Old tapes-analysis and convertion to text
Posted: Mon Dec 31, 2018 9:13 pm
I see your posts Symoon and perhaps you could supply some info on the oric/atmos tape system signal processing.
For a couple of months I have been attempting to take old tapes(print through different/poor playback deck) and correct their frequency response to allow decoding. This has been done on a win7x64pro computer using AVS audio Editor. The tape is recorded mono at 44.1KHz filtered and processed by some Fortran programs I have written. The programs show plots of 1: Histogram of half period zero crossing intervals 2: time plot of signal with superimposed zero crossings 3: plot of zero crossing intervals against time 4:number of cycles of the two frequencies in each burst 5: conversion to 1 and 0 bits assuming 8cycles per bit for high frequency and 4 for the low frequency. So I have now discovered that the tape preface stream is 13 bits 1010000111001 or the inverse?
Now I am faced with questions I cannot answer.
1/how is the information carried in the f1/f2 signal stream number of cycles per bit etc
2/having got a bit stream as shown for the tape synchronizing lead-in e.g.1010000111001101000011100110100001110011010000111001........ how is the data buried in this. I assume oric codes.
This all came about from my Backgammon program posting when I finally discovered that the listing I had was incomplete or a older one and the tapes I have cannot be entered into any oric/atmos because of degeneration and a perfect player needed even if they weren't spoiled.
Perhaps others will be happy to exchange painful experiences with tying to recover old tapes.
In expectation
Happy new year to all
For a couple of months I have been attempting to take old tapes(print through different/poor playback deck) and correct their frequency response to allow decoding. This has been done on a win7x64pro computer using AVS audio Editor. The tape is recorded mono at 44.1KHz filtered and processed by some Fortran programs I have written. The programs show plots of 1: Histogram of half period zero crossing intervals 2: time plot of signal with superimposed zero crossings 3: plot of zero crossing intervals against time 4:number of cycles of the two frequencies in each burst 5: conversion to 1 and 0 bits assuming 8cycles per bit for high frequency and 4 for the low frequency. So I have now discovered that the tape preface stream is 13 bits 1010000111001 or the inverse?
Now I am faced with questions I cannot answer.
1/how is the information carried in the f1/f2 signal stream number of cycles per bit etc
2/having got a bit stream as shown for the tape synchronizing lead-in e.g.1010000111001101000011100110100001110011010000111001........ how is the data buried in this. I assume oric codes.
This all came about from my Backgammon program posting when I finally discovered that the listing I had was incomplete or a older one and the tapes I have cannot be entered into any oric/atmos because of degeneration and a perfect player needed even if they weren't spoiled.
Perhaps others will be happy to exchange painful experiences with tying to recover old tapes.
In expectation
Happy new year to all