How to Preserve Your Own Digital Materials by the Digital Preservation Office at the University of Michigan Library
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How to Preserve Your Own Digital Materials By the Digital Preservation Office at the University of Michigan Library. Links to web sites and prices current as of May 2014 Our personal photos, letters, movies and paper documents serve as vital links to the past. While these documents have traditionally been tangible objects, much of the information we create is now digital, and must be preserved using different methods. This document will guide you in keeping your digital materials safe, so that you and your family can look at them in the future. You will notice that the same plan is repeated in each section: identify, decide, organize, and backup. This method can be used whether you want to preserve photos, e-mail, personal records, audio recordings, or videos, with particular concerns for each type. Several software programs and other products are mentioned by name. These are included as examples and should not be construed as specific endorsements by the University of Michigan Library. For All of Your Personal Digital Files Once you have them organized (see below), make copies and store them in different places • Make at least two of them to start, preferably 3 with one located “off site.” • One copy should stay on your computer or external hard drive. Put other copies on writeable DVDs, CDs, other hard drives, or store them on the Internet (there is a list of online backup solutions at the end of this handout). • Try to store copies in different physical locations in case of a disaster. • Update your archival collections and create new backups on a regular basis. Sometimes, for a few important text files or photos that you want to keep for decades or more, the most secure way is to print out copies of the file and preserve the hard copy. Digital Photographs Your photographs likely have deep personal meaning to you and your family. You will likely want to keep some of your photos for Quite a long time. It’s a good tactic to focus your attention on organizing your important photographs into related groups, and weeding out images you identify as unimportant. Identify where you have digital photos • You might have digital photographs on cameras, various computers, memory cards, USB sticks, and on the Web. Decide which photos are the most important to you • Select images you feel are especially important. This can be as many as you would like. - 1 - • If you have duplicates, you should save the version that is the highest quality. • The selection process is helpful, as it allows you to focus your efforts on the photos with the greatest meaning and importance to you, instead of every photo you ever took. In the digital environment, photos can accumulate Quickly! • It is helpful to “weed” as you go, rather than attempting to go back and do it later. Weeding out a few images every time you add new pictures from you camera, is much easier than attempting to sort through hundreds or thousands of images all at once. Organize the selected photos • Collect your photos together on one computer or external hard drive so you can work from a single location. • Create a directory/folder structure on your hard drive that allows you to organize your images in a way that makes sense to you. Some examples are: o Date-based: 2010/05 o Event-based: Vacations/New York City 2009 o Combination: 2010/05/New York City Vacation • Give your photos descriptive file names • Write a brief description of the directory structure and the photos • Photo organizing software can allow you to easily organize, describe, and “tag” your photos. Tag each photo of a family member with their name, and you can easily search for them across multiple groups of images. Examples of these software packages are: o Ulead Photo Explorer o Corel Photo Album o ACDSee o Picasa o Adobe Photoshop Album Starter Edition Digital Audio Your digital audio files might include music, lectures, and other important sound recordings. As they will have personal, financial, educational, or other long-term value, you will likely wish to keep them for a long time. Your audio files should be saved in open, non-proprietary (meaning the format is not owned by a particular entity) and popular file formats. This will ensure the most flexibility for future use. Identify where you have digital audio files • You might have digital sound recordings on audio players, various computers, memory cards, USB sticks, and so on. • Be sure to include files you manage through audio software. - 2 - Decide which audio recordings have long-term value to you • Select the recordings you feel are important. • If you have duplicates, you should save the version that is the highest quality. Organize the selected audio recordings • Collect your audio files together on a single computer or external hard drive so you can work from a single location • Create a directory/folder structure on your hard drive that allows you to organize your audio files in a way that makes sense to you. Some examples are: o Date-based: 2004/03 o Event-based: Interviews/John Smith 2004-03-12 o Combination: 2004/03/Interview with John Smith • Give your files descriptive names • Write a brief description of the directory structure and the audio files • If your files are in unpopular or older formats, you might consider encoding them in, or converting them to, more open formats such as WAV or MP3, which have a wide amount of support. Some software packages that can help you with this are: o Switch Audio File Converter – free version available for non-commercial use (http://www.nch.com.au/switch/index.html) o River Past Audio Converter - $19.95-29.95 (http://www.riverpast.com/en/prod/audioconverter/) o NoteBurner - $34.95 (http://noteburner.com/noteburner-audio-converter.html) o ImTOO Audio Encoder – $25.17 (http://www.imtoo.com/audio-converter-pro.html) Creating Digital Audio Files If you decide to convert some of your analog audio materials (LPs, cassettes, CDs, etc) into digital formats, you will certainly want to follow the three-steps outlined above (Identify, Decide, and Organize) once the files are digitized on your computer to help you preserve them into the future. However, when digitizing these media, you should keep a few extra things in mind because, when creating audio files yourself, you have more control over the technical specifications of recordings. There are four primary characteristics of digital audio files that you should keep in mind when digitizing your analog materials: file format, sampling rate, bit depth, and compression/bit rate. - 3 - File Format Possible formats to consider using, depending on which software you have available to you, include: WAV (.wav), MP3 (.mp3), AIFF (.aif), and MOV (Apple QuickTime; .mov) formats. While AIFF and MOV are both proprietary, they are in widespread, popular use and should be acceptable choices for your audio files if you have the software to play them. Using any of these formats helps to ensure that you will be able to enjoy your digital audio files for years to come. Sampling Rate “Sampling rate” refers to how many times per second the sound wave is measured and is expressed in kHz. Audio CDs have a sampling rate of 44.1 kHz, and DVD-quality audio has a sampling rate of 48 kHz. Using these specifications for your own audio files will help produce Quality files that will last over time, though if you are interested in higher Quality audio files, using a sampling rate of 96 kHz will give you higher resolution files. keep in mind, however, that files with this higher sampling rate will be larger and take up more space on a hard drive. Bit Depth “Bit depth” refers to the number of bits of information recorded in each sample. Both CDs and DVDs have audio tracks with 16-bit depth, and you should use this as your standard bit depth when creating your own audio files. If you are interested in creating very high Quality audio files, however, consider using a bit depth of 24 or higher, if your software allows you to do so. Compression and bit rate Compression reduces the size (and sometimes quality) of audio files, and compression schemes are often referred to as “codecs” (short-hand for the compression-decompression algorithm that encodes the data). There are two kinds of codecs: lossy and lossless. Lossy codecs eliminate certain segments of the file so that the resulting file size is smaller; although such lossy compression does provide smaller files that might be easier to store, it also removes data that cannot be recovered once lost. Lossless compression, on the other hand, creates larger files but maintains the full Quality of the original recording. If you’re interested in high quality files and have the hard drive space to store them, using a lossless compression scheme like FLAC (Free Lossless Audio Codec; .flac) is suggested; if you do not need such high resolution files, using a lossy codec like MP3 can also create digital audio with the potential to be preserved over time. For files in MP3 format, however, a higher bit rate is more desirable than a lower one; “bit rate” is a measurement of how many kilobits of data are stored per second. A bit rate of at least 128 Kbps is the absolute minimum, though files with bit rates of at least 192 Kbps are preferred. Bit rates up to 320 kbps produce the highest Quality MP3 files. - 4 - Hardware and Software for Digitizing Audio Materials Because hardware configurations for digitizing audio can vary widely depending on your specific needs and materials, hardware recommendations will not be discussed here.