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. However, if you are interested in this information, you can consult any of the step- by- step guides listed in the Digitizing Audio resources. There is also a wide variety of software packages for audio recording and editing available that can help you digitize your LPs, cassettes, and CDs and edit your digital audio files. Depending on your particular needs, different software will give you the ability to control different specifications for the files you create. The following is a list of sample audio editing software. Note that these are examples and not University of Michigan Library endorsements. Free, Open- Source Software o Audacity (http://audacity.sourceforge.net/) designed to work across several different operating systems, including Mac OS X, Microsoft Windows, and Linux o Power Sound Editor Free (http://www.free- sound- editor.com/features.html) a free audio editor for Windows o WavePad Audio Editing Software (http://www.nch.com.au/wavepad/index.html) works with Windows and Mac OS Proprietary Software o Adobe Audition CC priced according to Adobe license (http://www.adobe.com/products/audition.html) o AVS Audio Editor dependent on one year or unlimited access subscriptions (http://www.avs4you.com/avs- Audio- Editor.aspx) o Bias SoundSoap 3 for Mac OSX - $149 (http://www.soundness- llc.com/soundsoap3.html) o Diamond Cut 8 - $159 (https://www.diamondcut.com/catalog/dc8details.html) o Goldwave Digital Audio Editor - $59 (http://www.goldwave.com/) Recording Interfaces o Focusrite's Saffire 6 - $200 (http://www.focusrite.com/products/audio_interfaces/saffire_6_usb) o Presonus AudioBox USB - $200 (http://www.presonus.com/products/detail.aspx?productid=53) o Avid s Pro Tools Mbox Mini - $330 (http://www.avid.com/us/products/pro- Tools- plus- Mbox- Mini) - 5 -
Overall, when creating your own digital audio files remember that, while it is tempting to think you need the absolute best possible digital transfer in terms of sampling rate and bit depth, once you examine what sources you have and what your actual needs are you may find that standard, common formats suit your needs. You should balance the quality of your source audio recordings, potential future uses, and ease of access. For example, typical cassette recordings of spoken word will not suffer from transfer to a digital form at audio CD quality of 44.1 KHz/16 bits. This can be your master copy, and it offers the added advantage of allowing the direct creation of audio CDs. Digital Video Your digital video files might include home movies, vacations, lectures, interviews, or other important events. As they will have personal, financial, educational, or other long- term value, you will likely wish to keep them for a long time. Digital video files offer particular problems compared to digital photos or audio files. Not only are they frequently much larger than images or audio, the encoding formats for video are far more complicated and change more quickly than images or audio. Just like audio files, video files should be saved in open and popular file formats. Using open or popular file formats will ensure the most flexibility for future use. In practice, however, this can be difficult, as encoding video files in open formats is not always easy if your camera or video editing software does not allow for it. In general, open formats like MPEG- 2 (.mpg,.mpeg) and MPEG- 4 (.mp4) are good choices for your digital video files. Identify where you have digital video files You might have digital photographs on video cameras, various computers, memory cards, USB sticks, and so on. Be sure to include videos you may have on the Web. Decide which video recordings have long- term value to you Select the videos you feel are important. If you have duplicates, you should save the version that is the highest quality. If you edit your own videos, you might wish to save the originals, the edited versions, or both. Organize the selected videos Collect your video files 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 videos in a way that makes sense to you. Some examples are: o Date- based: 2005/10 o Event- based: Vacations/Disney World 2005 o Combination: 2005/10/Disney World Vacation Give your files descriptive names - 6 -
Write a brief description of the directory structure and the video files o If your files are in unpopular or older formats, you might consider encoding them in, or converting them to, a more open format such as MP4 (suggested by the Library of Congress), which has a wide amount of support. Some software packages that can help you with this are: AVS Video Converter free download and subscription rates available online (http://www.avs4you.com/avs- Video- Converter.aspx) Any Video Converter Pro - $39.95 (http://www.any- video- converter.com/products/for_video/) ImTOO Video Converter - $39.95 for the standard edition (http://www.imtoo.com/video- converter.html) Aimersoft Video Converter - $35.95 (http://www.aimersoft.com/video- converter.html) Xilisoft Video Converter - $29.95 - $49.95 (http://www.xilisoft.com/video- converter.html) Creating Digital Video Files If you decide to convert some of your analog video materials (videotapes such as VHS or Hi8 or film reels) 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 video files yourself, you have more control over the technical specifications of recordings. First of all, it s important to recognize that digital video files are, in reality, separate audio and video bit streams and have two parts, the wrapper that contains this audio and video data and the codec, the compression- decompression algorithm that encodes this data. There are six primary characteristics of digital video files, therefore, that you should keep in mind when creating your own digital video: file format, sampling rate, bit depth, frame rate, frame size, and aspect ratio. The following is a brief discussion and summary of these terms and how they are related to creating digital video. Your own needs and intended use of your video materials influence how much you want to apply these technical specifications; however, doing so will help to ensure that you will be able to use and enjoy your digital videos in the future. File Format As discussed previously, open formats are the most desirable choice for preserving all of your digital files, video materials included, although popular proprietary formats can also be reasonable options if you have the software necessary to play them. Both MPEG- 2 and MPEG- 4 currently stand as two of the best options for long- term storage of digital video files because both are used for commercial broadcast and by government institutions like the Library of Congress, increasing the likelihood that they will continue to be preservable, viable formats - 7 -
long into the future. Other formats that you might want to consider include DV (Digital Video Encoding;.dv), AVI (Audio Video Interleaved;.avi), which is the default Windows Media wrapper, and MOV (.mov), the default QuickTime wrapper. Although the last two of these (AVI and MOV) are proprietary, both are acceptable choices for digital video files because they are so widely adopted. Sampling Rate Although the term sampling rate is also used in reference to digital audio files, in the case of digital video sampling rate, the phrase means something a little different. Digital video files, in truth, have two sampling rates: a video sample rate and a color sample ratio. Your control over these sampling rates will be quite limited and usually dictated by your choice of hardware, software, or format. Understanding the details of video sample rate and color sample ratio, therefore, is not absolutely necessary when you are digitizing your own materials; however, a brief summary of what these two terms mean follows in order to clarify the difference between the two. 1. Video Sample Rate This term refers to how often the light intensity of the video lines is sampled and is measured in MHz. These values can range from 6.75 MHz to 74.25 MHz, depending on a variety of factors such as the digital video format itself. You won t have to be too concerned with this sampling rate, therefore, when digitizing your own video materials. 2. Color Sample Ratio A digital video signal has three components: luminance or brightness (Y ) and two chrominance or color values (C B and C R ). During digitization the encoder looks at each group of four video pixels and takes samples for recording. The color sample ratio represents the ratio of these luminance pixels sampled to the two chrominance pixels sampled, a ratio of Y : C B : C R, in other words. Thus, using 4:4:4 sampling, may seem like the ideal choice for creating high quality digital video files. However, in truth it is simply not a practical option. Doing so will require expensive hardware and will create huge files. Unless you know you need to have digital files that surpass current industry standards, you are unlikely to see any benefits that outweigh the pain of the process. With a 4:2:2 sampled video signal, all four of the luminance pixels are sampled, two of the C B pixels are sampled and two C R pixels are sampled. A color sampling ratio of 4:2:2 is common for most professional formats, but 4:1:1 sampling is a better choice for most needs. With a 4:1:1 signal, all four of the luminance pixels are sampled but only one pixel is sampled from each of C R and C B. This lower sampling rate records less color information and affects the accuracy and intensity of the color in the video signal. The advantage of 4:1:1 sampling is that you can record twice as much as 4:2:2 using a given amount of storage, though at the cost of some loss of - 8 -
quality. Some digitizing systems may not offer this as an option, and your choice of sampling ratio may be limited by the format you use. Bit Depth (Color Depth) The number of bits per sample determines how accurately information is stored within the file and is indicated by the term bit depth (or color depth ). Files with a bit depth of 24- bits ( Truecolor ) are recommended, although a 16- bit color depth ( Highcolor ) is the minimum standard you should use when creating your own digital video files. Frame Rate A digital video file s frame rate refers to the number of still pictures per unit of time that compose the video stream and is measured in frames per second (fps). Humans can perceive about a maximum of 75 fps. People vary in their sensitivity, but sampling done at a higher rate than this will not be perceptible by most viewers, and typically much lower values are fine. For example, motion pictures are recorded at 24 fps, and video is recorded at 25 fps (PAL, European standard) or 30 fps (NTSC, American standard). Your video files, therefore, should generally be at a range of 25-30 fps. In most cases, you will want to keep the frame rate of your original video. Using a higher frame rate will not get you more information. Using a lower frame rate which reduces your storage requirements, but at the cost of video information may be acceptable, depending on your content and your needs. Frame Size and Aspect Ratio 1. Frame Size The frame size or resolution of a digital video measures the size of the image in pixels, and when creating a digital video file, it is important to keep the resolution of your original format in mind. Use the same frame size as the original whenever possible/practical. In general, larger picture sizes are always preferred over smaller ones, although there will be no improvement in quality from using a frame size larger than the original. When converting from one digital format to another, maintaining the frame size of the original file is recommended, if possible. When creating a digital video file from an analog source, be sure to keep the resolution of that format in mind, because converting to a digital version with a much higher resolution will not produce an equal increase in quality. For instance, a typical VHS tape has a standard resolution of 720 x 483. If you convert this to a digital format and use an HD frame size of 1920 x 1080, the resulting digital video won t be high definition- quality. It will simply be a large file with quality comparable to the original analog format. - 9 -
Therefore, when creating a digital video file, it s important to keep in mind the intended file format, type of content in the file, and its intended future use. For digital video files, the following are suitable recommendations for resolution. For High Definition 1920 x 1080 1280 x 720 (minimum) For Standard Definition 720 x 480 pixels 640 x 480 pixels (minimum) The following resolutions commonly in use today might better inform your decisions when choosing a frame size for your own digital video files and are provided for reference: 1920 x 1080: 1080p. Used for high definition broadcasts and as the resolution for the high profile setting in MPEG- 2. Differs from 1080i, which refers to two 1920 x 540 fields that are interlaced (combined) to form a 1920 x 1080 image. 1280 x 720: 720p. Used in high definition broadcasts. 720 x 483: Standard component/composite. Historically used for broadcast transmissions and for VHS tapes, both NTSC and PAL standards (American and European, respectively). 720 x 480: Digital Standard Definition. Commonly known as 480p or 480i if interlaced. Also used as the resolution for the main profile setting in MPEG- 2. 352 x 240: Used as the low level profile setting resolution in MPEG- 2. 2. Aspect Ratio Also related to a video s resolution/frame size is its aspect ratio. The aspect ratio of a video refers to the ratio of the width to the height. For widescreen video files, an aspect ratio of 16:9 is the standard, while an aspect ratio of either 16:9 or 4:3 is the norm for Standard Definition resolutions. Overall, when deciding on a resolution and aspect ratio for your own digital video files, keep in mind the resolution and aspect ratio of your original source (whether it s another digital file or an analog source like a VHS tape). Using specifications higher than those of your source won t create higher quality files, just larger ones that will take up more storage space to keep. - 10 -
Software for Digitizing Video Materials There is a wide variety of software packages for video recording and editing available that can help you digitize your videotapes and film. Depending on your particular needs, different software will give you the ability to control different specifications for the files you create. The following is a list of sample video editing software and is meant to serve not as an endorsement of any of these software packages by the University of Michigan Library but as examples of what is available: Free, Open- Source Software o Avidemux (http://avidemux.sourceforge.net/) a free video editor designed to function on Mac OS X, Microsoft Windows, and Linux operating systems o AVS Video Editor (http://www.avs4you.com/avs- Video- Editor.aspx) a free video editor for Windows o Lightworks Beta (http://www.lightworksbeta.com/) a free, public version of the professional Lightworks editing software, for Windows o Open Movie Editor (http://www.openmovieeditor.org/) a free video editor for Linux Proprietary Software o Sony s Vegas Movie Studio HD starts at $49.95 (http://www.sonycreativesoftware.com/moviestudiohd) o Cyberlink s PowerDirector 9 - $74.99 (http://www.cyberlink.com/products/powerdirector/overview_en_us.html) o Nero s Video 2014 - $39.99 (http://www.nero.com/enu/products/nero- video/whats- new.php) o Adobe s Premiere Elements 12 - $99.99 (http://www.adobe.com/products/premiere- elements.html) o Apple s Final Cut Express 4 - $59.99 (http://www.apple.com/finalcutexpress/) o Roxio s Creator NXT 2 - $99.99 (http://www.roxio.com/enu/products/creator/suite/overview.html) Overall, when creating your own digital video files remember that, while it is tempting to think you need the absolute best possible digital transfer in terms of sampling rate and bit depth, once you examine what sources you have and what your actual needs are you may find that a standard, common format suits your needs. You should balance the quality of your source recordings, potential future uses, and ease of access. For example, typical VHS tapes will not suffer from transfer to a digital form at DVD quality of 4:1:1/24 bits. This can be your master copy, and it offers the added advantage of allowing the direct creation of DVDs. - 11 -
Personal Electronic Mail Just like paper letters, your e- mail messages document events, transactions, and relationships. Saving an e- mail involves archiving it outside of your e- mail program or online e- mail provider. They are not meant to keep information for a long time they can change or stop providing support at any time! Identify all your email sources Identify each of your personal e- mail accounts. Within each account, locate each folder, including archived messages that might be separate from your inbox. Decide which messages have long- term value Select the messages you feel are especially important. Remember to include the attachments that are part of your selections. Export the selected messages Online email providers do not provide the same exporting functionality as standalone software on your personal computer. You may need to investigate adding your online email provider to standalone software like Microsoft Outlook, so that it downloads your online email, which will allow you to export the messages. Use the Save As or Export command in your email software to export individual emails as text files. Save messages in an open format, such as plain text. Save the information about the messages, such as the header, which includes the subject, sender, recipient, and the time and date of the message. Organize the saved messages Give groups of messages, individual messages, and attachments meaningful names. Create a directory/folder structure on your hard drive that allows you to organize your messages in a way that makes sense to you. Write a brief description of the directory structure and the message files Example directory notes This is an example of a directory notes file for photographs, but the model can be applied to whatever you would like. Keeping notes about what is in each folder will allow you to more quickly find what you are looking for in the future: \2009 \10: New York City vacation; Karen s 12 th birthday party; washing the dog \11: Cats doing funny things; people downtown; first snowfall \12: Christmas; Charlie with Santa - 12 -
\2010 \01: New Years Party; dog outside in snow \02: Kids playing with toys; HUGE snowfall \03: Dinner with grandma and grandpa; portraits of friends \04: First flowers blooming; ice cream with kids Online cloud backup solutions (Reminder: Do your research before you choose or use an online backup solution!) Commercial Carbonite (http://www.carbonite.com/en/) o Unlimited backup capacity, starts at $59/year Dropbox Pro (http://dropbox.com/) o Priced at $9.99/user/month up to 100GB IBackup (http://www.ibackup.com/) o Various storage and pricing plans idrive Pro (http://www.idrive.com/) o Various storage and pricing plans Mozy (http://mozy.com/) o Monthly and annual rates for various storage requirements MyOtherDrive Pro (http://www.myotherdrive.com/) o 100GB: $5/month o 500GB: $240/year Free ADrive (http://www.adrive.com/) o 50GB of free storage Box (https://www.box.net/home) o 5GB of free storage DriveHQ (http://www.drivehq.com/) o 1GB of free storage, free access to file management system Dropbox Basic (http://www.dropbox.com) o 2GB of free storage, up to 100gb for paying customers idrive Basic (http://www.idrive.com/) o 5GB of free storage MyOtherDrive (http://www.myotherdrive.com/) o 2GB of free storage - 13 -