After we have migrated your analogue or digital tape to a digital file, we offer a range of delivery formats.

For audio visual these include Apple Quicktime /MOV in any codec, 10 bit uncompressed (recommended), AVI in any codec; any MacOS, Windows or GNU/Linux filesystem (HFS+, NTFS or EXT3); DVCAM / miniDV and DVD.

For audio we offer Broadcast WAV (B-WAV) files on hard drive or optical media (CD) at 16 bit/44.1 KHz (commonly used for CDs) or 24 bit/96 KHz (which is the minimum recommended archival standard) and anything up to 24 bit / 192 Khz. We can also deliver access copies on CD or MP3 (that you could upload to the internet, or listen to on an ipod, for example).

Why are there so many digital file types and what distinguishes them from each other?

The main difference that is important to grasp is between an uncompressed digital file and a compressed one.

On the JISC Digital Media website, they describe uncompressed audio files as follows:

‘Uncompressed audio files are the most accurate digital representation of a soundwave, but can also be the   most resource-intensive method of recording and storing digital audio, both in terms of storage and management. Their accuracy makes them suitable for archiving and delivering audio at high resolution, and working with audio at a professional level, and they are the “master” audio format of choice.’

Why uncompressed?

As a Great Bear customer you may wonder why you need a large, uncompressed digital file if you only want to listen to your old analogue and digital tapes again. The simple answer is: we live in an age where information is dynamic rather static. An uncompressed digital recording captured at a high bit and KHz rate is the most stable media format you can store your data on. Technology is always changing and evolving, and not all types of digital files that are common today are safe from obsolescence.

It is important to consider questions of accessibility not only for the present moment, but also for the future. There may come a time when your digitised audio or video file needs to be migrated again, so that it can be played back on whatever device has become ‘the latest thing’ in a market driven by perpetual innovation. It is essential that you have access to the best quality digital file possible, should you need to transport your data in ten, fifteen or twenty years from now.

Compression and compromise?

Uncompressed digital files are sound and vision captured in their purest, ‘most accurate’ form. Parts of the original recording are not lost when the file is converted or saved. When a digital file is saved to a compressed, lossy format, some of its information is lost. Lossy compression eliminates ‘unnecessary’ bits of information, tailoring the file so that it is smaller. You can’t get the original file back after it has been compressed so you can’t use this sort of compression for anything that needs to be reproduced exactly. However it is possible to compress files to a lossless format, which does enable you to recreate the original file exactly.

In our day to day lives however we encounter far more compressed digital information than uncompressed.

There would be no HD TV, no satellite TV channels and no ipods/ MP3 players without compressed digital files. The main point of compression is to make these services affordable. It would be incredibly expensive, and it would take up so much data space, if the digital files that were streamed to televisions were uncompressed.

While compression is great for portability, it can result in a compromise on quality. As Simon Reynolds writes in his book Retromania: Pop Culture’s Addiction to its Own Past about MP3 files:

‘Every so often I’ll get the proper CD version of an album I’ve fallen in love with as a download, and I’ll get a rude shock when confronted by the sense of dimension and spatiality in the music’s layers, the sculpted force of the drums, the sheer vividness of the sound. The difference between CD and MP3 is similar to that between “not from concentrate” orange juice and juice that’s been reconstituted from concentrate. (In this analogy vinyl would be ‘freshly squeezed, perhaps). Converting music to MP3 is a bit like the concentration process, and its done for much the same reason: it’s much cheaper to transport concentrate because without the water it takes up a lot loss volume and it weighs a lot less. But we can all taste the difference.’

As a society we are slowly coming to terms with the double challenge of hyper consumption and conservation thrown up by the mainstreaming of digital technology. Part of that challenge is to understand what happens to the digital data we use when we click ‘save as,’ or knowing what decisions need to be made about data we want to keep because it is important to us as individuals, or to wider society.

At Great Bear we can deliver digital files in compressed and uncompressed formats, and are happy to offer a free consultation should you need it to decide what to do with your tape based digital and analogue media.

The main work of Great Bear is to make analogue and digital tape-based media accessible for people living in a digital intensive environment. But once your tape-based media has been digitised, is that the end of the story? Do you never need to think about preservation again? What issues arise for information management in the future, and how do they relate to our actions in the present?

This year (2013) the National Archives in the UK are facing a huge challenge as the ’20-year rule‘, in which the government will be releasing records when they are 20 years old, instead of 30, comes into effect. A huge part of this process is the digitisation of large amounts of material so they can be easily accessible to the public.

What does this have to do with the digitisation of tape you may be wondering? Well, mostly it provides food for thought. When you read the guidelines for the National Archives’ digitisation strategy, it raises many points that are worth thinking about for everyone living inside an information intensive environment, professional archivist or not. These guidelines suggest that many of the problems people face with analogue media, for example not being able to open, play or use formats such as tape, floppy disks  or even digital media, such as a cd-r, do not go away with the move toward wholesale digitisation. This is summed up nicely in the National Archive’s point about digital continuity. ‘If you hold selected digital records that are not yet due for transfer, you will need to maintain their digital continuity. This means ensuring that the records can be found, opened, understood, worked with and trusted over time and through change’. This statement encapsulates the essence of digital information management – the process whereby records are maintained and kept up to date with each technological permutation.

Later on in their recommendations they state something which may be surprising to people who assume that digitisation equates to some form of informational omnipotence: ’Unlike paper records, digital records are very vulnerable and will not survive without active intervention. We cannot leave digital records on a shelf in an archive – they need active management and migration to remain accessible in the long term.’ These statements make clear that digital records are just as vulnerable as their analogue counterparts, which although subject to degrading, are in fact more robust than is often assumed.

What is the answer to ensuring that the data we create is usable in the future, is there an answer? It is clear on whatever format we choose to archive data there is always risk involved: the risk of going out of date, the risk of vulnerability, the risk of ‘not being able to leave them on the shelf’. Records, archives and data cannot, it seems, simply look after themselves. They have to adapt to their technological environments, as much as humans do.

As well as analogue tape, at Great Bear we also migrate digital tape to digital files. Digital media has become synonymous with the everyday consumption of information in the 21st century. Yet it may come as a surprise for people to encounter digital tape when we are so comfortable with the seemingly formless circulation of digital information on computers, at the cinema, on televisions, smartphones, tablets and other forms of mobile media. It is important to remember that digital information has a long history, and it doesn’t need to be binary or electronic – abacuses, Morse code and Braille are all examples of digital systems.

Digital Betacam tapes were launched in 1993 and superseded both Betacam and Betacam SP. Betacam remains the main acquisition and delivery format for broadcasting because there is very little compression on the tape. It is a very reliable format because it has a tried and tested mature transport mechanism.

While Digital Betacam is a current broadcast format, technology will inevitably move on – there is often a 10 year lifespan for broadcast media, as the parent company (SONY in this case) will cease to support the playing machines through selling spare parts.

We were sent some Digital Betacam tapes by Uli Meyer Animation Studios who are based in London. Uli Meyer make 3 and 2 D commercials, long and short films and TV commercials. 5-10 years ago the company would have had Digital Betacam machines, but as technology develops it becomes harder to justify keeping machines that can take up a lot of physical space.

Workflow in broadcasting is also becoming increasingly ‘tape less’, making digital tape formats surplus to requirements. Another issue facing the Digital Betacam is that it records information in Standard Definition format. With broadcasters using High Definition only, the need to transfer digital information in line with contemporary technological requirements is imperative for large parts of industry.

We often get sent Digital Audio Tapes or DAT’s for transfer to .WAV computer files. As these recordings are already digital or ‘born digital’ the process should be straightforward. Our audio interface cards accept the SPDIF or AES digital audio stream from the DAT machine and record this as a WAV or BWAV file. This file can then be burnt as a CD or delivered digitally on a hard drive or removable media.

The big problems though come with the tape that these digital recordings are made on. The tape is only 3.81 mm wide and moves at a very slow 8.15 mm/sec. The tape is also very thin at 13 microns. The recording system and transport used is helical scan just like in video recording but with the very slow tape speed and small tape dimensions any defects or problems with the tape can result in many errors which may not be correctable by the error correcting system of the DAT machine.

One problem we’re starting to see more and more are tapes that snap. The tape pictured above was a D120 which was never recommended by the DAT machine manufacturers but was still often used for it’s extended recording time. This tape snapped without warning a quarter of the way through the recording. There were no outward signs or potential problems just a sudden clean break on a diagonal.

To recover this tape it could have been spliced with splicing tape of the correct width like in analogue recording but there is a high risk if not done perfectly of unrepairable damage to heads on the drum. Even with this type of repair some of the material would have been lost. A safer solution is to rehouse each spool in another shell this lets you recover as much as possible from the tape without the risk of head damage.

Whichever solution you decide the DAT shell must be disassembled. A small crosshead screwdriver needs to be used to remove all the case screws. There are two hidden ones, accessed by sliding part of the cassette shell down:

You can now carefully lift both halves of the DAT shell apart, making a note of the tape path inside the shell. Be careful not to touch the tape with your bare skin as fingermarks and grease can cause head to tape contact problems and audio errors and dropouts.

 

 

 

We have several of these large, wonderful machines. It’s not often we need or want to get involved in DAT repair as generally they are not easy to service machines and many key transport parts are becoming unavailable. The Sony 7030 DAT though has been designed with easy servicing in mind. There’s alot of room in these things and each section is clearly marked and separated into distinct boards much like Sony Broadcast video machines.

These are timecode DAT machines and were once common in video post production houses and the more well funded recording studios. The problem with some of this well built kit though is exactly that it works too well and gets left on for long periods through it’s life and this can take a toll on certain components, especially electrolytic capacitors. Heat builds up in electronic circuits, especially in switch mode power supplies that larger broadcast items often use. Capacitors have a rated life at 85°C or 105°C at several thousand hours. With hotter environments, substandard parts and long operating hours these capacitors can soon outlive their original design life.

Our 7030 DAT had started behaving oddly and at first the display would flash on and off after a short while powered on. Another machine would power up for 30 secs then just die. Before delving into the enormous service volumes it’s always worth replacing the Switch Mode Power Supplies (SMPS). These like many broadcast machines use supplies that are sometimes generic made by other companies and which can be bought at Farnell or RS. We did it the harder was and desoldered all the old capacitors in the power supply and replaced these with high quality low ESR Panasonic ones which should give us another 6000 hours of running time. So far this machine has worked perfectly although you do need good soldering and desoldering technique on these boards. A powered air desoldering station is a good idea, much, much better than a hand solder pump.

We use time base correctors and frame synchronizers all the time in the transfer and digitising of analogue video tape.

One of our more flexible and high quality units had recently developed an annoying and very obvious fault on it’s video outputs. While the unit was working there were faint but distinct horizontal lines on the video. This phenomenon is often called a hum bar and can be caused by ground loops.

In this case we isolated the unit from the rest of our installation and using a separate power point the problem was still there. Looking at the unit itself it is a very deep and heavy 1U case with two 40mm cooling fans at the rear corners. It is quite old too and being designed for continuous studio use is likely to get hot and have been on for very long periods.

The video fault appeared to be AC ripple ‘riding’ on the DC power. It was time to look at the electrolytic capacitors in the power supply.

Although I could have tested each one, all these caps were old and only rated for 3000 hrs at 85 celcius so they all had to go! Here’s a list of them:

The only one hard to find was the large 400v dump one. Most units now are thinner and taller but eBay came to rescue here.

This shotgun approach worked beautifully and the fault had gone. While tracing the exact fault is always the best way, capacitor often get a hard life and will not last indefinitely, especially in switch mode power supplies.