Recommended File Formats
|Full Text of an ETD||
It is an abreviation for Portable Document Format Archival. It is a subset of Adobe Acrobat's PDF format, which leaves out features not conducive to long-term preservation. PDF/A is an international standard available in Adobe Acrobat 5 and later to better ensure long-term access to PDF files.
Microsoft PowerPoint presentations may be included.
When deciding what image format to use first weigh its original form to the output. Some formats are better for different data. If you intend that the image will or needs to be printed go for a format that produces a larger file size.
See above for general information on the PDF format. PDF is best used to store vector-based graphics (i.e. graphics drawn using lines and curves rather than pixels). Vector graphics stored in PDF format will be much smaller, will read more cleanly, and any included text will be searchable. Equations, charts, and diagrams that combine text with vector-graphics are particularly appropriate to store in PDF format.
The JPEG format is primary used to store photographs. JPEG is a "lossy" format, meaning that some image quality is sacrificed in order to produce much smaller files. Images of higher quality should be stored in TIFF format instead (see below). Non-photographic images such as graphs and charts will be smaller if stored in GIF format instead (see below).
CompuServe GIF (.gif)
The GIF format, developed by CompuServe, is best used to store screen-quality images that do not contain many colors. GIF files are typically very small, but cannot reproduce the range of colors necessary to reproduce photographic images (use the JPEG format instead -- see above).
The TIFF format is an archival format, meaning that it does not sacrifice image quality in order to reduce file sizes. TIFF images are excellent for storing detailed, high quality images. However, TIFF files tend to be much larger than either JPEG or GIF images, and cannot be opened using most web browsers without installing and configuring additional viewing software or plugins.
The PNG format is an open standard developed to replace the Compuserve GIF format. Like GIF files, low-color images stored in PNG format are typically quite small. Unlike the GIF format, the PNG format can also be used to store high-color images, which means it is also suitable for storing photographic content.
For images that are only intended to be viewed on screen, a resolution of 72 or 75 dpi will result in a small file that can be easily downloaded. A resolution of 600 dpi is recommended for images that are intended to be printed.
The MPEG format is the oldest and most widely supported format for movies. There are a wide range of viewers available for all platforms. The MPEG format is most commonly used as an output format from UNIX utilities that generate video content.
The Quicktime format was originally more of a Macintosh-specific format. These days, support for Quicktime movies is good on both the Macintosh and Windows, but not as good on UNIX.
Audio Video Interleaved (.avi)
The AVI format is more of a Windows-specific format, and is not as well supported on other platforms.
Suggestions Regarding Video Content
Video is one of the most resource-intensive types of multimedia. Unfortunately, video content that is of even half broadcast quality is often too large to download from home. Consider including lower quality versions of video content in addition to high quality originals.
The default standard for Windows sound files, is also supported for most other platforms.
The AIFF format is a Macintosh-specific equivalent of the WAV format. It is not as well supported on all platforms as the WAV format.
MPEG-3 (or MP3) format eliminates sound data which is not as strongly perceived by the human ear and brain, and as such creates files of reasonable quality that are as much as 10 times smaller than the raw data itself. MP3 files are good for storing long passages of sound content where high quality is not required.
Suggestions Regarding Sound
The quality used to store sound in electronic format reflect the quality of the original recording source. There is very little reason to store low fidelity recordings of speech content in a very high-quality format, as the added file size would not result in any increase in quality. Conversely, high-fidelity recordings should be stored at high-quality.