on utility supplied with the program fixes this problem.
== See also ==
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* [[AIFF]]
* [[FourCC]]
* [[BWF]] Broadcast Wave Format
== Some common RIFF file types ==
* [[.WAV]] (Windows audio)
* [[.AVI]] (Windows audiovisual)
* [[.RMI]] (Windows "RIFF MIDIfile")
* [[.CDR]] (CorelDRAW vector graphics file)
==External links==
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