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At 12:06 AM 2006-12-17, Steven C. Barr(x) wrote:

>Still...define "reversed" per .wav files...?!

Hello, Steven,

Here is the application:  I have a bunch of two-track mono tapes that 
need to be digitized (29 to be precise). They are oral histories. 
Both sides were recorded with the same recorder (as it turns out, the 
entire batch appeared to be recorded with the same recorder with the 
azimuth out the same amount on all tapes).

So, rewinding the tape and playing it through gives me a nice play 
wind and both sides transferred in one pass. BUT it leaves me with 
the first side reversed end-for-end. In other words, playing backwards.

Using an 8-channel 44.1/24 card (these were recorded at 1.88 in/s) I 
can ingest four tape machines simultaneously. I used four Sony 
APR-5000s. One tape was 3.75 in/s in the last batch, so I did that on 
the Studer A810 NAB 2-track since the APR-5000 I had it on wasn't set 
up for 3.75 with the slow-speed NAB head stack (slow speed 3.75 to 15 
rather than 7.5 to 30 in/s). I get the APRs to do 1.88 in/s by using 
-50% varispeed and a specially aligned register (there are three 
alignments per speed for each of 12 heads for each of three speeds, 
or 108 memory locations per machine)

Since no noise processing was involved, it doesn't hurt a thing.

Also, since it was recorded on the same machine, although it's 
counter-intuitive, draw it out...you'll find that the azimuth error 
for one side ends up being the same for the other and you get 
correction when played backwards. It's not 2x worse.

So, I had 28 files and reversing them takes about 5-10 minutes (24 
bit 44.1, 90 minutes each) Not something you want to sit and do 
manually when you can do it in a batch.

I feel good about buying a Canadian product to do this, although my 
primary editor, Samplitude from Magix, comes out of Germany as do the 
Algorithmix plug-ins I use for various cleanups. I'm not sure 
GoldWave will see a lot of use, but it will be fun to experiment with 
their filters and other batch things. Although with Samplitude, there 
is no latency to apply almost any effect (reversing is one that 
doesn't follow this rule) as most effects are done real time.

The average file I have to reverse is about 750 MB mono.

I know...more than you wanted to know, but the key do doing this is 
reliable, QC-able, but fast workflow. I have had my fill of 
simulating being at a party and listening to four conversations from 
four different speakers for a while. I didn't see (in the waveforms) 
nor hear any major head clogs--although 1.88 in/s is not very 
high-frequency rich in reel recordings. The 3.75 one was a breath of fresh air.

Cheers,

Richard


Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.