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Month: May 2008

MD5 Checksums bring peace of mind

If you ever worry about a bit error happening to your files and not finding out about it, you should use MD5 checksums (or some similar method) to be able to verify that the file has not changed.

The general theory behind a checksum (or “Message Digest” = “MD”) is that it provides a unique 128-bit number for each and every file, based on its content. If one bit changes, the MD5 checksum (sometimes called “hash”) changes. The checksum is repeatable, does not permit discovery of two different files that produce the same checksum, and is non-reversible (i.e. you can’t create the content from the checksum).

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Packing equipment for shipment

It has become obvious to me that there are good ways and bad ways to pack equipment for shipping.

There are some basic goals that one needs to achieve in the packing.

  1. Protect the equipment from excessive shock and vibration
  2. Keep the equipment solidly centred within the outer box(es)
  3. Keep the equipment safe from small object impacts
  4. Prepare it to be dropped

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CD-DVD printing revisited

For many years, I had been in favour of the Primera Z1 small optical disc printer. When Primera discontinued this several years ago, I was not pleased and purchased two as spares, hoping at least the ribbons would continue.

It appears that I am not alone in thinking this is a good product as it has resurfaced as the U-Print CDP78, now in black, and available from many online distributors. The cartridges appear to be interchangeable with the Primera. I can now suggest that this is a good alternative for safe, long-lasting, and reasonably attractive text labeling of CDs and DVDs. It appears that the Teac P11 is also similar. The last time I checked, the Casio required manual rotation of the disk, rather than the Primera’s automatic rotation.

Please provide me with any feedback pro or con—preferably as comments to this post.

Mono and stereo cassettes

The format page for 0.15 inch wide tape has a drawing (click for large version) that clearly shows that mono cassettes have one wide track and stereo cassettes split this track in half and add a small guard band. Most mono cassette recorders follow this format. It turns out that the mono Marantz PMD201 uses a two-channel head and records dual mono. Most other mono recorders seem to follow the standard.

While this is a theoretical problem, few if any good mono recorders are available for reproducing these tapes anyway, so most of us in the domain transfer field use good quality stereo machines for all cassette transfer work.

UPDATE 2012: While it is often possible to sum the channels if the Dragon finds proper azimuth, on many low-quality tapes this proper azimuth is not achieved. Now that azimuth correction (at least the time delay portion) is available for a reasonable price in iZotope RX2 Advanced, I have found that after correcting for time delay between channels that I can now sum both (if they are worthy of it) and reduce the noise prior to applying the noise reduction plug-in.

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