POWRR Digital Preservation Institute - Day 2

Reporting live from a Digital Preservation Institute hosted by POWRR (Preserving Digital Objects With Restricted Resources) to share my second day of learning. I'm here in Honolulu, at the University of Hawai'i, Mānoa, as a representative for T.A.P.E., generously funded by the National Institute for the Humanities.

Writing a Workflow

A digital preservation workflow is an iterative process made up of key processes: ingest, processing, access, storage, and maintenance. The key is making those processes part of your ecosystem and work for you! Since T.A.P.E. primarily works with digitized items, rather than "born-digital" items without an analog counterpart, we will adapt the workflows to best suit us. However, we are so excited to begin expanding support for digital home movies - not only in their preservation, but in the valuation of these items in the home movie landscape.

One of the most valuable takeaways was the idea that tools quickly become orphans, abandoned by creators, unsupported by new operating systems, or lose funding. The workflow and goals should come first, and the suite of tools should come second, with an eye toward interoperability. Increasing resilience and confidence, this model puts our goals first. 

We also discussed the value of different kinds of tools. Free is never really quite free, as it requires time, attention, training, and knowledge to operate and maintain open-source free tools. The analogy used was a kitten may be free, but it's not the same type of free like a beer from a friend that you can drink quickly. 

The kitten model extended further into the types of tools. A "barn cat" tool is one that requires little maintenance but usually completes one task (such as hunting mice). For example, a tool that only identifies duplicate files might be a barn cat. A "high maintenance" cat requires more attention but might do more complex tasks. A tool like a bit curator, which requires a Ubuntu-supported computer, does more complex tasks in an imaging environment but requires more infrastructure.  Knowing how much you need to invest in a tool is useful for assembling a suite of tools that best support your capacity. 

Digital Preservation Tool Grid

One of the most exciting parts of my training was getting to play around with digital preservation tools. Digital POWRR has created a tool grid, which outlines the value of different tools and access points to using them. This is critical for building a tool kit that assists in a workflow and getting started on using them.  

Data Accessioner

One of the most exciting tools we used was a Digital POWRR maintained tool called Data Accessioner. In the archive world, to "accession" something is to bring in formally into your archive, but putting it in relation to the rest of your collections and intitiating processing, which can also be understood as ingest. 

You enter this tool using a ./start.sh command in terminal and then a graphical user inferface (GUI) opens! The tool allows you to ingest digital media (photographs, text files, videos) stored on digital storage devices (optical disks, hard drives, etc.) using fixity checks and inserting additional Dublin Core Metadata. I.E. you're moving them off the storage device to a new digital environment and running checks to make sure the transfer was faithful. 

okay yes I changed my terminal color scheme to pretend I'm an early 2000s hacker, but I promise it's so easy to use!

Side Note: Optical Media is a category of physical storage device for digital information that uses laser light to encode and read digital information. This includes CDs, DVDs, Blu-Ray, and spinning hard drives. The way it works is that a laser beam burns onto the disk in a rapid pattern, with pits (burns) and lands (spaces) representing 0s and 1s. Depending on the type of media, some optical media (-R and -RW writable media especially) is made with organic dyes that degrade quickly. As the dyes degrade, the data becomes corrupted because it cannot be read properly. While manufacturers promised long lifespans, these discs are degrading in much shorter periods, (sometimes only lasting a few years). 

A microscopic view of three forms of optical media. Note how the more complex the data, the more pits we see encoded on the disc. These are all burned in and read by a microscopic laser.

A laser disc is an analog optical disc, so works a little differently as a direct representation of light and sound frequency like a vinyl (that's the analog part) rather than 0s and 1s). Laser discs are subject to something called laser rot, whereby the reflective disc surface begins to degrade or detach from the disc itself, making these an unstable format for the long-run. 

A microscopic comparison of a vinyl record (above) and a laser disc (below). Both utilize a continuous analog frequency to directly represent light and sound waves. 

Data Accessioner uses Dublin core for creating ingest metadata. Dublin Core is a family of standards used to describe objects using controlled vocabulary and standards. Highly flexible, interoperable, and easy to read, this metadata is designed to inject vital information at the site of ingest before it is lost. 

During ingest, Data Accessioner assigns the file an MD5 checksum. As I discussed in my earlier blog post, a checksum is a string of numbers and letters that serves as a tool to make sure our digital file has not changed (over time or through actions like moving it). 

(I also learned an exciting python script to force a program to recognize a command, instead of reading something as a directory - nerd shit). 

Side Note: "Command-Line" operations on your Terminal is an interface for talking directly to your computer and telling it what to od. But it can do a lot of the same times as software because it's fundamentally doing the same processing. But sometimes faster or perform functions that haven't yet been built into user-friendly software. 

Da-Mt

A great add on too for Data Accessioner is Da-Mt (pronounced damn-it). All that metadata and inventory you create in Data Acessioner is exported as an XML file, which is machine readable and durable, but not quite as human readable (mostly because of spacing and use of computing language).

XML File with Technical and Descriptive Metadata created during Ingest

 Da-Mt transforms XML raw information into human readable CSV and HTML files, which can be easily read and utilized in google sheets or excel. It's useful for transforming any XML information and certainly makes the ingest and inventory process easier. 

DA-MT in action! So easy!

Dupe Guru

A new essential for me is Dupe Guru, a tool that identifies duplicate files in a file directory and helps you decide what to delete. Not only does it search duplicate file names and file size, but also performs a fuzzy search. A fuzzy search is one that looks for approximate patterns, rather than exact replicas, with a column showing the percentage match so you can manually determine if you indeed have a duplicate. 

A game changer for storage management and inventory! 

DANNNG!

DANNNG! is a working group used for evaluating and resource building for ingest, packaging, and transfer, and imaging of digital files, designed for the cultural heritage sector. 

One great tool is decision tree for deciding whether to image or simply transfer the files on disc. I've always struggled with the decisions involved in the two. Disc Imaging is a process whereby you copy all the bits on a storage device. A disc image is only machine readable, not human readable, thus requiring a decoding software to interpret and represent the raw data. Migration is less intensive, and just inovlves moving the files contained on the storage device. While an older school of thought, which emerged - particularly from policing - forwarded disc imaging because of a desire to establish provenance and recover deleted files, disc imaging is often overkill for optical media. For optical discs (CDs and DVDs) in particular, the need to capture the raw data may excessive, because you wouldn't be looking for deleted files, taking up valuable storage space, labor time, and computing power. Additionally, the leading free disc imaging software, FTK Imager, emerges from policing, and for T.A.P.E., collusion with policing technology does not align with our values.  

Although it may be more complicated to run, I'm interested in exploring BitCurator as an alternative for imaging hard drives as a future T.A.P.E. service to recover data!

I am particularly excited to explore more of the tool decision factor documentation. In building digital preservation and workflow, we also aim to support other individuals, communities, and organizations in developing tools that assist in the preservation of their digital heritage! Undersanding many tools will help in adapting to many environments and needs! 

The other tools I plan to explore include batch renaming, migration and file moving tools with fixity checks, and more! I also want to try out DROID, which is a tool used to identify the type and age of file formats, which may not be needed now but is good for future projects related to personal storage device and digital home movie preservation. 

Packaging, such as the DART tool, would be great for wrapping up files for storage. Packaging relies on "bag it" tools, which provide an envelope for digital files, useful for long-term storage. Like a ZIP file, a bagit package helps keep related files together (like a Preservation Copy, Mezzanine File, Access Copy, metadata XLM, checksum) in one folder so it's ready to get shipped off and stored. DART (Digital Archivist's Resource Tool) is an open-source GUI (gooey or Graphical User Interface) and command-line tool for doing exactly that! Designed by and for archivists!

Overall, day 2 of the POWRR Institute was an exciting and nerdy time for me. I love learning about new tools and honing my command-line skills. Tomorrow is the final day! :(

T.A.P.E. is a 501(c) 3 non-profit dedicated to facilitating access to analog media making, preservation, and exhibition. To support our work and access great benefits, join our patreon at just $5/month. You'll get access to exclusive rates for our rental equipment library, access to our digital and physical videotape library, and other member benefits like free workshops. 

We've launched a $6,000 goal for GoFundMe to buy essential digitization equipment to provide more archival transfer services for more tape formats. A donation will advance the work of people-oriented digitization services!

https://tapeanalog.org/

https://www.instagram.com/tape_losangeles/

info@tapeanalog.org

Blog is written by Jackie Forsyte, T.A.P.E.'s Technical Director, and an audio-visual archivist.

POWRR Digital Preservation Institute - Day 1

Reporting live from a Digital Preservation Institute hosted by POWRR (Preserving Digital Objects With Restricted Resources) to share what I've learned on my first day! I'm here in Honolulu, at the University of Hawai'i, Mānoa, as a representative for T.A.P.E., generously funded by the National Institute for the Humanities.

I learned about Digital POWRR when researching digital preservation tools for home movies as part of my MLIS coursework. I was inspired by their grounded, material plans and tools and how they were committed to education. Earlier this year, I applied to attend one of their institutes and was delighted to not only be accepted but to receive financial support that could cover my travel and lodging. 

In my education, I've wanted more from digital preservation - more practical plans, open-source tools, and support, particularly for personal archiving and orgs with limited resources. Digital preservation can be daunting, frustrating, and endless, but after today, I feel much more connected to the material ways to empower myself and T.A.P.E.

Introduction to Digital Preservation

We started by defining some key terms, namely what is digital preservation?

I like the idea that it is the relationship between yesterday, today, and tomorrow with a digital object, whereby we can accurately store, provide access to, and sustainability check the fixity of a digital file over time. We want to create a system and process to hand off the digital file to future, so they can transform into the next sustainable container, with the best information and tools to do so. 

Digital preservation is also a risk mitigation process, thinking about how to prevent the total loss of a digital object as the result of media or file format obsolescence, disaster, failure, or decay. 

having fun with my new toy digital camera!

Some best practices? 

1. Important and overlooked - know what you have! An inventory of the items and their formats and where they are stored is such an impactful step. 

2. Keep more than one copy across different storage mediums

3. Have a plan for migration and storage media transfers

4. Use open formats that are more resilient against obsolescence and corporate enclosure i.e. a PDF is open whereas a Microsoft Word document is owned by a company and requires paid software to properly decode it

5. Use data fixity tools and practices

Fixity is ensuring that the item you have is actually the item you had and want to have. That it is the same as before. This is clearly important because you don't want your file to change, as one bit of changing can dramatically alter or corrupt the content, especially for visual information.  

Fascinating & scary slide - script created by the instructor that would change one bit in a digital photo, showing the visual results from significant changes to complete corruption. 

We use checksums to mathematically process this. A checksum is a string of numbers and letters that corresponds to a snapshot of your file, ideally as you create it or before you move it. If your file changes, the string of numbers and letters changes too, alerting you that something has changed. An ~okay~ analogy is like taping a piece of hair over a door as a security system - if the hair breaks, you know something happened, but you don't know what it is exactly. But you can look around the room and replace anything that was lost. At TAPE we run frameMD5s, a checksum part of the digitization tool vrecord, that assigns a string of letters and numbers to each frame of a video, allowing us to know the exact frame where the change ocurred, rather than only having a checksum for the file.

Notice how each iteration with an incorrect spelling changes the checksum, alterting us that something has changed

Assessment

The next presentation was on tools, rubrics, and processes for assessing your organization's digital preservation practices. This is a great tool for figuring out what you do well and some tangible steps for getting to the place you want to be. We also talked about how to adapt some of these frameworks to decouple corporate productivity from our work, instead building sustaining models rooted in the value of preservation. We looked at two assessments in depth, although we recieved a long list of options! The key is to pick one and start, and any work is meaningful. 

The National Digital Stewardship Alliance created the Levels of Digital Preservation Assessment to provide multiple axes for conversation and action. 

We also looked at the Digital Preservation Coalition's Rapid Assessment Model. 

There were a couple of things I'm excited to talk more about with T.A.P.E. members:

• Our first priority is to secure funding for more copies of our digitized files and to create a plan for migrating these files using digital fixity tools. 
• A big inventory of our digital files is needed & coming soon, as well as a plan for regular inventories and audits
• I'm also excited to write documentation on the types of formats we have and an assessment of the hardware and software needed to sustain the files we create. 
• I'm more urgent about tapping into networks of watchdogs who look out for file, hardware, and software obsolescence related to our work, including proactive planning and collaboration. (I'm cynical about these things for sure!)
• We are invested in the preservation of TAPE-produced content (print, still photo, and moving image) to preserve our own work, on our own terms. 
• We also talked about resource sharing and building powerful constoriums and relationships to pool resources for digital preservation

A big takeaway, there are very few tools for personal archiving, bringing things down to the individual, the family, kin and friend networks. Building relationships with artists who work with us to empower their preservation through knowledge and resource sharing is key. Not only in making the best practices accessible broadly, but in sustained plans for implementing them over time. A great starting point for T.A.P.E. is a new resource I learned about a personal archiving guide and worksheet from the State Library of North Carolina. We are going to build on these tools to create zines and information on personal digital archiving as part of the archival practices people are already doing. 

I'm delighted to expand upon this work, opening tools, knowledge, and workshops for personal digital preservation. Empowering ourselves and each other in caring for the materials that matter most to our lives!

Digital Preservation Policies

In the next session, we narrowed in on writing a digital preservation policy, using existing models and templates. This written policy facilitates greater clarity, awareness, and committment to digital preservation goals, ensuring that the things we create today have a pathway for access tomorrow. A policy promotes digital preservation as part of a living ecosystem of creating and saving, so that it sits alosngside other conversations we are having, it has a seat at the table. It outlines goals, committments, and current actions. 

One exciting digital preservation policy I looked at was from the Door County Public Library, which does a great job at defining purpose and methods of preservation. The Wisconsin Historical Society also hosts a number of student-made digital preservation policies with smaller organizations, as well as other digital preservation guides. The College of Menominee Nation has an excellent policy that not only demonstrates clear commitments, but also outlines their workflows, increasing transparency and knowledge sharing.

The College of Menominee Nation's Digital Preservation Policy

We also examined some templates that we can use to write our policies, including the Digital Preservation Policy Toolkit, Digital Preservation Step by Step, and the Sustainable Heritage Document. 

A clear goal for TAPE is to start writing this policy as we are writing our collections policy and boosting documentation in our AV League, as it will facilitate greater goal setting and tangible action. And when we make our policy accessible online, we aim to help others in the care of materials by reducing knowledge barriers that occlude a sense of empowered and informed action. 

A New Working Group?

One of the most empowering takeaways is the knowledge that as a collective, there is a group of passionate and smart TAPE members who are similarly invested in this work. Whereas many archives must confront buracracy and co-workers who may not support their passion, I know I have so much support and power from my peers. It's a really empowering feeling, inspiring action rather than defeat in the face of so many steps that need to happen. I'm delighted to work collectively to move forward with these much needed tools!

From this, I'm laying the groundwork for Digital Preservation Working Group, a sub-committee of the AV Working Group and Collections, to collaborate on the policy writing and assessment process, as well as grant-writing, zine making, and public workshops. This is an exciting new chapter!

T.A.P.E. is a 501(c) 3 non-profit dedicated to facilitating access to analog media making, preservation, and exhibition. To support our work and access great benefits, join our patreon at just $5/month. You'll get access to exclusive rates for our rental equipment library, access to our digital and physical videotape library, and other member benefits like free workshops. 

We've launched a $6,000 goal for GoFundMe to buy essential digitization equipment to provide more archival transfer services for more tape formats. A donation will advance the work of people-oriented digitization services!

https://tapeanalog.org/

https://www.instagram.com/tape_losangeles/

info@tapeanalog.org

Blog is written by Jackie Forsyte, T.A.P.E.'s Technical Director, and an audio-visual archivist.

CAT-A-THON: Collective Cataloging Day

On Sunday, T.A.P.E.'s Collections Working group organized a collective cataloging day in an effort to bring together the catalogs that T.A.P.E. volunteers have been working on for the past year. So on Sunday we compiled separtate catalogs into a giant spreadsheet, labeled each tape with a barcode, and affixed a status label so we'd be able to track the status of our work. 

In two short hours, we affixed barcodes, transcribed existing barcode numbers, and affixed status stickers for 218 tapes.

Earlier this month, the T.A.P.E. Collections Working Group met to establish a plan. One of the biggest needs we identified was to organize a collective day to get tapes in our collection barcoded & ready for access. Internally, we have spreadsheets with rich metadata about our collection, and we needed to refine and combine them into something that we can easily import into our circulation library interface, Tiny Cat. The goal is for our collection to be of great artistic and entertainment use, and to extend access to rare and important material on VHS through physical and digital circulation. We have an archive in use, a collection in motion.

The first step in our collections access project was combining all of the disparate spreadsheets into one unified page. Done by T.A.P.E. volunteer and Collections lead Russell, the unified spreadsheet is a springboard for concatenating all of our collections. The reason we have separate spreadsheets is because the provenance (origin) of the tapes is different - some come from the Echo Park Film Center, the Iota Center via the Museum of Jurassic Technology, others from private collectors such as Viva Video (major video distributor in the Philippines) or even fished from the trash!

Summary powerpoint ft. cats by Franny, review of cataloging efforts led by Franny and Alohie

The next step was to assign each tape a unique identifier (UID), *usually* a string of numbers that corresponds directly to a singular physical or digital item. If you have two VHS copies of Meshes of the Afternoon (1943), one would have a UID of 00012, while the other may have been brought into the collection later and is 00300. The UID helps us distinguish between the two copies that may be similar or even identical. A UID also assists in digitization, as we can understand the intellectual link between a physical VHS tape and its digital file in the form of an MKV preservation file or an MP4 access copy. Lastly, as we gear up to rent the physical tapes in our collection, we will use the UID as a tracking system for checking items out and returning them. 

Our UIDs come as a barcode from TinyCat, our library system. A barcode is a UPC (Universal Product Code) that turns numbers into a scannable symbol. That way, we can read the UID with our eyes, but it can also be read by our extremely adorable cat-shaped barcode scanner, providing multiple modes of access into the catalog. Barcodes are not infallible - because they are on paper, the barcode is subject to damage, so multiple checks of barcodes and cataloging is critical. In fact, there are profound parallels between digital videotape (like MiniDV) and barcodes as they are both digital information encoded on physical mediums vulnerable to damage and decay.

In the collections committee, we wanted to make the collective cataloging process easier and more accessible to new volunteers. A large part of that was creating a physical label that would indicate the status of the individual tape - whether it had been cataloged, digitized, its digital record imported into TinyCat, or if the tape was good for circulation. Collections Committee Admin Lee created stickers which allow us to easily visually identify the status of each tape. The new sticker allows for greater unity in our cataloging work across many people and long periods of time. 

We also performed metadata cleanup. For tapes not cataloged, we quickly added them to the spreadsheet. Using Open Refine, we identified duplicate entries in our cataloging to remedy errors. We will continue this work of metadata clean up so ensure the best and most consistent records for internal and circulation use!  

Past volunteers have diligently worked to catalog tapes in the T.A.P.E. Collection for the past eight months. This has included manually transcribing the written descriptions on the tape and its case, which often includes rich descriptive text. Much of this work we've done in other languages, including Russian, German, Spanish, Tagalog, and more. Volunteers have also identified the format, brand, and recording mode - technical metadata that is critical for digitization. And we have also initiated a robust collections assessment to identify items in our collection that are neither circulating on physical media nor online. For tapes that are highly rare, we are beginning a process of duplication, so a non-circulating preservation tape can live with T.A.P.E., and patrons can still watch the content on a physical or digital access copy. We have also begun a process of de-accessioning, a term that means taking things that do not apply to our collection scope out of our collection. We've de-accessioned tapes for content that is freely available online to make room for future collections in urgent need of preservation. This collective effort has occurred at desk shifts at T.A.P.E. through the passion, knowledge, and skill of dozens and dozens of T.A.P.E. volunteers. 

Collective cataloging days are a remarkable process that we aim to continue. It allows us to create and refine our standards collectively, in conversation with each other. We also get to prevent the problems associated with backlogs, particularly loss of institutional memory about the collections. Our first cataloging day in March, 2024 allowed us to get a massive jump start on cataloging hundreds of tapes in our collection. 

The idea is a springboard from Sydney Kysar, whose work with collective cataloging has served as an empowering model. Syd organized a collective cataloging day with the Bob Baker Marionette Theater where they also volunteer, and led the cataloging of 500 books in their library in one day. Further, they've organized collective cataloging days with Access Books, who collaborate with school librarians to vital services that enliven school libraries, including refreshed book donations and murals (Syd is the lead mural program coordinator). After learning that school librarians work for 2-3 years to catalog their entire library, Syd organized collective cataloging days where volunteers cataloged those same books in 2-3 days. It's radical work and we are delighted to have Syd contributing to our efforts!

Our next steps in our project include

• Drafting a collection policy on what we do & do not collection
• Writing a collection overview document which outlines the source of our collection
• Creating genre labels for easier identification for library circulation
• Performing a digital audit of our hard drives
• Uploading catalog records to TinyCat
• Creating a preservation plan & catalog for T.A.P.E. produced items
• Improving workflows & documentation

All of these projects are collectively driven, for ourselves, by ourselves. Our goal is to create a sustained collection that can circulate and provide artistic, entertainment, or research use. Rich metadata, no backlog!

We are SO EXCITED to keep launching additions to the Tiny Cat library for you all to explore, including renting physical tapes & viewing our digitized files. Check out our Tiny Cat Library and explore our collection here!

T.A.P.E. is a 501(c) 3 non-profit dedicated to facilitating access to analog media making, preservation, and exhibition. To support our work and access great benefits, join our patreon at just $5/month. You'll get access to exclusive rates for our rental equipment library, access to our digital and physical videotape library, and other member benefits like free workshops. 

We've launched a $6,000 goal for GoFundMe to buy essential digitization equipment to provide more archival transfer services for more tape formats. A donation will advance the work of people-oriented digitization services!

https://tapeanalog.org/

https://www.instagram.com/tape_losangeles/

info@tapeanalog.org

Blog is written by Jackie Forsyte, T.A.P.E.'s Technical Director, and an audio-visual archivist.

TBC 101!

Donate today to T.A.P.E. and you'll help us dramatically expand access to digitization equipment. Preservation for the people is within reach! 

When I first entered the preservation world, one of the most intimidating yet magical words thrown around was "TBC." And it's taken me a minute to figure out what it is, what it does, and how to explain it to people. That's because explanations are often brief & technical, originating from a television broadcast world where information must move quickly. But understanding a TBC and its role as an essential building block of digitization is within reach! And by understanding this device, we can better advocate for videotape and the magic of its content.

T ime 

B ase

C orrector

TBCs are also used in glitch art!

When you are connecting more than one device in analog video playback (lets say VCR to CRT or VCR to analog / digital converter) these devices rely on synchronization to correctly display the picture and audio. And that synchronization is based on pulses sent out at regular intervals that time each device together. 

Sync Pulses & Blanking Intervals 

Think of these pulses as the machines setting their watches at the same time, with each tick of the second hand across the watches moving in sync. 

     

Encoded on a videotape are these pulses known as horizontal and vertical sync pulses that communicate the limits of the video frame. Video is made up of lines that run horizontally to construct the image. You know how a digital photo is made up of square pixels, well an analog video is made up of lines, with each line replicating how bright or dark that part of the image is. A horizontal sync pulse is a pulse that says "this line has ended, time to start the next one!" Without the horizontal sync pulse, the line would continue on forever and forever, never starting over again.

CRT Refreshing Rate

Horizontal Timing

Video is also made up of two fields, a left and right one that interlace together to form one frame. A vertical sync pulse sends pulses saying "this field is ended, time to start the next one!" Without a vertical sync pulse, the frame would just keep building and never restart. 

Field Order for Analog Video

After the horizontal pulse at the end of the line, there is something called a horizontal blanking interval. The electron beam which creates the scan line from left to right must temporarily turn off so it can get back to the other side of the screen. Without the blanking interval, you'd see the beam retracing its steps from right to left. At the end of the field & frame, there is a vertical blanking interval which again is a blank image in between two frames. Without the vertical blanking interval, you'd see the beam go from the bottom to the top of the screen.

Scanning path

Blanking and sync pulses define the limits of the active picture, making sure it stays within the frame. These pulses are not visible. They exist at frequencies below the visual image. These synchronizing pulses power the video system, making sure that the receiver is in lockstep with the image. 

Waveform with analog video signals

Time Base Error

However, the devices we play videotape on and the devices we record on are not perfectly timed. And they often have issues in their mechanical functions too that maintain proper tension of the tape path. The tapes which contain the synchronizing pulses can be old, stretched, and warped. Therefore, these synchronizing pulses fall out of sync. To complete our metaphor, our watches are out of sync with each other because the gears inside start to wear down. 

As a result, a time base error occurs, whereby the picture starts to have visual errors and cannot faithfully reproduce the image. Some examples of time base errors include:

Flagging the top of the screen starts to look like a flag blowing in the wind

Skewing the bottom of the screen looks a few lines off from the rest of the image

Tearing the image looks smeared, like someone has pulled on some of the lines from one side of the screen. 

Jittering image flashes or rolls in and out of frame.

Time Base Errors

Time Base Error

You may also see a chroma noise, which looks like extra color "mist" (red and blue) that exists in the image or luma noise which looks like extra white "mist."

Chrominance Noise

So, what does a TBC do?

A TBC helps support all the different components in synchronization, properly containing the lines and fields within the frame. Here, the image is "jittering" or rolling and flashing in and out of frame. This is corrected by a TBC. 

It also corrects tearing on the line level!

Tearing corrected by TBC

TBCs can powerfully correct chroma noise and clean up noisy signals. 

Light tearing and chroma noise corrected by a TBC.

One of the most important functions of a TBC is that it can prevent dropped frames. Analog to Digital Converters and their capture devices are extremely sensitive to issues in synchronization. This is different than a CRT, which is far more tolerant to these changes. If the tape or playback device falls out of sync, the capture card will drop that frame completely, leading to consistent black images or loss of consistent picture. 

It brings our playback back into synchronization and cleans up noise, providing a clearer, better picture that is a faithful reproduction of the original content. 

Processing Amplifier

TBCs also often have a built-in Processing Amplifier, a device that reprocesses the video signal so as to alter the levels of the video. 

Video is constrained by broadcast standards a set of rules set for television that creates limits for how much light, dark, and color information can be broadcast to your television. Think of it like a set of standards for broadcasts to ensure the consistent images across many, many television sets. Any information broadcast outside of these standards is cut off, meaning information is lost if broadcast outside of the levels. These standards have become a critical part of videotape.

For Luma (Y') or brightness information, we use a scale from 0 to 100 IRE. IRE is a measure of the strength of electricity or the voltage of analog video signal, derived from the Institute of Radio Engineers. Reference Black (true black) is 7.5 IRE and reference white (true white) is 100 IRE. 

Black is 0 IRE or 0% energy exerted. White is 100 IRE or 100% energy exerted. (Reference or "visible" black is technically 7.5 IRE, as signal below 7.5 IRE is for blanking).

A Processing Amplifier (Proc Amp) allows you to contain your information within 100 - 7.5 IRE. The Set Up function lifts/reduces the black point. Ideally, you want this to sit just above 7.5 IRE to faithfully represent "true black."

Here you can see my friend D lifting the set up, watch as the analog waveform monitor shows the black point going up! 

When video information goes below 7.5 IRE, it is crushing. It looks like the image has lost detail in the blacks and can appear noisy. This is what we call “artifacting,” or adding noise that wasn’t there in the original video. Information is lost and cannot be retrieved. Furthermore, your file will incorrectly represent black information. 

The Video function adjusts the spread of brightness. It certainly adjusts the upper limit of white information, but also functions like an accordion, opening and reducing the brightness spread from a flat (closed) to a dynamic/naturalistic (open) image. You want the "true white" information to sit just below 100 IRE. 

Now the video knob! Particularly watch as the very top of the waveform transforms from a very flat line (clipping) to a more nuanced, bouncing shape as they set the brightness of the video signal within broadcast range. 

When video information goes above 100 (analog waveform), it is clipping. It looks like the image is blown out/crunchy in the whites. Think of when you shine a spotlight on someone, adding a second spotlight only washes the person out and reduces fine information. Furthermore, your file will incorrectly represent white information.

Here is clipping on an audio signal. The information is cut off, turned into a flat line, which means it is lost

We also use the proc amp to adjust the chroma and hue of the video. Chroma is the strength or saturation of the color information. There are limits to how much color you can display, similar to brightness/darkness. Any information that is outside of the legal color space, or defined limits of color, will appear dramatically oversaturated and that information will be lost. 

Hue is the "direction" of or calibration to the color standards. We calibrate colors to industry standards, known as color bars. However, for home movies, where there are no color bars on the tape to use as reference, we use our eyes to correctly set hue, ensuring naturalistic skin tones and common reference points (blue sky, green grass, or red sweater) to display natural color. 

We use a a vectorscope as reference for the Chroma (saturation) and Hue (direction) of color, meant to calibrate SMPTE color bars to the correct broadcast standards. The points on the graph should match the squares with the corresponding color. 

SMPTE Standard Color Bars for Analog Video, Allowing you to calibrate color hue and saturation

Each of the points of the star-like shape should align with the points, seen on the little square boxes at the tips of the shape.

A vectorscope displaying the color bars

R = Red

Mg = Magenta

B = Blue

Cy = Cyan

G - Green

Yl = Yellow

All of these parts of the processing amplifier are critical for ensuring high-quality transfers. In terms of the visual image, we want to make sure that home movies look how they should. They are imbued with such potent power and memory, we want them to evoke that sense memory of the event, particularly with skin color. For signal information, we want to preserve all information encoded on the tape. 

Without a processing amplifier, information will be lost at the upper and lower ranges of color and brightness, as it cannot be contained within broadcast standards. While this may not always read to our eyes, this is important for long-term preservation. Digital files made during digitization will be the new items passed on generationally or among people today. Making sure they set up to be the most faithful to the original is key to the valuation of these home movies and their preservation.

TBC Obsolescence 

Many professional decks have built-in TBCs and processing amplifiers. This means you can playback analog tape and perform these vital corrections all in one swoop. 

However, professional decks don't support all recording styles. Of highest concern for us at T.A.P.E. is the lack of support for Extended Play (EP) and LP (Long Play) modes. These recording styles were designed to encode x2, x3, x4 as much information on a regular tape by encoding the information closer together. Improving the affordability of videotape, EP and LP modes often have hours extra of footage in home recordings. 

These tapes will not play back in professional decks, which were not designed to support EP/LP recording or playback. Meaning, we cannot use them to digitize these home videos. Instead, we need an external TBC, or a device that is added to the signal flow of a consumer deck that does support EP/LP to stabilize and improve the quality of the signal. Without a TBC, an EP/LP signal coming out of a consumer deck is too unstable to be digitized, leading to information dropping out completely!

External TBCs are often hundreds, if not in the thousands, of dollars. They contain complex electronic circuitry and often die. They are in high demand and can often go to the person who has sustained commercial or other financial backing. This leaves most people and organizations stuck!

Hardware obsolescence is grim prospect. But by using crowd-funding to purchase our own TBC, we aim to provide wide access to our low-cost digitization services to the Los Angeles public. With the generous donations to our Go Fund Me this past week (!!!!) we are now able to purchase this critical piece of hardware, and dramatically expand our services.

Thank you so much to our donors. What a heartwarming and remarkable contribution. We are honored that you are part of this work.

Let's do more of it!

T.A.P.E. is a 501(c) 3 non-profit dedicated to facilitating access to analog media making, preservation, and exhibition. To support our work and access great benefits, join our patreon at just $5/month. You'll get access to exclusive rates for our rental equipment library, access to our digital and physical videotape library, and other member benefits like free workshops. 

We've launched a $6,000 goal for GoFundMe to buy essential digitization equipment to provide more archival transfer services for more tape formats. A donation will advance the work of people-oriented digitization services!

https://tapeanalog.org/

https://www.instagram.com/tape_losangeles/

info@tapeanalog.org

Blog is written by Jackie Forsyte, T.A.P.E.'s Technical Director, and an audio-visual archivist.