fpw Wrote:Well, it's on DAT, but it runs over 90 min. Wouldn't that be a HUGE file?
Standard CD audio is encoded at 16 bits per channel, 2 channels, and at a rate of 44,100 samples per second. (Using the Nyquist Theorem, we divide the sample rate in half and that gives us the frequency bandwidth that it allows. In the case of a CD, 44.1 kHz gives a bandwidth of 22.05 kHz, which pretty much covers the whole range of human hearing.) Multiplying all that together gives us 1,411,200 bits per second. A bit of math gives us an audio file of 10.09369 (10.1) megabytes per minute.
Since your commentary is speech; ie: mono, that gets cut in half to 5.05 megabytes per minute, so your audio file on a computer in uncompressed wav format would be 454.5 megabytes. And that's assuming your DAT has the audio in 16 bits per channel, 1 (mono) channel, with a sample rate of 44.1 kHz. If the sample rate or bits per channel are lower, your end result wav file will be smaller.
Proper encoding to mp3, or my preference, OGG Vorbis (higher quality, lower file size than mp3 but less portable device support), can cut that down to under 35 megabytes. 50 megabytes if you want slightly more quality.
I'd be more than happy to do the encoding for you, but I've nothing that can read a DAT, and I doubt I could instruct you on how to pull the audio off a DAT. I've never used one. Encoding, however, is easy enough. I rip and encode my CDs into OGG vorbis audio files all the time.
For your commentary, I would encode at Q -1.00 (45 kbps), re-sample to 16,000 Hz (that'll give you equal to 8 kHz bandwidth, plenty for the range of human speech) and encode to mono. That should leave you with a vorbis file slightly under 35 MB.